| Radiant air conditioning heat provides higher comfort,yet its current radiation terminal unit has low cooling capacity and high risk of condensation.In order to improve the cooling and anticondensation capacity of radiation terminal unit,a new type of tube-plate radiation heat exchanger with convection enhancement is proposed.The present study investigates the key factors affecting the cooling performance of the convection-enhanced radiant heat exchanger and the effect of using the convection-enhanced radiant heat exchanger on indoor thermal comfort by experiment and simulation.The main work content is as follows:A new type of convection-enhanced tube-to-plate radiant heat exchanger is designed and built and the relationship among the height of the plenum box,the aperture of the radiant orifice,the air supply rate,the air supply temperature and the water supply temperature and the cooling performance of the new type radiant terminal unit are studied.Based on the experimental data,the calculation formulas of the cooling capacity of the heat exchanger are obtained when the apertures of the radiant plates are 5 mm,7.5 mm and 10 mm respectively.A mathematical model for the heat transfer process of convection-enhanced tube-plate heat exchanger is established and solved numerically.After the comparison of the experimental results with the simulation results,it is found that the two results are in good agreement,which shows the correctness of the mathematical model.Based on the mathematical model,the cooling performance of a novel convection-enhanced tube-plate radiant heat exchanger is studied.The influences of air supply velocity(air supply rate),air supply temperature,orifice emissivity and high temperature cold water supply temperature on the cooling performance of the novel convection-enhanced tube-to-plate radiant heat exchanger are analyzed.The results illustrate that compared with the traditional floor radiant cooling and capillary radiant cooling,the novel convection-enhanced tube-to-plate radiant heat exchanger has higher cooling capacity under given operating conditions.Adopting the established mathematical model,this paper conducts studies on the thermal environment and thermal comfort of an air-conditioning system based on a novel convection-enhanced tube-plate heat exchanger,mainly including the indoor thermal environment and indoor thermal comfort of the novel convection-enhanced tube-plate radiant heat exchanger with different air supply speed(air supply volume),different air supply temperature,different orifice emissivity,and different high temperature cold water coil water supply temperature.In addition,the results also show that it is likely to dew in the window area of the radiant roof while under the radiant perforated plate in other areas the low temperature air layer will be formed,which can play a role in preventing condensation to some extent.To sum up,the convection-enhanced tube-plate radiant heat exchanger proposed in this paper has good cooling performance.It contributes to excellent thermal comfort by effectively improving the uniformity of room temperature.The research in this paper can provide technical support for the application and development of radiant air conditioning cooling technology This paper can make a contribution to building energy conservation and emission reduction... |
