Correct Answer - Option 3 : Working fluid is a fixed mass
Explanation:
Air-cycle refrigeration system:
Air cycle refrigeration systems belong to the general class of gas cycle refrigeration systems, in which a gas is used as the working fluid. The gas does not undergo any phase change during the cycle, consequently, all the internal heat transfer processes are sensible heat transfer processes. Gas cycle refrigeration systems find applications in air craft cabin cooling and also in the liquefaction of various gases.
Air Standard Cycle analysis:
Air cycle refrigeration system analysis is considerably simplified if one makes the following assumptions:
(1) The working fluid is a fixed mass of air that behaves as an ideal gas.
(2) The cycle is assumed to be a closed loop cycle with all inlet and exhaust processes of open loop cycles being replaced by heat transfer processes to or from the environment.
(3) All the processes within the cycle are reversible, i.e., the cycle is internally reversible.
(4) The specific heat of air remains constant throughout the cycle.
