Effect of flow mal-distribution on effective NTU in multi-channel counter-flow heat exchanger of single body

Most heat exchangers in services belong to multi-channel heat exchangers. The working fluid is distributed among the multiple channels. This kind of heat exchangers usually has a flow distribution problem. In general, the flow is not evenly distributed and, as a result, the thermal performance of the heat exchanger degrades due to it. In this paper, such flow distribution effect in a single body multi-channel heat exchanger is evaluated in an analytic way. Transverse conduction through the heat exchanger body which is caused by the mal-distributed flow is formulated and included in NTU evaluation. The NTU relationship between the well-balanced flow distribution and the ill-balanced one is obtained. According to the analysis result, the heat exchanger has the best performance in case of the well-balanced flow distribution, as is expected, and has the performance degradation in case of the ill-balanced flow. The performance degradation is very severe in the heat exchanger with poor transverse conduction.