A Reach On The Enhancement Of Heattransfer Of The Solar Evacuated Collector Tube

Trough solar collector system is the solar energy utilization device most widely usedat the high temperature and has broad application prospects in industry and daily life. Butthe trough solar collector exist the problems of low heat transfer coefficient, largeoccupation area and easy scaling in the evacuated collector tube.In this paper, technology of heat transfer enhancement with insert is used to improveevacuated collector tube. Three kinds of typical insert including twisted-taped, rotor andtwined coil is used to improve evacuated collector tube. The twisted-taped and rotor cancause non-attenuation swirl and turbulence, thereby increase the heat transferperformance and prevent deposition of scaling in the inner wall surface with self-cleaningeffect. The twined coil can improve the degree of fluid mixing through dispersion effect.The temperature gradient of boundary layer is increased to obtain the heat transferenhancement.The numerical simulation and the experiment are applied to study the effect of threekinds of interpolation on the heat transfer enhancement of evacuated collector tube.Themain research are as follows:(1)FLUNT software is used to simulate the evacuated collector tube withintwisted-taped and rotor and get the distribution of velocity, pressure and temperature. Theresults is compared with the plain tube. The effect of heat transfer enhancement withinsert is obvious. At the same time, the drag coefficient is increased. The effect of heattransfer enhancement of the interpolation rotor is much better than that of the interpolatedtwisted tape.(2)Experiments is used to test the practical effect of the rotor and twined coil. Theexperimental results show that the outlet temperature of the heat transfer medium is improved greatly with inser. However, power consumption is increase. These two inserthave the similar effect on heat transfer enhancement. But the power consumption of thetwined coil is less then rotor. Economically, the twined coil is more suitable for the solarevacuated collector.Through the reserach we can provide a theoretical basis for the application of heattransfer enhancement of interpolation technique to solar vacuum heat-collecting tube andselecting the appropriate interpolation.