Investigation of heat transfer in a rectangular packed duct with constant heat flux and asymmetrical wall temperatures

摘要

An experiment has been carried out for forced convection of air in a rectangular packed duct with large Rashig rings hard plastic packing. The experiments were conducted for a constant heat flux ranging from 50 to 550 W/m$sp2$ and Reynolds number ranging from 1000 to 5500 in a large rectangular channel of an aspect ratio W/H = 8. Heat supplied, air mass flow rate, pressure drop and temperature distribution inside the channel were measured. Experiments under the same operating conditions and without packing has been carried out for comparison between empty and packed channel thermal performance.;It is found that the value of Nu increases considerably in the packed channel as Re increases in the range of operating conditions considered in the study. Based on the experimental results, a correlative equation for Nu in terms of Re has been obtained as, $rm Nu = 0.8334 Resp{0.6836}$. It is also found that the value of Nu is about 6 times higher in the packed channel than in the empty one.;For predicting the pressure drop, velocity and temperature distribution in the packed channel a numerical simulation model has been developed. The comparison between the experimental and the predicted results for the air temperature distribution and Nu has shown a good agreement within the range of operating conditions considered in the study.