Convective Heat Transfer In The Structures Of Metal Foam And Pinfin

In the field of air-conditioning, it's very important to enhance the heat transfer for heat exchangers. The flow and heat transfer performances in evaporators and condensers will influence the power consumption, noise, etc, of the equipment. One of the key factors is to enhance the heat transfer performance in air-side.In this paper, the flow and heat transfer performances of metal foam and pinfin structures were investigated by the electric heating and air-water heat exchanger experimental systems.The flow and heat transfer characters of some structures of pinfin were also investigated by numerical simulation.The metal foam and pinfin structure were combined with multi-channel flat tubes in form of compact heat exchanger in the air-water heat exchanger experimental system. The inlet Renolds number was 960～3100 and the air convective heat transfer characters of nine types of structures were investigated. The inlet Renolds number of the electric heating experimental system was 2220～6410 with the constant heat flux boundary condition provided. In this part the convective heat transfer characters of four types of structures were investigated.The results show: the flow resistances and heat transfer performances of metal foam increase with the increase of pore density (PPI); the 30PPI copper foam has the highest heat transfer coefficients and greater pressure drops under low Renolds number, for it can effectively enhance the disturbance of air flow; the plane fin has better overall heat transfer performances both under low and high Renolds numbers; the effective heat transfer area plays an important role on the enhancement of heat transfer; the densed inline square pinfin doesn't have better heat transfer coefficients, though it has a higher finned coefficient.The inline square pinfin and plane fin were investigated by 3D-model simulation and the results agreed well with the experimental tests. The differences with numerical simulation and experiment for the average heat transfer coefficients are less than±10% for inline square pinfin and less than±20% for plane fin, respectively.The structure and size influences for the flow and heat transfer were also investigated under low Renolds number by 2D model. The interval between the pinfins and the angle of the slot both influence the heat transfer performances. Some optimized structures with better overall heat transfer performances were obtained from the above analytical results.