Optimal Design And Application Study Of Indirect-direct Evaporative Water Chiller

Indirect-direct evaporative water chiller uses dry air as driving force to produce cold water.The mechanism of evaporative cooling is introduced through the double membrane theory.Double membrane resistance are key factors in heat transfer and mass transfer,such as air film resistance,water film resistance,and air-water ratio,etc.The dry and wet bulb temperature differences,partial pressure differences of water vapor between outdoor air and saturated air were compared in 7 cities.According to the fundamental heat and mass transfer model of the indirect evaporative cooler,the method of selecting and checking the heat transfer coefficient between the water film and the tube wall in the wet channel was optimized.The traditional equipment structure is changed,and the horizontal fan is configured with single-side air inlet to reduce the height of the equipment.It is concluded that the two-stage pre-cooling of the cooling coil and the vertical heat exchanger are better than the single stage pre-cooling of the cooling coil through tests.The average sub-wet bulb efficiency of the two-stage pre-cooling are between 68.4% and 69.4%,and the average sub-wet bulb efficiency of the cooling coil single-stage pre-cooling are between 45.5% and 42.9%.A novel integrated evaporative cooling（condensing）water chiller was designed to meet data center annual cooling demand.Different operating modes are switched according to different outdoor weather conditions.The unit is designed with a closed circulating water system to ensure good water quality.In order to save area and facilitate transportation and installation,the unit is designed as an integrated unit.The experiment compares the padding composite coil cooling with the single-coil unit.The padding characteristic curve is fitted.The analysis reveals that the padding is placed in the upper part of the tower,which can increase the contact time and area of unsaturated air and spray water,reduce the water film temperature on the outer wall of the coil.This will help to produce a lower coil water supply temperature.A novel air conditioning system combines various operating modes of natural glycol cooling,water-side evaporative cooling,and mechanical refrigeration.Switching different modes of operation according to different weather conditions will improve the safety and reliability of cooling.The allowable deviation of the switching temperature is ±0.2℃.At the same time,a 2300 k W data room is used as an example to analyze the energy saving of the system.The sub-wet bulb efficiency and the air-side cooling efficiency of the padding have been tested,it also predicted the annual operating mode and hours of the composite cooling mode in the data centers of Urumqi,Beijing,and Shanghai.