Fluid Flow Distribution In Plate-Fin Heat Exchangers

Plate-fin heat exchanger (PFHE) has already been widely used in aerospace, chemical engineering and HVAC, etc. because of its small temperature difference, high heat transfer efficiency and compactness. The fluid flow maldistribution caused by many factors in designing, manufacturing, assembling and operating leads to performance deterioration of PFHE seriously.In the present study, experimental investigation of the fluid flow maldistribution characteristics in single side of the PFHE with size of 80mm×100mm×604mm is carried out, with the working fluids of liquid nitrogen, gas nitrogen and its two-phase fluid. A certain degree of flow maldistribution is found in this experimental PFHE, but strong special partiality on the cross section has not revealed. The flow distribution of three working fluids shows rather disparity under the same mass flux, gas nitrogen best among them, liquid nitrogen followed and two-phase fluid worst. The fluid flow maldistribution of two-phase fluid decreases when the mass flux increases, and doesn't change significantly within the inlet mass quality x range of 5.22%~50.67%, but changes rapidly within x <5.22% and the relationship is very complicated.Flow distribution is investigated in single plate-fin flow field by CFD. Numerical results of simplified model consistent well with the experimental ones. It's found that amplitude of flow mal-distributionφhas little to do with working fluids, thusφcan be recognized as a function of Re number. Both experimental and numerical calculations show that amplitude of flow mal-distributionφdecreases when the Re number increases within Re number of 5.7 ~ 12.7 and 62.1 ~ 112.3, which explains the experimental conclusions above. It's also found that the flow distribution of serrated fin is much better than straight fin, and with the Re number increasing, the comparative advantage of serrated fin is growing.Finally the paper studies the heat exchange experimental investigation of PFHE world-widely. On the base of the former experimental system, the experiment of heat exchange in PFHE has been designed and built. Then some preliminary experiments are carried out, some problems and improvement ideas pointed out through data analysis.