Experimental Study On Additive Drag Reduction In Air-Conditioning Chilled Water System

According to statistics, China's power consumption of transmission and distribution of air-conditioning water system, accounted for about 12% to 24% of the whole building power consumption during the summer cooling. It was a very urgent task to reduce the power consumption of air-conditioned water system transmission and distribution. Adding additive in the liquid could reduce its flow resistance significantly, however, present studies mostly focused on heating systems, research in the cooling system was little, so it had very important significance to carry out experimental study of additive resistance reduction in air-conditioning chilled water system.Firstly, the laboratory bench including drag reduction by additives was designed and built which was applied for air-conditioning chilled water system with the temperature range of 5℃to 15℃. In this laboratory bench, we could achieve continuous control and regulation of temperature through the cooling system and thermostat system, besides we also installed a capacitive transducer and electromagnetic flow meter to measure the pipe pressure and flow. To ensure the accuracy of the experiment, diameter calibration experiments were done, the results showed that the 15mm and 6mm diameter pipeline were respectively 15.66mm and 5.76mm after calibration.Secondly, we studied the characteristics of drag reduction for CTAC in air-conditioning chilled water system with the temperature range of 5℃to 15℃, it showed that the drag reduction effect was not good in this temperature range, with the largest percentage of drag reduction only 30%, which was found under conditions of concentration of the additive 300ppm, the fluid temperature 15℃, diameter 15.66mm. Meanwhile, we did the drag reduction experiments for the mixed drag reducing agents of CTAC and two dodecyl trimethyl ammonium methyl sulfate, the results showed that the drag reduction effect of the mixed drag reducing agents was much better than the single addition of CTAC in 5℃to 15℃temperature range, with the largest percentage of drag reduction up to 68%, which was found under conditions of concentration of the additive 400ppm, the fluid temperature 15℃, diameter 15.66mm. Besides, an anti-shear property of the mixed solution experiment was done to found that drag reduction effect of the mixed drag reducing agents had little change after the test-bed 24h or 48h continuous operation, that was to say the mixed drag reducing agents had good shear resistance.Finally, on the basis of experiments we extended the simulation of diameter effect using the diameter enlarged methods proposed by Hoyt. We simulated the actual engineering system by Simulink of Matlab to get the drag reduction effect of the mixed solution in practical engineering, the results showed that the drag reduction effect greatly reduced to 20% in practical application.This work provided some reference for additive drag reduction in the air-conditioning chilled water system and a reference for the future in-depth study.