A reversible device operates between a cold reservoir at temperature TC=260K and a hot reservoir at temperature TH=310K.
(i) Calculate the coefficient of performance when the device is used as a refrigerator.
(ii) Calculate the coefficient of performance when the same device is used as a heat pump between the same two reservoirs.
(iii) Determine the percentage by which the heating mode reduces the required work input compared with the cooling mode for transferring the same quantity of heat per cycle.
(iv) Keeping TH fixed at 310K, sketch qualitatively on the same axes how the two COPs vary with TC in the range 240K to 300K and label the curves clearly.