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  • 51.
    Björk, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mogensen, Palne
    Nowacki, Jan-Erik
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Weber, Kenneth
    Bergvärme på djupet: Boken för dig som vill veta mer om bergvärmepumpar2013 (ed. 100)Book (Other (popular science, discussion, etc.))
    Abstract [sv]

    I den här boken får du lära dig mer om bergvärmepumpar. Hur fungerar en värmepump? Hur gör man en lönsamhetskalkyl? Hur upphandlar man? Kan man trimma sitt system? Dessutom: lär dig mer om radiatorsystemet, berget och kollektorn.

  • 52.
    Björk, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Nordenberg, Johan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A thermographic study of the on-off behavior of an all-refrigerator2010In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 14-15, p. 1974-1984Article in journal (Refereed)
    Abstract [en]

    In this work a thermographic camera is used to observe the temperature distribution of a household refrigerator cooling system operating at on off cycling conditions. This technique offers an alternative method to analyze the cooling system compared to conventional thermocouples. In particular it is interesting to view the overall picture of how the refrigerant charge is distributed over the cooling system at transient conditions. In addition, four sources of energy losses were identified and discussed. Out of these losses, two would have been difficult to find using conventional thermocouple temperature measurements. (C) 2010 Elsevier Ltd. All rights reserved.

  • 53.
    Björk, Erik T.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Flow boiling heat transfer at low flux conditions in a domestic refrigerator evaporator2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 6, p. 1021-1032Article in journal (Refereed)
    Abstract [en]

    This paper investigates the flow boiling heat transfer in a typical domestic refrigerator evaporator with horizontal flow, frequent bends and a non-circular cross-section. The mass flux was varied between 21 and 43 kg/m(2) s, the heat flux between 1 and 5 kW/m(2) and the vapour quality between 0.2 and 0.8. In spite of a predicted stratified to wavy-stratified flow pattern complete tube perimeter wetting was believed to occur except for the lowest mass flux and for positions upstream of the first bend. it was concluded that the bends helped wetting the tube perimeter. The experimental data revealed heat transfer coefficients higher than predicted with conventional correlations. This was suggested to be explained by thin film evaporation at a perimeter repeatedly wetted by liquid slugs. A simple correlation based on the pure convective part of the Shah correlation [3] was derived from the experimental data. The mean deviation of this was 16.9% compared to Shah's 54.7%.

  • 54.
    Björk, Erik T.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Performance of a domestic refrigerator under influence of varied expansion device capacity, refrigerant charge and ambient temperature2006In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 29, no 5, p. 789-798Article in journal (Refereed)
    Abstract [en]

    This paper reports experimental results of an on/off cycling domestic refrigerator at varied expansion device capacity (EDC), quantity of charge and ambient temperature. It was found that the energy consumption is insensitive to varied EDC and charge within a wide range of settings. For the charge this is explained by the low side accumulator, which buffers over- and undercharge. It was also found that the optimum charge increased at lower ambient temperature. The paper describes an experimental procedure on how to determine the capillary tube length and the quantity of charge for a domestic refrigerator/freezer. This procedure is recommended since it takes different thermal masses and loads into consideration and since the potential for energy saving with a more sophisticated method appears to be limited.

  • 55.
    Björk, Erik T.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Refrigerant mass charge distribution in a domestic refrigerator. Part I: Transient conditions2006In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, no 8-9, p. 829-837Article in journal (Refereed)
    Abstract [en]

    Experimental results are presented of the refrigerant mass charge distribution in a steadily cycling domestic refrigerator. In detail it is shown how the charge is displaced at compressor start-up and shut-down. At start-Lip it was found that the charge was temporarily displaced towards the condenser before returning to a steady state distribution in the latter part of the on-period. As a result, initially the evaporator was starved with a lowered evaporation temperature and a peak 10 degrees C superheat. The superheat disappeared within 3 min as the evaporator was gradually refilled with refrigerant. At shut-down the pressure equalised within 3 min as refrigerant was pushed into the evaporator from the condenser. The losses due to charge displacements were estimated to 11% (capacity) and 9% (efficiency). Possible ways to reduce the losses are discussed.

  • 56.
    Björk, Erik T.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Refrigerant mass charge distribution in a domestic refrigerator. Part II: Steady state conditions2006In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, no 8-9, p. 866-871Article in journal (Refereed)
    Abstract [en]

    Experimental results are presented of the refrigerant mass charge distribution in a steady state operating domestic refrigerator at varied thermal loads. It was found that the charge decreased in the evaporator and increased in the condenser and compressor upon increased thermal load. No subcooling or superheat was observed over the range of capacities tested (74-145 W). The combination of a low side accumulator and an expansion device with high capacity (short capillary tube) explained this. The study suggests that a capillary tube throttled cooling system, with a floating condensation temperature, can handle large load variations without becoming destabilised (superheat or subcooling) just like a more sophisticated thermostatic expansion device control system.

  • 57.
    Björk, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Tjahyo Setiawan, Arrie
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Air Side Heat Transfer of a Domestic Refrigerator Plate-Type Evaporator2003Conference paper (Other academic)
  • 58. Bontemps, Andre
    et al.
    Palm, Björn
    KTH.
    Thonon, Bernard
    Heat transfer in components and systems for sustainable energy technologies: Heat-SET 2005, 5-7 April 2005, Grenoble, France - Foreword2006In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 47, no 20, p. 3509-3509Article in journal (Other academic)
  • 59. Bontemps, Andre
    et al.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Thonon, Bernard
    Heat transfer in components and systems for sustainable energy technologies: Heat-SET 2005, 5-7 April 2005, Grenoble, France - Preface2006In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 47, no 20, p. 3507-3508Article in journal (Other academic)
  • 60. Celata, G. P.
    et al.
    Chmiel, K.
    Kulenovic, R.
    Martín-Callizo, Claudi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    McPhail, S.
    Mertz, R.
    Owhaib, Wahib
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Sobierska, E.
    Zummo, G.
    Frictional pressure drop in single-phase flow in narrow channels2006In: Proceedings of the 4th International Conference on Nanochannels, Microchannnels, and Minichannels, Pts A and B, 2006, p. 717-724Conference paper (Refereed)
    Abstract [en]

    An evaluation of frictional pressure drop in micro-conduits was carried out, taking into consideration such quantities as channel diameter, shape and aspect ratio, inclination, working fluid and heat input. Experiments took place at three different institutions and results were confronted with classical theory, using a simulation model where necessary. Excellent agreement was verified between the experimental friction factor data and the Hagen-Poiseuille and Blasius equations for all conditions and diameters. The difference in behaviour between circular and rectangular channels is minimal within the aspect ratios considered, but in the case of large temperature variation the effect of viscosity change must not be disregarded. For inclined channels, the frictional contribution to the total pressure drop exceeds the gravitational part only after a given value of the mass flux. This value increases for larger diameter and fluid density.

  • 61.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Conventional and advanced exergyanalysis of an ejector refrigeration systemManuscript (preprint) (Other academic)
  • 62.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Investigation of ejectors in refrigeration system: Optimum performance evaluation and ejector area ratios perspectives2014In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 64, no 1-2, p. 182-191Article in journal (Refereed)
    Abstract [en]

    This paper presents an ejector model to determine the optimum performance as well as obtaining the design area ratio of an ejector in a refrigeration system. Working fluid properties and auxiliary dynamic equations are used to model the processes in the ejector. The normal compression shock in the mixing chamber is considered. Experimental data from literature are used to validate the model, and the agreement with the model at optimum operating conditions is very good. The deviation between the model and the experimental data at non-optimum conditions is slightly larger. A study of working conditions for refrigerants R123 and R141b indicates that the condenser temperature has more influence than the generator and evaporator temperatures on the area ratio and the entrainment ratio in the ejector. Furthermore, area ratios need to keep up the pace with the variation of entrainment ratio as operating conditions are changed. A variable-geometry ejector seems a very promising alternative to ensure that the ejector refrigeration system operates at its optimum conditions. Ejector efficiencies play a very important role in the present model, and the influence of the efficiencies on the ejector performance is investigated. This ejector model may be used for parametric analysis and optimum performance evaluation as well as ejector design.

  • 63.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Parametric analysis of ejector working characteristics in the refrigeration system2014In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 69, no 1-2, p. 130-142Article in journal (Refereed)
    Abstract [en]

    A detailed investigation of ejector working characteristics in terms of refrigeration efficiency, ejector entrainment ratio, and irreversibilities in each ejector component (nozzle, mixing chamber and diffuser) is carried out by using R141b, R245fa and R600a as the working fluids. The aim of this paper is to generalize the interactions and relationships of various ejector parameters to get better understanding of the ejector working characteristics in the refrigeration system. External and internal ejector parameters are studied separately. The operating conditions and ejector component efficiencies have significant influence on the ejector behavior, and different refrigerants perform distinctively different in the ejector refrigeration system. However, effects of superheat of the three working fluids are negligible. The irreversibility related to the shock process dominates in the diffuser and plays an important role in the ejector performance. Further attention is paid on an analysis of quantifying the ejector component efficiencies based on published test data. Correlations are established to estimate the ejector efficiency and to show how ejector parameters interact.

  • 64.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Screening of working fluids for the ejector refrigeration system2014In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 47, p. 1-14Article in journal (Refereed)
    Abstract [en]

    For an ejector refrigeration system, the working fluid significantly influences the ejector behavior and system performance as well as ejector design. There are three categories of working fluids: wet fluids, dry fluids and isentropic fluids. Four wet fluids (R134a, R152a, R290 and R430A), four dry fluids (R245fa, R600, R600a and R1234ze) and one isentropic fluid (R436B) are selected in the paper. Special consideration is paid to the superheat of the ejector primary flow. This superheat is needed not only for wet fluids, but also for dry fluids and isentropic fluids at some cases, to eliminate droplets inside the ejector. A minimum superheat is found, and it is dependent on the used working fluid and the operating temperatures as well as the ejector nozzle efficiency. The comparison among these nine candidates indicates that R600 is a good candidate for the ejector refrigeration system due to a relatively high COP and its low environmental impact.

  • 65.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Thermoeconomic optimization of an ejector refrigeration system working with isobutane2014In: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL 2014, 2014, p. 286-294Conference paper (Refereed)
    Abstract [en]

    Thermoeconomics is a new branch of thermodynamics and consists of exergy analysis, economic modeling and thermoeconomic analysis on an energy conversion system. In this study, thermoeconomic concepts are applied to an ejector refrigeration system (ERS) that uses natural refrigerant R600a as the working fluid and has 100 kW cooling capacity. The system is investigated from thermodynamic and thermoeconomic perspectives. To optimize such a system, the objective function is defined as the sum of the costs of brine side fluids, electricity, and costs related to capital investment and operation and maintenance expense. The pinch point temperatures in the three heat changers are considered as the decision variables, with two different economic scenarios imposed to the system. An iteration technique is employed to minimize the objective function. It shows that the optimized objective function is reduced by 8.1% and 7.5% respectively compared to the non-optimized cases for the two scenarios.

  • 66. Chen, Jianyong
    et al.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Chen, Y
    An Experimental Study of Vapor Ejectors Working with R245fa2017In: Second Thermal and Fluids Engineering Conference, 2017, p. 925-928Conference paper (Refereed)
    Abstract [en]

    The vapor ejector is the key component in the ejector refrigeration system. The ejector determines the working stability and performance of the whole system. A specific test rig was designed and built with a focus on the performance of ejector itself. Instead of a circulation pump and a generator in the ejector refrigeration system, a compressor was used as the driving source. R245fa was selected as the working fluid. The important parameters, like pressure, temperature and mass flow rate, were measured and recorded. The entrainment ratio was obtained at a maximum value of 0.28. It was found that using ideal gas law and an appropriate value of the ejector nozzle isentropic efficiency could provide reasonable predictions of the mass flow rate through the ejector nozzle. Moreover, the insignificant impact of the superheat of the secondary flow on entrainment ratio was verified.

  • 67.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Conventional and advanced exergy analysis of an ejector refrigeration system2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 144, p. 139-151Article in journal (Refereed)
    Abstract [en]

    This paper presents a comprehensive investigation of an ejector refrigeration system using conventional and advanced exergy analysis. Splitting the exergy destruction within each system component into endogenous/exogenous and avoidable/unavoidable parts provides additional useful information and improves the quality of the exergy analysis. Detailed calculations of the exergy destruction parts are schematically illustrated. Conventional exergy analysis indicates that about half of the total exergy destruction is caused by the ejector and about one quarter occurs in the generator. The advanced exergy analysis reflects the strong interactions between system components. The ejector has the highest priority to be improved, followed by the condenser and then the generator. The temperature difference in the condenser has the largest influence on the exergy destruction compared to that in the generator and the evaporator, and the ejector efficiencies are also very crucial for the exergy destruction. The system performance can be largely enhanced through improvements of the ejector and the condenser as well as the generator.

  • 68.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Jarall, Sad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Havtun, Hans
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A review on versatile ejector applications in refrigeration systems2015In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 49, p. 67-90Article, review/survey (Refereed)
    Abstract [en]

    This paper presents a useful knowledge of ejector working principles and the versatility and diversity of its applications in refrigeration technologies. Various ejector refrigeration systems are described with the associated studies, and categorized as conventional ejector refrigeration system, advanced ejector refrigeration systems, combined refrigeration systems and ejector enhanced vapor compression systems. This paper also presents the important elements that affect the optimum performance of the ejector system, and the results of studies that have generally confirmed their energy saving, great potential for large refrigerating temperature scales and performance enhancement.

  • 69.
    Chen, Jianyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A new ejector refrigeration system with zeotropic mixtures2011In: 23RD IIR INTERNATIONAL CONGRESS OF REFRIGERATION, 2011, p. 2043-2050Conference paper (Refereed)
    Abstract [en]

    A new ejector refrigeration system (NERS) using zeotropic mixture is theoretical studied in the paper.R32/R134a, R32/R152a, R134a/R142b, R152a/R142b, R290/R600a and R600a/R600 are selected as theworking fluids in the analysis. The comparison between this NERS and the conventional ejector refrigerationsystem (CERS) is made under the same operating condition. It is found that this new system has higherCOPs than the CERS. The effect of operating conditions and the composition on the performance of this newsystem are presented. An exergy analysis is carried out to study the loss within each component of thesystem. It is observed that the irreversibility in the ejector represents more than 50% of the total exergy loss.This also emphasizes the necessity for good ejector design and manufacture.

  • 70.
    Chen, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A Nobel Gas-Water Heat Exchanger with Minichannels2008Conference paper (Refereed)
  • 71.
    Chen, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A NOVEL GAS-WATER HEAT EXCHANGER WITH MINICHANNELS2009In: HT2008: PROCEEDINGS OF THE ASME SUMMER HEAT TRANSFER CONFERENCE - 2008, VOL 2, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2009, p. 157-164Conference paper (Refereed)
    Abstract [en]

    In the current study, a novel gas water heat exchanger with minichannels is designed, built and tested. The heat exchanger is mainly composed of a number of concentric ring shaped plates, which are made tip of several heat exchanger tubes. The ring shaped plates are arranged in parallel and placed in a shell. The heat exchanger is designed as a counter current heat exchanger with laminar flow on the heat exchanger's shell-side (gas side) and therefore has a very low pressure drop on the shell side. The heat exchanger was tested with water and hot air on its tube-side and shell-side respectively. All the necessary parameters like inlet and outlet temperatures on tube-side and shell-side as well as the pressure drop, flow rate of fluids, etc. were measured. Different existing correlations were used to calculate the overall heat transfer coefficient and the results were compared with the measured value. The measured results show that the new designed heat exchanger can achieve a good heat transfer performance and also maintain a low pressure drop on shell-side (gas side).

  • 72. Dovic, D.
    et al.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Svaic, S.
    Generalized correlations for predicting heat transfer and pressure drop in plate heat exchanger channels of arbitrary geometry2009In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 52, no 19-20, p. 4553-4563Article in journal (Refereed)
    Abstract [en]

    Characteristics of the flow in chevron plate heat exchangers are investigated through visualization tests of channels with beta = 28 degrees and beta = 61 degrees. Mathematical model is then developed with the aim of deriving correlations for prediction off and Nu for flow in channels of arbitrary geometry (beta and 1511). Thermal and hydraulic characteristics are evaluated using analytical solutions for the entrance and fully developed regions of a sinusoidal duct adapted to the basic single cell. The derived correlations are finally adjusted so as to agree with experimental results from tests on channels with beta = 28 degrees and beta = 65 degrees. f and Nu calculated by the presented correlations are shown to be consistent with experimental data from the literature at Re = 2-10,000, beta = (15-67)degrees and b/l = 0.26-0.4.

  • 73. Dovic, D.
    et al.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    Svaic, S.
    Visualtization of one-phase flow in chevron-plate heat exchangers end their performance2000In: Strojniski vestnik, ISSN 0039-2480, Vol. 46, no 7, p. 429-435Article in journal (Refereed)
    Abstract [sl]

    Modern plate heat exchangers with chevron corrugation patterns are spread across a range of applications both in one- and two-phase flow regimes due to their compactness and superior thermal-hydraulic performance when compared to the other types of heat exchangers. Recently a limited number of experimental studies have been undertaken to understand the influence of corrugation angles and the ratio of corrugation depth to,wave length (b/l) On the flow pattern and in turn on the heat transfer and pressure drop. In order to clarify this complex issue, visualization tests have been performed on a model of a Plate heat exchanger (PHE) having only a single channel composed of one metal and one plastic transparent plate with identical corrugation.

  • 74.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Han, Han
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    KTH, Superseded Departments, Energy Technology.
    The Solubility of Propane (R290) with Commonly Used Compressor Lubrication Oils2003In: Compressors and Their Systems, 2003, Vol. 4, p. 157-166Conference paper (Refereed)
    Abstract [en]

    An ongoing project called "Charge minimisation of a small capacity heat pump" is aimed to minimise the refrigerant charge in heat pumps, refrigeration and air-conditioning systems. The experimental heat pump was run with propane as refrigerant and the designed heat capacity (condenser capacity) was over 5kW. Tests were done to investigate the refrigerant charge distribution in different sections of the heat pump, while it was running. The experiments done so far have shown that the amount of refrigerant in the compressor is higher than expected.

    This paper presents the measured refrigerant masses in a hermetic scroll compressor together in suction line and the calculated refrigerant mass dissolved in the compressor lubrication oil at different evaporation temperatures. Finally, solubility tests of propane with different lubricating oils are presented. The tests show that the propane is more soluble in POE than PAG oils.

  • 75.
    Fernando, W. Primal D.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ameel, Tim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A Minichannel Aluminium Tube Heat Exchanger - Part 1: Evaluation of Single-Phase Heat Transfer Coefficients by the Wilson Plot Method2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 4, p. 669-680Article in journal (Refereed)
    Abstract [en]

    A prototype liquid-to-refrigerant heat exchanger was developed with the aim of minimizing the refrigerant charge in small systems. To allow correct calculation of the refrigerant side heat transfer, the heat exchanger was first tested for liquid-to-liquid (water-to-water) operation in order to determine the single-phase heat transfer performance. These single-phase tests are reported in this paper. The heat exchanger was made from extruded multiport aluminium tubes and was designed similar to a shell-and-tube heat exchanger. The heat transfer areas of the shell-side and tube-side were approximately 0.82 m(2) and 0.78 m(2), respectively. There were six rectangular-shaped parallel channels in a tube. The hydraulic diameter of the tube-side was 1.42 mm and of the shell-side 3.62 mm. Tests were conducted with varying water flow rates, temperature levels and heat fluxes on both the tube and shell sides at Reynolds numbers of approximately 170-6000 on the tube-side and 1000-5000 on the shell-side, respectively. The Wilson plot method was employed to investigate the heat transfer on both the shell and tube sides. In the Reynolds number range of 2300-6000, it was found that the Nusselt numbers agreed with those predicted by the Gnielinski correlation within +/- 5% accuracy. In the Reynolds number range of 170-1200 the Nusselt numbers gradually increased from 2.1 to 3.7. None of the previously reported correlations for laminar flow predicted the Nusselt numbers well in this range. The shell-side Nusselt numbers were found to be considerably higher than those predicted by correlations from the literature.

  • 76.
    Fernando, W. Primal D.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ameel, Tim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A minichannel aluminium tube heat exchanger - Part II: Evaporator Performance with Propane2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 4, p. 681-695Article in journal (Refereed)
    Abstract [en]

    This paper presents heat transfer data for a multiport minichannel heat exchanger vertically mounted as an evaporator in a test-rig simulating a small water-to-water heat pump. The multiport minichannel heat exchanger was designed similar to a shell-and-tube type heat exchanger, with a six-channel tube of 1.42 mm hydraulic diameter, a tube-side heat transfer area of 0.777 m(2) and a shell-side heat transfer area of 0.815 m(2). Refrigerant propane with a desired vapour quality flowed upward through the tubes and exited with a desired superheat of 1-4 K. A temperature-controlled glycol solution that flowed downward on the shell-side supplied the heat for the evaporation of the propane. The heat transfer rate between the glycol solution and propane was controlled by varying the evaporation temperature and propane mass flow rate while the glycol flow rate was fixed (18.50 l min(-1)). Tests were conducted for a range of evaporation temperatures from -15 to +10 degrees C, heat flux from 2000 to 9000 W m(-2) and mass flux from 13 to 66 kg m(-2) s(-1). The heat transfer coefficients were compared with 14 correlations found in the literature. The experimental heat transfer coefficients were higher than those predicted by many of the correlations. A correlation which was previously developed for a very large and long tube (21 mm diameter and 10 m long) was in good agreement with the experimental data (97% of the data within 30%). Several other correlations were able to predict the data within a reasonable deviation (within 30%) after some adjustments to the correlations.

  • 77.
    Fernando, W. Primal D.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ameel, Tim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A minichannel aluminium tube heat exchanger - Part III: Condenser Performance with Propane2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 4, p. 696-708Article in journal (Refereed)
    Abstract [en]

    This paper reports heat transfer results obtained during condensation of refrigerant propane inside a minichannel aluminium heat exchanger vertically mounted in an experimental setup simulating a water-to-water heat pump. The condenser was constructed of multiport minichannel aluminium tubes assembled as a shell-and-tube heat exchanger. Propane vapour entered the condenser tubes via the top end and exited sub-cooled from the bottom. Coolant water flowed upward on the shell-side. The heat transfer areas of the tube-side and the shell-side of the condenser were 0.941 m(2) and 0.985 m(2), respectively. The heat transfer rate between the two fluids was controlled by varying the evaporation temperature while the condensation temperature was fixed. The applied heat transfer rate was within 3900-9500 W for all tests. Experiments were performed at constant condensing temperatures of 30 degrees C, 40 degrees C and 50 degrees C, respectively. The cooling water flow rate was maintained at 11.90 l min(-1) for all tests. De-superheating length, two-phase length, sub-cooling length, local heat transfer coefficients and average heat transfer coefficients of the condenser were calculated. The experimental heat transfer coefficients were compared with predictions from correlations found in the literature. The experimental heat transfer coefficients in the different regions were higher than those predicted by the available correlations.

  • 78.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Andersson, Klas
    KTH, Superseded Departments, Energy Technology.
    Mini-Channel Aluminium Heat Exchangers with Small Inside Volumes2003In: Proc. 21st IIR International Congress of Refrigeration, Washington DC, August 17-22, 2003, 2003Conference paper (Refereed)
  • 79.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Samoteeva, Oxana
    KTH, Superseded Departments, Energy Technology.
    Anderson, Klas
    KTH, Superseded Departments, Energy Technology.
    The Behaviour of Small Capacity (5kW) Heat pump with Micro-Channelled Flat Tube Heat Exchangers2002Conference paper (Refereed)
  • 80.
    Fernando, W. Primal D.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Performance of a single-family heat pump at different working conditions using small quantity of propane as refrigerant2007In: Experimental heat transfer, ISSN 0891-6152, E-ISSN 1521-0480, Vol. 20, no 1, p. 57-71Article in journal (Refereed)
    Abstract [en]

    The performance of a domestic heat pump that uses a low quantity of propane as refrigerant has been experimentally investigated. The heat pump consists of two minichannel aluminium heat exchangers, a scroll compressor, and an electronic expansion valve. It was charged with the minimum amount of refrigerant propane required for the stable operation of the heat pump without permitting refrigerant vapor into the expansion valve at incoming heat source fluid temperature to the evaporator of +10 degrees C The inlet temperature of the heat source fluid passing through the evaporator was varied from +10 degrees C to -10 degrees C while holding the condensing temperature constant at 35 degrees C, 40 degrees C, 50 degrees C, and 60 degrees C, respectively. The minimum refrigerant charges required at above-tested condensing temperatures were found to decrease when the condensing temperature increased and were recorded as 230 g, 224 g, 215 g, and 205 g, respectively. The results confirm that a heat pump with 5 kW capacity can be designed with less than 200 g charge of refrigerant propane in the system. Due to the high solubility of propane in compressor lubrication oil, the amount of refrigerant which may escape rapidly in case of accident or leakage is less than 150 g.

  • 81.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Propane Heat Pump with Low Refrigerant Charge: Design and Laboratory Tests2004In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 27, no 7, p. 761-773Article in journal (Refereed)
    Abstract [en]

    Independently of the choice of refrigerant, environmental and or safety issues can be minimised by reducing the amount of refrigerant charge per heat pump or refrigeration system. In the investigation reported here, a laboratory test rig was built, simulating a water-to-water heat pump with a heating capacity of 5 kW. The system was designed to minimize the charge of refrigerant mainly by use of mini-channel aluminium heat exchangers. It was shown that the system could be run with 200 g of propane at typical Swedish operating conditions without reduction of the COP compared to a traditional design. Additional charge reduction is possible by selecting proper compressor lubrication oils or by using a compressor with less lubrication oil.

  • 82.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Samoteeva, Oxana
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Charge Distribution in a 5kW Heat Pump Using Propane as Working Fluid: Part 1: Experimental Investigation2001In: Proc. 16. Nordiske Kølemøde og 9. Nordiske Varmepumpedage29.-31. August 2001, 2001, p. 299-Conference paper (Refereed)
  • 83.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Li, Shanghua
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of an evaporator enhanced with a micro-porous structure in a two-phase thermosyphon loop2009In: HT2008: PROCEEDINGS OF THE ASME SUMMER HEAT TRANSFER CONFERENCE - 2008, VOL 2, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2009, p. 327-334Conference paper (Refereed)
    Abstract [en]

    Following is an experimental study of six different evaporators in a closed two-phase thermosyphon loop system, where the influence of various evaporator dimensions and surfaces was investigated. The evaporators featured a 30 mm long rectangular channel with hydraulic diameters ranging from 1.2-2.7 mm. The heat transfer surface of one of the tested evaporators was enhanced with copper nano-particles, dendritically connected into an ordered micro-porous three dimensional network structure. To facilitate high speed video visualization of the two-phase flow in the evaporator channel, a transparent polycarbonate window was attached to the front of the evaporators. Refrigerant 134A was used as a working fluid and the tests were conducted at 6.5 bar. The tests showed that increasing channel diameters generally performed better. The three largest evaporator channels exhibited comparable performance, with a maximum heat transfer coefficient of about 2.2 W/(cm(2)K) at a heat flux of 30-35 W/cm(2) and a critical heat flux of around 50 W/cm(2). Isolated bubbles characterized the flow regime at peak performance for the large diameter channels, while confined bubbles and chaotic churn flow typified the evaporators with small diameters. In line with previous pool boiling experiments, the nucleate boiling mechanism was significantly enhanced, tip to 4 times, by the nano- and micro-porous enhancement structure.

  • 84.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Use of a novel nano- and micro-porous structure for enhanced boiling in a plate heat exchanger2008In: Proceedings of the 9th IEA heat pump conference, Zürich, CH, Zürich, CH: Academic Conferences Publishing, 2008Conference paper (Refereed)
  • 85.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Dendritically ordered nano-particles in a micro-porous structure for enhanced boiling2006In: Proceedings of 13th International Heat Transfer Conference, NAN-07, 2006, Vol. NAN-07Conference paper (Refereed)
    Abstract [en]

    Presented research is an experimental study of the pool boiling performance of copper surfaces enhanced with a newly developed structure. The enhanced surfaces were fabricated with an electrodeposition method where metallic nano-particles are formed and dendritically connected into an ordered micro-porous structure. To further alter the grain size of the dendritic branches, some surfaces underwent an annealing treatment. The tests were conducted with the test objects horizontally oriented and submerged in a refrigerant: R134A, at saturated conditions and at an absolute pressure of 4 bar. The heat flux varied between 0.1 and 10 W/cm2. The boiling performance of the enhanced surfaces was found to be dependent on controllable surface characteristics such as thickness of the structure and the interconnectivity of the grains in the dendritic branches. Temperature differences less than 0.3 °C and 1.5 °C at heat fluxes of 1 and 10 W/cm2 respectively have been recorded, corresponding to heat transfer coefficients up to 7.6 Wcm-2K-1. The micro-porous structure has been shown to facilitate high performance boiling, which is attributed to its high porosity (∼94%), a dendritically formed and exceptionally large surface area, and to a high density of well suited vapor escape channels (50 – 470 per mm2).

  • 86.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Li, Shanghua
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Tuprak, MUHAMMET
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Muhammed, MAMOUN
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Porous layer2006Patent (Other (popular science, discussion, etc.))
  • 87.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Boiling heat transfer on a dendritic and micro-porous surface in R134a and FC-722011In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 31, no 16, p. 3595-3603Article in journal (Refereed)
    Abstract [en]

    A visualization study was conducted with the aim of deepening the understanding of the boiling mechanism in a dendritic and micro-porous copper structure for enhanced boiling heat transfer. The unique structure has earlier been shown to enhance heat transfer in pool boiling applications as well as in convective boiling in both small and large channels. Pool boiling tests were conducted in R134a and in the dielectric fluid FC-72 and were visualized with a high speed imaging system. Data on bubble size, bubble frequency density, heat transfer coefficient and the latent and sensible heat flux contributions were collected and calculated at heat flux varying between 2 and 15 W/cm(2). The enhanced surface produces smaller bubbles and sustains a high bubble frequency density in both fluids, even at low heat flux. An enhanced latent heat transfer mechanism of up to 10 times, compared to that of a plain reference surface, is the main reason for the improved boiling heat transfer performance on the enhanced surface. The data also suggests that the high nucleation bubble frequency density leads to increased bubble pumping action and thus enhancing single-phase convection of up to 6 times. The results in this study highlight the importance of both two and single-phase heat transfer within the porous structure.

  • 88.
    Furberg, Richard
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    The Use of a Nano- and Microporous Surface Layer to Enhance Boiling in a Plate Heat Exchanger2009In: Journal of heat transfer, ISSN 0022-1481, E-ISSN 1528-8943, Vol. 131, no 10Article in journal (Refereed)
    Abstract [en]

    Presented research is an experimental study of the performance of a standard plate heat exchanger evaporator, both with and without a novel nano- and microporous copper structure, used to enhance the boiling heat transfer mechanism in the refrigerant channel. Various distance frames in the refrigerant channel were also employed to study the influence of the refrigerant mass flux on two-phase flow heat transfer. The tests were conducted at heat fluxes ranging between 4.5 kW/m(2) and 17 kW/m(2) with 134a as refrigerant. Pool boiling tests of the enhancement structure, under similar conditions and at various surface inclination angles, were also performed for reasons of comparison. The plate heat exchanger with the enhancement structure displayed up to ten times enhanced heat transfer coefficient in the refrigerant channel, resulting in an improvement in the overall heat transfer coefficient with over 100%. This significant boiling enhancement is in agreement with previous pool boiling experiments and confirms that the enhancement structure may be used to enhance the performance of plate heat exchangers. A simple superposition model was used to evaluate the results, and it was found that, primarily, the convective boiling mechanism was affected by the distance frames in the standard heat exchanger. On the other hand, with the enhanced boiling structure, variations in hydraulic diameter in the refrigerant channel caused a significant change in the nucleate boiling mechanism, which accounted for the largest effect on the heat transfer performance.

  • 89. Granryd, Eric
    et al.
    Palm, Björn
    Värmeväxlarvägg anordnad med en tunn, hålförsedd metallfolie för att förbättra värmeövergången vid kokning respektive kondensation: [Heat transfer element]1986Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A heat exchanger wall incorporates a partition wall (11-12), one side of which is in contact with a heat exchange medium. A mechanically stable part (11) of the partition wall (11-12) has provided on one surface thereof a thin metal foil (12), which is provided with a large number of small through-passing holes (121) and which is attached directly to the said part (11), such as to form a minute gap (13) between the foil and the mechanically stable part. According to one embodiment the element comprises a tube (11) and the foil has provided therein a longitudinally extending slot (122) and/or a plurality of folds or bends (31, 32) directed towards the stable part (11), and/or a fold or bend (51) facing away from the stable part (11). In addition to occurring through the intrinsic rigidity of the foil, the thin gap is formed by providing one side of the foil (12) with a rough or irregular structure, or by forming the holes in the foil in a manner such as to leave burrs around the defining edges of the holes, or by providing in the foil a number of folds or bends (31, 32) which face towards the mechanically stable part.

  • 90.
    Grozdek, Marino
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of ice slurry heat transfer in horizontal tube2009In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 32, no 6, p. 1310-1322Article in journal (Refereed)
    Abstract [en]

    Heat transfer of ice slurry flow based on ethanol-water mixture in a circular horizontal tube has been experimentally investigated. The secondary fluid was prepared by mixing ethanol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 degrees C). The heat transfer tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 22% depending on test performed. Measured heat transfer coefficients of ice slurry are found to be higher than those for single phase fluid, especially for laminar flow conditions and high ice mass fractions where the heat transfer is increased with a factor 2 in comparison to the single phase flow. In addition, experimentally determined heat transfer coefficients of ice slurry flow were compared to the analytical results, based on the correlation by Sieder and Tate for laminar single phase regime, by Dittus-Boelter for turbulent single phase regime and empirical correlation by Christensen and Kauffeld derived for laminar/turbulent ice slurry flow in circular horizontal tubes. it was found that the classical correlation proposed by Sieder and Tate for laminar forced convection in smooth straight circular ducts cannot be used for heat transfer prediction of ice slurry flow since it strongly underestimates measured values, while, for the turbulent flow regime the simple Dittus-Boelter relation predicts the heat transfer coefficient of ice slurry flow with high accuracy but only up to an ice mass fraction of 10% and Re-cf > 2300 regardless of imposed heat flux. For higher ice mass fractions and regardless of the flow regime, the correlation proposed by Christensen and Kauffeld gives good agreement with experimental results. (C) 2009 Elsevier Ltd and IIR. All rights reserved.

  • 91.
    Haghighi, Ehsan Bitaraf
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Anwar, Zahid
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Lumbreras, Itziar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mirmohammadi, Seyed Aliakbar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Behi, Mohammadreza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Screening Single Phase Laminar Convective Heat Transfer of Nanofluids in a Micro-tube2012In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 395, article id 012036Article in journal (Refereed)
    Abstract [en]

    Nano scale solid particles dispersed in base fluids are a new class of engineered colloidal solutions called nanofluids. Several studies reported enhancement of heat transfer by using nanofluids. This article reports convective single-phase heat transfer coefficients in an open 30 cm long, 0.50 mm internal diameter stainless steel test section. The setup is used for screening single phase laminar convective heat transfer with water and three different nanofluids: water based Al2O3, ZrO2, and TiO2 (all with 9 wt% of particles). A syringe pump with adjustable pumping speed is used to inject fluids into the test section. Thirteen T-type thermocouples are attached on the outer surface of the test section to record the local wall temperatures. Furthermore, two T-type thermocouples are used to measure inlet and outlet fluid temperatures. A DC power supply is used to heat up the test section and a differential pressure transducer is used to measure the pressure drop across the tube. Furthermore, the effective thermal conductivities of these nanofluids are measured using the Transient Plane Source (TPS) method at a temperature range of 20 - 50 degrees C. The experimental average values of heat transfer coefficients for nanofluids are compared with water. Enhancement in heat transfer of nanofluids is observed only when compared at constant Reynolds number (Due to higher viscosity for nanofluids, higher velocity or mass flow rate is required for nanofluids to reach the same Reynolds number). The other methods of comparison: equal mass flow rate, volume flow rate, pressure drop and pumping power did not show any augmentation of the heat transfer coefficient for the tested nanofluids compared to water.

  • 92.
    Haghighi, Ehsan Bitaraf
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Nikkam, Nader
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Accurate basis of comparison for convective heat transfer in nanofluids2014In: International Communications in Heat and Mass Transfer, ISSN 0735-1933, E-ISSN 1879-0178, Vol. 52, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Thermal conductivity and viscosity of alumina (Al2O3), zirconia (ZrO2), and titania (TiO2) nanofluids (NFs) were measured at 20°C. All the NF systems were water based and contained 9wt.% solid particles. Additionally, the heat transfer coefficients for these NFs were measured in a straight tube of 1.5m length and 3.7mm inner diameter. Based on the results, it can be stated that classical correlations, such as Shah and Gnielinski, for laminar and turbulent flow respectively, can be employed to predict convective heat transfer coefficients in NFs, if the accurate thermophysical properties are used in the calculations. Convective heat transfer coefficients for NFs were also compared with those of the base fluids using two different bases for the comparison, with contradictory results: while compared at equal Reynolds number, the heat transfer coefficients increased by 8-51%, whereas compared at equal pumping power the heat transfer coefficients decreased by 17-63%. As NFs have higher viscosity than the base fluids, equal Reynolds number requires higher volumetric flow, hence higher pumping power for the NFs. It is therefore strongly suggested that heat transfer results should be compared at equal pumping power and not at equal Reynolds number.

  • 93.
    Haghighi, Ehsan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Utomo, A. T.
    Pacek, A. W.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Experimental study of convective heat transfer in nanofluids2015In: Heat Transfer Enhancement with Nanofluids, CRC Press , 2015, p. 181-206Chapter in book (Other academic)
    Abstract [en]

    The term nanofluid describing diluted suspensions of metal or metal oxide nanoparticles in water was first introduced by Choi and Eastman in 1995 during the International Mechanical Engineering Congress and Exhibition (ASME) congress [1]. They claimed, based on rather limited number of experimental data, that diluted suspensions of metal/metal oxide nanoparticles in water have unusually high thermal conductivity, much higher than expected based on the commonly used effective medium theory [2]. This chapter and the concept of “exceptional” nanofluids went rather unnoticed, and between 1995 and 2001, there were only a few papers published on nanofluids. In 2001, a US patent was granted [3], supported by two graphs with no error bars, claiming that thermal conductivity of fluids can be substantially increased by the addition of small amounts of metal/metal oxide nanoparticles. Since then the research on nanofluids has steeply accelerated with more than 2500 papers published between 2001 and 2014. It needs to be stressed here that despite this exponential growth in the number of publications, only part of heat transfer research community accepted the claims about exceptional properties of nanofluids. One of the authors attended a conference on heat transfer in nanofluids [4], where nearly 50% of the participants were highly skeptical about exceptional thermal properties of the nanofluids. The acceleration in research and very strong interest in nanofluids were not surprising. If the claims made in the US patent were correct and stable suspensions of nanoparticles with high thermal conductivity and relatively low viscosity could be produced at reasonable cost, this would be a serious breakthrough in a wide range of processes, in which the heat transfer is frequently a limiting step such as engine cooling, cooling of electronic devices, and nuclear systems cooling, to name a few [5]. 

  • 94.
    Ignatowicz, M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Melinder, Å.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, B,
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ethyl alcohol based secondary fluid: Effect of corrosion inhibitors on thermophysical properties2016In: Refrigeration Science and Technology, International Institute of Refrigeration , 2016, p. 602-609Conference paper (Refereed)
    Abstract [en]

    Currently available commercial ethyl alcohol (EA) based secondary fluids in Sweden and other Nordic countries contain up to 10 wt-% denaturing agents (in concentrate alcohol) in form of propyl alcohol and n-butyl alcohol but no corrosion inhibitors. These studies were initiated due to a growing need for providing any protection against corrosion and extending the lifetime of the system. A literature search has been made to find the compatible corrosion inhibitors that can effectively protect the system. Afterwards, measurements have been performed to investigate the effect of these corrosion inhibitors on the thermophysical properties of the base fluid. Results showed that the different corrosion inhibitors can affect the thermophysical properties even when added in small concentrations. The presences of corrosion inhibitor had a positive effect and decrease the freezing point. Additionally, the presence of corrosion inhibitor in 30 wt-% ethyl alcohol samples had no significant effect on the dynamic viscosity and only EA25 + 0.01 SG (sodium gluconate) sample showed lower dynamic viscosity value by up to 10 %. The corrosion inhibitors had negative effect on the thermal conductivity in the full temperature range. EA25 and EA30 samples containing sodium gluconate, benzotriazole and sodium molybdate had higher specific heat capacity than the pure solutions. This study showed that both benzotriazole and 2-mercaptobenzothiazole seem to be the most promising corrosion inhibitor for ethyl alcohol based secondary fluids.

  • 95.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mazzotti, Willem
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Methods of BHE flushing, charging and purging in Sweden2016In: Proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    In Sweden, there are more than 500 000 small and about 500 relatively large ground source heat pumps (GSHP) having a total installed capacity of about 5.6 GW delivering approximately 15 TWh. yr-1 of heating and cooling energy in Sweden. The operational lifetime and reliability of any GSHP depends heavily on the way the system is designed, installed and operated. In order to provide a good system performance after installation, aspects such as borehole heat exchanger (BHE) system flushing, charging and purging, among others, should be taken into consideration. The aim of this work has been to review some existing methods of system flushing, charging and purging in order and make observations that may be applicable for the GSHP industry. Two Swedish case studies have been followed up and compared to existing strategies suggested by IGSHPA.The results show that there is a lack of specific recommendations regarding the flushing and purging procedures for BHEs in Sweden. A well-defined range or adaptation of similar IGSHPA standards could help in defining the minimum flush velocity. The two case studies showed different practices, with flushing velocities being significantly higher than the minimum flushing velocity recommended by IGSHPA. Flushing flow rates based on this standard are presented in this work for some typical BHE pipe sizes used in Europe.

  • 96.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mazzotti, W.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Melinder, A.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Alternative alcohol blends as secondary fluids for ground source heat pumps2016In: Refrigeration Science and Technology, International Institute of Refrigeration , 2016, p. 610-617Conference paper (Refereed)
    Abstract [en]

    The most common secondary fluid used for the borehole heat exchangers in Sweden is an aqueous solution of ethyl alcohol (EA) due to its relatively good thermophysical properties and low toxicity. Commercially available ethyl alcohol based fluids in Sweden contain up to 10 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA). The aim of this paper was to investigate the performance of the existing ethyl alcohol blend containing two denaturing agents and alternative alcohol blends in terms of the pressure drop and heat transfer in the BHE and comparison with ethyl alcohol based secondary fluid. Experimental results showed that the presence of these denaturing agents improves thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. EA18 + PA1.6 + BA0.4 and EA18.4 + PA1.6 present the best characteristics in terms of the heat transfer and pressure drop. Both blends are giving higher heat transfer coefficient by 9.4 % (EA18 + PA1.6 + BA0.4) and 8.11 % (EA18.4 + PA1.6) than pure EA20. Both blends are giving as well lower pressure drop than EA20 by up to 2.7 % (EA18 + PA1.6 + BA0.4) and 3 % (EA18.4 + PA1.6). EA18 + PA1.6 + BA0.4 gives 1.4 % higher heat transfer coefficient and EA18.4 + PA1.6 gives lower pressure drop by up to 0.4 % when these two blends are compared.

  • 97.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mazzotti, Willem
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Melinder, A.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Different ethyl alcohol secondary fluids used for GSHP in Europe2017Conference paper (Refereed)
    Abstract [en]

    The most common secondary fluid used for the borehole heat exchangers in Sweden is aqueous solution of ethyl alcohol (EA). Commercially available ethyl alcohol based fluids in Sweden and other European countries contain various denaturing agents. Ethyl alcohol based secondary fluids in Sweden are distributed as ethyl alcohol concentrate, including up to 12 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA). In other European countries, like Switzerland and Finland, the commercial products containing a mixture of methyl ethyl ketone and methyl isobutyl ketone (up to 4.5 vol-%) are used for GSHP application. The chemical character of these denaturing agents can in different ways affect the thermophysical properties. Therefore, the aim of this paper was to investigate the performance of commercially available alcohol blends in Europe in terms of pressure drop and heat transfer in the BHE. The results show that the most commonly used product in Sweden (EA18+PA1.6+BA0.4) presents the best characteristics in terms of higher heat transfer (up to 10 %) and lower pressure drop (up to 2.7 %) among different commercial products found in Europe. Another commercial product used in Switzerland showed second best performance in terms of higher heat transfer (up to 5 %) and lower pressure drop (up to 2 %). Moreover, other products containing higher concentrations of denaturing agents presented the worst performance in terms of lower heat transfer (up to 8 %) and higher pressure drop (up to 1 %) than EA20.

  • 98.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mazzotti, Willem
    Rogstam, Jörgen
    Energi & Kylanalys.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Secondary Fluid Impact on Ice Rink Refrigeration System Performance2014Conference paper (Refereed)
    Abstract [en]

    Sweden has 352 ice rinks in operation which annually use approximately 1000MWh. A refrigeration system usually accounts for about 43% of the total energy consumption and can present a significant energy saving potential. More than 97% of the Swedish ice rinks use indirect refrigeration system and thermo-physical properties of secondary fluid have a direct impact on the heat transfer and pressure drop. A theoretical model and two case studies focusing on the importance of the secondary fluid choice were investigated. The results showed that potassium formate had the best heat transfer properties while ammonia lead to the lowest pressure drops and pumping power. Propylene glycol showed the worst performance in both cases. Ammonia and potassium formate showed respectively 5% and 3% higher COP than calcium chloride for typical heat loads of 150kW. When controlling the pump over a temperature difference (ΔT), the existence of the optimum pump control or optimum flow was highlighted. For typical cooling capacity of 150kW optimum pump control temperature difference ΔT was around 2,5K for calcium chloride and around 2K for ammonia. Järfälla case study showed a potential energy saving of 12% for the refrigeration system when increasing the freezing point of the secondary fluid. An energy saving of around 10,8 MWh/yr per 1K increase of the secondary fluid freezing point was found.

  • 99.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ethyl and isopropyl alcohol blends as alternative secondary fluids2015In: Refrigeration Science and Technology, International Institute of Refrigeration, 2015, p. 2224-2231Conference paper (Refereed)
    Abstract [en]

    Methyl and ethyl alcohol based secondary fluids are commonly used in different indirect refrigeration systems due to relatively good thermophysical properties. Methyl alcohol is considered toxic and not permitted for use as secondary fluid in most of Europe. Ethyl alcohol based secondary fluids are commonly used in Sweden due to their low toxicity and good properties. Commercially available ethyl alcohol based fluids contain up to 10 wt-% denaturing agents in form of propyl alcohol (2-propanol, isopropanol) and nbutyl alcohol (n-butanol). Results show that presence of propyl alcohol in the ethyl alcohol based secondary fluid improves its thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. The aim of this paper is to investigate the thermophysical properties of various ethyl and isopropyl alcohol blends in order to find the most optimal blend as well as to evaluate if this blend could become a competitive alternative secondary fluid.

  • 100.
    Ignatowicz, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Evaluation of thermophysical properties of ethyl alcohol based secondary fluids2014In: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL 2014, 2014, p. 100-107Conference paper (Refereed)
    Abstract [en]

    Ethyl alcohol (ethanol) based secondary fluids are commonly used in different types of indirect refrigeration systems in Scandinavia due to low toxicity, relatively good thermophysical properties and environmental regulations regarding leakage. Ethyl alcohol based commercial products available in Scandinavia contain different types of denaturing agents but no corrosion inhibitors. The most common denaturing agents are isopropyl alcohol (isopropanol), n-butyl alcohol (n-butanol), methyl ethyl ketone and methyl isobutyl ketone. Property measurements recently performed at KTH showed that presence of these additives in ethyl alcohol based secondary fluid improved thermophysical properties especially in terms of specific heat, thermal conductivity, and dynamic viscosity. Additionally, it was found that the specific heat capacity tendency is different than previously reported.

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