Refrigerant 134a is the working fluid for vapor-compression refrigeration cycle. the evaporator temperature is 8°c and the condenser pressure is 12 bar. saturated vapor enters the compressor and superheated vapor enters the condenser at 60°c and exits the condenser as saturated liquid. for a refrigeration capacity of 8 tons or 2.816 x104 j/s determine the following: (1) the refrigerant mass flow rate in kg/s; (2) the compressor isentropic efficiency (hint: interpolation is required); (3) the compressor power in kw; (4) the system coefficient of performance; and (5) sketch the ts diagram.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.