The concept of a new approximate relation for exchanger heat transfer effectiveness for a cross-flow heat exchanger with unmixed fluids

This paper presents an approximate relation for the heat transfer effectiveness for a counter-flow heat exchanger, which was compared with the exact solution. Based on the obtained approximate relation for a counter-flow heat exchanger the approximate heat transfer effectiveness for a cross-flow heat exchanger in which both fluids do not mix is proposed. This approximate exchanger heat transfer effectiveness was compared with the exact solution proposed by Mason, the most well-known relation. A comparison between the most frequently used approximate formula and the exact solution proposed by Mason was made, too. The exchanger heat transfer effectiveness was analyzed for the ratio of the heat capacity rate of fluids C in the range from 0 to 1 and the number of transfer units NTU from the most common range 0-5.