| Author: | Nie, Yidan |
| Title: | Experimental investigation on the thermal properties and dehumidification performance of a new mixed liquid desiccant |
| Advisors: | Lu, Lin (BSE) |
| Degree: | M.Eng. |
| Year: | 2018 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Air conditioning Drying agents |
| Department: | Department of Building Services Engineering |
| Pages: | xv, 96 pages : color illustrations |
| Language: | English |
| Abstract: | Nowadays, energy storage and environmental pollution have been challenges in the world. The traditional air conditioning system which uses electricity consumes a large amount of energy. The new mixed liquid desiccant cooling system is proposed for the purpose of getting better indoor air quality with less environmental pollution. It has many advantages. Firstly, it employs renewable energy to regenerate the diluted liquid desiccant, which is energy saving. Secondly, it separately controls the humidity and temperature of the process air for the sake of providing cool and dry air. Besides, the liquid desiccant has the ability to sterilization, which is beneficial for improving indoor air quality. This thesis focuses on the liquid desiccant which is the key component to dehumidification and presents the literature review on the operation of the novel cooling system and some traditional liquid desiccants. The components of traditional solution are inorganic solutions like LiCl, or organic solution such as triethylene glycol (TEG). Some researchers found that a mixture of organic and inorganic solution which combines the advantages of two kinds of solution has lower vapor pressure. However, previous studies ignored that some mixtures are toxic and volatile, which can enter into the room and damage people. Besides, the corrosion test and dehumidification experiment haven't been performed before. Therefore, a new mixed liquid desiccant was studied in this thesis. Besides, this paper provides the objective and methodology of the dehumidification experiment. The objective of the experiment is to find a kind of new mixed liquid desiccant which has higher dehumidification performance and better physical properties. In order to achieve the objective and fill the research gap, the methodology are as follows. Finding a suitable constitute of the mixed solution and measuring and the physical properties of the mixed solution was the first step. Then, the effect of various parameters on dehumidification performance was investigated. After trying some mixed solutions, the mixture of 39% hydroxyethyl urea solution and 25% LiCl solution and 36% water was adopted in the experiment. The solution is non-toxic, nonirritant, nonvolatile, and has high chemical stability. The physical properties of the mixed solution were compared with the 35% LiCl solution, including viscosity, density, conductivity, causticity, and water vapor pressure. The vapor pressure, thermal conductivity of the new mixed liquid desiccant were smaller than that of 35% LiCl solution under the same condition and increased with the increase of temperature, while there was an opposite trend for the density and viscosity of the new mixed liquid desiccant. Besides, the causticity of the new mixed liquid desiccant was smaller than 35% LiCl solution. Moreover, some temperature-based polynomial of physical properties to predict other values under various temperatures were listed. There were five parameters changed to certain value for the purpose of investigating the effect of different parameters on the dehumidification efficiency, including air flow rate, air inlet humidity, air temperature, solution flow rate and solution temperature. For all situations, the absolute moisture change and dehumidification effectiveness of the new mixed liquid desiccant were higher than 35% LiCl solution. The air flow rate, air inlet humidity and solution temperature can remarkably influence the dehumidification effectiveness. The absolute moisture change increased with the increase of air inlet humidity for the change of air inlet humidity. There was an opposite trend for air flow rate and solution temperature. However, air temperature and solution flow rate hardly affected the dehumidification effectiveness. In conclusion, the new mixed liquid desiccant has lower vapor pressure which provides enough driving force for dehumidification. However, it has high viscosity which influence the stable operation of dehumidification process. So, the viscosity of the mixed solution could be studied in the future. Besides, the dehumidification performance of the new mixed liquid desiccant is better than 35% LiCl solution under the same working condition. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991022168751403411.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 1.69 MB | Adobe PDF | View/Open |
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