Numerical Simulation Of Detouring Tube Bundle For Study Reynolds Number And Its Characteristic Length And Experimental Research Of Water Film Evaporative Air Cooler

A new method for calculating Reynolds number and the characteristic length in detouring tube bundles is proposed according to the numerical simulation. The characteristic length is related not only to the tube diameter, but also to the tube spacing and line spacing of the bundle as well as the flow rates between tubes. Based on the software ?Fluent?, a 2-D simulation model of 8×8 in-line bundle and 8×8 staggered bundle was built to study the air crossing the tube bundle, and the standard k-? model was adopted. The pressure drop of detouring flow was equivalent to the drop along the path, the pressure drop variation under different bundle sizes and flow rates was analyzed, the relationship of Reynolds number and characteristic length with b undle structural parameters and flow rates was studied too. The results show that the new method to calculate the characteristic length could describe the influence of structural parameters and flow rates more truly on characteristic length in detouring tube bundles.The water evaporative air cooler bench was built and the measurement system of air-cooled was debugged. 125 working conditions(5 temperature of hot water×5 flow rate of hot water× 5 face wind velocity) were selected for the experiment. Thermal resistance were setted at inlet and outlet of each tube box to measure the hot water temperature in the tube path, and then heat transfer were calculated by the temperature measured. That the heat transfer and hot water temperature in axial distribution influenced by temperature of hot water, flow rate of hot water and face velocity, were analyzed. A special new device was designed to measure three kinds of parameters such as spraying water temperature, air temperature and humidity in the rain zone within the bundle, and parameters distribution in vertical direction were analyzed in the paper.The experiments and analysis show that before the flow rate of hot water increases to 6m3/h, the heat transferred gets to larger with the increasing of flow rate of hot water, but after 6m3/h, t as the flow rate of hot water increases, the change curve of heat transfer is gradually flattening. The quantity of heat transfer enlarges with the riseing of hot water temperature. Before face wind velocity increases to 2.788m/s, the heat transferred gets to larger with the increasing of face velocity, but after 2.788m/s, as the face velocity increases, the changes of heat transfer gently flattening.The results indicate that the temperature drop of hot water in top bundle is always the largest, and the temperature drop in middle and bottom bundle are approximately equal to each other. After the water spray out of the nozzle, the temperature of spraying water drops to minimum when it is close to the top tube. The spraying water absorbs heat on the top bundle and middle bundle, its temperature rise to the peak. and then it flows through the bottom bundle, via the rain zone, to the bottom tank, its temperature decreases gradually. In this experimental device the optimal face velocit y range to maintain maximum heat tranferred is 2.788m/s~3.129m/s as the spray volume is 0.8 m3/h.