Effectiveness of 3-Row Crossflow Heat Exchangers With Alternating Circuitry

Air-cooled heat exchangers with three tube rows are commonly seen in domestic air-conditioning systems. The analytical solutions of heat exchanger effectiveness for three-row plate fin-and-tube heat exchangers with alternating circuitries have been derived and expressed explicitly in terms of heat capacity ratio and number of transfer units in the recent study. These set of exact solutions serve as a basic tool in designing heat exchanger circuitry to its most accurate possible effectiveness. Comparison of plate-fin-tube heat exchanger effectiveness between airside unmixed and mixed for three-row configurations shows that the effectiveness could be different from 0.3 to 2.4% for the NTUs (Number of Thermal Units) range from 1.0 to 3.0. On the other hand, the result of the comparison of effectiveness between identical and alternating circuiting for 3-row crossflow heat exchangers shows that alternating circuiting could have less effectiveness than identical circuiting from 0.4 to 8.8% in the NTUs range from 1.0 to 3.0. Nevertheless, alternating circuit has its benefit for lower NTU cases, result shows that it could have 1.7 to 0.1% advantages over identical flow arrangement for 2-row heat exchangers with NTUs range from 1.0 to 2.0.