Circulating Water Systems

Abstract

In accordance with the second law of thermodynamics, operation of a power cycle requires that heat be rejected at the low temperature of the cycle. The efficiency of the power cycle typically improves as the temperature at which the heat is rejected is lowered. This is illustrated by reference to the Carnot cycle for a two-phase working fluid as shown in Fig. 12-1. The power cycle thermal efficiency is generally defined as follows:

$${\eta _{{\rm{Th}}}}{\rm{ = }}\frac{{{\rm{Work produced by the cycle}}}}{{{\rm{Heat supplied to the cycle}}}}$$

For the Carnot cycle,the thermal efficiency becomes the following:

$$ {\eta _{Th}} = \frac{{{T_h} - {T_l}}}{{{T_h}}} $$

(12-1)

Where T _h = absolute temperature of the high-temperature heat source; and T _l = absolute temperature of the low-temperature heat reservoir, or heat sink.