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  • 1. Belman-Flores, J. M.
    et al.
    Rodriguez-Munoz, A. P.
    Gutierrez Perez-Reguera, C.
    Mota-Babiloni, Adrián
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. Universitat Jaume I, Spain.
    Experimental study of R1234yf as a drop-in replacement for R134a in a domestic refrigerator2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 81, p. 1-11Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental study for three identical domestic refrigerators using R1234yf as a drop-in replacement for R134a. An alternative methodology was proposed to estimate the optimal mass charge for R1234yf; with the use of such methodology, new evidences were sought on the thermal behavior of the refrigerator compartments as well as at the heat exchangers. Additionally, energy performance for both refrigerants was measured, and, finally, a TEWI analysis was conducted. For the type of refrigerator evaluated, results showed that R1234yf presented an average (for the 3 refrigerators) of 0.4 degrees C for the fresh food compartment, and 1.2 degrees C for the freezer, among different charges with respect to R134a. The optimal charge for R1234yf was 92.2 g, which is about 7.8% lower than the one for R134a, which represents a small increase of 4% in energy consumption in comparison to R134a. Finally, the TEWI analysis for the R1234yf was 1.07% higher than the R134a.

  • 2.
    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%.

  • 3.
    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.

  • 4.
    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.

  • 5.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Correction of Logarithmic Mean Temperature Difference in a compact brazed plate evaporator assuming heat flux governed flow boiling heat transfer coefficient2005In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 4, p. 573-578Article in journal (Refereed)
    Abstract [en]

    The heat transfer in heat exchangers is commonly calculated using the concept of Logarithmic Mean Temperature Difference (LMTD). As is well known this approach is only valid for counter-current and co-current heat exchanger configurations. For other configurations, corrections for the deviation from pure counter-current are introduced. From any standard text book in heat transfer it may be found that the LMTD approach may also be used if condensation and evaporation occurs in the heat exchanger. The purpose of the present paper is to investigate if the LMTD approach can be used in a compact brazed plate evaporator. It will be shown through integration of the governing equations that the LMTD approach indeed may be used for practical cases, even though deviations occur at small logarithmic mean temperature differences. The article presents suggestions on the correction factor (F) needed under some simplified assumptions in a compact brazed plate heat exchanger operating as an evaporator for heat pump and refrigeration applications.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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.

  • 10.
    Granryd, Eric
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Analytical expressions for optimum flow rates in evaporators and condensers of heat pumping systems2010In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 33, no 7, p. 1211-1220Article in journal (Refereed)
    Abstract [en]

    The flow velocities on the air or liquid side of evaporators and condensers in refrigerating or heat pump systems affect the system performance considerably. Furthermore the velocity can often be chosen rather freely without obvious first cost implications. The purpose of the paper is to show analytical relations indicating possible optimum operating conditions. Considering a base case where the design data are known, simple analytical relations are deduced for optimum flow rates that will result in highest overall COP of the system when energy demand for the compressor as well as pumps or fans are included. This optimum is equivalent to the solution for minimum total energy demand of the system for a given cooling load. It is also shown that a different (and higher) flow rate will result in maximum net cooling capacity for a refrigerating system with fixed compressor speed. The expressions can be used for design purposes as well as for checking suitable flow velocities in existing plants. The relations may also be incorporated in algorithms for optimal operation of systems with variable speed compressors.

  • 11.
    Granryd, Eric G.
    KTH, Superseded Departments, Energy Technology.
    Hydrocarbons as refrigerants - an overview2001In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 24, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    Possibilities and problems of using hydrocarbons as working fluids in refrigerating equipment are discussed. An overview of safety standards is given. Different hydrocarbon alternatives are listed and characteristics in terms of thermodynamic cycles as well as heat transfer are shown. The general conclusion is that hydrocarbons offer interesting refrigerant alternatives for energy efficient and environmentally friendly refrigerating equipment and heat pumps. However, safety precautions due to flammability must be seriously taken into account. For some applications this can be done without adding noticeably to the total installation cost, but not in the general case.

  • 12.
    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.

  • 13.
    Gunasekara, Saman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kumova, Sofia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Gubkin Russian State University of Oil and Gas, Russia.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental phase diagram of the dodecane–tridecane system as phase change material in cold storage: [Diagramme de phase expérimental du système dodécane–tridécane comme matériau à changement de phase pour des applications d'entreposage frigorifique]2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 82, p. 130-140Article in journal (Refereed)
    Abstract [en]

    Integrating thermal storage with phase change materials (PCMs) in refrigeration and air conditioningprocesses enables energy performance improvements. Herein, the experimental phase diagram of thealkanes system dodecane-tridecane (C12H26-C13H28) is evaluated to find PCMs for freezing applications.For that, the Temperature-history method was coupled with a Tammann plot analysis. The obtainedC12H26-C13H28 phase diagram indicated a congruent minimum-melting solid solution and polymorphs. Theminimum-melting liquidus and the polymorphs identified here, agree with previous literature. However,the system does not represent a eutectic, as previously was proposed. The minimum-meltingcomposition is here identified within 15-20 mol% C13H28 compositions. The 17.7 mol% C13H28 is thenarrowest minimum-melting composition among those analyzed, melting and freezing between -16 to -12 °C and -17 to -15 °C, with: the enthalpies 185 kJ kg-1 and 165 kJ kg-1; no supercooling; and only minorhysteresis. Hence, this blend has potential as a PCM in freezing refrigeration applications.

    The full text will be freely available from 2019-06-08 10:30
  • 14.
    Halasz, Boris
    et al.
    Univ. Zagreb.
    Grozdek, Marino
    Univ. Zagreb.
    Soldo, Vladimir
    Univ. Zagreb.
    Development of computer program for simulation of an ice bank system operation, Part I: Mathematical modelling2009In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 32, no 6, p. 1323-1335Article in journal (Refereed)
    Abstract [en]

    Since the use of standard engineering methods in the process of an ice bank performance evaluation offers neither adequate flexibility nor accuracy, the aim of this research was to provide a powerful tool for an industrial design of an ice storage system allowing to account for the various design parameters and system arrangements over a wide range of time varying operating conditions. In this paper the development of a computer application for the prediction of an ice bank system operation is presented. Static, indirect, cool thermal storage systems with external ice on coil building/melting were considered. The mathematical model was developed by means of energy and mass balance relations for each component of the system and is basically divided into two parts, the model of an ice Storage system and the model of a refrigeration unit. Heat transfer processes in an ice silo were modelled by use of empirical correlations while the performance of refrigeration unit components were based on manufacturers data. Programming and application design were made in Fortran 95 language standard. Input of data is enabled through drop down menus and dialog boxes, while the results are presented via figures, diagrams and data (ASCII) files. In addition, to demonstrate the necessity for development of simulation program a case study was performed. Simulation results clearly indicate that no simple engineering methods or rule of thumb principles could be utilised in order to validate performance of an ice bank system properly.

  • 15. Hägg, Cecilia
    et al.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Pressure Drop Experiments and Background for Choosing Suitable Fluid for Low Temperature Ice SlurrIn: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081Article in journal (Other academic)
  • 16.
    Jarall, Sad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Study of refrigeration system with HFO-1234yf as a working fluid: Etude sur un système frigorifique utilisant le HFO-1234yf comme fluide actif2012In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 35, no 6, p. 1668-1677Article in journal (Refereed)
    Abstract [en]

    Theoretical cycle data and heat transfer of HFO-1234yf were calculated and compared with those of R134a. Drop-in tests for R134a and HFO-1234yf were carried out using refrigeration unit of a hermetic rotary compressor of 550 W nominal output power and plate heat exchangers. Results of the evaporator cooling effect and heat transfer, COP, and compressor efficiency at a defined condensation temperature and similar evaporation temperatures for the two refrigerants were calculated and compared.

  • 17.
    Karampour, Mazyar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Energy Efficiency Evaluation of Integrated CO2 Trans-critical System in Supermarkets: A Field Measurements and Modelling Analysis2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 82, p. 470-486Article in journal (Refereed)
    Abstract [en]

    This paper investigates energy efficiency of an integrated CO2 trans-critical booster system installed in a supermarket in Sweden. The supermarket has applied several features to improve energy efficiency including space and tap water heating, air conditioning (AC), and parallel compression.  

    Using field measurements data, the system performance is evaluated in a warm and a cold month. Furthermore, this integrated energy system concept is modelled and compared with stand-alone HFC-based energy systems. 

    The results show that the system provides the entire AC demands and recovers a great share of the available heat, both with high COP values. The comparative analysis shows that integrated CO2 system uses about 11% less electricity than stand-alone HFC solutions for refrigeration (i.e. indirect HFC), heating and AC in North of Europe.

    Energy efficiency analysis of the integrated CO2 system proves that this system is an environmentally friendly all-in-one energy efficient solution suitable for cold climate supermarkets.

  • 18.
    Karampour, Mazyar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    State-of-the-Art Integrated CO2 Refrigeration System for Supermarkets: a Comparative Analysis2018In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 86, p. 239-257Article in journal (Refereed)
    Abstract [en]

    This paper investigates the integrated and state-of-the art features of CO2 trans-critical booster systems. The main objective is to identify the most promising solutions in terms of energy efficiency impacts.

     

    First, the performance of modified features and integrated functions have been compared with the standard CO2 system and alternative heating and air conditioning solutions. Subsequently, the performance of the defined state-of-the-art CO2 system is compared to natural refrigerant-based cascade and HFC/HFO-based DX and indirect refrigeration solutions operating in cold and warm climates.

     

    The results indicate that two-stage heat recovery, flooded evaporation, parallel compression and integration of air conditioning are the most promising features of the state-of-the-art integrated CO2 system. This compact and environmentally friendly system is the most energy efficient solution in cold climates, and is also an efficient solution in warm climates, with comparable efficiency to cascade and HFC/HFO DX systems, but with no existing or potential limitations.

  • 19.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Heat transfer in the evaporator of an advanced two-phase thermosyphon loop2005In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 2, p. 190-202Article in journal (Refereed)
    Abstract [en]

    As heat generation from electronic components increase and the limit of air-cooling is reached, the interest for using liquid cooling for high heat flux applications has risen. Thermosyphon cooling is an alternative liquid cooling technique, in which heat is transferred as heat of vaporization from evaporator to condenser with a relatively small temperature difference. The effect of fluid properties, the structure of wall surfaces, and the effect of system pressure was investigated and reported previously by the author. In this paper, the influence of heat flux, system pressure, mass flow rate, vapor fraction, diameter of evaporator channel and tubing distance between evaporator and condenser on the heat transfer coefficient of an advanced two-phase thermosyphon loop is reported. The tested evaporators were made from small blocks of copper with 7, 5, 4, 3 and 2 vertical channels with the diameters of 1.1, 1.5, 1.9, 2.5, and 3.5 mm, respectively and the length of 14.6 mm. Tests were done with isobutane at heat fluxes ranging between 28.3 and 311.5 kW/m(2).

  • 20.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Pressure drop in riser and evaporator in an advanced two-phase thermosyphon loop2005In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 5, p. 725-734Article in journal (Refereed)
    Abstract [en]

    This study presents an experimental investigation of pressure drop in the evaporators and the riser of an advanced thermosyphon loop. The thermosyphon was designed for the cooling of three parallel high heat flux electronic components. The tested evaporators were made from small blocks of copper in which 7, 5, 4, 3, 2, 1 vertical channels with the diameters of 1.1, 1.5, 1.91 2.5, 3.5 and 6 mm, respectively, and a length of 14.6 mm were drilled. Tests were done with isobutane at heat fluxes ranging between 22.4 and 303 kW/m(2). For prediction of the pressure drop, in the riser, different combinations of frictional pressure drop and void fraction correlations were tested. Regarding the evaporator a simple correlation based on a homogeneous model [M.B. Bowers, I. Mudawar, Two-phase electronic cooling using mini-channel and macro-channel heat-sinks-part 11, flow rate and pressure drop constraints, ASME J Electron Packaging H 6 (1994) 298-305. [1]] has been used to predict the pressure drop.

  • 21.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundquist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in ground source heat pump systems part II: Comparative analysis between on/off controlled and variable capacity systems2011In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 34, no 8, p. 1934-1942Article in journal (Refereed)
    Abstract [en]

    In the present paper, as the second part of two, modeling and simulation was carried out for a Ground Source Heat Pump (GSHP) system in the presence of all the most important interacting sub-systems such as building, ground heat source, electrical auxiliary heater, and the heat pump unit in order to make a fair and comprehensive comparison between the annual performance of on/off controlled and variable capacity systems. The annual modeling showed that dimensioning of the on/off controlled GSHP based on the peak heat demand of the building plays a significant role when the two control strategies are compared: if the on/off controlled GSHP is dimensioned to cover only 55% of the peak heat demand of the building, the electrical auxiliary, which then covers about 10% of the annual heating demand of the building, makes the SPF of the on/off controlled GSHP to be lower than the one of the variable speed system. On the contrary, when the on/off controlled system is dimensioned to cover more than 65% of the building's peak heat demand, i.e. more than 95% of the annual heat demand of the building, there is no considerable difference between the SPFs of the on/off controlled and variable capacity systems.

  • 22.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Roccatello, Erica
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A comprehensive study on the important faults in heat pump system during the warranty period2014In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 48, p. 19-25Article in journal (Refereed)
    Abstract [en]

    The heat pump market has become mature in many countries. There are millions of heat pumps installed worldwide. So any improvement in the installation, operation, and maintenance of heat pump systems can save a considerable amount of energy and cost, and reduce Green House Emissions to a large extent. The present study suggests a Smart Fault Detection and Diagnosis (SFDD) mechanism as the essential part of the next generation of heat pumps. A SFDD mechanism can minimize the installation and control errors, decrease the performance degradation during operation, avoid unnecessary visual inspections and components replacement, and reduce the maintenance cost and down-time of the system. To develop a SFDD mechanism, the first essential step is to obtain knowledge about the most common and expensive faults experienced by heat pumps. The heat pump manufacturers are one of the best sources to find out the most common and costliest faults occurring in heat pump systems during the first few years of their life. The present paper, as the first part of two, describes the results from a comprehensive study done on the most recent faults which were reported to some of the heat pump manufacturers in Sweden during the warranty period. The most common and the costliest faults in the Air/Air, Air/Water, Brine/Water, and exhaust air heat pumps are presented. Some of the faults such as faulty pressure switches or fans are only related to the heat pump unit, i.e. the thermodynamic cycle which facilitates the heat pumping cycle. Some of the common and expensive faults such as faulty shuttle or shuntvalve are related to the faulty components in the heating systems. Generally, the results show that faults in Control and Electronics are almost the most common and costliest faults in all types of heat pumps. Faults in Control and Electronics include any fault related to control unit, electrical faults (such as short circuit, etc.), Printed Circuit Board (PCB), display, soft starter, overcurrent and motor protection relay, etc.

  • 23.
    Madani Larijani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundquist, Per Gunnar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in ground source heat pump systems Part I: modeling and simulation2011In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 34, no 6, p. 1338-1347Article in journal (Refereed)
    Abstract [en]

    The present paper, as the first part of two, suggests a method to approach the challenge of capacity control in Ground Source Heat Pumps (GSHP). The paper describes the development of a model of the system which includes several sub-models such as the heat pump unit, building, ground source, thermal storage tank, auxiliary heater, and climate. The developed computer model can be used for comparative analysis of different control methods and strategies aiming at the improvement of the system seasonal performance. With this model, on/off controlled and variable capacity GSHPs, with a single speed or variable speed pumps in the systems, can be evaluated in a wide range of operating conditions and more energy efficient methods of the system control can be found. The computer model is developed in the two environments EES and TRNSYS utilizing so-called co-solving technique.

  • 24.
    Mader, Gunda
    et al.
    Danfoss A/S, Denmark .
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Elmegaard, Brian
    DTU.
    Maldistribution in air-water heat pump evaporators: Part 1: Effects on evaporator, heat pump and system level2015In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 50, p. 207-216Article in journal (Refereed)
    Abstract [en]

    This paper presents an approach to quantify the effect of evaporator maldistribution on operating costs of air-water heat pumps. In the proposed simulation model maldistribution is induced by two parameters describing refrigerant phase and air flow distribution. Annual operating costs are calculated based on heat pump performance at distinct operating conditions. Results show that percentage increase of operating costs is similar for the three considered climate zones, even though the effect of maldistribution on heat pump performance varies with operating conditions. Differences in terms of absolute cost increase for the climate zones arise mainly due to a varying number of operating hours. Absolute cost increase is considerable in the average and especially colder climate zone and can only partly be reduced by enlarging the evaporator.

  • 25.
    Mader, Gunda
    et al.
    Danfoss AS Refrigerat & Air Conditioning, Denmark.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Elmegaard, Brian
    DTU.
    Maldistribution in air-water heat pump evaporators. Part 2: Economic analysis of counteracting technologies2015In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 50, p. 217-226Article in journal (Refereed)
    Abstract [en]

    In this study a methodology is applied to quantify the effect of evaporator maldistribution on operating costs of air-water heat pumps. The approach is used to investigate the cost-effectiveness of two technologies enabling to counteract maldistribution: a flash gas bypass setup and the individual superheat control in parallel evaporator channels. In the total cost of ownership analysis, different scenarios for climatic conditions, severity of maldistribution, and economic framework are considered. Results show that the flash gas bypass system is cost-effective only in a few conditions, namely severe maldistribution, high electricity prices, and colder climate. Investment in the individual superheat control technology, however, can be quickly amortized in many scenarios. For the warmer climate zone with a small number of operating hours counteracting of maldistribution does not pay off under the used economic assumptions.

  • 26.
    Makhnatch, Pavel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mota-Babiloni, Adrián
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. ISTENER Research Group, University Jaume I, Castellón de la Plana, 12071, Spain.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental study of R450A drop-in performance in an R134a small capacity refrigeration unit2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081Article in journal (Refereed)
    Abstract [en]

    The Kigali's amendment to the Montreal Protocol has highlighted the hydrofluorocarbons (HFCs) phase out as a priority to reduce the future global Earth's mean temperature increase. R134a is the most abundant HFC in the atmosphere and therefore it must be substituted using environmentally benign alternatives. In the short term, blends of HFCs and hydrofluoroolefins can replace R134a. This paper experimentally evaluates R450A (GWP of 547), a non-flammable mixture of R1234ze(E) and R134a, in an R134a small capacity refrigeration system. The controlled experimental conditions cover evaporating temperatures from -15 to 12.5 °C and condensing temperature of 25, 30 and 35 °C (36 tests in total for each refrigerant). The experimental results showed that with only a thermostatic expansion valve adjustment the average R450A cooling capacity and COP are 9.9 and 2.9% lower than those measured using R134a. Besides, the observed compressor discharge temperature values of R450A are not greater than that of R134a.

  • 27.
    Makhnatch, Pavel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mota-Babiloni, Adrián
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Rogstam, Jörgen
    Energi & Kylanalys AB.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Retrofit of lower GWP alternative R449A into an existing R404A indirect supermarket refrigeration system2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 76, p. 184-192Article in journal (Refereed)
    Abstract [en]

    R404A is going to be phased out from most of the commercial refrigeration systems due to its high GWP value of 3943. R449A (GWP of 1282) has been proposed to replace R404A with only minor system modifications in supermarkets. This paper presents the measurements of a light retrofit replacement of R404A using R449A in a medium temperature indirect refrigeration system (secondary fluid temperature at the evaporator outlet between −9 and −4 °C). It has been demonstrated that with a slight expansion device adjustment and 4% increase of refrigerant charge, R449A can be used in this refrigeration system designed for R404A because of its suitable thermodynamic properties and acceptable maximum discharge temperature. At a secondary fluid temperature at condenser inlet of 30 °C, the COP of R449A nearly matches that of R404A (both were between 1.9 and 2.2), despite having approximately 13% lower cooling capacity. As a conclusion, attending to the GWP reduction and similar energy performance, it was demonstrated using the TEWI methodology that the use of the recently developed refrigerant R449A in these applications can reduce the total CO2equivalent emissions of an indirect supermarket refrigeration system designed for R404A refrigerant.

  • 28.
    Melinder, Åke
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Properties and other aspects of aqueous solutions used for single phase and ice slurry applications2010In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 33, no 8, p. 1506-1512Article in journal (Refereed)
    Abstract [en]

    Indirect systems with aqueous solution have long been used to minimize the charge and leakage of (primary) refrigerants. In ice slurry applications such aqueous solutions are used below the freezing point, benefitting from the enthalpy change resulting from ice melting. Accurate thermophysical property data and a general knowledge of other secondary fluid properties are useful for selection of fluid and for technical calculations of the system. This paper introduces a new IIR publication, Properties of secondary working fluids for indirect systems. Tables and charts with fluid properties, property relations of ice and of ice slurry, enthalpy-phase diagrams and related charts are here given for sodium chloride and water, as an example. This new IIR publication that also considers corrosion aspects and environmental impact of such fluids is intended to be used by industry and researchers working with single phase as well as ice slurry applications.

  • 29.
    Melinder, Åke
    et al.
    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.
    Using property values of aqueous solutions and ice to estimate ice concentrations and enthalpies of ice slurries2005In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 1, p. 13-19Article in journal (Refereed)
    Abstract [en]

    For ice slurry calculations and modeling, it is important that they are performed with accurate thermophysical property values of the aqueous solution and of ice. For ice slurry applications there is a need for accurate freezing point data and for more basic thermophysical property data at low concentrations. The article covers some phenomena in connection with freezing of aqueous solutions. Charts with ice concentration curves as a function of temperature and additive concentration are given for a number of aqueous solutions. A main purpose of using ice slurry is to benefit from the latent heat or enthalpy difference at melting. The article shows how an enthalpy-phase diagram can be constructed, gives charts with enthalpy values and charts giving apparent specific heat as a function of temperature and concentration for aqueous solution of propylene glycol, ethyl alcohol and potassium formate. These charts for ethyl alcohol-water are in good agreement with works earlier reported on.

  • 30.
    Melinder, Åke
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ignatowicz, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Properties of seawater with ice slurry use in focus2015In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 52, p. 51-58Article in journal (Refereed)
    Abstract [en]

    Seawater is the most common fluid on earth and ice generating machines are increasingly used on fishing vessels to produce ice slurry from seawater with up to 60% ice to be poured over the catch. In this study, a literature search has been made to establish physical property data of seawater as function of salinity and temperature. Ice slurry properties of seawater have been generated and are presented by means of an enthalpy-phase diagram and related tables with ice concentration, enthalpy change and density. This material confirms that an initial salt content of 2-3 % is optimal and it can help determine the potential for long preservation of catch on board and during transport, improving seafood quality. As seawater is known to be corrosive, a brief discussion on corrosion factors and problems, the use of corrosion inhibitors and choice of materials is included in this paper.

  • 31.
    Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Design and optimization of regenerators of a rotary magnetic refrigeration device using a detailed simulation model2018In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 88, p. 260-274Article in journal (Refereed)
    Abstract [en]

    In this work a comprehensive simulation of a magnetic refrigeration device is presented, validated, and used for redesigning the regenerators of an existing prototype. The redesigning process includes choosing the magnetocaloric materials and number of layers and optimizing for particle size, flow, and operation frequency. The simulation consists of the model of the magnetic field, parasitic heat transfer and active regeneration. The model of the magnetic field and parasitic heat transfer are embedded in the 1D model of the active regeneration cycle. The detailed model of the magnetic field, taking the effect of presence of the magnetocaloric materials into account, is described and validated separately against measured magnetic field. An innovative method for including the parasitic heat transfer in the active regeneration model without compromising the accuracy is used. The influence of the properties of the binding agent on the performance of the bonded beds as regenerators are also investigated.

  • 32.
    Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Simulation of solid-state magnetocaloric refrigeration systems with Peltier elements as thermal diodes2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, no 74, p. 322-330Article in journal (Refereed)
    Abstract [en]

    Magnetic refrigeration as an alternative for vapor-compression technology has been the subject of many recent studies. Most of the studies focus on systems with limited cycle frequency in which a fluid transfers heat to and from the magnetocaloric material. A suggested solution for increasing the frequency is use of solid-state magnetic refrigeration in which thermal diodes guide the heat from the cold end to the warm end. In this work a solid-state refrigeration system with Peltier elements as thermal diodes is modeled in details unprecedented. The performance of Peltier elements and magnetocaloric materials under their transient working conditions after reaching cyclic steady state are simulated by two separate computer models using finite element method and finite volume method. The models, in parts and as a whole, are verified. The verified finite element model is used for a parametric study and the results are analyzed.

  • 33.
    Monfared, Behzad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Furberg, Richard
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Magnetic vs. vapor-compression household refrigerators: A preliminary comparative life cycle assessment2014In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 42, p. 69-76Article in journal (Refereed)
    Abstract [en]

    This paper seeks to shed light on the question whether a magnetic household refrigerator with permanent magnets is more environmentally friendly than a conventional, vapor-compression refrigerator. Life cycle assessment has been used as a tool to investigate the environmental impacts associated with the life cycle of a magnetic refrigerator. The results of the assessment have been compared with those of a conventional, vapor-compression refrigerator with the same functionality. The comparison reveals that the magnetic refrigeration has higher environmental impacts mainly due to the use of rare-earth metals used in the magnet material. The possibility of compensating for this shortcoming through reuse of the magnetic materials or improving the design and efficiency of the magnetic refrigerator has been examined. In addition, the effect of the electricity mix consumed during the use phase, as one of the key factors determining the life cycle environmental impacts, has been investigated.

  • 34.
    Monfared, Behzad
    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.
    Corrigendum to “Optimization of layered regenerator of a magnetic refrigeration device” (International Journal of Refrigeration (2015) 57 (103–111)(S0140700715001267)(10.1016/j.ijrefrig.2015.04.019))2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 78Article in journal (Refereed)
    Abstract [en]

    The authors regret that, in three instances on page 105 the term “Maxwell equations” is used mistakenly instead of “thermodynamic relations”. However, this does not affect any results or conclusions and is just a correction in the terminology. The authors would like to apologise for any inconvenience caused.

  • 35.
    Monfared, Behzad
    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.
    Optimization of layered regenerator of a magnetic refrigeration device2015In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 57, p. 103-111Article in journal (Refereed)
    Abstract [en]

    Magnetic refrigeration, as an alternative to vapor-compression technology, has been the subject of many recent investigations. A technique to enhance the performance of magnetic refrigerators is using layers of different materials in the regenerator of such devices. In this study the choice of magnetocaloric materials in a multi-layered packed bed regenerator is investigated in order to optimize the performance. A numerical model has been developed to simulate the packed bed in this study. Optimized packed bed designs to get maximum temperature span or maximum efficiency are different. The results indicate that maximum temperature span can be achieved by choosing the materials with the highest magnetocaloric effect in the working temperature range, while maximum Carnot efficiency is achieved by choosing materials with Curie temperatures above the average layer temperature.

  • 36.
    Mota-Babiloni, Adrián
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. ISTENER Research Group, University Jaume I, Castellón de la Plana, 12071, Spain.
    Makhnatch, Pavel
    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.
    Recent investigations in HFCs substitution with lower GWP synthetic alternatives: Focus on energetic performance and environmental impact2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 82, p. 288-301Article in journal (Refereed)
    Abstract [en]

    Kigali's amendment on Montreal Protocol has recognized the great impact of hydrofluorocarbons (HFCs) on climate change. In the European Union, the Regulation (EU) No. 517/2014 (F-gas Regulation) controls the use of HFCs in several applications. This paper reviews the recent investigations performed because of F-gas Regulation, with focus on lower global warming potential (GWP) synthetic alternatives. The GWP limit and the date of prohibition have an influence on the studies found for each application. The major relevance of the studies has been observed on mobile air conditioners for pure hydrofluoroolefins (HFOs), possibly caused by the earlier control. Additionally, a great number of studies have been found for stationary refrigeration systems using several mixtures and residential air conditioners using R32. An important number of articles investigate synthetic alternatives for domestic refrigerators given the flammability barriers for hydrocarbons in some countries. Despite higher GWP allowance on cascade supermarket systems, few articles are available on this topic. Given the extent of the current studies and the rate of new refrigerant developments, an increase in studies using the new synthetic mixture is expected in the coming years.

  • 37.
    Mota-Babiloni, Adrián
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. Polytechnic University of Valencia, Spain; University Jaume I, Spain.
    Makhnatch, Pavel
    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.
    Navarro-Esbrí, J.
    Experimental assessment of R134a and its lower GWP alternative R513A2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 74, p. 680-686Article in journal (Refereed)
    Abstract [en]

    Lower GWP refrigerants are essential to mitigate the impact of refrigeration systems on climate change. HFO/HFC mixtures are currently considered to replace HFCs in refrigeration and air conditioning systems. The aim of this paper is to present the main operating and performance differences between R513A (GWP of 573) and R134a (GWP of 1300), the most used refrigerants for medium evaporation temperature refrigeration systems and mobile air conditioners. To perform the experimental comparison, 36 tests are carried out with each refrigerant at evaporating temperatures between −15 and 12.5°C and condensing temperatures between 25 and 35°C. The conclusion of the experimental comparison is that R513A can substitute R134a with only a thermostatic expansion valve adjustment, achieving better performance and higher cooling capacity. The discharge temperature of R513A is always lower than that of R134a.

  • 38. Navarro, E.
    et al.
    Granryd, Eric G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Urchueguia, J. F.
    Corberan, J. M.
    A phenomenological model for analyzing reciprocating compressors2007In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 30, no 7, p. 1254-1265Article in journal (Refereed)
    Abstract [en]

    A new model for hermetic reciprocating compressors is presented. This model is able to predict compressor efficiency and volumetric efficiency in terms of a certain number of parameters (10) representing the main sources of losses inside the compressor. The model provides users with helpful information about the way in which the compressor is designed and working. A statistical fitting procedure based on the Monte Carlo method was developed for its adjustment. The model can predict compressor performance at most points with a maximum deviation of 3%. A possible gas condensation on cold spots inside the cylinder during the last part of the compression stroke was also evaluated.

  • 39. Navarro, E.
    et al.
    Urchueguia, J. F.
    Corberan, J. M.
    Granryd, Eric G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Performance analysis of a series of hermetic reciprocating compressors working with R290 (propane) and R407C2007In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 30, no 7, p. 1244-1253Article in journal (Refereed)
    Abstract [en]

    In this paper, a series of compressors with different capacities and geometries working with propane as refrigerant are analyzed in terms of the compressor model developed by [E. Navarro, E. Granryd, J.F. Urchueguia, J.M. Corberan, A phenomenological model for analyzing reciprocating compressors, International Journal of Refrigeration, in this issue, doi:10.1016/j.irefrig.2007.02.006]. The relative influence of the diverse compressor losses is estimated as a function of the operating conditions. In addition, a comparison study between propane and R407C was carried out for one compressor and the observed differences were analyzed in terms of the compressor model. This study was also useful to verify the model's goodness with the aim of predicting the compressor performance with an untested refrigerant.

  • 40. Oro, Eduard
    et al.
    Miro, Laia
    Farid, Mohammed M.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Cabeza, Luisa F.
    Energy management and CO2 mitigation using phase change materials (PCM) for thermal energy storage (TES) in cold storage and transport2014In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 42, p. 26-35Article in journal (Refereed)
    Abstract [en]

    Low temperature sensitive products transport and storage is an issue worldwide due to changes of the lifestyle population increase. Thermal energy storage (TES) is nowadays one of the most feasible solutions in facing the challenge of achieving energy savings. Many researchers have investigated energy efficiency of different cold units by applying TES systems using phase change materials (PCM). This paper provides an overview of the existing Spanish and European potential energy savings and CO2 mitigation by incorporating TES systems to cold storage and transportation systems. Data on energy savings were compiled from different case studies. Results depend on the scenarios studied and the extent of TES systems implementation; in the case of Europe for instance, yearly CO2 emissions may be cut down between 5% and 22% in reference to 2008 CO2 emissions from cold production considering that the proposed implementation of PCM TES in the case studies found in the literature is done.

  • 41.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Hydrocarbons as refrigerants in small heat pump and refrigeration systems - A review2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 4, p. 552-563Article, review/survey (Refereed)
    Abstract [en]

    Due to the concern for the effects of the release of HFC refrigerants on the global environment caused by the high global warming potential of these substances, there is a large interest in Europe and elsewhere for the use of hydrocarbons as refrigerants. This article presents a comparison of the properties and performance of hydrocarbons as refrigerants in small-size heat pump and refrigeration systems (< 20 kW cooling). A listing of several commercially available systems is also presented. The designs, safety precautions and performances of some of these systems are described. As a general conclusion, it is shown that using hydrocarbons will result in COPS equal to, or higher than, those of similar HFC systems. It is also shown that components suitable for hydrocarbon systems are available on the market, even though the number of large-size hermetic compressors is limited. A major concern, which should not be taken lightly, is the safety issue. Reduced charge through indirect systems and compact heat exchangers, outdoor placing of the unit, hydrocarbon sensors and alarms and forced ventilation are all steps which may be applied to reduce the risks under normal operation.

  • 42.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ammonia in low capacity refrigeration and heat pump systems2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 4, p. 709-715Article in journal (Refereed)
    Abstract [en]

    Ammonia has been used as refrigerant in large vapour compression systems continuously since the beginning of the era of refrigeration. In small systems, it has hardly been used at all since the introduction of the halogenated hydrocarbons around 1930. Lately, with the search for alternatives with less influence on global warming, the use of ammonia in small systems has come into focus again. In the present paper, the work done at the Royal Institute of Technology (KTH) with the aim of developing a prototype of a domestic water to water heat pump with a heating capacity of 9 kW is presented. it has been shown that such a system can be designed to operate with about 100 g of ammonia. Crucial problems in the development of the direct expansion system were to arrange for oil return, and to achieve good heat transfer in the evaporator. These problems were solved by use of an oil which is soluble in ammonia. The main obstacle for introducing this technology commercially is the limited supply of components. Particularly, there are no hermetic or semi-hermetic compressors for ammonia available in this size range.

  • 43.
    Pridasawas, Wimolsiri
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvisti, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A year-round dynamic simulation of a solar-driven ejector refrigeration system with iso-butane as a refrigerant2007In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 30, no 5, p. 840-850Article in journal (Refereed)
    Abstract [en]

    In this paper, the performance of the solar-driven ejector refrigeration system with iso-butane (R600a) as the refrigerant is studied. The effects that both the operating conditions and the solar collector types have on the system's performance are also examined by dynamic simulation. The TRNSYS and EES simulation tools are used to model and analyze the performance of a solar-driven ejector refrigeration system. The whole system is modelled under the TRNSYS environment, but the model of the ejector refrigeration subsystem is developed in the Engineering Equations Solver (EES) program. A solar fraction of 75% is obtained when using the evacuated tube solar collector. In the very hot environment, the system requires relatively high generator temperature, thus a flat plate solar collector is not economically competitive because the high amount of auxiliary heat needed to boost up the generator temperature. The results from the simulation indicate that an efficient ejector system can only work in a region with decent solar radiation and where a sufficiently low condenser temperature can be kept. The average yearly system thermal ratio (STR) is about 0.22, the COP of the cooling subsystem is about 0.48, and the solar collector efficiency is about 0.47 at Te 15 °C, Tc 5 °C above the ambient temperature, evacuated collector area 50 m2 and hot storage tank volume 2 m3.

  • 44.
    Sakellari, Dimitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Forsén, Martin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Lundqvist, Per Gunnar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Investigating Control Strategies for a Domestic Low-Temperature Heat Pump Heating System2006In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 29, no 4, p. 547-555Article in journal (Refereed)
    Abstract [en]

    Despite energy conservation regulations and efforts for improving HVAC operations, numerous domestic buildings do not perform energy efficiently and many times the indoor environment is far away from specified comfort levels. Especially in houses served from low-temperature heating systems the low ability of the heating system to respond to fast changing thermal loads is common. In such cases, the implementation of new, sophisticated controls is an important issue. In this study, we use a reference model of a domestic low temperature heat pump heating system developed in TRNSYS-EES and analyse its operation. Several methods of control strategies have been applied for specified time periods in order to keep the comfort within reasonable ranges. Prognostic climatic control and increased ventilation rates when required are some of these methods. The results depict the influence of the control method on the indoor temperature and the comfort indexes of PMV and PPD. The highest indoor temperature difference for a chosen day reaches 4 degrees C when there is no shading and when there is internal shading with the option of applying prognostic climatic control. Generally, the findings highlight the importance of dynamics in controlling functions and the difficulty of incorporating in models unpredictable factors as the solar radiation.

  • 45.
    Sakellari, Dimitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Lundqvist, Per Gunnar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Modelling and Simulation Results for a Domestic Exhaust-Air Heat Pump Heating System2005In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 7, p. 1048-1056Article in journal (Refereed)
    Abstract [en]

    Energy consumption in residential buildings has gained an increasing interest the latest years due to the rising demand for efficient energy use and higher comfort standards. In tight building constructions with controlled ventilation, heat recovery with exhaust-air heat pump connected to floor heating is regarded as energy efficient heating system that optimises the energy use in buildings while maintaining an acceptable level of thermal comfort. In this study, we use the computational tools TRNSYS and EES to model and analyse the performance of a residential house, its ventilation system and its floor heating system based on an exhaust air heat pump. The system analysis focuses particularly on the influence of internal and solar gains on the operation of the heating system and the thermal comfort of the house. Furthermore, the way that gains influences the performance of the floor heating system is examined. Overall, the results bring to light the impact of factors that are not easy to predict on the indoor climate and the thermal comfort.

  • 46.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Investigation of heat recovery in CO2 trans-critical solution for supermarket refrigeration2012In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 36, no 1, p. 145-156Article in journal (Refereed)
    Abstract [en]

    Using computer simulation modeling this study investigates the performance of a CO2 trans-critical system with heat recovery from the de-superheater. The influence of sub-cooling (or further cooling) in the condenser/gas cooler on system performance is investigated. Following the suggested control strategy in this study, the extra operating energy demand required to recover the needed heating energy from the analyzed CO2 system is smaller than what a typical heat pump would require for the same load. This is the case for almost all ambient temperatures over a full season. When taking the simultaneous heating and cooling loads into account, the CO2 trans-critical system has lower annual energy usage in an average size supermarket in Sweden when compared to a conventional R404A refrigeration system with separate heat pump for heating needs. CO2 trans-critical systems are efficient solutions for simultaneous cooling and heating needs in supermarkets in relatively cold climates.

  • 47.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Theoretical evaluation of trans-critical CO2 systems in supermarket refrigeration. Part I: Modeling, simulation and optimization of two system solutions2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 3, p. 516-524Article in journal (Refereed)
    Abstract [en]

    Using CO2 trans-critical system solutions in supermarket refrigeration is gaining interest with several installations already running in different European countries. Using a computer simulation model, this study investigates the performance of two main system solutions: centralized with accumulation tank at the medium temperature level and parallel with two separate circuits for low and medium temperature levels. Both system solutions are presented and the simulation model is described in details. Calculations have been performed to design the systems and optimize their performances where basic layout and size of each solution have been defined. For ambient temperature range of 10-40 degrees C, the reference centralized system solution shows higher COP of about 4-21% than the reference parallel solution. Using two-stage compression in the centralized system solution instead of single stage will result in total COP which is about 5-22% higher than that of the reference centralized system and 13-17% higher than that of the improved two-stage parallel system. The two-stage centralized system solution gives the highest COP for the selected ambient temperature range.

  • 48.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Theoretical evaluation of trans-critical CO2 systems in supermarket refrigeration. Part II: System modifications and comparisons of different solutions2008In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 3, p. 525-534Article in journal (Refereed)
    Abstract [en]

    The performance of CO2 refrigeration systems strongly depends on the operating conditions. The specific characteristics of low critical temperature and high operating pressure limit its applications and imply the implementation of different control strategies. This study compares the performance of different CO2 system solutions for supermarket refrigeration with R404A system. Some possible modifications and improvements on the CO2 system have been investigated. The COP of the investigated CO2 system solution can be improved by about 3-7% along the ambient temperature range of 10-40 degrees C. The annual energy consumption calculations in three different climates; cold, moderate and hot, show that the centralized trans-critical CO2 system is good solution for cold climates whereas the NH3-CO2 cascade system has the lowest energy consumption in hot climates. Both systems proved to be good alternatives to R404A DX system for supermarket refrigeration.

  • 49. Zhao, L.
    et al.
    Yang, X.
    Deng, S.
    Li, Hailong
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Yu, Z.
    Performance analysis of the ejector-expansion refrigeration cycle using zeotropic mixtures2015In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 57, p. 197-207, article id 3043Article in journal (Refereed)
    Abstract [en]

    Abstract To evaluate the performance of the ejector-expansion refrigeration cycle (EERC) using zeotropic mixtures, a numerical study is conducted. A constant-pressure two-phase ejector model for zeotropic mixtures is established. The effects of both the fluid composition and the working conditions are investigated. Mixture R134a/R143a is selected as the working and the simulation results reveal that, the cycle COP increases first and then decreases as MF<inf>t</inf> (the mass fraction of R134a) increases in the researched condition. The COP gets a maximum value of 4.18 with MF<inf>t</inf> of 0.9 and yields a minimum value of 3.66 with MF<inf>t</inf> of 0.5. With mixture 0.9/0.1, the COP improvement reaches a maximum value of 10.47%. This improvement rises at high condensing temperature or low evaporating temperature. The exergy analysis shows that the compressor and ejector contribute the most exergy destruction, and the cycle exergy efficiency achieves a maximum value with MF<inf>t</inf> of 0.7.

1 - 49 of 49
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