| Under the general social background of energy saving, this study takes researching energy saving and high efficient TIEC as starting point and researches the heat and mass transfer enhancement methods intensively. These concrete measures include that aluminum foil tube was coated by water absorbent fiber fabric, aluminum foil surface was coated by hydrophilic membrane, the best ratio of volume of secondary air and primary air and water-spraying density were determined by performance test.First of all, the work was started from theory study of enhancement of heat and mass transfer for TIEC and several methods of heat and mass transfer enhancement were described, including that selecting better tube material, special treatment of heat exchanging tube, coating hydrophilic membrane on aluminum foil surface, designing reasonable influent distribution system and adding wetting agent in spray water. Based on correlation analyses, this paper considered that hydrophilic aluminum foil tube material, tubes were coated by stainless steel net, metallic fiber fabric or polypropylene fiber fabric, tubes were coated with hydrophilic membrane are several effective methods of enhancement of heat and mass transfer of TIEC.In addition, this paper researched hydrophilic membrane theory deeply and analyzed hydrophilic membrane's properties, including hydrophilic, protracted hydrophilic, corrosion resistance and odorless property. This paper introduced properties and mechanism of three kinds of hydrophilic membrane in detail. Based on above study, this paper designed and prepared one hydrophilic membrane, according to requirement of TIEC heat exchange tube. Furthermore, this paper measured hydrophilic and protracted hydrophilic and discussed hydrophilic mechanism of this hydrophilic membrane. The results showed that:(1) The solution, which was composed of Sodium Silicate, Zinc Oxide and Polyacrylamide and so on, can form hydrophilic membrane on aluminum foil surface. This membrane's hydrophilic was very good, and the contact angle of water on this surface was less than 10°. In the meantime, the protracted hydrophilic of the membrane is good, and the contact angle of water on this surface was also less than 20°after 10 dry-wet cycles.(2) This membrane's hydrophilic had significant improvement after adding surfactant. However, protracted hydrophilic of hydrophilic membrane had not obvious improvement, because of the poor water resistance of surfactant. Besides, the amount of surfactant had one best value. At this point, the contact angle of water on the hydrophilic membrane surface was smallest and hydrophilic of hydrophilic membrane was best. Hydrophilic will decrease if the amount of surfactant was too less or too more. The best amount of surfactant was 0.1 in this paper.(3) This paper used impregnation method and coating method respectively to handle surface of aluminum foil with hydrophilic solution. By comparison, we found that both two methods can form uniform hydrophilic membrane on aluminum foil surface. However, protracted hydrophilic of membrane by impregnation method was not good, and hydrophilic membrane was damaged after 10 dry-wet cycles. Average and viselike hydrophilic membrane can be formed on aluminum foil surface by coating method. Furthermore, hydrophilic and protracted hydrophilic were both good and solution quantity could be reduced.The experiment showed that solution had well hydrophilic. Proper curing agent, water-soluble organic polymer and surfactant can increase the performance of hydrophilic membrane greatly. In addition, uniform and solid hydrophilic membrane formed on aluminum foil surface by coating method. Hydrophilic and protracted hydrophilic were both good. This research has high use value and wide application prospect.In order to research the efficiency and temperature drop of TIEC as the ratio of volume of secondary air and primary air and water-spraying density were changed, one functional section of evaporative central-station air handing units with air flow of5000m~3/h——tubular indirect evaporative cooler (TIEC) was selected as the test object inthis study. The results showed that: (1) Heat transfer effect reached best when velocity inside heat exchange tube was 9.32m/s. In future design of tubular heat exchanger, optimization velocity inside heat exchange tube can be 8～10m/s. (2) The experiment got the best ratio of volume of secondary air and primary air was 0.7 in the middle humidity areas. In this case, efficiency can reach 81% and temperature drop can reach 15.23℃. By analysis, this ratio can be extended to other tubular heat exchangers in other climate. This research provides guidance for next design of tubular indirect evaporative cooler. (3) When the ratio of volume of secondary air and primary air was 0.7, curves of efficiency and temperature increase as the water-spraying density rises. However, slope of curves decrease gradually. The efficiency and temperature drop of TIEC reached highest when the water-spraying density was 0.64 m~3/h·m. Then although the water-spraying density was increased, the efficiency and temperature drop of cooler was changed less. Therefore, to tubular indirect evaporative cooler of 5000m~3/h, we can consider that 0.64m~3/h·m of water-spraying density is the best on this experimenting unit.Based on experiments, the study provided some details in improving heat exchange effect of TIEC and perfected application way of TIEC in middle humidity area of China. Researching fruit of writer should have application of evaporative cooling get wider extension.
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