Study On Water Quality Issues Of Evaporative Air Conditioning System In Northwest China

At present, the water quality issues of Evaporative Cooling is one of the main limiting factors for the popularization and application of Evaporative Air Conditioning technology. Corrosion, scaling and bacterium issues are severely affecting the actual Evaporative Cooling project, Making the cooling efficiency decreased and the service life of the equipment reduced. Poor environment and water shortage has increased the water quality of Evaporative Air Conditioning System more severely in Northwest China. However, there has been little domestic research on the water quality issues of Evaporative Cooling and less concern about water quality variation of Evaporative Cooling.Therefore, this paper studies the water quality variation of the Evaporative Air Conditioning System in the practical application, and puts forward the corresponding water treatment scheme for different evaporative cooling equipments.The study about the general rule of water quality in actual Evaporative Cooling projects is based on the theoretical analysis and test result.Firstly, according to the different circulating cooling water system, conventional Evaporative Cooling equipments are classified to accurately describe the unique characteristics of evaporative cooling water quality. The Recirculating Cooling Water System of Evaporative Cooling is divided into three parts: Indirect Opened Recirculating Cooling Water System, Direct Opened Recirculating Cooling Water System, and Indirect-Direct Opened Recirculating Cooling Water System.Secondly, this paper summarizes the forward and common water treatment methods of Recirculating Cooling Water System and compares the structure, applicable conditions, operating conditions, investment costs and environmental effects of these methods. The suitable water treatment method for Evaporative Air Conditioning System is summed up, such as: the physical methods which contains about low-voltage electrostatic treatment and high-frequency electromagnetic treatment, other treatments like: ozone treatment, chemical treatment, membrane treatment, quantum treatment. We analysed the actual water treatment of evaporative cooling projects in the Northwest China.Thirdly, three evaporative cooling units are selected for testing the water quality of three different types of Recirculating Cooling Water System. The three evaporative cooling units are High Pressure Jet-Indirect Evaporative Cooling Air Conditioning unit, Evaporative Air Cooler, and Closed Riser Rube Type Indirect Evaporative Cooling Chiller. We tested three key indexes, such as corrosion, scaling and bacterium indicators to show the water quality variation of the three evaporative cooling units and the effect of changing operating conditions. The result shows that the scaling and conductivity indexes of Recirculating Cooling Water Systems are growing with time goes by, it indicates that the three units are prone to be fouling. The high alkalinity and conductivity index of Recirculating Cooling Water Systems may cause the under-deposit corrosion. The result shows that the trend of p H, alkalinity and bacterium indexes in these three Recirculating Cooling Water Systems are different as time goes by. The replenishing water quality plays an important role in Recirculating Cooling Water Systems of evaporative cooling units. We change the operation parameters of the three units at the same time, it shows that the calcium hardness index of the High Pressure Jet-Indirect Evaporative Air Conditioning unit reaches a maximum when the secondary air volume to the primary air volume ratio is 1.45, which the maximum calcium hardness index is 150mg/L, and the calcium hardness index of the Closed Riser Tube Type Indirect Evaporative Cooling Chiller reaches a maximum when the water flow is 10m3/h, which the maximum calcium hardness index is 304mg/L.Finally, solutions and design steps of the water quality in evaporative air conditioning system are studied for dealing with the water quality issues of evaporative cooling equipments. The suggestions about equipment selection and water treatment are made to different evaporative cooling equipments according to the characteristics of three Recirculating Cooling Water Systems and the actual experiment of Evaporative Air Conditioning unit.