Thermo-hydraulic Performance Wind Tunnel Test Study Of Indirect Dry Cooling System

Ambient winds seriously affect the air flow and heat transfer performances of indirect dry cooling system, so it is of use to study the wind effects on the thermo-hydraulic performances of internal air and overall indirect dry cooling system.In order to obtain the change conditions of thermal performance of indirect dry cooling system impacted by the environmental wind, this paper adopts the test method with physical model. The model experimental tower and heat exchanger are made according to proportion and principle of similitude, so as to conduct model test in low turbulent wind tunnel and under thermal state. Hence the flow and temperature field of the air in the model tower are measured under the condition of different wind speed, on which basis, the change rule of airflow rate and heat exchange amount in the tower is obtained. Furthermore, the change rule of air temperature at the outlet of heat exchanger influenced by surrounding air speed is also acquired. In addition, the tests against different tower models are also conducted, in order to study the influence of different tower models on fluid heat exchange performance of air cooling tower. The results prove that:the distribution of flow field of the air inside the tower under the action of environmental wind is totally different from that of no-wind condition, and shows obvious space characteristics. It is parallel to the wind direction, among which, a maximum speed value exists in the front of the tower, and a minimum speed value exists in the back of the tower center. Environmental wind will has extinction effect on heat exchange capability of cooling tower, including two aspects, namely airflow rate and heat exchange amount. Both airflow rate and heat dissipating capacity will increase along with the increasing of thermal load in the absence of any wind. However, when it reaches up the certain heating power under the action of wind, with the increasing of heating power, the airflow rate in the tower will be almost constant under certain external wind speed. While with the enhancing of external wind speed, the heat dissipating capacity will have a negative correlation with thermal load. There is a critical wind speed at which the airflow rate in the tower is minimal. While before the critical wind speed, the airflow rate in the tower will decrease along with the increasing of external wind speed, after it, the airflow rate in the tower will increase along with the increasing of external wind speed. Under the action of environmental wind, the heat exchange capability of heat exchanger at the position of windward side and leeward side is best, which will be strengthened with the increasing of wind speed; however, the heat exchange capability of heat exchanger at the position of crosswind surface is worst, existing a value of external wind speed, at this point the deterioration of heat exchange capability is the most serious. When the wind speed is on a low level, the pudgy tower has the strongest resisting ability to the adverse effect. While the resisting ability of the spindly to the adverse effect is strongest under higher wind speed.The study in this paper will have great significance to the stable and safe operation of indirect air cooling system. Meanwhile, it will also provide technical support for site selection of indirect air cooling system.