Channel Blockage and Flow Maldistribution during Unsteady Flow in a Model Microchannel Plate heat Exchanger

This paper describes the problem of channel blockage as a result of flow maldistribution between the channels of a model mini channel plate heat exchanger consisting of one pass on each leg. Each leg of the heat exchanger contains ۵۱ parallel and rectangular minichannels of four hydraulic diameters namely ۴۶۱ µm, ۵۷۱ µm, ۷۵۰ µm and ۸۲۳ µm. In addition, a more complex geometry has been investigated where for the sake of breaking the development length the inclined transverse cuts have been incorporated. The moment of liquid phase transition through the exchanger (the working medium: water) was recorded for the mass fluxes ranging from ۱۸.۶۷ to ۲۷۷.۷۶ kg/m۲s in ۵۱ parallel channels with the use of a fast speed camera. The Reynolds numbers Re in the individual channels were from ۱۰.۷۶ to ۹۰.۰۴. The relationship between the mass flux and the size of the minichannels in the presence of the maldistribution is discussed here. The existence of the threshold in the mass flux below which the phenomenon occurs has been shown. Two mechanisms of channel blocking have been recorded and described in detail. A miniscale variation of one of them containing the extended geometry was created as well.

Keywords:

Minichannel , Minigeometries , Microgeometries , Transient state