- 學位論文
噴射式太陽能輔助熱泵製冷供熱系統研究
Study of Solar-Assisted Ejector Cooling/Heating System
摘要
傳統的熱驅動式製冷系統，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。 本研究提出的太陽能輔助熱泵製冷供熱系統，係結合太陽能集熱系統、無動件噴射式製冷系統與熱泵空調系統，利用熱泵空調系統獨立運轉提供穩定的空調冷能，並在太陽熱能的輔助下，驅動噴射式製冷系統來冷卻熱泵空調系統冷凝溫度，提升熱泵空調系統的運轉性能，以節省能源。 本研究先進行太陽能輔助熱泵製冷供熱系統之系統設計與經濟效益分析，並以4 m × 4 m的辦公室為例進行個案研究，其冷房負載為3.5 kW (1 RT)，每天的製冷時間為10 hr (8:00-18:00)，一天總冷房負載35 kW (10 RT)。研究結果顯示，對SACH-1系統(串聯方式)，為了減少50%的熱泵空調系統耗能，假如噴射式製冷系統運轉性能COPe=0.4提升至0.6，在台北地區所需太陽能集熱器集熱面積由約58 m2減少至約40 m2(減少31%)，在台南地區所需太陽能集熱器集熱面積由約46 m2減少至約31 m2(減少33%)。換句話說，噴射式製冷系統運轉性能提升可以減少太陽能集熱器的成本。對SACH-2系統(並聯方式)，為了減少50%的熱泵空調系統耗能，噴射式製冷系統性能COPe=0.2時，在台北需要太陽能集熱器集熱面積40 m2，而在台南則需要31 m2。熱水供應方面，SACH系統在冬天，每天產生水溫升40oC的熱水量供應時，在台北和台南分別需要太陽能集熱器集熱面積約36 m2和30 m2，每天熱水供應量在4月約1,000 L，而在1月約500 L，足夠提供20-40人使用。經濟分析的結果，在SACH-1與SACH-2案例，噴射式製冷系統設計製冷量分別大於4 RT與3 RT時，其回本時間不到3年。這項結論對於未來發展成商業產品是很重要的參考值。 本研究改良了汪[55]系統，重新設計無動件噴射式製冷系統自動切換控制進行電熱能輔助測試，噴射式製冷系統最佳冷媒充量為21.24 kg、室外35oC、室內25oC及熱負載3.52 kW時，節省電能為45%，與汪[55]之TACH系統性能比較，更換傳熱面積較大之換熱器使其節省電能提升1.57倍。將其連結太陽能集熱系統進行測試，並設計一套中央控制系統使其能連續運轉，實測結果顯示，利用太陽能集熱系統驅動噴射式製冷系統製冷以降低熱泵空調系統冷凝溫度，可使熱泵空調系統節省電能56%。 為了應用於高溫環境，需採用SACH-1(串聯方式)之設計，在高溫環境導致冷凝溫度升高時，可以將噴射式製冷系統蒸發溫度同時提高，以維持噴射器性能。模擬在高溫環境下，利用已知實驗數據反推，當使用不同方式進行噴射器冷凝器散熱時，噴射式製冷系統所能提高蒸發溫度的極限。在高溫環境45-50oC，假設噴射式製冷性能為0.4時，根據Reversed Rankine cycle分析期望之省電量，不管是使用水冷或氣冷方式冷卻噴射式製冷系統的冷凝器，則可藉由噴射式製冷系統的輔助使熱泵空調系統節省電能15%以上。 總結本論文的研究結果，太陽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，解決隨天氣變化太陽能操作的自動控制問題，並成功與太陽熱能連結，對於商業化及應用上有顯著的貢獻。
並列摘要
The conventional heat power cooling system uses auxiliary heater to provide steady cooling effect, while thermal energy is unstable. It is very unsuitable to consume a lot of energy; therefore, solar-assisted ejector cooling/heating system (SACH-1) was developed in this study for improving the defects of conventional heat power cooling system. SACH combines solar heating system and ejector cooling system with thermal pumping together which provides steady cooling energy with the heat pump system. While using solar energy, the ejector cooling system can reduce the condensing temperature of heat pump and also increase its COP for decreasing the compressor power input. This study first performs design of the system and analysis of economical benefit and takes an office with an overall size, 4 m × 4 m for a project research. Its cooling load is 3.5kW (1 RT) with a cooling period, 10 hours (8 o’clock am. to 6 o’clock pm.), so an overall cooling load in a day is 35kW (10 RT). First, in SACH-1, if COP of ejector cooling system can increase from 0.4 to 0.6, for reducing 50% power consumption of heat pump system, the required area of solar heating system can reduce from 58 m2 to 40 m2 (reducing 31%) in Taipei region and the required area of solar heating system can reduce from 46 m2 to 31 m2 (reducing 33%) in Tainan region. That is to say, increasing of COP in ejector cooling system can reduce the cost of solar heating system. In SACH-2 with COP=0.2 of ejector cooling system, to reduce 50% power consumption of heat pump system, the required area of solar heating system is 40 m2 in Taipei region and the required area of solar heating system is 31 m2 in Tainan region. Secondly, to generate hot water with a difference temperature, 40oC on SACH system in winter days, the required area of solar heating system is 36 m2 in Taipei region and the required area of solar heating system is 30 m2 in Tainan region. The amount of hot water supply in April is 1000 liter and in January is 500 liter which enough provides the usage of 20 to 40 people. Finally, in SACH-1 and SACH-2, if cooling capacities of ejector cooling system are more than 4RT and 3RT respectively, the period of cost recovery is less than 3 years. This conclusion is a very important reference for commercial products in future development. This study improves Wang’s [55] system, redesigns ejector cooling system with thermal pumping, and tests the performance with thermal energy assisted using automatic control. The ejector cooling has an optimum filling capacity of refrigeration is 21.24 kg. With the following operating conditions, out-door temperature at 35oC, in-door temperature at 25oC, and heat loading at 3.52kW, the power consumption reduces to 45%. Compared with Wang’s [55] TACH, replacing an intercooler with a bigger heat-exchange area promotes energy-saving to 1.57%. Combining with solar heating system and designing a central control system for continuous operation, the result shows that by driving from solar energy, the condensing temperature of heat pump system can reduce, which saves power consumption to 56%. Utilizing SACH-1 (series configuration), even if environment with high temperature causes condensing temperature rising, evaporating temperature of ejector cooling system can increase at the same time, which maintains the performance of ejector. When using different types to cool down condenser in ejector cooling system, the limit of increasing evaporating temperatures in ejector cooling system are inferred by experimental data in a simulation of high-temperature environment. According to reversed Rankine cycle, supposed COP of ejector cooling system at 0.4 and high-temperature environment at 45oC to 50oC, SACH can save energy more than 15% whether using water-cooling or air-cooling. The summary of this study is the SACH improving the defects of conventional heat power cooling system, solving the problem of automatic-operating via weather variations, successfully combining with solar energy. It produces a marked effect on commerce and application.