| The liquid desiccant cooling system,which is composed of liquid desiccant technology and evaporative cooling technology,is an important system type to realize the independent treatment of heat and humidity.A novel system is proposed which consists of a liquid desiccant system with self-cycles,an indirect evaporative cooler and a direct evaporative cooler with adjustable by-pass flow.The performance and optimization strategies of this system have been studied,the detailed content and results are shown in the following.Firstly,the size of filler,solution self-cycle ratio(R_s)and working to intake air flow ratio(R_a)were optimized.The results show that,under the design condition,the recommended range of dehumidifier inlet air velocity is between 1m/s and 1.5m/s,and the recommended range of regenerator inlet air velocity is between 1.5m/s and 2m/s.The increase of solution self-cycle ratio will lead to the deterioration of the system performance,however,it will also reduce the heat consumption of regeneration.The recommended value for solution self-cycle ratio is between 0.6 and 0.8.The cooling capacity of system and TCOP reach the maximum value when R_a is equal to 0.1 while the cooling capacity of indirect evaporative cooler reaches the maximum value when R_a is equal to 0.3.The recommended value for working to intake air flow ratio is between 0.2 and 0.3.Secondly,the performance of the system was compared with that of conventional liquid desiccant evaporative cooling air-conditioning system under different outdoor environment conditions and different regenerator inlet solution temperatures.Due to the setting of self-cycles and indirect evaporative cooler in the proposed system,the proposed system has higher TCOP and more stable system performance than conventional ones under different outdoor environments.The results show that the TCOP of the proposed system are higher than conventional systems by increasing 8%under the typical summer condition of Nanjing,besides,the novel system can utilize lower temperature heat source and achieve a higher thermal coefficient of performance.In addition,the influence of the key parameters on performance of the system were investigated.The results show that the performance of the system deteriorates as the dehumidifier inlet solution temperature increases so that a lower solution temperature is required.The recommended inlet mass fraction ratio of solution to air of dehumidifier is 1.25 under the typical operating condition.With the increase of solution self-cycle ratio of dehumidifier,cooling capacity and regenerative heat consumption decrease while TCOP increase.The solution self-cycle ratio of regenerator has opposite effects on the system,with the increase of solution self-cycle ratio of regenerator,cooling capacity and regenerative heat consumption increase while TCOP decrease.Finally,the effects of mass concentration of mixed solution on performance of this system were investigated based on the dimensionless experimental correlations of Sherwood number of mixed solution proposed by our research group,at the same time,the performance of LiCl aqueous solution and mixed solution was compared.The results show that the dehumidification ability of mixed solution is comparable to that of LiCl aqueous solution.Besides,the increase of mass concentration of mixed solution leads to the increase of temperature and humidity ratio of supply air with better thermal performance.Therefore,it is necessary to select the appropriate solution concentration to meet the requirements of supply air while maintaining high thermal performance.At last,the cost of using mixed solution was lower than that of LiCl aqueous solution by up to 14.2%.The dehumidification ability of mixed solution was slightly lower than that of LiCl aqueous solution while TCOP using mixed solution about 2.1%higher than that LiCl aqueous solution. |
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