11 the coefficient of performance decreases as the average temperature of the refrigerant in the evaporator decreases and as the average temperature of the refrigerant in the condenser increases
12 Refrigerant 134a is the working fluid in an ideal vapor-compression refrigeration cycle that communicates thermally with a cold region at 0C and a warm region at 26C. Saturated vapor enters the compressor at 0C and saturated liquid leaves the condenser at 26C. The mass flow rate of the refrigerant is 0.08 kg/s. Determine(a) the compressor power, in kW,(b) the refrigeration capacity, in tons,(c) the coefficient of performance, and(d) the coefficient of performance of a Carnot refrigerationcycle operating between warm and cold regions at 26 and 0C, respectively.
14 Modify Example 1 to allow for temperature differences between the refrigerant and the warm and cold regions as follows. Saturated vapor enters the compressor at 10C. Saturated liquid leaves the condenser at a pressure of 9 bar. Determine for the modified vapor-compression refrigeration cycle(a) the compressor power, in kW,(b) the refrigeration capacity, in tons,(c) the coefficient of performance.Compare results with those of Example 1.
16 Working fluid :up to 1990’s most common refrigerants were chlorinated fluorocarbons (CFCs), e.g., Freon-12 (CCl2F2), Freon-22 (CHClF2)chlorine destroys earth’s ozone layer so CFCs bannedA common refrigerant used in most hockey rinks in Canada is ammonia (NH3)
17 Heat Pump Systemto maintain a warm region at a temperature upper the temperature of its surroundings
19 An ideal vapor compression refrigeration cycle, with Refrigerant 12 (R-12) as the working fluid, has an evaporator temperature of -20 C and a condenser pressure of 9 bar. Saturated vapor enters the comressor, and saturated liquid exits the condensor. The mass flow rate of the R-12 is 3 kg/min. Determine :COPb. THE REFRIGERANT CAPACITY, in TONS
20 Vapor compression refrigeration cycle, with Refrigerant 12 (R-12) as the working fluid, has an evaporator and condenser pressure of 1,4 bar and 12 bar. The refrigerant passes through each heat exchanger with a negligible pressure drop. At inlet and exit of the comressor, the temperature are -10 C and 80 C. The heat transfer rate from the condenser is 15 kw, and saturated liquid exits at 12 bar. If the compressor operates adiabatically, determine :the compressor power input, kwb. COP
21 Fatimah akan merintis usaha ice cream buah yang lagi digemari masyarakat. Setelah survey, ia tahu bahwa tingkat konsumsi masyarakat akan ice cream sangat tinggi, yaitu 300 paket ice cream perharinya. Setelah dihitung, untuk menghasilkan 300 paket ice cream ia butuh sebuah freezer dengan kemampuan pendinginan 10 ton.Kemudian Fatimah pergi ke toko elektronik untuk membeli freezer yang ia butuhkan. Ternyata, semua freezer yang dijual memiliki COP 3,5 , seperti yang tertulis pada name plate.Nah, Fatimah binggung, ia mesti pilih freezer dengan daya kompresor berapa agar usaha ice cream itu lancar?
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