基于低压沸腾的热源塔热泵系统溶液再生研究

发布时间：2018-02-23 06:14

本文关键词： 热源塔热泵理论分析数学模型实验研究溶液低压沸腾再生　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：热源塔热泵是一种新型的建筑冷热源方案,利用一套机组便可满足建筑夏季制冷和冬季供热的需求,其夏季制冷时具有水冷冷水机组的高效,冬季供热时利用溶液在塔中与空气换热,吸取空气的热量作为热泵的低位热源,从根本上避免了空气源热泵的结霜问题。但热源塔热泵在冬季制热运行时,溶液温度较低,在塔中与空气直接接触,当其水蒸汽分压力小于空气侧水蒸汽分压力时,空气中水分进入溶液,引起溶液浓度降低、冰点升高,系统运行将存在溶液结冻的危险。为使系统安全可靠运行,需通过溶液再生调节溶液浓度,保证溶液冰点稳定、满足使用要求。本文采用理论分析、数值模拟和实验研究相结合的方法,对热源塔热泵的溶液再生进行了较深入的研究。提出了一种基于低压沸腾的溶液再生方法,为解决热源塔热泵的溶液再生问题提供指导,也对溶液除湿系统的再生研究有一定的参考意义。根据液体沸点会随环境压力降低而降低的原理,本文针对热源塔热泵冬季运行的工质,提出了基于低压沸腾的溶液再生方法,即让溶液处于低压环境中沸腾,利用液体沸腾强烈的汽化特性快速蒸发出溶液中的水分,并使蒸汽凝结成液体排出,从而溶液浓度得以提高,达到溶液再生的目的。以热源塔热泵运行的常规工质——乙二醇溶液为例,基于拉乌尔定律和康诺瓦罗夫定律绘制出乙二醇溶液的汽液平衡关系图,研究溶液再生过程中溶液沸腾和蒸汽凝结时气、液两相中的溶质含量的变化规律。并在溶液焓浓图中,深入揭示乙二醇溶液的低压沸腾再生的机理。通过构建溶液低压沸腾再生的可行性验证试验台,进行实验验证溶液进行低压沸腾再生具有可行性,并对比分析乙二醇溶液在低压沸腾和常压沸腾时的挥发性。在此基础上,设计并完善溶液低压沸腾再生系统,研究溶液低压沸腾再生过程。建立溶液进行低压沸腾再生的数学模型,模拟溶液在不同工况再生时的参数变化规律。基于热泵提供冷热源,搭建了一套溶液低压沸腾再生的实验台。通过数值模拟和实验对比研究得出溶液再生过程中装置压力、溶液温度、蒸汽凝结率和再生溶液质量浓度等参数的变化规律。并深入研究了热水进口温度、冷却水进口温度和溶液初始质量浓度对溶液再生性能的影响规律,验证所建立数学模型的准确性,结果表明,加热热水温度和溶液初始质量浓度对溶液再生速率的影响较大,冷却水温度的影响较小。本文研究结果为解决热源塔热泵的溶液再生和溶液除湿的再生问题提供了新思路。
[Abstract]:Heat source tower heat pump is a new type of building cooling and heat source scheme. Using one set of units can meet the needs of building cooling in summer and heating in winter. The heat source tower heat pump has the high efficiency of water-cooled chillers when it is cooled in summer. When heating in winter, the solution is used in the tower to exchange heat with the air, and the heat from the air is absorbed as the low heat source of the heat pump, which fundamentally avoids the frosting problem of the air source heat pump, but when the heat source tower heat pump is heated in winter, the temperature of the solution is relatively low. In direct contact with air in the tower, when the water vapor partial pressure is less than the air side steam partial pressure, the water in the air enters into the solution, causing the solution concentration to decrease and the freezing point to rise. In order to make the system run safely and reliably, it is necessary to adjust the concentration of solution through solution regeneration, to ensure the stability of solution freezing point and to meet the requirements of application. In this paper, the solution regeneration of heat source heat pump is studied by combining numerical simulation with experimental research. A solution regeneration method based on low pressure boiling is proposed, which provides guidance for solution regeneration of heat source heat pump. According to the principle that the boiling point of liquid will decrease with the decrease of environmental pressure, a solution regeneration method based on low pressure boiling is proposed for the working fluid of heat source tower heat pump in winter. That is, boiling the solution in a low pressure environment, using the strong vaporization characteristic of liquid boiling, rapidly evaporating the water in the solution and condensing the steam into a liquid, thus increasing the concentration of the solution, In order to achieve the purpose of solution regeneration, the vapor-liquid equilibrium diagram of ethylene glycol solution is drawn based on Raoul's law and Conovarov's law, taking the conventional working medium of heat source tower heat pump as an example. The variation law of solute content in gas and liquid phase during solution boiling and steam condensation during solution regeneration is studied, and in the solution enthalpy concentration diagram, The mechanism of low pressure boiling regeneration of ethylene glycol solution was deeply revealed. The feasibility of low pressure boiling regeneration was verified by constructing a feasibility test rig for low pressure boiling regeneration of the solution. The volatility of ethylene glycol solution during low pressure boiling and atmospheric pressure boiling is analyzed. Based on this, the regeneration system of low pressure boiling solution is designed and perfected. The process of low pressure boiling regeneration of solution is studied. A mathematical model of low pressure boiling regeneration of solution is established to simulate the variation of parameters when the solution is regenerated under different conditions. Based on the heat pump, the heat and cold source is provided. A set of experimental bench for low pressure boiling regeneration of solution was set up. Through numerical simulation and experimental comparison, the pressure and temperature of the solution during the process of solution regeneration were obtained. The influence of inlet temperature of hot water, inlet temperature of cooling water and initial mass concentration of solution on the regeneration performance of the solution was studied. The accuracy of the established mathematical model is verified. The results show that the temperature of heated hot water and the initial mass concentration of the solution have great influence on the regeneration rate of the solution. The results of this paper provide a new idea for solution regeneration and solution dehumidification regeneration of heat source tower heat pump.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU83

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