A refrigeration cycle using air is shown in fig. E. Air enters the compressor at atmospheric pressure (?3 =14.7 psia) and its pressure is raised at ?4 = 210 psia. The temperatures at points 2, 3, 5, 6 are ?2 = −50 ℉, ?3 = 55 ℉, ?5 = 65 ℉ , ?6 = −45 ℉ . Consider the expander as a turbine. Take into account that the expander is connected to the compressor. Consider air to be an ideal gas throughout the cycle with a heat capacity at constant pressure independent of the temperature. Determine a mean heat capacity based on the temperatures of the cycle and the data in table 2.2.2 The expander and the compressor operate ideally. (a) Is this a one or a two stage refrigeration cycle? Please, explain! [one sentence is fine] (b) Take into consideration no pressure drop in the evaporator, heat exchanger and condenser. Then, estimate the pressure at points 1, 2, 5, 6. (c) Calculate the temperature at the exit of the expander/compressor (?1/?4 ).
A refrigeration cycle using air is shown in fig. E. Air enters the compressor at atmospheric pressure (?3 =14.7 psia) and its pressure is raised at ?4 = 210 psia. The temperatures at points 2, 3, 5, 6 are ?2 = −50 ℉, ?3 = 55 ℉, ?5 = 65 ℉ , ?6 = −45 ℉ . Consider the expander as a turbine. Take into account that the expander is connected to the compressor. Consider air to be an ideal gas throughout the cycle with a heat capacity at constant pressure independent of the temperature. Determine a mean heat capacity based on the temperatures of the cycle and the data in table 2.2.2 The expander and the compressor operate ideally.
(a) Is this a one or a two stage refrigeration cycle? Please, explain! [one sentence is fine]
(b) Take into consideration no pressure drop in the evaporator, heat exchanger and condenser. Then, estimate the pressure at points 1, 2, 5, 6.
(c) Calculate the temperature at the exit of the expander/compressor (?1/?4 ).
(d) Calculate the coefficient of performance of the cycle.
(e) Given that the temperatures ?5 and ?2 are constant, determine the maximum/minimum possible temperature for ?3/ ?6 .
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