Sizing, selection, and comparison of heat exchangers considering the lowest saving-investment ratio corresponding to the area at the tag end of the heat exchanger

E functions are obtained and represented on ε-NTU charts for all type of heat exchangers. Based on these charts, heat exchanger area can be determined for a given E value corresponding to the area at the tag end of the heat exchanger. By comparing the ε or NTU values of different type heat exchangers having the same E values, the best one is chosen.