Study On Dropwise Condensation Of Envelope Surface And Thermal Environment In Cold Radiation System

The condensation problems in cold radiation systems haven't been solved completely. Common methods for engineering design to avoid condensation are the increase of chilled water temperature,introduction of fresh air, the use of special devices to deal with the dewdrops,or the appliance of automatic control to monitor the whole radiant process.Owing to the existence of condensation problems,the efficiency of cold radiation systems is relatively low and the system cost is very expensive.The simulation of building envelopes and the thermal environment by use of CFD software(e.g.the simulation of condensation on industrial plant envelops) can give a simple understanding of the conditions in which the condensation takes place, but the condensing degree and the quantity of dew can't be calculated only through this simulation method.Meanwhile,the consideration of steady humidity or the negligence of the walls'emits of moisture affects the accuracy of the simulation results.So an equation about the quantity of dew is highly needed.Therefore, the calculation of dew quantity and study of thermal environment influences on cold radiation plays an important role in investigation of wet boundary simulations and the analysis of mold envelope structures.To solve these above problems,this paper integrated the researches to do the following work:(1)Describe the mechanism of condensation and build an actual condensation model of radiation cooling systems by comprehensive review of literatures home and abroad.(2)Change the inlet water temperature to derive different envelop heat flux and study condensation on walls.Adopt a new experimental method to collect the dew and shoot pictures of the process of condensation.(3)According to the experimental data and the heat and mass transfer theory, use dimensionless criteria and MATLAB software to derive a correlation among the wall heat flux,thermal environment, temperature and humidity and condensation quantity.(4) Study the changing processes of thermal & humid conditions on wet boundaries and the different condensation appearances under different water inlet temperature and heat flux.Then give a brief analysis about the cooling radiation systems's thermal environment.