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- Madani, Hatef
(författare)
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Capacity-controlled Ground Source Heat Pump Systems for Swedish single-family dwellings
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall objective of this thesis is to develop a structured method to approach the challenge of better understanding the techniques and potential for capacity control in Ground Source Heat Pump (GSHP) systems used in Swedish single-family dwellings. This thesis aims at development of a generic model of the system that can be used for comparative, descriptive, and predictive analysis of capacity controlled GSHP systems in single-family dwellings.In order to develop the generic model, first, a conceptual model of the reality of interest is developed based on the objective of the model. Second, a quantitative model of the system is developed based on the conceptual model. Third, experimental studies are carried out in order to obtain better understanding of the behavior of the system and its components and also to validate the capabilities of the model. Furthermore, some examples are presented to show how the generic model developed and evaluated at the previous stages can be used to address the questions in the context of capacity control in GSHP systems.As the first example of applications of the generic model, a comparative analysis is made between the annual performance of on/off-controlled and variable-capacity GSHP systems. The results show that dimensioning of the on/off-controlled GSHP unit based on the peak heat demand of the building plays a significant role when the annual performance of the on/off controlled GSHP system is compared with that of the variable speed GSHP system. As the second example, another comparative analysis is performed, this time to compare three common methods whose purpose is to control on/off-controlled GSHP system. Based on the results from the detailed analysis of these three control methods, it is recommended not to use the constant hysteresis method to avoid large supply temperature oscillation or large deviation from the required temperatures.Finding a proper brine mass flow rate, either variable or constant, is a challenge when a variable capacity heat pump system (a heat pump system equipped with a variable speed compressor) is designed. Therefore, as the third example of applications of the generic model, analysis is performed on a variable-capacity GSHP system equipped with a variable speed compressor and variable speed pump in U-pipe borehole heat exchanger. The results show that a single speed liquid pump but with a very carefully-selected brine mass flow rate would be still an appropriate option for variable speed heat pump systems, if COP maximization is the main concern.Finally, as the fourth example, the performance of a run-around coil heat recovery system equipped with a variable capacity heat pump unit is evaluated over a year. The results show that by retrofitting a well-sized variable capacity heat pump unit to the system, there is a potential to increase the amount of heat provided by the recovery system by more than 70%.In addition to the examples shown, the systematic approach and the generic model used in the present study can be applied to improve other control techniques and strategies and find new opportunities which can lead to saving energy and money, reducing the greenhouse gas emissions, and gaining higher credibility for GSHPs in the market.
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| 2. |
- Andersson, Catrine, 1982-
(författare)
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Hundra år av tvåsamhet : Äktenskapet i svenska statliga utredningar 1909-2009
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the thesis is to study the concept of marriage and discursive constructions linked to marriage in Swedish policy documents, SOU, 1909-2009. Focusing on marriage as a formal institution, and on form, rather than content – marriage is considered one of several ways of regulating intimate relationships, and the analysis is thus centred on the intimate and erotic aspects of marriage as an institution. Using queer and sociological theories on late modern intimacy, state regulation and concepts of norms, theoretical tools which make possible exploring historical discursive shifts of heteronormativity and coupledom are developed. Policy documents (SOU) are analysed using discourse analysis inspired by archaeology and history of concepts. In three chapters, each covering a part of the period 1909-2009, the discursive landscape of state intervention in marital and other coupled relations is traced. Three themes emerge in this analysis. Firstly, a discursive movement can be seen, from marriage, as a morally superior form of relation, to family, as one of several more or less encouraged forms of relations. Secondly, in using the theoretical framework of heteronormativity, it is suggested that heteronormativity is reshaped in paradoxical ways. The seemingly non-heteronormative, gender neutral marriage law introduced in 2009 was built discursively on a concept of love used from the 1980s in these materials for motivating extended civil rights for homosexuals. It was, however, a logic of love based on difference and essentialised homosexual identity. A non-heteronormative law was thus introduced on a heteronormative discursive basis, enforcing extended norms of coupledom in the process. Thirdly, the question of what discursive role marriage plays in relation to society is explored. By enforcing differentiation between sexual and non-sexual, reproductive and non-reproductive, coupled and non-coupled relationships, social order is maintained. For one hundred years, despite major changes, coupledom is constant.
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| 3. |
- Cowan, David, et al.
(författare)
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REFRIGERANT LEAKAGE AND CONTAINMENT - OVERVIEW OF THE ACTIVITIES OF THE IIR WORKING PARTY ON MITIGATION OF DIRECT EMISSIONS OF GREENHOUSE GASES IN REFRIGERATION
- 2011
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Ingår i: 23RD IIR INTERNATIONAL CONGRESS OF REFRIGERATION. - : INT INST REFRIGERATION. - 9782913149885 ; , s. 3833-
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Konferensbidrag (refereegranskat)abstract
- In recent years Global emissions due to leakage of F-Gases from refrigeration and air conditioning equipment have continued to increase as HCFC and CFC refrigerants are replaced by non-ozone depleting, but higher GWP, HFC refrigerants. Although lower GWP HFO and natural refrigerants such as CO2, ammonia and hydrocarbons are increasingly used in new system designs, the upward trend in the use of HFC refrigerant and consequent emissions are likely to continue for some years in the future. The environmental damage caused by direct emissions from escape of refrigerant can be 30% or more of the total environmental impact of a RAC system. However, effective mitigation measures can reduce this significantly, to the extent that the total equivalent warming impact (TEWI) of systems containing high GWP refrigerants can be similar to (or even lower than) systems containing lower GWP refrigerants. Mitigation measures can take several forms including legislative, fiscal, the use of alternative technologies and refrigerants, improvements in design and work practices and skills training. The IIR has set up a Working Party to research, collate and disseminate information on such mitigation measures. This will be made available via the FRIDOC database. The objectives and progress against these objectives are described in this paper.
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| 4. |
- Svane, Örjan, et al.
(författare)
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Negotiated outcomes - Actor-oriented modelling of energy efficiency in a Stockholm city district renewal
- 2012
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Ingår i: Proceedings of the 6th Biennial Meeting of the International Environmental Modelling and Software Society. ; , s. 1768-1775
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Konferensbidrag (refereegranskat)abstract
- "What if the renewal of Rinkeby-Kista, Stockholm, were to make it part of a 2 kW Society?" Renewal of the city district's 25 000 flats from the 1970s is due and a network organisation, "Järva Boost" is established. A cross-disciplinary team of KTH researchers develop a computerised model to simulate energy efficiency gains resulting from actors' decisions. Inputs are measures that building owners, energy providers, residents, planners etc. might propose. They can be technical institutional or socio-cultural. Outputs are energy use in kW/person and CO2 emissions. To guide model development, an "ideal type" usage situation is outlined. The energy system is modelled "upstream" from end use, to identify larger efficiency potentials. The model interface is designed to enable the "staging" of actors' negotiations: The manager influences the properties of the climate shell, the residents the energy used for cooking, and the energy provider the primary energy mix. The concepts of "Household Activities System" and "Energy Usage Systems" give theoretical framework for modelling. The former conceptualises residents' activities, the latter the technology providing services to the activity. Simulations give contrasting outcomes: "business as usual" vs. "most favourable". Used in practice, simulations might simplify negotiations and coming to agreement.
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| 5. |
- Yang, Chen, 2011-
(författare)
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Thermodynamic Cycles using Carbon Dioxide as Working Fluid : CO2 transcritical power cycle study
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The interest in utilizing the energy in low‐grade heat sources and waste heat is increasing. There is an abundance of such heat sources, but their utilization today is insufficient, mainly due to the limitations of the conventional power cycles in such applications, such as low efficiency, bulky size or moisture at the expansion outlet (e.g. problems for turbine blades). Carbon dioxide (CO2) has been widely investigated for use as a working fluid in refrigeration cycles, because it has no ozonedepleting potential (ODP) and low global warming potential (GWP). It is also inexpensive, non‐explosive, non‐flammable and abundant in nature. At the same time, CO2 has advantages in use as a working fluid in low‐grade heat resource recovery and energy conversion from waste heat, mainly because it can create a better matching to the heat source temperature profile in the supercritical region to reduce the irreversibility during the heating process. Nevertheless, the research in such applications is very limited. This study investigates the potential of using carbon dioxide as a working fluid in power cycles for low‐grade heat source/waste heat recovery. At the beginning of this study, basic CO2 power cycles, namely carbon dioxide transcritical power cycle, carbon dioxide Brayton cycle and carbon dioxide cooling and power combined cycle were simulated and studied to see their potential in different applications (e.g. low‐grade heat source applications, automobile applications and heat and power cogeneration applications). For the applications in automobile industries, low pressure drop on the engine’s exhaust gas side is crucial to not reducing the engine’s performance. Therefore, a heat exchanger with low‐pressure drop on the secondary side (i.e. the gas side) was also designed, simulated and tested with water and engine exhaust gases at the early stage of the study (Appendix 2). The study subsequently focused mainly on carbon dioxide transcritical power cycle, which has a wide range of applications. The performance of the carbon dioxide transcritical power cycle has been simulated and compared with the other most commonly employed power cycles in lowgrade heat source utilizations, i.e. the Organic Rankin Cycle (ORC). Furthermore, the annual performance of the carbon dioxide transcritical power cycle in utilizing the low‐grade heat source (i.e. solar) has also been simulated and analyzed with dynamic simulation in this work. Last but not least, the matching of the temperature profiles in the heat exchangers for CO2 and its influence on the cycle performance have also been discussed. Second law thermodynamic analyses of the carbon dioxide transcritical power systems have been completed. The simulation models have been mainly developed in the software known as Engineering Equation Solver (EES)1 for both cycle analyses and computer‐aided heat exchanger designs. The model has also been connected to TRNSYS for dynamic system annual performance simulations. In addition, Refprop 7.02 is used for calculating the working fluid properties, and the CFD tool (COMSOL) 3 has been employed to investigate the particular phenomena influencing the heat exchanger performance.
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