Study On Performance Of Solid-concentrator-heat-storage-type Dimmers

In buildings with greater proportion of transparent materials in exterior enclosing structure,excessive solar rays usually get into the interior space so that people may feel uncomfortable and photothermal environment is poor.Adjusting the shading rate of transparent building envelope is an effective way to solve this problem.However,the existing dimming and condensing devices generally have problems such as high initial investment and complex tracking system.In order to solve this problem,this paper proposes a solid-concentrator-heat-storage-type dimmers,and presents three realization forms of the device,respectively,the solid compound-parabolicconcentrator-heat-pipe-type(CPCH),the solid trapezoid-concentrator-heat-pipetype(TCHP)and the solid trapezoid-concentrator-water-heat-transfer-type(TCWH)dimmers.This paper mainly studies the dimming performance and the effect on indoor heat gain of these three types of solid-concentrator-heat-storage-type dimmers.At the same time,the heat collecting performance of the three concentrating devices is also studied.Through the study,we can get the following conclusions :(1)As can be seen from the experimental studies,the three devices have the functions of adjusting the indoor illuminance and indoor irradiance,and can also store and reuse excess solar energy.The CPCH dimmer had the strongest adjustment capacity upon the illumination and solar radiation intensity,followed by the TCHP and the TCWH dimmers.And the cooling section of the water tank temperature can be maintained in a certain range,which indicates that the three devices have achieved the function of heat collection.(2)As can be seen from the simulation studies,for the CPCH dimmer,with the increase in angle of incidence,the receiver rate gradually decreased.Also,the reflectivity increased at first before decreasing,while the transmittance decreased before increasing.For the TCHP dimmer,with the increase of angle of incidence,the receiver rate gradually decreased,while the reflectivity increased first beforedecreasing.For the TCWH dimmer,with the increase of angle of incidence,the receiver rate and reflectivity gradually decreased,while the transmittance gradually increased.The time slot of both TCHP and TCWH during which the low transmittance could be maintained was smaller than that of CPCH.(3)As can be seen from the comparison of simulation and experimental results,the transmittance variation trend of the three devices is similar,but the dimming effect in the simulation is better than that in the experiment.The reason for this phenomenon is that the scattered light is not considered in the simulation process.Moreover,the transparent material is smooth,the transmittance is high(100%)and remains unchanged.However,the sun rays have both scattered and direct rays in the course of the experiment.The transparent material used has undergone cutting,polishing,and other processes,resulting in a rough surface of the dimming cover plate,resulting in a reduction in transmittance(the highest transmittance is only about 70%),which further affects the dimming effect.