The Experimental Study And Numerical Simulation Of Microchannel Flat Solar Collector Fluid Heat Collecting Effect

A systematic investigation on the strengthening measures of flat plate solar collectors effect which scholars at home and abroad have studied. A thermal performance test platform of micro-channel flat solar collectors has been set up which bases on the well understanding of micro-channel flat solar collector and heat-absorbing plate micro-channel flow channel structure. And mathematical models on the absorber plate inside the micro-channel flow channel fluid flow and heat transfer is established which include the models of mass, momentum, energy conservation equation and RNG k-ε turbulence. The collector performance of flat plate solar micro-channel collectors were studied with the combination of experiment and numerical simulation. Furthermore the entire plate absorber plate micro-channel flow channel fluid flow and heat collection process were analyzed, the effect of micro-channel absorber plate section parameters on the media flow characteristic distribution, temperature distribution, pressure drop and heat transfer characteristics are discussed systematically. The main conclusions can be drawn as follows:1.The results showed that the maximum instantaneous collector efficiency of the micro-channel heat absorbing plate is up to 86.1% and the heat loss coefficient is only 4.179 W/(m2·℃), 14.1% higher, 1.82 W/(m2·℃) lower than the national standard, respectively, suggesting that it has strong collector performance and good insulation properties.2.A lateral diversion role was produced while the micro-channel plate increased the contact area of the heat transfer fluid, effected the distribution of medium flow resistance. Full flow medium velocity within the channel is small without flow blind, Temperature distribution can be divided into three stages, the diffusion region, a stable region, the contraction zone according to the state of media flow. That optimizing core structure size or running parameters can increase the stability region, reduce the diffusion area and contraction area, is the effective method to further improve the performance of micro-channel heat collector.3.Micro-channel with the discharge tube interchange gradual emergence of there is a local expansion and contraction interchange in the micro-channel and the discharge tube. With the media in turn flowing through the expansion, contraction and micro-channels. In the cycle, the gradual contraction zone, the working fluid border wall rapid collection, flow rate increases, the pressure decreases; micro-channels in pressure loss along the diameter uniform, gradually decreasing. In the micro-channel, the medium flow state is smooth, belonging to a laminar flow state, the pressure loss in the pipe is uniform distribution, gradually decreasing. During circulation, the media flow is basically the same, but the drop is significant. Drain pipe wall thermal boundary layer flow channel is narrow, cut uniform temperature is uniform distribution, the temperature difference between the flow path distribution is obviously.4.An appropriate extension of the micro-channel width D can enhance the surface forces, viscous forces and increase the pressure loss along the way. The shortening of runner section major axis intercept can increase the Side wall height to width ratio, cross-sectional velocity, partial loss and decrease the cross-sectional area. Vortex effect after the first generation increased firstly and then decreased, Also, the medium flow line up areas gravitating to the central and dispersed uniformly by a side wall near the peak or trough. The exhaust pipe crimp height H increased and runner section major axis intercept unchanged can enhanced side wall height to width ratio, partial pressure loss gradient constriction, the cross-sectional area and decrease sectional flow rate decreases, medium flow line gradually shifted to the side wall of peaks or troughs in the drain pipe flow path by the central dense, vortex gradually. An appropriate extension of the micro-channel width D and reduced exhaust pipe crimp height H can be enhanced heat transfer effect, save the plate. However, the drawbacks of the increased power consumption should be considered.5.The mathematical characterization of micro-channel heat plate Nu, f is summarized. The heat transfer enhancement is the best when the optimize micro-channel width is 8.7mm, exhaust pipe crimp height is 3.00 mm.