空调蒸发器用管翅式换热器开缝翅片的数值设计

通过三维层流数值模拟,与平片计算结果对比,设计了适用于低流速和Re数(迎面风速1-3 m／s,对应Re数 901-2702)下的空调蒸发器用管翅式换热器的开缝翅片形式。研究表明:在上述迎面风速和Re数范围内,开缝翅片性能曲线和平片性能曲线不可避免地有一个交叉点,对应Re数称为转折Re数,在交叉点前的速度和Re数范围内,平片换热器的综合性能优于开缝翅片,而在高于转折Re数后,随着迎面风速的增大,开缝翅片的综合换热性能将越来越优于平片;依据“前疏后密”原则适当减少开缝翅片换热器开缝的条数,可以有效降低转折Re数,并显著改善低流速和Re数下换热器的综合性能。另外,再次验证了场协同理论-温度场和速度场的协同性与换热器换热量间的必然联系。

NUMERICAL DESIGN OF SLOTTED FIN OF TUBE-FIN HEAT EXCHANGER USED IN EVAPORATOR OF AIR CONDITIONING

Though 3D numerical simulation of laminar flow and comparison of the simulated results of slotted fin surface with plain plate surface, this paper optimizes the designs of slotted fin of tube-fin heat exchanger used in evaporator of air conditioning under low velocity and Re number (inlet velocity is 1-3 m/s, and Re number is about 901-2702). It is found that, within the inlet velocity range studied, the performance curve of slotted fin and plain plate heat exchanger has inevitably a crossing point whose Re number is called turning Re number; if the Re number is lower than this turning Re number, the performance of plain plate surface is better than that of slotted fin surface; however, if the Re number is higher than this turning Re number, the larger the velocity, the better the slotted fin surface performance compared with the plain plate fin surface. Moreover, if the strip numbers of slotted fin surface is decreased according the rule of 'front sparse and rear dense', the performance of heat exchanger can be enhanced effectively and the turning Re number can be decreased evidently. In addition, the results of the present study once again show the consistent relationship between the higher heat transfer rate of the slotted fin surface with their better synergy between velocity and temperature gradient.