Thermal characteristic of a tube fitted with porous media inserts in the single phase flow

In this paper, the heat transfer rate and the pressure drop of metal porous media inserts are analyzed in the single phase. The testing range of the Reynolds number is between 3654 and 14617. Tap water is used as the working fluid. The effect of particle size and particle shape on the heat transfer performance is studied. The results show that an optimal value existed among the testing samples for dendritic particle. The best heat transfer rate is resulted by the sample D-125 instead of by the sample D-25 with the small particle size, which is approximately 2.2-3.0 times as that of the smooth tube. This is mainly because the velocity at the inlet of inserts increases greatly and the fluid mixing intensity at the annular is also high. Two factors work together to bring about a best heat transfer coefficient. The friction factor increases with the decrease in the particle size. The best Performance Evaluation Criterion (PEC) value is resulted by sample D-125, which is about 1.26-1.71. The particle shape also has an impact on the heat transfer rate. The heat transfer coefficient of the spherical particle is higher than that of dendritic particle. However, the higher heat transfer rate is paid at the cost of high flow resistance. This high flow resistance finally deteriorates the heat transfer performance. As a result, the best heat transfer performance is achieved by the dendrictic particle, which brings a high heat transfer rate as well as a low flow resistance. Therefore, the PEC values have to be taken into consideration in the design of heat exchanger.