| Parallel flow heat exchanger has a wide range of applications in the petrochemicalindustry, automotive air conditioning and other fields due to its compact, light weight andhigh efficiency heat transfer characteristics. Parallel flow heat exchanger is made inaluminum alloy, and it consists of multi-channel flat tube and louvered fins, and haswidespread application prospect because of its low cost and less refrigerant quantity.The flow rate distribution in each flat tube of parallel flow heat exchanger was studiedby numerical simulation. The model was appropriately simplified by confirming that thepositions of inlet and outlet having no effect on flow distribution in the second and thirdprocess flat tubes. Ultimately, the influences of inlet position, outlet position and the depth offlat tubes insert to header to flow distribution were investigated.On the basis of the flow distribution, the parallel flow heat exchanger was divided toinlet-header, the first process flat tubes, downward header, the second process flat tubes andoutlet-header five parts, the influence of structural parameters on local resistance was studied.The f-factor correlations of each part of parallel flow heat exchanger were obtained by usingthe least square method and multiple parameters regression method. When contrasted therelational forecast data to the actual data, it was found that more than91%of the forecasteddata’ error were within5%, while all the forecasted data error within15%.Many studies have focused on the influence of the structure of parallel flow heatexchanger on flow distribution, but few of them focused on the influence of flow distributionon heat transfer characteristics. In this paper, the heat transfer rate of parallel flow heatexchanger was obtained in the condition of non-uniform flow distribution by3D numericalsimulation. The maximum theoretical heat transfer rate of parallel flow heat exchanger wasobtained through1D calculation. Ultimately, the correlation of the influence of non-uniformflow distribution on heat transfer efficiency was obtained by the comparative analysis of non-uniform flow distribution and heat transfer efficiency and regression calculation. It wasfound that the forecasted heat transfer efficiency error of correlation was within2%.In order to show the boiling phenomenon of refrigerant in flat tube, the phase changeprocess was realized by writing UDF program. Gas-liquid two phase distribution among theflow was obtained by establishing flow boiling heat transfer model, the influence of thestructure parameters, such as geometry, the hydraulic diameter, the roughness, etc. to boilingflow was studied. |
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