Thermohydraulic maldistribution reduction in mini heat exchangers

Paweł Dąbrowski

doi:10.1016/j.applthermaleng.2020.115271

Thermohydraulic maldistribution reduction in mini heat exchangers

Abstract

A detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel 1 mm × 1 mm rectangular minichannels and 1 mm depth minigap section with rectangular, trapezoidal, triangular or concave manifolds in Z-type flow configuration. The working medium was ethanol and the mass flow rate was 5 × 10−4 kg/s. Both sections were heated from the bottom side. Heat flux of 10 000 W/m2 and 5000 W/m2 was applied to the minichannel and minigap section respectively. The method of the flow maldistribution mitigation in the diabatic flow has been checked. Thanks to introducing a threshold, the maldistribution coefficient can be reduced about twice in the minigap section or three times in the minichannel section with the 0.5 mm threshold as compared to the conventional arrangement. The velocity profile and temperature profile over the heat exchanger’s surface have been analyzed. Reduction of the maldistribution results in lower maximum temperature over the surface. The distribution is more uniform in the minichannel section than in the minigap section. This is due to a two-dimensional flow over a minigap. Hence, a two-dimensional approach to define maldistribution coefficients in minigap sections, which has not been distinguished in literature yet was used.