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  • 151.
    Mazzotti, Willem
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Jiang, Yifeng
    INSA Lyon.
    Monzó, Patricia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lazzarotto, Alberto
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Acuña, José
    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.
    Design of a Laboratory BoreholeStorage model2018In: Research Conference Proceedings / [ed] Jeffrey Spitler, José Acuña, Michel Bernier, Zhaohong Fang, Signhild Gehlin, Saqib Javed, Björn Palm, Simon J. Rees, 2018, p. 400-410Conference paper (Refereed)
    Abstract [en]

    This paper presents the design process of a 4x4 Laboratory Borehole Storage (LABS) model through analytical and numerical analyses. This LABS isintended to generate reference Thermal Response Functions (TRFs) as well as to be a validation tool for borehole heat transfer models. The objective of thisdesign process is to determine suitable geometrical and physical parameters for the LABS. An analytical scaling analysis is first performed and importantscaling constraints are derived. In particular, it is shown that the downscaling process leads to significantly higher values for Neumann and convectiveboundary conditions whereas the Fourier number is invariant. A numerical model is then used to verify the scaling laws, determine the size of the LABS,as well as to evaluate the influence of top surface convection and borehole radius on generated TRFs. An adequate shape for the LABS is found to be aquarter cylinder of radius and height 1.0 m, weighing around 1.2 tonnes. Natural convection on the top boundary proves to have a significant effect on thegenerated TRF with deviations of at least 15%. This convection effect is proposed as an explanation for the difference observed between experimental andanalytical results in Cimmino and Bernier (2015). A numerical reproduction of their test leads to a relative difference of 1.1% at the last reported time.As small borehole radii are challenging to reproduce in a LABS, the effect of the borehole radius on TRFs is investigated. It is found that Eskilson’sradius correction (1987) is not fully satisfactory and a new correction method must be undertaken.

  • 152. Mirmohammadi, S. A.
    et al.
    Behi, M. R.
    Suma, A. B.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Multi-criteria analysis, evaluation and modeling of future scenario for the energy generation sector - A case study2014In: ASME 2014 Power Conference: Volume 2: Simple and Combined Cycles; Advanced Energy Systems and Renewables (Wind, Solar and Geothermal); Energy Water Nexus; Thermal Hydraulics and CFD; Nuclear Plant Design, Licensing and Construction; Performance Testing and Performance Test Codes; Student Paper Competition, ASME Press, 2014Conference paper (Refereed)
    Abstract [en]

    Renewable energy continues to attract much interest due to the depletion of fossil fuels and unsettled political disputes. This study aims to evaluate the current status of energy generation on the campus of Eindhoven University of Technology (TU/e). Furthermore, it looks for ways for the TU/e to improve sustainability by finding and proposing alternative solutions. Therefore, a broad scope of various renewable energy sources (RES) has been investigated. From many aspects, the analysis of RES proves that biomass is the most appropriate source of renewable energy for the TU/e campus. Thus, the capability of harvestable biomass fuel in energy generation throughout a year has been investigated for this project, and it has been concluded that solid biomass waste from the campus can provide 1314 MWh heat load annually. In order to achieve as much energy from biomass as possible, a combined heat and power unit (CHP), in order to produce both heat and electricity for new student houses on the campus, has been modeled. Finally, the project results show that a small-scale CHP cycle is capable of producing 366 MWh electricity, as well as 772 MWh heat, annually.

  • 153.
    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.

  • 154.
    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.

  • 155.
    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.
    Design and Test of a Domestic Heat Pump with Ammonia as Refrigerant2011In: 4th IIR Conference: Ammonia Refrigeration Technology, France: International Institute of Refrigeration, 2011Conference paper (Other academic)
    Abstract [en]

    Among alternative refrigerants, ammonia with zero Ozone Depleting Potential (ODP) and Global Warming Potential (GWP), and favorable thermodynamic properties is a sensible choice as a replacement for the synthetic refrigerants, which are powerful greenhouse gases.

    In this paper, the results of experiments done on a new ammonia water-to-water heat pump prototype at different evaporation temperatures and compressor speeds are reported. The heat pump is designed to deliver 7 kW heat at evaporation temperature of -5°C and condensation temperature of 40°C. The hot discharge gas from compressor is utilized to provide sanitary hot water, and the rest of the heat is used for preheating the tap water and space heating of a single-family house. The compact design of the heat pump helps reducing the refrigerant charge. To reduce the charge further and to prevent oil accumulation at the bottom of evaporator, a minichannel aluminum heat exchanger is used as evaporator.

  • 156.
    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.
    Design and Test of a Small Ammonia Heat Pump2011In: 10th IEA Heat Pump Conference 2011, 2011, p. s3_p18-Conference paper (Other academic)
    Abstract [en]

    Since synthetic refrigerants may cause environmental damages, by depleting the ozone layer or by contribution in global warming, many researchers, in recent years, have focused on the use of natural refrigerants such as ammonia to replace the synthetic ones. Although ammonia has been used in large refrigeration systems, its application in small units, say a small heat pump, is quite rare.

    The work presented in this paper is design and test of a small water-to-water ammonia heat pump, providing about 7 kW heat, sufficient for space heating and tap water heating of a single-family house. To reduce the charge and to overcome the problem of accumulation of oil at the bottom of evaporator, a minichannel heat exchanger is used as evaporator. Oil miscible in ammonia is also used to facilitate the oil return to compressor. A permanent magnet motor together with an inverter is used to run the compressor. Supplying the 7 kW heat, the heat pump runs efficiently with heating capacity to compression work ratio of 5.1 at evaporation and condensation temperatures of -5 °C and 40 °C.

  • 157.
    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.
    Material requirements for magnetic refrigeration applications2018In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 96, p. 25-37Article in journal (Refereed)
    Abstract [en]

    A primary motivation underlying the research on room-temperature magnetic refrigeration is reaching energy efficiency levels beyond what is achievable with vapor-compression technology. However, the goal of building commercially viable magnetic refrigeration systems with high performance and competitive price has not been achieved yet. One of the obstacles to reach this goal is the inadequate properties of the currently existing magnetocaloric materials. In this article, the needed improvements in the properties of the magnetocaloric materials are investigated. Two existing vapor-compression refrigerators are used as reference for the required performance, and magnetic refrigerators are simulated using a numerical model. Apart from the requirements such as uniformity of transition temperature for each layer, small increment in transition temperature in adjacent layers, and mechanical strength of the materials, the study shows that for the investigated cases materials with adiabatic entropy change 2.35 times larger than the existing materials are needed to outperform vapor-compression systems.

  • 158.
    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.
    New magnetic refrigeration prototype with application in household and professional refrigerators2016In: Refrigeration Science and Technology Proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    The number of magnetic refrigeration prototypes with high cooling capacity and large temperature span islimited and there is ample room for new designs and improvements. In this paper a new prototype, designedand built, aiming at 200 W cooling capacity and about 40 K temperature span is presented. Such a unit issuitable for applications in household and professional refrigerators. In the current work, design of theprototype is described, practical issues solved to make the prototype running are explained, and preliminarytest results are presented.

  • 159.
    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.

  • 160.
    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.
    Small Ammonia Heat Pump with Variable Speed Compressor2012Conference paper (Refereed)
    Abstract [en]

    Ammonia is a natural refrigerant which has been used continuously for more than 100 years. From almost any technical perspective, it is an attractive refrigerant, having good cycle efficiency, good heat transfer properties and low pressure drop compared to most other refrigerants. The volumetric refrigerating effect is also higher than for other fluids of the same vapor pressure. Applications are nowadays restricted almost exclusively to large industrial or commercial systems.

    We have previously demonstrated that ammonia is also a viable refrigerant for small systems (Palm 2008, Monfared and Palm 2011). In this paper we report on additional tests with a small capacity (7.2 kW) water to water heat pump for sanitary hot water production and space heating. Particularly, the losses in the compressor, electric motor and variable speed drive are investigated under full and part load conditions. New data for the general performance of the heat pump in terms of heat delivered at 60 °C for sanitary hot water production and at 40 °C for space heating, energy efficiency, etc. will also be reported.

  • 161.
    Monzó, Patrcia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuna, Jose
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Fossa, Marco
    University of Genova.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Numerical generation of the temperature response factors for  a borehole heat exchanger field2013In: Numerical generation of the temperature response factors for  a borehole heat exchanger field, 2013Conference paper (Refereed)
    Abstract [en]

    Ground Coupled Heat Pump (GCHP) systems connected to a set of vertical ground heat exchangers require short and long term dynamic analysis of the surrounding ground for an optimal operation. The thermal response of the ground for a multiple Borehole Heat Exchanger (BHE) field can be described by proper temperature response factors or “g-functions”. This concept was firstly introduced by Eskilson (1987). The g-functions are a family of solutions of the transient heat conduction equation and each of them refer to a given borehole field geometry. Furthermore the g-functions are the core of many algorithms for simulating the ground response to a GCHP system, including the well-known commercial software EED.

    Analytical approaches based on the Finite Line Source (FLS) model have been developed by Eskilson (1987), Zeng et al. (2002) and later by Lamarche (2007). Such solutions can be in principle applied together with space superposition to infer the thermal response for any BHE configuration.

    This study is a continuation of the previous work presented in Acuña et al. (2012), and a further investigation is devoted to optimize a numerical model of a squared configuration of 64 boreholes using the commercial software Comsol Multiphysics©. Symmetry conditions and different Fourier numbers have been applied and explored together with the effects related to the dimensions of the calculation domain with respect to the BHE depth and BHE field width. Furthermore, a parametric analysis is addressed to boundary conditions, which points out possible limits on the calculation domain extension. The results of the proposed numerical model are compared with the g-functions embedded within the EED software as well as those calculated by FLS method through the spatial superposition. In a closer approximation to reality, the numerical model is also studied accounting for an adiabatic part at the top of the BHE.

  • 162.
    Monzó, Patrcia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuna, Jose
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mogensen, Palne
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A study of the thermal response of a borehole field in winter and summer2013In: : ICAE2013-524, 2013Conference paper (Refereed)
    Abstract [en]

    A Ground Source Heat Pump system is a well-known technology used to provide space heating and cooling in residential and commercial buildings. For large energy demands, a number of boreholes, which can vary between tens and hundreds, may be required. The boreholes can be arranged in linear, square, rectangular, or any other configuration not necessarily symmetric. The heat exchangers in the boreholes are typically connected in parallel. Recently, the idea of a more flexible configuration of multiple Borehole Heat Exchangers (BHEs) has been introduced in commercial applications, enabling the system to operate in a more versatile manner, dividing the ground into different thermal zones. In this new arrangement, the BHEs are connected into thermal sub-groups allowing them to operate separately as sub-systems, depending on the building energy needs and the seasonal periods.

     

    In this project, the temperature response of a multiple BHE configuration is obtained from simulations in a numerical model using FEM software, Comsol Multiphysics© under different operational conditions. First, the loads are imposed under the usual conditions so that all boreholes are operated to provide heating in winter and cooling in summer. The results of this study show that our numerical model presents a good agreement with the ones generated from EED when the system is balanced. Moreover, some hypothetical scenarios with respect to the BHEs arrangement and the operational mode are performed thanks to the flexibility of our numerical model. The hypothetical scenarios provide a first approach about the thermal behavior of the boreholes and their interactions within the field with respect to its wall temperature, previous operation and thermal storage. Further work will be devoted to study more realistic scenarios.

  • 163.
    Monzó, Patricia
    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.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Analysis of the influence of the heat power rate variations in different phases of a Distributed Thermal Response Test2012Conference paper (Refereed)
  • 164.
    Mälhammar, Åke
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Kylsystem för Elektronik1995Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a cooling system, especially for electronic components, comprising a hermetically closed pipe conduit including evaporator and condenser and utilizing thermosiphon circulation of the refrigerant used in the pipe conduit, the evaporator being in heat conducting contact with a heat emitting component to be cooled and absorbs heat therefrom, the heat being transported through the pipe conduit by the refrigerant to the condenser and dissipated therein. According to the invention the pipe conduit (3) includes a plurality of evaporators (1a, 1b, 1c) in series, each being in heat conducting contact with a heat emitting component, and the condenser (2) is placed so that the liquid level of the condensed refrigerant is below the uppermost situated evaporator (1c) in the pipe conduit (3). This is rendered possible by the increased pumping action achieved by the evaporators (1a, 1b, 1c) connected together in series in the circulation direction after the evaporators partly evaporated refrigerant used in the pipe conduit (3).

  • 165.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Bitaraf Haghigh, Ehsan
    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.
    Behi, Mohammadreza
    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.
    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.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Experimental study on preparation and base liquid effect on thermo-physical and heat transport characteristics of α-SiC nanofluids2014In: International Communications in Heat and Mass Transfer, ISSN 0735-1933, E-ISSN 1879-0178, Vol. 55, p. 38-44Article in journal (Refereed)
    Abstract [en]

    Nanostructured solid particles dispersed in a base liquid are a new class of nano-engineeredcolloidal solutions, defined with a coined name of nanofluids (NFs). These fluids have shownpotential to enhance heat transfer characteristics of conventional base liquids utilized in heattransfer application. We recently reported on the fabrication and thermo-physical propertyevaluation of SiC NFs systems, containing SiC particles with different crystal structure. In thisstudy, our aim is to investigate the heat transfer characteristics of a particular α-SiC NF withrespect to the effect of α-SiC particle concentration and different base liquids on the thermophysicalproperties of NFs. For this purpose, a series of NFs with various α-SiC NPsconcentration of 3, 6 and 9wt% were prepared in different base liquids of distilled water (DW)and distilled water/ethylene glycol mixture (DW/EG). Their thermal conductivity (TC) andviscosity were evaluated at 20 oC. NF with DW/EG base liquid and 9wt% SiC NPs loadingexhibited the best combination of thermo-physical properties, which was therefore selected forheat transfer coefficient (HTC) evaluation. Finally, HTC tests were performed and compared indifferent criteria, including equal Reynolds number, equal mass flow rate and equal pumpingpower for a laminar flow regime. The results showed HTC enhancement of NF over the baseliquid for all evaluation criteria; 13% at equal Reynolds number, 8.5% at equal volume flow and5.5% at equal pumping power. Our findings are among the few studies in the literature where theheat transfer enhancement for the NFs over its base liquid is noticeable and based on a realistic situation.

  • 166.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Ghanbarpour, Morteza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Haghighi, Ehsan Bitaraf
    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.
    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.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Experimental investigation on thermo-physical properties of copper/diethylene glycol nanofluids fabricated via microwave-assisted route2014In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 65, no 1-2, p. 158-165Article in journal (Refereed)
    Abstract [en]

    This study investigates the fabrication, thermal conductivity and rheological characteristics evaluation of nanofluids consisting of copper nanoparticles in diethylene glycol base liquid. The fabricated Cu nanofluids displayed enhanced thermal conductivity over the base liquid. Copper nanoparticles were directly formed in diethylene glycol using microwave-assisted heating, which provides uniform heating of reagents and solvent, accelerating the nucleation of metal clusters, resulting in monodispersed nanostructures. Copper nanoparticles displayed an average primary particle size of 75 ± 25 nm from SEM micrographs, yet aggregated to form large spherical particles of about 300 nm. The physicochemical properties including thermal conductivity and viscosity of nanofluids were measured for the nanofluids with nanoparticle concentration between 0.4 wt% and 1.6 in the temperature range of 20-50 C. Proper theoretical correlations/models were applied to compare the experimental results with the estimated values for thermal conductivity and viscosity of nanofluids. For all cases, thermal conductivity enhancement was higher than the increase in viscosity showing the potential of nanofluids to be utilized as coolant in heat transfer applications. A thermal conductivity enhancement of ∼7.2% was obtained for nanofluids with 1.6 wt% nanoparticles while maximum increase in viscosity of ∼5.2% was observed for the same nanofluid.

  • 167.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Bitaraf Haghighi, Ehsan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ghanbarpour, Morteza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet
    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.
    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.
    Design and Fabrication of Efficient Nanofluids Based on SiC Nanoparticles for Heat Exchange Applications2013Conference paper (Other academic)
  • 168.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Haghighi, Ehsan Bitaraf
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ghanbarpour, Morteza
    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.
    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.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Fabrication, Characterization and Thermo-physical Property Evaluation of SiCNanofluids for Heat Transfer Applications2014In: Nano-Micro Letters, ISSN 2150-5551, Vol. 6, no 2, p. 178-189Article in journal (Refereed)
    Abstract [en]

    Nanofluids (NFs) are nanotechnology-based colloidal suspensions fabricated by suspending nanoparticles (NPs) in a base liquid. These fluids have shown potential to improve the heat transfer properties of conventional heat transfer fluids. In this study we report in detail on the fabrication, characterization and thermo-physical property evaluation of SiC NFs, prepared using SiC NPs with different crystal structure, for heat transfer applications.  For this purpose, a series of SiC NFs containing SiC NPs with different crystal structure (α-SiC and β-SiC) were fabricated in a water (W)/ethylene glycol (EG) mixture (50/50 wt % ratio). Physicochemical properties of NPs/NFs were characterized by using various techniques such as powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Zeta Potential Analysis were performed. Thermo-physical properties including thermal conductivity (TC) and viscosity for NFs containing SiC particles (α- and β- phase) were measured. The results showed among all suspensions, NF fabricated with α-SiC particles have more favorable thermo-physical properties compared to the NFs fabricated with β-SiC; the observed difference was attributed to combination of several factors, including crystal structure (β- vs. α-), sample purity, and residual chemicals exhibited on SiC nanoparticles. A TC enhancement of ~20% while 14% increased viscosity were obtained for a NF containing 9wt% of particular type of α-SiC NPs indicating promising capability of these kind of NFs for further heat transfer characteristics investigations. 

  • 169.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Li, S
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet
    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.
    Bitaraf Haghighi, Ehsan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn E
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Novel Nanofluids Based on Mesoporous Silica for Enhanced Heat Transfer2011In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 11, p. 6201-6206Article in journal (Refereed)
    Abstract [en]

    Nanofluids, which are liquids with engineered nanometer-sized particles suspensions, have drawn remarkable attraction from the researchers because of their enormous potential to enhance the efficiency in heat-transfer fluids. In the present study, water-based calcined mesoporous silica nanofluids were prepared and characterized. The commercial mesoporous silica (MPSiO2) nanoparticles were dispersed in deionized water by means of pH adjustment and ultrasonic agitation. MPSiO2 nanoparticles were observed to have an average particle size of 350 ± 100 nm by SEM analysis. The concentration of MPSiO2 was varied between 1 and 6 wt%. The physicochemical properties of nanofluids were characterized using various techniques, such as particle size analyzer, zeta-potential meter, TEM, and FT-IR. The thermal conductivity was measured by Transient Plane Source (TPS) method, and nanofluids showed a higher thermal conductivity than the base liquid for all the tested concentrations.

  • 170.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet
    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.
    Bitaraf Haghighi, Ehsan
    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
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Microwave-assisted Synthesis of Copper Nanofluids for Heat Transfer Applications2011Conference paper (Refereed)
  • 171.
    Nikkam, Nader
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet
    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.
    Haghighi, E.B.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Khodabandeh, R.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, B,
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Rheological Properties of Copper Nanofluids Synthesised by Using Microwave-Assisted Method2012In: Proceedings of the 4th International Conference on Nanostructures (ICNS4), 2012, p. 1555-1557Conference paper (Refereed)
  • 172.
    Owhaib, Wahib
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Martín-Callizo, ClaudiKTH, 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 Visualization and Heat Transfer in a Single Vertical Microchannel2005Conference proceedings (editor) (Refereed)
  • 173.
    Owhaib, Wahib Suleiman
    et al.
    KTH, Superseded Departments, Energy Technology.
    Martín-Callizo, Claudi
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Evaporative heat transfer in vertical circular microchannels2004In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 24, no 8-9, p. 1241-1253Article in journal (Refereed)
    Abstract [en]

    This paper presents new experimental results on saturated flow boiling in microchannels. Heat transfer coefficients were measured for saturated boiling of R134a in vertical circular tubes with internal diameters of 1.7, 1.224 and 0.826 mm, and a uniformly heated length of 220 mm. Heat transfer coefficients were obtained for a heat flux range of 3-34 kW/m(2), a mass flux range of 50-400 kg/m(2) s, and vapour qualities up to 0.6. Experiments were conducted at two different pressures, 8.626 and 6.458 bars. Heat transfer coefficients were found to be a strong function of the wall heat flux and system pressure, while being fairly independent upon mass flux and vapour quality. This suggests that the heat transfer mechanism is strongly related to that in nucleate boiling.

  • 174.
    Owhaib, Wahib Suleiman
    et al.
    SWEP International AB, Landskrona.
    Martín-Callizo, Claudi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Two-phase flow pressure drop of R-134a in a vertical circular mini/micro channel2008In: Proceedings of the 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, 2008, p. 343-353Conference paper (Refereed)
    Abstract [en]

    This paper presents new experimental results on saturated flow boiling pressure drop in microchannels. The two-phase pressure drops were measured for vertical saturated boiling of R-134a in circular tubes with internal diameters of 1.700, 1.224, and 0.826 mm, and a uniformly heated length of 220 mm, the total flow length is 580 mm. The total pressure drops were obtained for a heat flux range of 10-30 kW/m(2), a mass flux range of 100-400 kg/(m(2)s), and outlet vapor qualities up to 0.6. Experiments were conducted at the average saturation pressure of 8.62 bar. The experimental data was compared to predictions by correlations available in the literature both for microchannels and larger diameter tubes.

  • 175.
    Owhaib, Wahib Suleiman
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Experimental investigation of single-phase convective heat transfer in circular microchannels2004In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 28, no 2-3, p. 105-110Article in journal (Refereed)
    Abstract [en]

    In this study, the heat transfer characteristics of single-phase forced convection of R134a through single circular micro-channels with 1.7, 1.2, and 0.8 mm. as inner diameters were investigated experimentally. The results were compared both to correlations for the heat transfer in macroscale channels and to correlations suggested for microscale geometries. The results show good agreement between the classical correlations and the experimentally measured data in the turbulent region. Contrary, none of the suggested correlations for microchannels, agreed with the test data. In the laminar regime, the heat transfer coefficients were almost identical for all three diameters.

  • 176.
    Owhaib, Wahib Suleiman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Martín-Callizo, Claudi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    A visualization study of bubble behavior in saturated flow boiling through a vertical mini-tube2007In: Heat Transfer Engineering, ISSN 0145-7632, E-ISSN 1521-0537, Vol. 28, no 10, p. 852-860Article in journal (Refereed)
    Abstract [en]

    Forced convection saturated R-134a boiling experiments were conducted in a vertical mini-quartz tube coated with a transparent heater; the inner diameter of the tube was 1.33 mm and the heated length 235.5 mm. The dynamics of the saturated boiling process, bubble characteristics, and behavior were studied using a high-speed CCD camera at different mass fluxes in up-flow at 6.425 bar. The heat fluxes were 5 and 20 kW/m(2). The flow visualization results show that the bubble departure frequency generally inc

  • 177.
    Owhaib, Wahib Suleiman
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Martín-Callizo, Claudi
    KTH, Superseded Departments, Energy Technology.
    Experimental investigation of single-phase pressure drop in circular minichannelIn: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606Article in journal (Refereed)
  • 178.
    Owhaib, Wahib Suleiman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martín-Callizo, Claudi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Flow boiling visualization in a vertical circular minichannel at high vapor quality2006In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 30, no 8, p. 755-763Article in journal (Refereed)
    Abstract [en]

    This paper reports on an experimental study of saturated flow boiling of R134a inside a circular vertical quartz tube coated with a transparent heater. The inner diameter of the tube was 1.33 mm and the heated length 235.5 mm. The flow pattern at high vapor qualities and the dryout of the liquid film were studied using a high speed CCD camera at the mass fluxes 47.4 and 124.4 kg/m(2) s in up flow at 6.425 bar. The heat fluxes ranged from 5 to 13.6 kW/m(2) for the lower mass flux and from 20 to 32.4 kW/m(2) for the higher mass flux.

    The behavior of the flow close to dryout was found to be different at low and high mass flux. At low mass flux the location of the liquid front fluctuated with waves passing high up in the tube. In between the waves, a thin film was formed, slowly evaporating without breaking up.

    At high mass flux the location of the liquid front was more stable. In this case the liquid film was seen to break up into liquid streams and dry zones on the tube wall.

  • 179.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Charge minimizaton in a 30 kW air to water heat pump2014In: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL 2014, 2014, p. 987-994Conference paper (Refereed)
    Abstract [en]

    Modern manufacturing technology allows production of tubes and channels with small hydraulic diameters. Heat pumps and refrigeration equipment designed using such tubes may have considerably lower charge than conventional systems while having just as good thermal performance. In this paper, the possibilities of charge reduction are investigated, using a 30 kW propane air to water heat pump as an example. It is shown that changing the tubing in the evaporator and condenser is a vital first step, but that considerable additional charge reduction can be reached by careful consideration in the selection and designs of other parts of the system as well. In particular it is important to avoid headers where liquid may be trapped and oversized receivers. Additionally, in a well-designed system a substantial part of the refrigerant may be absorbed in the compressor oil. Reducing the amount of refrigerant in this component requires novel thinking concerning the compressor design.

  • 180.
    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.

  • 181.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Refrigerants of the future2011In: Proc 10thIEA Heat Pump Conference 2011, 2011Conference paper (Other academic)
    Abstract [en]

    The high global warming potential of most HFC fluids is forcing a change to fluids with less environmental impact. The search for the ideal refrigerant is not new, but has been ongoing for one hundred years, even though the reason for the search has changed.

    The paper gives a background to the present search for new refrigerants, discusses the criteria for the selection and gives some information on the status concerning introduction of new fluids.

    In conclusion, there is only one new refrigerant close to be put on the market, HFO1234yf. Other closely related fluids, such as HFO1234ze may be alternatives in the future. Beside these new fluids, it is believed that natural refrigerants like hydrocarbons, ammonia and carbon dioxide, as well as the low GWP, but flammable, HFC152a, will all find a place in future refrigeration and heat pump systems.

  • 182.
    Palm, Björn
    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. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Sustainable Building Systems.
    Effektiva plattvärmeväxlare som förångare i värmepumpar: Vidare studier. Slutrapport2005Report (Other academic)
  • 183.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ammonia as refrigerant in small-capacity systems2008In: IEA Heat Pump Centre Newsletter, ISSN 2002-018X, Vol. 26, no 4Article in journal (Refereed)
    Abstract [en]

    Ammonia is widely used in large systems because of its excellent thermodynamic and transport properties, resulting in energy-efficient systems with little environmental impact. Nevertheless, despite its favourable properties, ammonia has not been used in small systems. The present paper reports on work on small ammonia systems being performed as part of the EU SHERHPA project, aimed at developing heat pumps with natural refrigerants. First, the availability, and lack, of components for small ammonia systems is considered. Second, potentials and problems specific to small ammonia systems are discussed. Finally, the paper describes the design of a 9 kW water-to-water heat pump that contains as little as 100 g of ammonia, producing domestic hot water at close to 60 ° C while having a condensing temperature of below 50 °C. The text is partly identical to that in previously published reports to the Commission.

  • 184.
    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.

  • 185.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ammonia in Small Capacity Heat Pump and Refrigeration Systems2005In: Proc. IIR Conf. Ammonia Refrigeration Systems, Renewal and Improvements, Ohrid, Macedonia, May 2005., Ohrid, Macedonia: Academic Conferences Publishing, 2005Conference paper (Refereed)
  • 186.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ammonia in Small Capacity Refrigeration and Heat Pump Systems2007In: Proceedings of IIR Conference: Ammonia Refrigeration Technology for Today and Tomorrow, Academic Conferences Publishing, 2007Conference paper (Refereed)
  • 187.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    Heat transfer in microchannels2001In: Microscale thermophysical engineering (Print), ISSN 1089-3954, E-ISSN 1091-7640, Vol. 5, no 3, p. 155-175Article, review/survey (Refereed)
    Abstract [en]

    In this article an attempt has been made to review the literature regarding heat transfer and pressure drop in one- and two phase flow in microchannels. The emphasis has been on reports presented during the last few years. For single phase flow, channels with hydraulic diameters less than 1 min have been considered. For two phase flow, very little information is available for such small channels. Also, for two phase flow, deviations from large-tube behavior start at diameters of a few millimeters. For these reasons a slightly larger diameter range has been considered in this case. As a conclusion, it can be stated that the understanding of flow, in microchannels is increasing steadily, but that there are still many questions to be answered concerning the reasons for deviations from classical theory developed for larger channels.

  • 188.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Refrigeration systems with minimum charge of refrigerant2007In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 27, no 10, p. 1693-1701Article in journal (Refereed)
    Abstract [en]

    Concern for the environmental effects of HFC-refrigerants as well as the use of flammable refrigerants has resulted in a need of decreasing the refrigerant charge in refrigeration and heat pump systems. This paper discusses the possibility of such reductions, both at the systems- and the component level. It is shown that a move towards indirect systems, using secondary refrigerants, on both the cold and the hot side of the system may result in considerable reduction of charge. However, this reduction may come at the cost of slightly reduced system performance, which in itself is detrimental from an environmental point of view. At the component level, it may be shown that the main contents of refrigerant is usually contained in the heat exchangers. By selecting compact designs the charge may be reduced to extremely low levels. Specifically, mini-channel heat exchangers can be used for reaching low charge. With proper selection of heat exchangers, the system performance should not be influenced by the reduction of charge. For indirect systems, the amount of refrigerant solved in the compressor oil may be comparable to the amount in the (compact) heat exchangers. A possible solution to reduce this amount is to use compressors with less oil. With components selected for minimum charge, the system design may be different than what is usual. Instead of a high pressure receiver and a thermostatic expansion valve, a capillary tube may be used in combination with a minimal low pressure receiver, similar to the system design used in household refrigerators.

  • 189.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Summarizing a Decade of Experience on Charge Reduction for Small Hydrocarbon, Ammonia and HFC Systems2009In: RCR 2009, Proc. 1st IIR Workshop on Refrigerant Charge Reduction in Refrigerating Systems, Academic Conferences Publishing, 2009Conference paper (Refereed)
  • 190.
    Palm, Björn E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Andersson, Klas
    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.
    Samoteeva, Oxana
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Designing a Heat Pump for Minimum Charge2005In: IEA HPC newsletter, Vol. 232, p. 17-1§Article in journal (Refereed)
  • 191.
    Palm, Björn E.
    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.
    Plate heat exchangers, calculation methods for single- and two-phase flow2005In: ICMM 2005, Proceedings of the 3rd International Conference on Microchannels and Minichannels, Pt A, 2005, p. 103-113Conference paper (Refereed)
    Abstract [en]

    Plate heat exchangers were first developed about 100 years ago, but have won increasing interest during the last two decades, primarily because of the development of methods of manufacturing brazed plate heat exchangers. This type of heat exchanger offers very good heat transfer performance in single-phase flow as well as in evaporation and condensation. Part of the reason is the small hydraulic diameters, typically being less than 5 mm. Other advantages of plate heat exchangers are the extremely compact design and the efficient use of the construction material. In spite of their long use, the calculation methods for predicting heat transfer and pressure drop are not widely known. It is the purpose of this article to present such calculation methods for singe phase flow and for flow boiling and to discuss some of the specifics of this type of heat exchangers.

  • 192.
    Palm, Björn E.
    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.
    Plate heat exchangers: Calculation methods for single-and two-phase flow2006In: Heat Transfer Engineering, ISSN 0145-7632, E-ISSN 1521-0537, Vol. 27, no 4, p. 88-98Article in journal (Refereed)
    Abstract [en]

    Plate heat exchangers were first developed about 100 years ago but have won increasing interest during the last two decades, primarily due to the development of methods of manufacturing brazed plate heat exchangers. This type of heat exchanger offers very good heat transfer performance in single-phase flow as well as in evaporation and condensation. Part of the reason is the small hydraulic diameters, typically being less than 5 mm. Other advantages of plate heat exchangers are the extremely compact design and the efficient use of the construction material. In spite of their long use, the calculation methods for predicting heat transfer and pressure drop are not widely known. It is the purpose of this article to present such calculation methods for single-phase flow and for flow boiling and to discuss some of the specifics of this type of heat exchangers.

  • 193.
    Palm, Björn E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Fernando, Primal
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Andersson, Klas
    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.
    Samoteeva, Oxana
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Designing a Heat Pump for Minimum Charge of Refrigerant2005In: Proc. IEA Heat Pump Conference, Las Vegas, USA, June 2005, Academic Conferences Publishing, 2005Conference paper (Refereed)
  • 194.
    Palm, Björn E.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Khodabandeh, Rahmatollah
    KTH, Superseded Departments, Energy Technology.
    Choosing working fluid for two-phase thermosyphon systems for cooling of electronics2003In: Journal of Electronic Packaging, ISSN 1043-7398, E-ISSN 1528-9044, Vol. 125, no 2, p. 276-281Article in journal (Refereed)
    Abstract [en]

    The heat fluxes from electronic components are steadily increasing and have now, in some applications, reached levels where air-cooling is no longer sufficient. One alternative solution, which has received much attention during the last decade, is to use heat pipes or thermosyphons for transferring or spreading the dissipated heat. In this paper two-phase thermosyphon loops are discussed. Especially, the choice of fluid and its influence on the design and performance is treated. The discussion is supported by results from simulations concerning heat transfer and pressure drop. In general it is found that high-pressure fluids will give better performance and more compact designs as high-pressure results in higher boiling heat transfer coefficients and smaller necessary tube diameter.

  • 195. Paulino, T. D. F.
    et al.
    de Oliveira, R. N.
    Maia, A. A. T.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Machado, L.
    Modeling and experimental analysis of the solar radiation in a CO2 direct-expansion solar-assisted heat pump2019In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, p. 160-172Article in journal (Refereed)
    Abstract [en]

    In the present work is presented the dynamic model of an evaporator of a Direct Expansion Solar Assisted Heat Pump (DX-SAHP), charged with CO2. This dynamic model was used to analyze the evaporator response to sudden variations in the solar radiation. Two strategies are used to make the system reach the steady state after the heat pump start-up. The first one is the usual balances of mass, energy and momentum. The second strategy consisted in impose an equal refrigerant mass flow rate at the evaporator inlet and outlet. Both strategies were able to conduct the system to a steady state, however, the second one required less computational effort. The mathematical model was validated using experimental data and employed to perform several simulations. The results obtained with the mathematical model revealed that a small variation of the solar radiation leads to a significant variation in the superheat, therefore requiring an immediate action of the expansion device. It was concluded that an Electronic Expansion Valve (EEV) would be better suited to meet the needs of rapid interventions on the mass flow rate at the evaporator inlet, and also because the DX-SAHP could operate in a continuous transient condition in some seasons.

  • 196.
    Pelletier, Olivier
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    Two-Phase Flow Pattern between an expansion valve and an evaporator2004Conference paper (Refereed)
  • 197.
    Piscopiello, Salvatore
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mazzotti, Willem
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Nota, Carla
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sawalha, Samer
    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.
    Performance evaluation of a large capacity water-water heat pump using propane as refrigerant2016In: Refrigeration Science and Technology, International Institute of Refrigeration, 2016, p. 803-810Conference paper (Refereed)
    Abstract [en]

    The use of natural refrigerants has become of increasing concern in recent years due to the high GWP and ODP of commonly used CFCs, HCFCs and HFCs. The use of hydrocarbons can be considered as potential long term solution in heat pump applications. Propane is highly flammable and potentially explosive, however; with proper safety measures in place it can be a suitable candidate for residential heat pump as it has a negligible ODP and a low GWP (3). This study presents the analysis of experimental data obtained from tests on a 45 kW heating capacity water-water heat pump. The unit is tested in heating mode, i.e. production of hot water for space heating with the possibility of simultaneous-generation of domestic hot water. The performance evaluation is carried out at system level, based on the two key parameters: heating capacity (Qh) and andehtheating COP (COP1). A map of the heat pump performance under different working conditions is developed. Simulations using the modelling software IMST-ART are performed and compared to the experimental results. The results of this study were developed in the framework of the FP7 European project 'Next Generation of Heat Pumps working with Natural fluids' (NxtHPG).

  • 198.
    Saleemi, Mohsin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Ma, Ying
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Wang, Xiaodi
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Nikkam, Nader
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Haghighi, Ehsan Bitaraf
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ceria Nanofluids for Efficient Heat Management2010Conference paper (Refereed)
  • 199.
    Samoteeva, Oxana
    et al.
    KTH, Superseded Departments, Energy Technology.
    Granryd, Erik
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Fernando, Primal
    KTH, Superseded Departments, Energy Technology.
    Modelling of the amount of refrigerant and pressure drop in a rectangular copper microchannel evaporator2002In: Proceedings of Zero leakage-Minimum Charge IIR/IIF conference, Stockholm, August 2002, Stockholm, 2002Conference paper (Other academic)
    Abstract [en]

    The present study covers modelling of the amount of refrigerant and of the pressure drop in a rectangular copper microchannels evaporator. The evaporator has been tested in a test rig simulating a small-capacity heat pump and all the modelled parameters are compared to the measured ones. All the calculations are performed using EES software program [4].

    The void fraction was calculated in order to predict the amount of refrigerant in the evaporator. The choice of the model for the calculation of the void fraction has a big influence on the prediction of the amount. The void fraction was predicted, using several available correlations, out of which the Hughmark, UI ACRC[1]and CISE models seem to give the best approximation. The mass of refrigerant was calculated out of these data and compared to the experimental results. The pressure drop was determined, using the Friedel, Pierre and Granryd’s adjustment ofPierre[2]models. Afterwards results were compared to the experimentally measured pressure drop. Granryd’s model seems to give the closest approximation. 

    Comparisons of the predicted results with the measured ones are presented in figures and analysed. Conclusions regarding the models tested for determination of the void fraction and pressure drop in the present application and probably other applications with rectangular microchannels are drawn. 

  • 200.
    Samoteeva, Oxana
    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.
    Boiling heat transfer and pressure drop in single rectangular microchannel2006In: Proceedings of the 13th International Heat Transfer Conference 13-18 August 2006, Sidney, Australia, 2006Conference paper (Refereed)
    Abstract [en]

    One of the goals of this paper is to investigate the two-phase flow characteristics of the refrigerant changing phase in a high aspect ratio (1:30) rectangular vertically placed microchannel. The hydraulic diameter of the channel is 0,39 mm. The experimental data were collected for the refrigerant R134a for mass fluxes varying from 200 to 970 kg/m2s and a heat flux range of 0,6-28 kW/m2. The results of the heat transfer investigation have shown that the heat transfer coefficient is not influenced by the mass flux or vapour quality but only by heat flux, thus indicating the dominance of nucleate boiling or a related mechanism. In comparison to several conventional correlations from the literature, it was shown that the correlations by Lazarek and Black, 1982 predict the heat transfer coefficient best, the data scattering up to 35%. Measurements have shown that the pressure drop increases approximately linearly with the mass flux.

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