The influence of flow maldistribution on the performance of inhomogeneous parallel plate heat exhangers

The heat transfer performance of inhomogeneous parallel plate heat exchangers in transient operation is investigated using an established model. A performance parameter, denoted the Nusselt-scaling factor, is used as benchmark and calculated using a well-established single blow technique. A sample of 50 random stacks having equal average channel thicknesses with 20 channels each are used to provide a statistical base. The standard deviation of the stacks is varied as are the flow rate (Reynolds number) and the thermal conductivity of the solid heat exchanger material. It is found that the heat transfer performance of inhomogeneous stacks of parallel plates may be reduced significantly due to the maldistribution of the fluid flow compared to the ideal homogeneous case. The individual channels experience different flow velocities and this further induces an inter-channel thermal cross tal

The effect of flow maldistribution in heterogeneous parallel-plate active magnetic regenerators

The heat transfer properties and performance of parallel-plate active magnetic regenerators (AMRs) with heterogeneous plate spacing are investigated using detailed models previously published. Bulk heat transfer characteristics in the regenerator are predicted as a function of variation in plate spacing. The results are quantified through a Nusselt number scaling factor that is applied in a detailed 1D AMR model. In this way, the impact of flow maldistribution due to heterogeneous parallel plate stacks on AMR performance is systematically investigated. It is concluded that parallel-plate stacks having a standard deviation greater than about 5% on their plate spacing are severely penalized in terms of both cooling power and achievable temperature span due to the inhomogeneity of the stacks