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  • 201.
    Sawalha, Samer
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Energy Consumption Evaluation of Indirect Systems with CO2 as Secondary Refrigerant in Supermarket Refrigeration2003Conference paper (Refereed)
    Abstract [en]

    In this study, we investigate the influence of the pressure and temperature drops in the suction and return lines on the energy consumption of a supermarket refrigeration plant. We calculate the energy consumption of CO2indirect systems with R404A, ammonia or propane as the primary refrigerant and compare it to conventional direct expansion (DX) system with R404A or R502. CO2pressure drop and the corresponding saturation temperature drop in the indirect circuit is calculated and compared to that of R404A. The energy consumption of R404A/CO2indirect systems was found to be very close to R404A-DX system using the same pipe size in the return and suction lines. Replacing R404A by ammonia or propane in the indirect system reduced the energy consumption. This study indicates that it is more economical to use CO2indirect system with proper primary refrigerant rather than using the conventional DX systems.

  • 202.
    Sawalha, Samer
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Safety Analysis of CO2 as a Refrigerant in Supermarket Refrigeration2002Conference paper (Refereed)
    Abstract [en]

    In this study we analyse some safety aspects related to the usage of CO2 in supermarket refrigeration. The concentration levels in the supermarket’s shopping area and machine room that result from different accident scenarios are calculated for a selected practical example. The ventilation requirements in the supermarket under normal conditions and during a leakage accident are taken into consideration.

    For the selected case, the analysis of the calculations’ results showed that CO2 does not enclose a heath hazard for the customers and workers within the shopping area, whereas safety requirements expressed by efficient ventilation and proper alarm system must be installed in the machine room

  • 203.
    Sawalha, Samer
    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.
    Securité d’utilisation du CO2 dans un supermarché2004In: Revue General du Froid, ISSN 0755-7868, no 1042, p. 39-43Article, book review (Other academic)
  • 204.
    Sawalha, Samer
    et al.
    KTH.
    Palm, Björn
    KTH.
    Rolfsman, Lennart
    CO2 as Secondary Refrigerant in Sweden2000Conference paper (Other academic)
    Abstract [en]

    The selection of an available natural alternative to replace harmful artificial refrigerants depends on the application, which defines the system boundaries and the operation range. In the last ten years, CO2 was introduced as a semi ideal refrigerant due to its environmentally friendly and good performance characteristics. In some applications the unique thermophysical and performance properties of CO2 match the boundary conditions of the system and make it very close to be the ideal working fluid for that specific application.

    Since the rediscovery of CO2 as a refrigerant [Lorentzen, 1990], the studies focussed on finding the possible applications of CO2 according to its properties. Commercial refrigeration accounts for almost 17% of worldwide refrigerants consumption, 11% is the percentage in cold storage applications, 28% in total (135576 tons/year) [DOE/AFEAS, 1991]. CO2 as a phase changing secondary refrigerant was studied and applied successfully in Sweden in the applications of supermarkets and cold stores. By the year 2000, 40 plants are running with capacities ranging from 10 to 280 kW; the refrigerants used in the machine room are NH3, R404, and Care50 (ethane/propane). Two and single-stage plants are used for chilling and freezing needs within the supermarkets.

    This study present the basics of technologies applied in these specific applications and the main results obtained compared to the old systems with artificial refrigerants.

    Installation and running costs, of the systems and the technical problems appearing during the installation of the CO2 systems are discussed. Another important issue discussed in this study is the possibility of converting the old plants to CO2 secondary systems.

    The operation and the analysis of the existing plants proved that CO2 could be successfully used as an alternative for the artificial refrigerants within the application of refrigeration in supermarkets. In addition to the obvious environmental advantages by using such systems, an extra economical achievement was observed during the installation and running of the plants.

  • 205.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Muyingo, Henry
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    af Klintberg, Tord
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Björk, Folke (Commentator for written text)
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Madani, Hatef (Contributor)
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Photovoltaic Systems for Swedish Prosumers: A technical and economic analysis focused on cooperative multi-family housing2016Report (Other academic)
    Abstract [en]

    This report is designed to be a comprehensive information resource for Swedish prosumers considering an investment in solar PV systems. The target audience are multi-family cooperative houses, however much of the information is applicable to other building owners and solar energy more broadly. The primary question to be answered; is a rooftop PV investment profitable in Sweden? Naturally there are many variables that can affect the answer; therefore a Monte Carlo methodology is used to convert the uncertainties into risks, where the results can be presented as probabilities rather than a vast collection of sensitivity analyses. Several policy scenarios are tested, where the relative impact of each current program on profitability can be seen.

  • 206.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    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.
    Heating solutions for residential buildings in China: Current status and future outlook2018In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 177, p. 493-510Article in journal (Refereed)
    Abstract [en]

    With continuing of urbanization, improving of life quality as well as combating against air pollution, China is facing comprehensive challenges to supply modem clean heating to a majority of its citizens. For space heating solutions, currently in urban areas of north China, coal based district heating is prevalent. In urban areas of south China, distributed heating solutions are used. In rural areas, de-centralized coal stoves and biomass stoves are still commonly used. As renewable building heating solution, ground source heat pumps are installed for large scale applications. Building floor areas heated by ground source heat pumps increased tremendously during past ten years. Air source heat pump is being promoted in north Chinese rural areas as part of coal to clean heating project. Solar water heater and electric water heater for domestic hot water supply is widely used in north China and gas water boiler is widely used in south China. A series of policies have encouraged clean fossil fuel district heating in north China. National development plans are also supporting and subsidizing renewable heating technology such as heat pumps. Different building heating technologies have their own advantages and disadvantages from techno-economic and environmental perspectives. The choice of building heating solutions for different geolocations of China is strongly affected by spatial parameters such as local climate condition, population distribution, natural resource availability etc. Therefore, a spatial data analysis method is essential to help stakeholders decide proper building heating solutions in different parts of China by key performance indicators reflecting lower primary energy use, economic affordability and lower environmental impact.

  • 207.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    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.
    Building heating solutions in China: A spatial techno-economic and environmental analysis2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 179, p. 201-218Article in journal (Refereed)
    Abstract [en]

    Fast urbanization process and promotion of life standard in China requires a great amount of energy input in building heating sector. North China now faces challenges of upgrading existing fossil fuel based high emission district heating systems into more environmental friendly heating systems. South China is discussing to choose proper building heating solutions for new and existing buildings which lack proper heating facilities. Renewable heating technologies such as ground source heat pump and air source heat pump are candidates to upgrade traditional heating solutions such as fossil fuel boilers and electric heaters. In order to find the most feasible building heating solution for different geolocations of China, this paper proposes a spatial data based techno-economic and environmental analysis methodology to fulfill such research gap. Case studies are carried out in two selected cities by using proposed methodology. Evaluation model shows that, heat pumps is quite competitive in south China compared with electric heaters, whereas in north China heat pumps have to reach several preconditions to be competitive with coal boiler district heating system under current techno-economic and environmental situations. In north China, a heat pump should reach a minimum seasonal coefficient of performance of 2.5-3.7 (for ground source heat pump) or 2.7-3.0 (for air source heat pump) to become CO2 and PM2.5 emission neutral as well as economically competitive compared with coal boiler district heating system. The advantage of proposed methodology is its simplicity in execution and could be repeated to other areas as the data required are available.

  • 208.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    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.
    Spatial Data Assisted Ground Source Heat Pump Potential Analysis in China, a Case of Qingdao City2019In: INNOVATIVE SOLUTIONS FOR ENERGY TRANSITIONS / [ed] Yan, J Yang, HX Li, H Chen, X, ELSEVIER SCIENCE BV , 2019, p. 6099-6104Conference paper (Refereed)
    Abstract [en]

    Nowadays, China faces challenges of further implementing heat pump technology for meeting building heating and cooling demand. The utilization of heat pumps, especially ground source heat pump (GSHP) is associated with a number of geological, hydrological as well as meteorological criteria. Thus it is essential to systematically address the feasibility of ground source heat pumps application using quantitative evaluation. Spatial data analysis is a method widely used in energy field to investigate renewable energy potential. Therefore, this study strives to provide an estimation of electricity driven GSHP's potential in north China using spatial data assisted tools. Followed by a case study using the methodology recommended, a spatial data assisted GSHP potential evaluation model is built for Qingdao city in north China. The evaluation model is constructed and analyzed through spatial data processing software visualized by ground source heat pump potential maps. The result maps show that, places with most potential of GSHP application locate in south Qingdao close to the sea. Such places have a higher ground extractable heat and relatively low drilling cost.

  • 209.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Heat pump application in the Chinese market, a review of the recent ten years2015In: Refrigeration Science and Technology, International Institute of Refrigeration, 2015, p. 4866-4873Conference paper (Refereed)
    Abstract [en]

    Heat pumps is regarded as a renewable energy technology in China, and it is mainly used in building sector. This paper provides a review of the heat pump implementation for the past ten years in the Chinese market, concentrating on related governmental policy and applications in renewable energy in buildings including green buildings. Both ground source heat pumps (GSHP) and air source heat pumps (ASHP) are reviewed. By analysing the relationship between policy and market, it can be concluded that the heat pump market in China is dominated by governmental financial subsidies. A period of market recession can be expected once the subsidy stops. Heat pumps should be implemented based on specific local conditions and be considered as a part of the energy system. Analysis of the local conditions, system design and construction, and system operation are equally important for a successful heat pump project.

  • 210.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Potential of natural refrigerant in China, the case of the heat pump market2016In: Refrigeration Science and Technology, International Institute of Refrigeration , 2016, p. 341-347Conference paper (Refereed)
    Abstract [en]

    Heat pumps is regarded as renewable technology for heating systems in China. Phasing out traditional HCFC and HFC refrigerants is compulsory under various international conventions and protocols. This paper presents the current application status for R744 (carbon dioxide / CO2), R290 (propane) and R717 (ammonia / NH3). The potential of each natural refrigerant in the heat pump market is analyzed from the perspective of policy makers, manufacturers and end-users. The analysis shows that CO2, propane and ammonia are still at early stage of commercialization, while propane is the most promising candidate among the three. Finally, this paper concludes that there is a significant potential for natural refrigerant on the Chinese heat pump market. As technology advances, national regulations are enforced and national standards revised, choosing natural refrigerant will become both technically and economically feasible.

  • 211. Utomo, Adi T.
    et al.
    Haghighi, Ehsan B.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Zavareh, Ashkan I. T.
    Ghanbarpourgeravi, Morteza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Poth, Heiko
    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.
    Pacek, Andrzej W.
    The effect of nanoparticles on laminar heat transfer in a horizontal tube2014In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 69, p. 77-91Article in journal (Refereed)
    Abstract [en]

    Heat transfer coefficient in laminar flow of water-based alumina, titania and carbon nanotube nanofluids in a straight pipe with constant heat flux at the wall have been investigated independently by two universities. The nanoparticles affect the thermo-physical properties of the suspensions, however, nanopartides presence and movement due to Brownian diffusion and thermophoresis seemed to have insignificant effect on heat transfer coefficient. The Nusselt number of all investigated nanofluids followed standard heat transfer correlations developed for liquids within +/- 10% suggesting that all investigated nanofluids can be treated as homogenous fluids. Different methods of comparison between heat transfer coefficient in nanofluids and base fluid are also critically discussed.

  • 212.
    Xu, Tianhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. KTH.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Experimental investigation on cylindrically macro-encapsulated latent heat storage for space heating applications2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 182, p. 166-177Article in journal (Refereed)
    Abstract [en]

    The integration of latent heat thermal energy storage (LHTES) units with heating systems in buildings is regarded as a promising technology for heating load management; however, so far a limited number of experimental studies have been reported that focus on space heating applications on a representative scale. In this study, we develop and test a 0.38 m3 LHTES unit containing cylindrically macro-encapsulated phase change materials (PCMs) with a melting temperature range of 44–53 °C and with gross mass of 154 kg. The unit has been tested with two tank orientations, horizontal and vertical. In the horizontal orientation tests, parametric studies show that increasing the difference between heat transfer fluid (HTF) supply temperatures and phase-change temperatures of PCMs, as well as increasing HTF flowrates, can both reduce the complete melting/solidification and complete charging/discharging time. Non-linear charging/discharging rates in PCMs are observed. The vertical orientation enables the forming of either a stratified or mixed flow regime in the tank. For charging, the stratified flow provides higher charging rates in PCMs compared to the mixed flow. When discharging the unit with a stratified HTF flow at 35 °C, lower HTF flowrates prolong the discharging time during which the released heat sustains an outlet temperature above 45 °C. Finally, comparisons between horizontal and vertical orientation tests reveal that although the vertical orientation can shorten the charging/discharging time by up to 20% for the entire unit to reach an energy density of 30 kWh/m3, it leads to decrease in PCM thermal capacity by at most 8.2%. The speculated cause of this loss is phase segregation suggested by observed fluid motions in PCM cylinders. This study comprehensively characterizes an LHTES unit providing insights to optimizing its operating strategies considering its coupling with space heating systems.

  • 213.
    Xu, Tianhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Navarro-Peris, Emilio
    Piscopiello, Salvatore
    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.
    Corberán, José M.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Large-Capacity Propane Heat Pumps for DHW Production in Residential Buildings2018In: Refrigeration Science and Technology, Valencia, Spain, 2018, p. 1222-1230Conference paper (Refereed)
    Abstract [en]

    Using heat pump technology to provide Space Heating (SH) and to produce Domestic Hot Water (DHW) for residential buildings has been widely applied during past decades. In this study, two scenarios adopting large-capacity propane heat pumps are defined and evaluated. These two scenarios, which are named after Scenario A and Scenario B respectively, provide SH and DHW either separately by two units or integrally by one unit. The COP1s of two scenarios are compared based on the simulation results from experimentally validated models. The results show that two scenarios have almost equal efficiency; the relative difference is within 6%. In the optimization analysis of Scenario B, varying DHW heating capacity produced by the desuperheater in the heat pump is modelled. The DHW demand ratio varies from approximately 9% to 20% with no detectable influences on the COP1. The corresponding COP1s and temperature profiles in the heat exchangers are demonstrated. The simulation results indicate that increasing DHW capacity in Scenario B can narrow down the temperature approach in the condenser and insignificantly improves the overall COP1s.

  • 214.
    Xu, Tianhao
    et al.
    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.
    Mazzotti, Willem
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Björn, Palm
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Performance Evaluation of a Large Capacity Air-Water Heat Pump Using Propane as Refrigerant2016Conference paper (Refereed)
    Abstract [en]

    Heat pump applications working with hydrocarbons as refrigerant have been under significant development along with the gradual phasing-out of conventional HFC systems. In this study, a large capacity air-water heat pump prototype using propane as refrigerant is tested to evaluate its heating performance under different operating conditions. The experimental set-up is briefly explained. The results of the experimental investigations of the heat pump prototype are presented in terms of the COP1, heating capacity and the compressor efficiency. At the design point, the experimental COP1 and heating capacity are 3.43 and 36.59 kW respectively. Experimental results for all test conditions are compared to simulation results generated from the model, which is created by the software IMST-ART. The model is validated through comparisons of those parameters since a good agreement between simulated and experimental data have been found. The maximum discrepancies of COP1 and heating capacity are around 5% and 10% respectively.

  • 215. Yang, Z. L.
    et al.
    Kazachkov, Ivan
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    An analytical model on the instability of thin film flow dynamics in a micro-gap channel2001In: Journal of Enhanced Heat Transfer, ISSN 1065-5131, E-ISSN 1563-5074, Vol. 8, no 3, p. 175-184Article in journal (Refereed)
    Abstract [en]

    In this paper, a mathematical model is developed to investigate the liquid film dynamics in micro-gap channels, in which a liquid film flows along the wall surfaces and gas flows in the channel core. It is assumed that the Reynolds numbers for both gas and liquid flow are very low and there is no mass transfer at the interface. The instability behavior of the interface of two-phase flow is analysed by employing Stoke's equations, which are solved by non-linear boundary conditions. The solution shows that if the perturbations at the interface are small, they do not grow, however, kinematic waves still exist. All perturbations on the film surface are convoyed by gas flow without growing or decreasing. From the analytical results it is also found that in a micro-gap-channel in the case of constant pressure gradient, the perturbations on both sides of the gap interface are strictly interconnected, and their relationship has been obtained.

  • 216. Yang, Z. L.
    et al.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    Sehgal, B. R.
    Numerical simulation of bubbly two-phase flow in a narrow channel2002In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 45, no 3, p. 631-639Article in journal (Refereed)
    Abstract [en]

    An advanced numerical simulation method on fluid dynamics - lattice-Boltzmann (LB) method is employed to simulate the movement of Taylor bubbles in a narrow channel, and to investigate the flow regimes of two-phase flow in narrow channels under adiabatic conditions. The calculated average thickness of the fluid film between the Taylor bubble and the channel wall agree well with the classical analytical correlation developed by Bretherton. The numerical simulation of the behavior of the flow regime transition in a narrow channel shows that the body force has significant effect on the movement of bubbles with different sizes. Smaller body force always leads to the later coalescence of the bubbles, and decreases the flow regime transition time. The calculations show that the surface tension of the fluid has little effect on the flow regime transition behavior within the assumed range of the surface tension. The bubbly flow with different bubble sizes will gradually change into the slug flow regime. However, the bubbly flow regime with the same bubble size may be maintained if no perturbations on the bubble movement occur. The slug flow regime will not change if no phase change occurs at the two-phase interface.

2345 201 - 216 of 216
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