跨臨界二氧化碳熱泵系統之開發與研究

The Development and Investigation of the Transcritical Carbon Dioxide Heat Pump

蔡宗澔(Zong-Hao Cai)

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(2014年)

https://doi.org/10.6342/NTU.2014.11116

摘要

高緯度地區的平均氣溫偏低，全年氣溫平均在零下度者比比皆是，這些地區若是使用傳統的氟氯烷熱泵會造成系统性能低下的問題，或是完全無法使用。為此，市場上迫切需要能在如此低溫環境下工作的熱泵，因此使得CO2熱泵的開發逐漸受到重視，吸引了許多研究者與企業爭相投入開發相關產品。傳統熱泵的加熱是透過顯熱熱傳過程進行流體的加熱，在傳統的（次臨界）的熱泵循環，低臨界溫度是一個缺點，因為它限制系統操作溫度的範圍，高於臨界溫度時熱量沒有辦法被傳遞。此外，在靠近且低於臨界溫度的範圍時，汽化的焓值會減少。這會使加熱功率降低並且會導致系統性能下降。
但在跨臨界熱泵的使用上，加熱段的壓力(氣體冷卻器壓力)會大於超臨界壓力，熱傳遞的溫度不再受限於臨界溫度。可輕易的將水加熱到90oC以上，高溫的水在儲存上可以減少儲水槽的空間，這對與工業上製程的使用或是一般家庭的使用上都是非常便利的，本研究針對跨臨界CO2熱泵進行設計與開發，希望藉由CO2熱泵的使用來改善人們對石化燃料的依賴，使用對環境更友善的方式進行加熱。

關鍵字

二氧化碳 ； 跨臨界循環 ； 熱泵 ； 壓縮系統 ； 性能

並列摘要

Areas with average temperature lower than 0℃ can be found almost everywhere in high latitudes. Owing to the low temperature, traditional Freon heat pumps will be at low efficiency or even not work in high latitudes. Therefore, heat pumps which can survive the extreme situation are desirable on the market. This is the reason why CO2 heat pumps are becoming more popular than the old days. And they also attract many researchers and companies to invest in them. Traditional heat pumps heat the fluid through sensible heat transfer process. And their critical temperature is lower than other cycles, which is a drawback. The low critical temperature limits the temperature range of the operation. If the temperature is higher than the critical temperature, the heat can not be transferred. If the temperature is close to or lower than the critical temperature, the enthalpy of vaporization will reduce. And this will lower the efficiency of the heating process and of course the system.
However, when it comes to supercritical cycles, things change. The pressure of the heating process (also the pressure of the gas cooler) is higher than supercritical pressure, which leads to the result that the temperature of heat transfer is not limited by the critical temperature anymore. We can easily heat water to higher than 90oC and reduce the need of water tank vacancy. And this is very beneficial to households and factories. This thesis is mainly about the design and the development of transcritical CO2 heat pumps. It is expected that CO2 heat pumps will reduce the dependency of fossil fuels for human beings and also people can treat our Mother Earth more friendly.

並列關鍵字

Carbon dioxide ； Transcritical cycle ； Heat pump ； Compression system ； Performance

參考文獻

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