Fluid Dynamic Characterization of Printed Circuit Heat Exchanger Channels

Printed circuit heat exchangers are composed of numerous ondulated microchannels, which allow for high heat transfer performance. The particular zig-zag configuration with which the channels are designed makes it necessary to study pressure drops, since, during the design of a PCHE exchanger, an optimization between improving thermal performance and increasing pressure drops is performed. The prediction of the friction factor for the channels can be carried out using hydraulic correlations that allow to know the dependence of the pressure drops on the geometrical parameters of the channels. Although several studies have been conducted in the field of thermo-hydraulic performance of zig-zag channels, the amount of correlations in the literature is extremely limited. In this study, several laboratory tests were conducted on 110 zig-zag channels, each characterized by a different combination of geometric parameters. Using water as the fluid, pressure drops and friction factors were measured in both laminar and turbulent regimes (2000≤Re≤13000). Using the data collected in the tests, the dependence of the friction factor on different combinations of parameters was investigated, looking for significant correlations. The results of the experiments showed a rather strong correlation between the friction factor and the ratio of the relative length of a zig-zag fundamental unit (LR/Dh) to the associated angle of deflection. The correlations obtained allow the friction coefficient to be determined from the above geometric parameters as the Reynolds number varies. The experimental tests were conducted at the research laboratory of the company Microchannel Devices S.r.l., which not only supplied the necessary components but also produced the prototype channels on which the measurements were conducted.