Numerical Analysis And Experimental Research On Heat Transfer Performance And Influence Factor Of Solar Enhanced Natural Draft Dry Cooling Tower

In this paper,we introduce an innovative and resource-saving cooling tower on the basis of solar chimney power generation technology and natural draft cooling tower,named solar enhanced natural draft dry cooling tower(SENDDCT).The paper analyzes process of heat transfer in the SENDDCT,then a three-dimensional numerical model is developed by using Fluent to study the effects of solar radiation intensity,ambient temperature and combined factors on the cooling performance of the SENDDCT.The results show that:solar radiation intensity is the main influence factor for SENDDCT to enhance cooling efficiency.The higher solar radiation intensity,the more air flow through the heat exchanger,the greater heat transfer rate.When other parameters keep constant,solar radiation intensity increased from 100W/m~2 to 1000 W/m~2,heat transfer rate increased from 1.524kW to 1.747kW.At the noontime,ambient temperature and solar radiation intensity reach the highest value simultaneously in a day,heat transfer performance of traditional natural draft cooling tower decreased rapidly,while SENDDCT uses solar energy to prevent adverse effect of high ambient temperature on the heat transfer performance.When ambient temperature is 30℃,solar radiation intensity is 1000 W/m~2,heat transfer rate of NDDCT is 0.899kW,heat transfer rate of SENDDCT is 1.154kW,heat transfer rate is improved by 0.255 kW.The increase of heat transfer rate for SENDDCT when solar radiation intensity is 1000 W/m~2completely offsets the reduce of heat transfer rate for traditional cooling tower when the ambient temperature rises 4℃.Based on the numerical simulation,a same-size SENDDCT experimental system is established to investigate the cooling performance and main influence factors of SENDDCT.The experimental results show that:the average air temperature of cooling tower entrance with solar radiation is 5℃higher than that without radiation;the average heat transfer rate with solar radiation is 4.91kW,the average heat transfer rate without solar radiation is 4.51kW,SENDDCT use solar energy to enhance heat transfer rate by 9.1%.Ambient temperature increases from 19.6℃to 31.3℃,the heat transfer rate decreases from 4.85kW to 2.58kW.The increase of circulating water inlet temperature can improve the heat transfer rate.Opening the auxiliary fan increase the air flow through the cooling tower system,electric power consumed by the fan is0.275 kW,the average heat transfer rate is improved by 0.40kW.The experimental results are basically consistent with the numerical simulation results.It is proved that the CFD model proposed in this paper can be effectively applied to analysis of the cooling performance in SENDDCT.And this paper provides experimental data supported for SENDDCT research and application.