Experimental Study On Parallel-flow Condensers Which Applied To Refrigerated Cabinet

It’s important to optimize the performance of compressor and heatexchangers for the refrigerator. A high performance-price ratio compressorwould be chosen to improve the refrigerator’s performance. Therefore, improvethe heat exchangers performance would be one of the most important ways tooptimize the performance of refrigeration system. Parallel-flow condenser hasbeen used in the automobile air-conditioning system for years owing to it’scompact structure, light weight, high heat transfer coefficient and less refrigerantcharge. In this paper, parallel-flow condensers had been applied to therefrigerated cabinet. The work as follows:Air side heat transfer coefficient and pressure drop characteristics ofparallel-flow condensers were researched in this paper. The correlationsproposed by Chang had been chosen to determine parallel-flow condenser’scalculation model and then analyzed how the air side heat transfer coefficientand pressure drop affected by the structure of parallel-flow condenser. Theresults demonstrated that (1) The heat transfer coefficient and pressure dropincreasement with the face velocity and the speed of pressure drop is faster thanheat transfer coefficient, especially at high face velocity.(2) As for mini-typerefrigeration and air conditioning device, the air side heat transfer coefficientcan be improved by selecting louvered angle（25°~31°）, louvered length（4mm~7mm）, fin pitch（1mm~1.4mm）, fin height（5mm~8mm） andcondenser thickness （16mm~20mm） and pressure drop control in thereasonable scope.(3) The trend of the heat transfer coefficient and pressure dropwould be different with the increasement of condenser thickness. The pressuredrop increases with the condenser thickness, because the increase of the flowdistance and contact time between air and condenser will cause larger pressuredrop. However, when Re＜1000, belongs to laminar flow, the boundary layerthickness increase with the condenser thickness, block the heat transfer and finally cause the decrease of air side coefficient.Single and double parallel-flow condensers were designed in this paper andthe fin-and-tube condenser applied to the same refrigerated display cabinet. Thedata was collected by the procedure written with the LabVIEW. The data wascalculated and analyzed to show the results as follows (1) Condensers of single,double parallel and fin-and-tube compressor power consumption was minimal ina working cycle with refrigerant charge was550g,650g and800g respectively.The refrigeration system which applied with double parallel-flow condenser wasthe least compressor power consumption in a working cycle, at least22%smaller than the other two systems, while which of the single parallel-flow andfin-and-tube condensers refrigerator system were almost the same.(2) Therefrigeration system which applied with double parallel-flow condenser was therun time accounted for the smallest proportion of cycle time,17%smaller thanthe other two systems, while the single parallel-flow and fin-and-tubecondensers refrigerator system were almost the same.(3) Parallel-flowcondensers’ air side heat transfer capacity is better than which of fin-and-tubecondenser in this experimental system.