Thermal performance analysis of liquid desiccant evaporative cooling air-conditioning system driven by low-grade heat

doi:10.11949/j.issn.0438-1157.20161411

Abstract

Abstract:

Liquid desiccant evaporative cooling air-conditioning system (LDECS),which combines both advantages of liquid desiccant and evaporative cooling technology,is a very promising alternative to the non-vapor-compression air-conditioning system.In this paper,a LDECS driven by low-grade heat is proposed,which consists of a liquid desiccant system with self-cycles that handles the total latent load and a regenerative evaporative cooler that removes the sensible heat.Mathematical models of the major components of the system are established to investigate the effects of four key parameters,namely,regenerator inlet solution temperature T_s,reg,in,solution-to-solution heat exchanger effectiveness ε_SSHX,ambient air temperature and relative humidity on steady-state thermal performance of the LDECS used as a dedicated outdoor air system.The results show that the supply air of 17.9℃ and 9.2 g·kg^-1 with the thermal coefficient of performance TCOP of 0.56 can be achieved under the typical summer condition of Nanjing. The T_s,reg,in of about 70℃ can achieve a high TCOP with the qualified supply air condition. The impacts of ε_SSHX on TCOP and the capacities of solution heater and cooler are more significant when the value of self-cycle ratio is smaller.Besides,the proposed LDECS is suitable for the application in hot-humid zone.

Key words: aqueous solution, evaporative cooling, regeneration, low-grade heat, mathematical modeling

摘要：

溶液除湿蒸发冷却空调系统（LDECS）结合了溶液除湿与蒸发冷却技术的优势，是一种具有广阔发展前景的非压缩式空调系统。提出了一种低品位热能驱动的LDECS，该系统由处理全部湿负荷的溶液除湿系统和承担显热负荷的再生式间接蒸发冷却器构成。建立了系统各主要部件的数学模型，研究了再生器进口溶液温度T_s，reg，in、液-液热交换器效率ε_SSHX、室外空气温度和相对湿度对该系统用作全新风机组时稳态热力性能的影响。结果表明，在南京夏季典型工况下，该系统送风参数为17.9℃、9.2 g·kg，热力系数TCOP可达0.56。T_s，reg，in在70℃左右时可以满足送风参数的要求同时保持较高的TCOP。自循环比越小，ε_SSHX对TCOP以及溶液加热器和冷却器负荷的影响越大。此外，该系统适合应用在夏季高温高湿地区。

关键词: 水溶液, 蒸发冷却, 再生, 低品位热能, 数学模拟

CLC Number:

TU831.6

ZHANG Fan, YIN Yonggao. Thermal performance analysis of liquid desiccant evaporative cooling air-conditioning system driven by low-grade heat[J]. CIESC Journal, 2016, 67(S2): 275-283.

张凡, 殷勇高. 一种低位热驱动除湿冷却空调系统的热性能分析[J]. 化工学报, 2016, 67(S2): 275-283.

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