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Experimental and Numerical Study of the Use of Phase Change Materials on the Performance of Compression Refrigeration Systems

Riahi, Alireza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53667 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. In this study, a vapor-compression cooling system utilizing different PCMs has been studied whereby the electricity consumption peak load is shifted. More specifically, the dynamic performance of cooling systems with and without using PCM is evaluated for the hottest day of the year. The proposed system uses the cooling energy to freeze, or “discharge” the PCM during nighttime when the cooling load is minimally needed and uses the stored thermal energy during the peak load hours by melting, or “charging” the PCM. This leads to better performance during peak load hours when higher cooling loads are needed. Different PCMs including Oleic acid, SP224A, CL, CaCl2.6H2O have been investigated. The system performance has been investigated by considering several parameters such as coefficient of performance, compressor power consumption, accessible cooling load and, melting fraction of PCM. The effect of different volumes of PCM on the performance of the cooling system has been evaluated, as well. The results indicated that with using the PCM, the accessible cooling load raises and the electricity consumption falls during hours of the peak load. Peak load reduction in the on-peak period is different for various PCMs. In comparison with the conventional cooling system, the peak load alters from 315W to 170, 164, 93 and, 74W for CL, Oleic acid, CaCl2.6H2O, and, SP224A, respectively. The evaluation of different PCM illustrated that for the volume of 150 liters, the peak load shaving for SP224A is the most value which is 76.3 %. By increasing the volume of oleic acid phase change material from 38 to 309, the available cooling power and power consumption are reduced by 6.9% and 4.5%, respectively. Therefore, the coefficient of performance has been reduced by 2.7%. however, the peak load shaving has increased by about 56%, which is considerable. Therefore, it can be seen that for a small decrease in the coefficient of performance, the energy consumption has shifted considerably.After simulation, a test setup is designed and constructed to test the performance of the system. The cooling system is tested in two modes with and without a PCM storage tank for 24 hours. The test setup is designed in such a way that the air temperature in the test chamber is kept constant at about twenty degrees of Celsius, so that the cooler is turned on and the power of heaters is adjusted by the control system to keep the temperature constant. The volume of the storage tank is about 300 liters and the initial temperature of the tank is 25 degrees Celsius. Water is considered as PCM. Testing of the cooling system with and without PCM is performed on two consecutive days with a same ambient temperature. The discharge time is considered from 1 to 10 and the charge time is considered from 12 to 19. Using the water as cooling storage, the overall performance of the system has increased from 2.17 to 2.33 (7% increase). It should be noted that by using the cooling storage system, the amount of accessible cooling has decreased from 58.4 kWh to 56.2 kWh (3.7% reduction) and also the amount of energy consumed in the compressor has decreased from 26.9 to 24.1 kWh (10.3% reduction)
  9. Keywords:
  10. Peak Load Shaving ; Phase Change Material (PCMs) ; Cooling Storage System ; Vapor Compression Refrigeration ; Power Consumption ; Peak Load of Power Consumption

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