熱能輔助熱泵製冷供熱系統研究

Study of Thermal-Energy Assisted Heat Pump Cooling/Heating System

汪金華(Jin-Hua Wang)

指導教授 ： 黃秉鈞

國立臺灣大學/工學院/機械工程學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.01542

摘要

傳統的熱驅動式製冷系統，如噴射式、吸收式及吸附式等，在熱能不穩定時，為提供穩定的空調冷能，往往利用加裝加熱器之方式以彌補熱能的不足，因而造成能源的浪費與不便。
本研究提出的熱能輔助熱泵製冷供熱系統，係結合噴射式製冷技術及熱泵技術，利用熱泵空調系統之獨立運轉提供穩定的空調冷能，並在其他的熱能輔助下，以驅動噴射式製冷系統來提升熱泵空調系統運轉性能。其製作之原型機具有變頻的功能，可以供應熱水，如同市售的熱泵熱水器，也可以進行儲冰與融冰運轉以轉移尖離峰用電量。
應用於本研究的噴射式製冷技術採用無動件設計，不需要循環泵浦，配合自動控制設備可以穩定連續運轉。為避免臭氧層的破壞，噴射式製冷系統使用的工作流體為R365mfc，針對此工作流體研究噴射器的設計。結果顯示，只要設計符合R365mfc的噴射器，R365mfc可以取代傳統噴射式製冷系統的工作流體─R141b。
本研究的噴射式製冷系統需要運轉於較高的蒸發溫度(>8oC)，針對此特殊情形研究噴射器的設計。結果顯示，工作流體R365mfc搭配面積比10.33的噴射器，在產生器溫度89.7oC、冷凝溫度35.4oC及蒸發溫度19.4oC下，噴射式製冷系統的製冷能力為1.57kW，COPe為0.49，可以符合熱能輔助熱泵製冷供熱系統的應用。
熱能輔助熱泵製冷供熱系統以台灣的環境氣候作為測試基準，即室外溫度35oC、室內溫度25oC。依據壓縮機運轉頻率20到80Hz，噴射式可以降低熱泵空調系統的冷凝溫度12.6~7.3oC，提升空調製冷能力29.4%~17.1%，降低消耗功率28.6%~12.9%，提升空調運轉性能約81.2%~34.5%。
本項研究應用於較高室外溫度時，將會增加熱泵空調系統的冷凝溫度，使得與之熱交換的噴射式制冷系統的蒸發溫度提高，只要噴射器運轉於雙阻塞模態下，噴射式製冷系統的製冷能力會增加，可以更有效降低熱泵空調系統的冷凝溫度、提升空調運轉性能。經實驗測試，在室外溫度45oC、室內溫度25oC時，依據壓縮機運轉頻率20到80Hz，噴射式可以降低熱泵空調系統的冷凝溫度18.6~8.7oC，提升空調製冷能力41.1%~18.2%，降低消耗功率35.3%~12.4%，提升空調運轉性能約118.1%~34.9%。
總結本論文的研究結果，熱能輔助熱泵製冷供熱系統改善傳統的熱驅動式製冷系統缺失，配合以時間為控制依據的中央控制系統，分別進行空調、製熱水、儲冰及融冰運轉，可以滿足全天候的空調及熱水供應，具有相當的實用價值。

關鍵字

噴射器 ； 噴射式製冷系統 ； R365mfc ； 熱泵系統

並列摘要

The conventional heat power cooling system, such as ejector, absorption and adsorption, uses auxiliary heater to drive for providing steady cooling effect, while thermal energy is unstable. It is very unsuitable to consume a lot of energy. Therefore the thermal-energy assisted heat pump cooling/heating system (TACH) was developed in this study for improving the defects of conventional heat power cooling system.
TACH combines the ejector cooling system and the heat pump system together. The connection between those two sub-systems is at the “heat exchanger”, which serves as the evaporator for the ejector cooling system and as the condenser for the heat pump. It provides for stable air-condition with the heat pump system. To use another thermal energy, such as solar or waste heat, drives the ejector cooling system to reduce the heat pump condensing temperature and increase its COP for decreasing the compressor power input.
The prototype according the TACH has the inverter-type compressor. It could recover the rejected heat from heat pump to supply hot water which is the same as heat pump water heater. Beside, the heat pump uses of the off-peak electricity to produce ice storage and then releases the cold to do the air conditioning load during on-peak period. So, it can reduce the on-peak power load.
In this study, the ejector cooling system utilizes multi-function generator as a thermal pumping device to eliminate the mechanical circulating pump. The automatic controller is also used to obtain full-cycle continuous operation and constant evaporator temperature. To avoid damaging ozone layer, the present study uses R365mfc as the working fluid of ejector cooling system. This requires research of ejector design in order to get a high COPe. The experimental result shows that R365mfc can replace R141b, which has good performance for ejector cooling system, at no payoff of system performance as long as the ejector design is optimized.
In the TACH, the ejector cooling system needed to operate at higher evaporator temperature. The present study also investigates the design of ejector for this case, in order to obtain a good performance of ejector cooling system. The experimental result show that the ejector cooling system which used R365mfc as working fluid with ejector area ratio of 9.10 can be operated at generator temperature 89.7 oC, condenser temperature 35.4 oC and evaporator temperature 19.4 oC with cooling capacity up to 1.57kW and COPe up to 0.49. So, it is can be applied to the TACH.
The TACH was tested at outdoor temperature 35oC and indoor temperature 25oC which bases on Taiwan climate. The experimental results show that the ejector cooling system can reduce heat pump condensing temperature around 12.6 to 7.3oC, increasing cooling capacity is 29.4%~17.1%, decreasing power consumption is 28.6%~12.9% and increasing COPc is 81.2%~34.5% for the compressor operating frequency varied between 20 and 80Hz.
This study applied the higher outdoor temperature will increase the condensing temperature of heat pump. However the ejector cooling system can obtain more performance to decrease more condensing temperature when it operates at critical mode. At outdoor temperature 45oC and indoor temperature 25oC, the ejector cooling system can reduce heat pump condensing temperature around 18.6 to 8.7oC, increasing cooling capacity is 41.1%~18.2%, decreasing power consumption is 35.3%~12.4% and increasing COPc is 118.1%~34.9% for the compressor operating frequency varied between 20 and 80Hz.
The summary of this study is the TACH improving the defects of conventional heat power cooling system. To use the center control system of according timing process air-condition, recover the rejected heat from heat pump to supply hot water, ice storage and released the ice storage. It is value for air-condition and hot water supported all the day.

並列關鍵字

ejector ； ejector cooling system ； R365mfc ； heat pump

參考文獻

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