A Carnot refrigerator operates in a room in which the temperature is 25°C and consumes 2 kW of power when operating. If the food compartment of the refrigerator is to be maintained at 3°C, determine the rate of heat removal from the food compartment.

An ideal Otto cycle with Argon as the working fluid has a compression ratio of 6.8. The minimum and maximum temperatures in the cycle are 450 R and 2,260 R. Assuming constant specific heats, determine

(a) the amount of heat transferred to the argon during the heat-addition process

(b) the thermal efficiency

(c) the thermal efficiency of a Carnot cycle operating between the same temperature limits

An ideal Otto cycle has a compression ratio of 10.5, takes in air at 90 kPa and , and is repeated 2500 times per minute. Using constant specific heats at room temperature, determine the thermal efficiency of this cycle and the rate of heat input if the cycle is to produce 90 kW of power.

A regenerative gas turbine power plant is
shown in Fig. P1. Air enters the compressor at 1
bar, 27ºC with a mass flow rate of 0.562 kg/s and
is compressed to 4 bar. The isentropic efficiency of
the compressor is 80%, and the regenerator
effectiveness is 90%. All the power developed by
the high-pressure turbine is used to run the
compressor. The low-pressure turbine provides the
net power output. Each turbine has an isentropic
efficiency of 87% and the temperature at the inlet
to the high-pressure turbine is 1200 K. Sketch the
corresponding T – s diagram and determine: (a) The net power output, in kW. (b) The thermal
efficiency. (c) The temperature of the air at states
2, 3, 5, 6, and 7, in K.