摘要
溶液调湿空调系统由于具有高效率,能够实现湿度的精确调节、废热的利用并且能提高室内舒适度等优点被越来越广泛地利用。在溶液调湿空调系统中,溶液除湿剂直接与空气接触,实现对空气的除湿目的,是非常重要的组成部分,直接关系到溶液调湿空调系统的效率和性能。而目前对溶液除湿剂的研究大部分仅限于溶液除湿剂的基本物理化学性质,而没有将溶液的基本物理化学性质与溶液调湿空调机组相联系来分析溶液性质对机组的具体影响。基于此问题,论文主要对溴化锂和氯化锂溶液进行了以下研究。
首先,整理了LiBr、LiCl和CaCl2溶液的基本物化性质数据,包括结晶线、表面蒸汽压、比热容、密度、粘度和比焓5项基本性质。
然后,分析了溶液除湿剂对溶液调湿空调系统能耗的影响,主要从热湿传递性能和输配能耗两方面考虑。对于热湿传递性能,实验测试了溴化锂和氯化锂溶液的除湿和再生能力,通过拟合公式比较了两种溶液在相同工况下的再生和除湿性能的差异。对于输配能耗,理论计算了一个典型的余热驱动型溶液调湿空调系统在分别使用溴化锂和氯化锂溶液时的系统溶液泵耗。承担相同除湿负荷时,不同溶液带来的溶液泵耗不同。
接着,分析了溶液除湿剂对溶液调湿空调系统安全性的影响,主要包括腐蚀性能和对空气品质的影响。对于溶液的腐蚀性,通过浸泡实验和理论分析对溶液空调内的腐蚀机理做出了描述,初步探讨了缓蚀方法。对于空气品质的影响,通过文献资料证实溴化锂和氯化锂溶液毒性很低,与食盐处于同一量级,而且实测的带液结果远远低于国际的空气中限值标准,目前的仪器未检出机组送风有带液情况。
最后,基于两种溶液除湿剂对机组的具体影响情况,评价了溴化锂和氯化锂溶液的优劣,结论为两种溶液差异很小,氯化锂溶液略占优势。
本文从机组的效率和性能出发对溶液除湿剂进行评价,为新型溶液除湿剂的开发提供了思路。但是,溶液除湿剂对机组性能的影响机理仍有待进一步深入研究,并提出有效的改进方法。
With high efficiency, accurate control of humidity ratio, making use of exhaust heat and advancing indoor comfort, liquid desiccant air conditioning system (LDAS) is more and more widely utilized. Liquid desiccant directly contacts air in LDAS and realizes dehumidification, so it is an important component which concerns efficiency and performance of LDAS. At present, the research on liquid desiccant is mostly about the basic properties, while the properties of liquid desiccant’s affect on LDAS is usually not considered. Consequently, this thesis will research on the following aspects on lithium bromide and lithium chloride solution.
Firstly, basic property data of LiBr, LiCl and CaCl2 solution are sorted, including crystal line, surface vapor pressure, specific heat, density, viscosity and enthalpy, which provide foundation for the following research.
Then, liquid desiccant’s affect on system energy consumption is analyzed considering the mass and heat transfer efficiency and energy consumption for delivering desiccant. For mass and heat transfer efficiency, the dehumidification and regeneration ability of LiBr and LiCl is obtained from experiments, and the difference on dehumidification and regeneration ability of LiBr and LiCl is compared by fitting formula. For energy consumption for delivering desiccant, the energy consumption of solution pumps in a typical LDAS driven by exhaust heat is calculated. When the dehumidification load is the same, different solution brings different energy consumption of solution pumps.
Additionally, liquid desiccant’s affect on system safety is analyzed considering corrosion and affect on indoor air quality. For corrosion, basic principle of corrosion in LDAS is described according to experiments and theoretical analysis, and corrosion inhibition method is discussed preliminarily. For the affect on indoor air quality, toxicity of LiBr and LiCl is very low which are in the same order with food salt according to literatures. The tested liquid entrainment in inlet air is much less then limit value in air and the equipments couldn’t detect solution in air.
Finally, based on the affects of LiBr and LiCl on LDAS, the two desiccants are estimated. The result is that the difference is very small and LiCl is a little better than LiBr.
This thesis estimates liquid desiccants according to the affect on efficiency and performance of LDAS, which will provide a principle for the development of new liquid desiccant. However, the effect theory of liquid desiccant on LDAS still needs profound research, and some improving means should be introduced in the future.
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