Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Experimental Performance Investigation and Variable Speed Compressor Implementation of a Household Refrigerator(Izmir Institute of Technology, 2013) Ağakay, Veysel Egemen; Özkol, Ünver; Özkol, Ünver; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe objective of this thesis is to investigate the performance of a household refrigerator in steady state operating conditions and reveal the effect of variable speed compressor implementation on the system performance. This work is based on experimental studies which include energy consumption (EC) tests in accordance with ISO 15502 standard and implementation of a variable speed compressor (VSC) to a household refrigerator. To accomplish these works, the household test refrigerator is instrumented with various sensors and a comprehensive test program is prepared for data acquisition, analysis, and control of the VSC. During the EC tests, the refrigeration cycle performance is tracked simultaneously by real time analyses of each refrigeration cycle component which include calculations of heat transfer from each component, mass flow rate of the refrigerant, and work inlet to the compressor. In this study, three tests of refrigerators utilizing single speed compressor (SSC) with different condenser lengths, and one test of the refrigerator with a VSC are conducted in an air chamber in which the ambient temperature is kept at 25oC and the relative humidity is under 75%. The VSC is controlled by temperature feedbacks of air stream from the freezer and the fresh-food compartments to maintain the required temperatures in those compartments.Master Thesis Evaluation of the Performance of a Household Refrigerator Using a Variable Speed Compressor With 1d Simulations(Izmir Institute of Technology, 2013) Kanargı, Ömer Buğra; Özkol, Ünver; Özkol, Ünver; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyInefficient use of electricity is considered as an indirect contributor to the emission of greenhouse gases into the atmosphere. One way to reduce these emissions is to improve the energy conversion efficiencies of the electric equipment. The household refrigerators are designed to satisfy the maximum cooling load to which they are exposed. However, they operate under part load conditions for most of their lifetime. In the literature, some refrigeration capacity control methods are presented such as on/off control, hot gas bypass, evaporator temperature control, clearance volume control, multiple compressor control, cylinder unloading and the variable speed compressor (VSC) control. VSC control has been reported to be the most useful refrigeration capacity modulation method in many studies in terms of its ability to match the refrigeration capacity to the instantaneous cooling load while at the same time decreasing the average and instantaneous power requirements, therefore the total energy consumption (EC) of a refrigerator. In this thesis, three different VSC control algorithms are studied utilizing the 1D model of a commercial household refrigerator. The ECs and the cooling performances are compared with those of the standard on/off compressor control algorithm at the nominal frequency of 50 Hertz (Hz). Temperature management of the cold store and the freezer compartments are investigated in detail, considering the regulations on household refrigerating appliances, characteristics and test methods declared by the British Standards Institute. In addition to the standard EC calculations during the steady state operating conditions, the performances of the VSC control algorithms are evaluated under transient cooling load conditions, as well. It is shown that using a VSC control algorithm to modulate the refrigeration capacity of a refrigerator, when the refrigerator operates under part load conditions, could provide considerable energy savings.