An air-conditioning unit is required to remove heat from a room at the rate of 3.0 kW while the outdoor temperature is 35 °C. Compare two operating situations and answer the questions that follow.
(i) When the room is maintained at 25 °C, determine the ideal (Carnot) COP of the unit.
(ii) If the thermostat setting is lowered so that the room is now maintained at 20 °C, determine the new ideal COP.
(iii) Calculate the percentage decrease in COP caused by the change in room temperature.
(iv) For the same heat-removal rate of 3.0 kW, compute the minimum electrical power input required in each case and hence find the percentage increase in power consumption due to lowering the room temperature.