双管多曲面槽式空气集热器热性能数值研究

Numerical Study on Thermal Performance of Double-pipe Multi-curved trough Air Collector

为了研究双管多曲面槽式空气集热器的传热特性,通过TracePro软件与Fluent软件探究了不同太阳辐照度、管内风速及进口温度对集热管管壁温差、瞬时集热量和瞬时集热效率的影响。结果表明,双管管壁因太阳辐射引起的热流密度分布十分不均匀;当太阳辐照度从800 W/m^(2)增加到1200 W/m^(2)时,管1(-30,30)的径向温差增加了171.4℃,轴向温差增加了101.8℃;管2(40,118)的径向温差增加了56.7℃,轴向温差增加了56.8℃;集热器的瞬时集热量最大为991 W,瞬时集热效率最大为61.6%;当管内风速增大时,集热管的轴向温差和径向温差都会减小,进口风速的变化对瞬时集热量和瞬时集热效率的影响规律是相同的,管内最大风速不宜超过2.8 m/s;进口温度对集热器集热性能的影响较大,双管的径向温差和轴向温差都随进口温度的增加而减小,但轴向温差的下降速率高于径向温差。此外,当进口风速从1.4 m/s增加到3 m/s时,双管进出口压降均增大了约1.6倍,管内流动阻力有较大增长,综合集热性能与节能考虑,管内风速取值2.2~2.4 m/s为最佳。该研究结果可为此种多曲面槽式太阳能空气集热器的应用提供参考。

In order to study the heat transfer characteristics of double-pipe multi-curved trough air collector as the heat source of active-passive heating system in solar greenhouse,the influence of different solar irradiance,inlet wind speed and inlet temperature on the axial temperature difference,radial temperature difference of the pipe and heat collection efficiency of the collector were explored by combining TracePro and Fluent,and verified by the experimental results.The results show that the wall heat flux distribution of the two pipes is different.When the total solar irradiance received by the inclined surface of collector increases from 800 W/m^(2)to 1200 W/m^(2),the temperature difference of pipe 1(-30,30)changes greatly,and its axial and radial temperature differences increased by 101.8℃and 171.4℃respectively.However,the axial and radial temperature differences of pipe 2(40,118)only increased by 56.8℃and 56.7℃;When the inlet wind speed is more than 1.8 m/s,the effect of increasing inlet wind speed on the collector efficiency is limited.The inlet temperature has a great influence on the heat collect efficiency.The radial temperature difference and the axial temperature difference decrease with the increase of inlet temperature,but the axial temperature difference decreases faster than the radial temperature difference.Considering the heat collect effect,resistance characteristics and energy saving of the collector,the inlet wind speed of the collector pipe is 2.2~2.4 m/s.The research results can provide some reference for the combined application of trough solar collector and solar greenhouse heating system.