Numerical Simulation And Experimental Research On Cooling Performance Of Solar Enhanced Natural Draft Dry Cooling Tower

Solar Enhanced Natural Draft Dry Cooling Tower(SENDDCT),based on natural draft dry cooling tower(NDDCT),is an innovative and resource-saving cooling tower,which uses solar energy as auxiliary energy to enhance the cooling efficiency,with good economic and environmental benefits.Its cooling performances is related to several factors,such as ambient temperature,solar radiation intensity,radiation angle,crosswind speed,cooling water working conditions,etc.In this thesis,a numerical calculation model was established to study the heat transfer characteristics and the main influencing factors of SENDDCT.The data processing is obtained by dimensionless analysis method,that is,dimensionless the heat rejection and crosswind speed under different types,different heights and different crosswind conditions,at the same time several optimization measures are proposed for the negative effect of crosswind.The results show that: SENDDCT is less sensitive to crosswind than NDDCT under low crosswind speed,it is more sensitive to crosswind than NDDCT when crosswind speed raise beyond 7m/s;when the crosswind speed is lower than 5m/s,the windbreak walls with the distribution angle of 120 o can alleviate the negative effect of crosswind effectively;while the crosswind speed is higher than 5m/s or the range of speed is larger,we'd better choose the deflectors;the coupling mode of deflectors and the windbreak walls with the distribution angle of 120 o is the most effective measure to against crosswind under large variation of crosswind velocities,and the heat rejection can be increased by 10.6%;both the heat rejection rate and air mass flow of SENDDCT decline significantly with the increasing of ambient temperature,but the heat rejection rate increases with the enhancement of solar radiation intensity.Based on numerical simulation,a 1.5 m high SENDDCT experimental system is established;the main factors of heat rejection rate and heat transfer characteristic were studied.The experimental results show that: the temperature field changes according to the solar radiation angle,in the evening,it tends to decrease from the bottom to outlet evenly,which is consistent with the numerical results;in the morning,the south temperature is higher than north at bottom,it is opposite at outlet;at noon,the tower center temperature is low,but the temperature at the edge of solar heat receiver is high;the increasing of water flow rate and inlet temperature cause the heat rejection rate improving,but the rising rate become flat due to the limitation of air-side convection heat transfer coefficient;compared with the ambient temperature,solar radiation intensity effects on the SENDDCT cooling performance is relatively weak;the experimental research is basically the same with numerical simulation results and the numerical simulation method proves to be true;this paper provides a powerful experiment data support for the feasibility of SENDDCT.