| As the low temperature in northern china and heat disparity in the cooling tower, there were easy to be frozen in the bottom surface of the filler zone, air inlet and base torus of cooling tower. And it affected the normal operation of the unit. To prevent the cooling tower from freezing, we usually installed the windshield at the air inlet. Currently, because of manual installation of the windshield, it was difficult to adjust the cooling tower operating conditions. So it was necessary to study a wind installations to automatically control the windshield’s hanging location and size according to the environment temperature. In order to find the cooling tower’s precise hanging layers under the different environment temperature and horizontal wind speed, this paper used numerical simulation software FLUENT to study the numerical simulation about the natural draft wet cooling tower of600MW units. And the simulation results were close to the actual situation. It provided a reference for manual and automatic hanging windshield.This paper established a heat and mass transfer model. Using the theory of natural draft cooling tower, the discrete phase model was adopted in the spray and rain zone, while porous medium model was adopted and source terms of the control equation were described by user-defined function (udf) in the filler zone. On the basis of the model, this paper mainly simulated and analyzed the air temperature field variation in the cooling tower and the minimum water temperature and the minimum air temperature variation in the cooling tower affected by the different horizontal wind speed and environment temperature. In the end, this paper analyzed and summarized the anti-icing law of installing different layers’windshield under the different wind speed and environment temperature. The results indicated that:while the wind speed was lower than4m/s, the air temperature in the leeward of cooling tower was higher, and the higher temperature zones moved to the windward of the cooling tower with the increasing of wind speed. The minimum water temperature and the minimum air temperature of the characteristic plane increased at first and then reduced with the increase of horizontal wind speed. And these two temperature reached the maximum when the horizontal wind speed was4m/s. While the environment temperature was low and the wind speed was higher than6m/s, it had a great impact on the outlet water temperature. Because the heat transfer efficiency of the air and water was strengthened in the rain zone, the outlet water temperature was lower and easy to be frozen. The minimum water temperature and the minimum air temperature became lower as the environment temperature decreased. Cooling tower running in the variable parameter operations, calculations should reveal the followings:①When the environment temperatures was-10℃and the wind speed respectively were2m/s,6m/s and8m/s, hanging a layer of windshield could effectively prevent the characteristics of plane from being frozen.②When the environment temperatures was-17℃and the wind speed respectively were2m/s,4m/s,6m/s and8m/s, the optimal layers of windshield which prevented three characteristics of planes from being frozen were1,1,2and4layers.③When the environment temperatures was-23℃and the wind speed respectively were2m/s,4m/s,6m/s and8m/s, the optimal layers of windshield which prevented three characteristics of planes from being frozen were4,1,3and5layers.Besides, the automatic control device of the windshield board was researched. PLC (Programmable Logic Controller) controlled the rotation of the motor automatically by the environment temperature measured by the temperature sensor or the manual button. In this way the effective area of the windshield changed air different environment temperatures. This paper provided the theoretical foundation for the further optimization of the cooling tower’s design and operation. |
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