壁面材料对太阳能降膜吸收特性影响的实验研究

EXPERIMENTAL INVESTIGATION ON EFFECT OF DIFFERENT SOLID SURFACES ON FALLING FILM BEHAVIOR IN SOLAR-ASSISTED ABSORPTION PROCESS

为探索壁面特性对降膜吸收及太阳能利用的影响,实验研究了不同竖壁表面(不锈钢、PTFE塑料及这两者的超亲水改性表面)上的氯化锂气液吸收过程。结果表明,更小的表面接触角不仅有利于液膜铺展及膜厚降低,还可增强表面波动频率与振幅,从而促进了传质。不锈钢壁面上的液膜厚度较PTFE壁面上薄20%,传质量提升35%以上。超亲水改性后不锈钢表面上的膜厚进一步降低15%,振幅/膜厚比提高25%,传质量提升了30%以上。与不锈钢表面相比,塑料表面超亲水改性对传质的提升更为明显。基于实验获得了降膜形态随填料表面接触角变化的经验关联式,并预测了对系统能耗及太阳能利用率的影响,为太阳能除湿空调、吸收式制冷、蒸发冷却等相关工程应用提供参考。

To investigate the effect of solid surface characteristics on the mass transfer process of falling film absorption and other solarassisted applications,the lithium chloride-air absorption of on different vertical surfaces(stainless steel,PTFE plastic and each of these with super-hydrophilic modified surfaces)was experimentally studied. Results show that the smaller liquid contact angle on the solid surface was not only conducive to the expansion of liquid film and the reduction of film thickness,but also increased the frequency and amplitude of film surface waves. Thus,the liquid/air mass transfer could be promoted significantly. The liquid film thickness on stainless steel surface is 20% lower than that of the PTFE. The mass transfer rate is increased by 35% simultaneously. After the super-hydrophilic modification,the film thickness was further reduced by 15%. The amplitude/film thickness ratio was increased and the mass transfer rate was increased by 30% accordingly. The super-hydrophilic modification of plastic surfaces is more effective for improving the mass transfer performance. Though experiments,the empirical formulas that the falling film wavelength and amplitude vary with the contact angle on solid surface were obtained,and predicted the effects on the energy consumption and solar utilization rate of practical airconditioning systems. This study can help the engineering application in the fields of solar-assisted air conditioning,absorption refrigeration and evaporative cooling,etc.