| In China, the water availability per capita is only1/4of the world average.Circulating cooling water, which takes up60~80%of the industrial water demands, islost mainly in the cooling tower. The water-saving eco-friendly cooling tower can savewater and remove the mist by the addition of upper air heat exchanger which matcheswith non-evaporative and evaporative cooling load. This article establishes the modeland analyzes the thermal performance of different kinds of water-saving eco-friendlycooling towers. The main contents are as follows:The thermal calculation model of water-saving eco-friendly cooling tower isestablished. The closed mechanical draft tower calculation model, coupling thecalculation of air heat exchanger and coil tube, and the open natural draft towercalculation model, coupling the calculation of air heat exchanger and packing, canachieve thermal calculation and parameter prediction of both towers. Demist rate,representing the demist effect of new type tower compared to the old one, is firstbrought in for characterization of cooling tower’s demist effect.The thermal performance of closed mechanical draft and open natural draftwater-saving eco-friendly cooling tower is analyzed. The operating conditions are:20~20oC air dry-bulb temperatures and70%relative humidity. The result shows that thecooling performance of the closed mechanical draft water-saving eco-friendly coolingtower is better than the traditional one. The performance on water saving is better in alower environment temperature. The maximum demist rate reaches87%, which issignificant in removing the mist of tower outlet. The open natural draft water-savingeco-friendly cooling tower is equal to the pure wet tower in cooling performance, butits water saving characteristic is better than that of the closed cooling tower. In themeantime, the lower the environment temperature is, the higher the water-saving rateachieves. The open natural draft water-saving eco-friendly cooling tower performs wellin demisting, with a maximum demist rate of41%.The thermal performance of open mechanical draft water-saving eco-friendlycooling tower is analyzed. The operating conditions are: air dry-bulb temperature40~40oC, relative humidity84%. The result shows that both the cooling performance and the water-saving performance improve with the decline of environment temperature.The maximum of water-saving rate is40%. The maximum of demist rate is80%,which is significant.To further enhance the water-saving and demist performance of open mechanicaldraft water-saving eco-friendly cooling tower, two new operating modes, loweropening of the shutters and disable packing, are proposed. Under the first mode, thewater-saving and demist performance is improved by reducing the opening of theshutters. Under the second mode, both the water-saving and the demist rates are100%.Furthermore, the method for selecting an optimal mode of open mechanical draftwater-saving eco-friendly cooling tower in winter operating condition is proposed. Bydrawing a thermal characteristics graph of the cooling tower, the optimal operatingmode can be determined based on the actual operating conditions. Under that mode,the cooling tower has the best water-saving and demist effect, and satisfies therequirement at the same time. |
PDF Full Text Request