結合低溫再生週期式全熱交換器之微電空調系統

Low-carbon Desiccant Cooling System with Combination of Low-temperature Regenerative Periodic Total Heat Exchanger

楊承閔(Cheng-Min Yang)

指導教授 ： 陳希立

國立臺灣大學/工學院/機械工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01101

摘要

近年來，室內空氣品質逐漸受到大家的重視，而為了維持良好的室內空氣品質，勢必要引進新鮮空氣，但引進室外空氣會造成空調設備的負荷提升，所以使用全熱交換器回收室內較低溫低濕空氣的顯熱與潛熱，可降低空調機的負荷。本研究使用吸附填充床作為全熱交換器的本體以吸附空氣中的水分並回收室內的冷能，並以風扇週期式的運轉來取代轉輪式全熱交換器。傳統的轉輪除濕系統使用高溫低濕的氣體對填充床進行再生，以達到較好的吸附除濕效果，然而一般的居住環境對濕度的要求並非如此地高，因此本研究使用低溫再生式的全熱交換器來處理引進的外氣，如此將能節省相當多的能源，並結合自來水輻射冷排與傳統空調機構成一低碳的微電空調系統。
本研究的第一部分探討低溫再生空氣對全熱交換器性能的影響，並進行吸附材料實驗與週期運轉測試。在25℃的再生條件下，氧化鋁填充床有較好的吸附與脫附能力，所以適合低溫再生條件下的全熱交換器使用。在週期運轉方面，顯熱有效度與潛熱有效度均隨週期運轉時間的縮短而有所提升，當運轉週期為兩分鐘時，全熱交換器有最好的顯熱、潛熱及全熱有效度，分別為84.2%、63.8%及70.9%。
第二部分探討自來水輻射冷排在不同入水溫度下的性能，並由實驗量測的數據進行熱傳分析進而求得冷排系統的製冷能力。當入水溫度較低時，管排有較好的製冷能力，但可能發生結露的現象。此外，將溫度約22℃的自來水直接通入管排，系統單位面積的冷卻能力可達65.0W/m2，其中對流熱傳率與輻射熱傳率分別為30.6 W/m2與34.4 W/m2。
最後，探討本微電空調系統的元件與運轉模式，並將此系統安裝於台北自來水園區的辦公室進行實際的運轉測試。根據測試的結果，與直接使用空調機調節溫濕度相比，若先行使用自來水輻射冷排對室內預冷，則可使全載運轉狀態下的空調機節省三分之二的運轉時間但達到同樣的室內環境條件。另外，與直接引進未處理的室外空氣做比較，使用微電空調系統來處理引進的空氣，可使空調機節省67.4%的耗能。本文最後則提出一結合雙效型熱泵與自來水冷排的微電空調系統，以取代傳統耗能的空調機。

關鍵字

週期式全熱交換器 ； 低溫再生 ； 填充床 ； 輻射冷排 ； 微電空調系統

並列摘要

Nowadays, indoor air quality has become a critical issue in the air-conditioning industry. To maintain a healthy indoor environment, it is inevitable to ventilate with outdoor air. Nevertheless, this ventilation causes dramatic energy loss. One solution to this problem is to install a total heat exchanger. In contrast to the conventional rotary-type total heat exchanger, this research employs the periodic flow to fixed desiccant wheels. Moreover, to maintain solid adsorptive effect, traditional desiccant dehumidifier uses high temperature and low humidity gas to regenerate the desiccant wheel. The request for environmental humidity control of the general residential space is , however, not so rigorous. As a result, the total heat exchanger in this research adopts the lower regeneration condition to fulfill the requirement for comfortable environment, which could save substantial energy since the additional regeneration heat source would not be needed. Finally, this research aims at investigating the practical performance and the energy conservation of the low-carbon desiccant cooling system.
The first part of this research investigates the performance of low-temperature regenerative periodic total heat exchanger based on the experimental method. The experiments are divided into two parts, one are material tests and the other are periodic operation tests. According to the result of the fundamental material tests, activated alumina packed bed has great capacities for both the adsorption and desorption as the temperature of the regeneration air is 25℃, which shows that activated alumina packed bed is more applicable to the total heat exchanger under the low-temperature regeneration condition. In addition, the result of the periodic operation of the total heat exchanger displays that the sensible heat effectiveness and latent heat effectiveness of the total heat exchanger increase as the time of operating period is abridged. At a operating period of 2 minutes, the total heat exchanger has the highest sensible, latent, and total heat effectiveness, which are 84.2%, 63.8%, and 70.9% respectively.
The second part of the research investigates the performance of the radiant ceiling cooling piping with different inlet water temperatures. The theoretical model is established to determine the cooling capacity of the system based on the experimental data. The results indicate that the cooling capacity of the cooling piping increases as the decreasing of the inlet water temperature. In addition, as the system operates with the 22℃ tap water, the cooling output is about 65.0W/m2, and the natural convection and radiation heat flux are 30.6 W/m2 and 34.4 W/m2 respectively.
In the last part of this research, the components and the operating mode of the low-carbon desiccant cooling system are depicted in detail. Furthermore, the actual performance of the system are investigated in an office room located at Taipei Water Department, and the result indicates that the usage of the radiant ceiling cooling piping for precooling the indoor environment enables the traditional air conditioner to reduce two-third of the original operating time. Besides, the test of the whole system is conducted in the same office, and it is observed that using this system to handle the incoming air could save up to 67.4% of the energy consumption compared to the case that the untreated fresh air is directly introduced. Finally, a design of an ameliorative low-carbon desiccant cooling system without using a traditional air conditioner, which is composed of a heat pump, radiant ceiling cooling piping, and a desiccant dehumidifier, is proposed.

並列關鍵字

Periodic total heat exchanger ； Low-temperature regenerative ； Packed bed ； Radiant ceiling cooling piping ； Low-carbon desiccant cooling system

參考文獻

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