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Study on Adsorption Heat Pump Using Composite Natural Mesoporous Material as Low-Carbon Air Conditioning
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| Title: | Study on Adsorption Heat Pump Using Composite Natural Mesoporous Material as Low-Carbon Air Conditioning |
| Other Titles: | 天然メソポーラス材料を用いた吸着式ヒートポンプによる低炭素空調 |
| Authors: | 薛, 成勲1 Browse this author |
| Authors(alt): | Seol, Sung-Hoon1 |
| Issue Date: | 25-Sep-2020 |
| Publisher: | Hokkaido University |
| Abstract: | The energy demand on heating, cooling and domestic hot water supply, which account for around half of the energy in the residential sector, are primary factor increasing the energy consumption in the sector throughout the world. Also the cases require cooling or refrigeration all day are frequently found in commercial facilities and office buildings in urban area. Meanwhile, the massive amount of low-level waste heat around 80℃ is discharged from co-generation systems and industries to the environment. In order to supply cooling energy, refrigeration systems are needed. They are categorized into the vapor compression and thermally- driven systems. In terms of the thermally-driven systems, absorption chillers employing sorbents such as lithium bromide and adsorption chillers applying adsorbents such as a silica gel are the most representative. Among them, the system that can utilize the low-level thermal energy more efficiently is known to be the adsorption cooling system, and it is commonly named adsorption heat pump (AHP). The concept of technology of the adsorption has been existed from the past. However, low effective thermal conductivity due to the porosity of the adsorbent leads limitation of enhancement of heat and mass transfer rate have resulted in the huge system volume of AHP systems. Additionally, high-performance synthesis is too expensive, and the AHP system itself could not obtain economic competitiveness yet. For these reasons, there are only several commercial AHP units throughout the world yet, and the chance to utilize an AHP system properly at energetic and economic aspects is highly limited. Based on these background, this research deals with a low cost and high-performance AHP system applying the natural mesoporous material named Wakkanai Siliceous Shale (WSS) and its application. WSS is obtained from the north part of Hokkaido and mainly consists of silicon dioxide (SiO2).
In Chapter 1, researches and developments of AHP are reviewed including the general background and cost of commercialized units. Upon them, this chapter describes the motivation and target of this study.
In Chapter 2, the natural mesoporous material based composite adsorbent impregnated with lithium chloride (LiCl) is introduced. Equilibrium adsorption characteristics, so called, isotherms of the adsorbents are experimentally measured under the operating pressure and temperature of AHP. At the same time, it is confirmed that LiCl concentration preventing carryover is 20 wt.% for the case of WSS.
In Chapter 3, the measurement of mass transfer of water vapor on the coated composite adsorbent is provided. The composite material is prepared by mixing the submicron-scale WSS particles, LiCl solution and acrylic binder which does not disturb water vapor adsorption severely. The particles of adsorbent is able to be sprayed on the metal surface of the sample plate owing to its fine particle size. Samples which are coated by the adsorbent layer with the different thickness are used to separate interfacial mass transfer at the surface and internal mass transfer inside of the layer. The interfacial mass transfer characteristics are successfully yielded by the novel experimental method making the coated adsorbent layer as thin as possible and the Linear Driving Force (LDF) model.
In Chapter 4, heat and mass transfer coefficients of the WSS composite filled between the fins of the corrugated-type heat exchanger are measured. For the comparison, the same experiments applying the A-type silica gel are also conducted. The zero-dimensional simulation model based on these experimental estimation of coefficients calculates the cooling performance of AHP. As a result, the adsorber applying the WSS composite presents 6-17 % higher COP compared to the A-type silica gel, proving the competitiveness of the WSS composite.
In Chapter 5, the performance of a solar AHP applying a WSS composite is estimated, together with analysis on reduction of CO2 emission and economic advantages according to local electricity cost of various major regions. Four regions having distinct climate conditions are selected as targets in this chapter, namely, Hawaii, Dubai, Florida and Tokyo. As a result, Hawaii presents the shortest payback period of 6.6 years owing to the expansive electricity cost in it. Although CO2 reduction in Dubai is the highest, the payback period in Dubai is 15.6 years due to the low local electricity cost.
In Chapter 6, energy and exergy analysis through the experimental data using 1 kW-scale AHP unit are conducted. The cooling capacity with the regeneration temperature of 70℃ is about 36 % reduced than that of the case with the regeneration water of 80℃, meanwhile the exergy efficiency is approximately 20 % increased by lowering the chilled water temperature as 10℃.
In Chapter 7, the hybrid system combining CO2 compression and AHP systems are introduced as a future research, and the general conclusions of the research are provided.
It is valuable in this study that the heat and mass transfer coefficients of the composite natural adsorbent are estimated by the novel experimental methodology. These characteristics are essential information in designing the AHP system. Also the actual cooling performance of the AHP system which can produce cooling energy by using the low-level heat source below 80℃ is proved. Furthermore, application effect of the solar AHP system in four major regions are studied based on its annual performance, economic and environmental analysis. It is believed that these research works above contribute to the low-carbon society. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第14242号 |
| Degree Level: | 博士 |
| Degree Discipline: | 工学 |
| Examination Committee Members: | (主査) 教授 長野 克則, 特任教授 羽山 広文, 教授 濱田 靖弘, 教授 田部 豊, 准教授 葛 隆生 |
| Degree Affiliation: | 工学院（空間性能システム専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/79440 |
| Appears in Collections: | 学位論文 (Theses) > 博士 （工学）
課程博士 (Doctorate by way of Advanced Course) > 工学院(Graduate School of Engineering)
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