工學院: 機械工程學研究所指導教授: 孫珍理許菩引Shu, Pu-YinPu-YinShu2017-03-132018-06-282017-03-132018-06-282016http://ntur.lib.ntu.edu.tw//handle/246246/278274本研究利用氙弧燈模擬太陽光做為熱源，建立了一朗肯循環系統，探討操作壓力及工作流體組成對循環之理論輸出功率、真空管集熱器之熱傳效率及朗肯循環系統熱效率的影響，並利用熱阻分析探討真空管集熱器內的熱耗散量。所使用的工作流體種類有純水、乙醇/水系統及乙二醇/水系統三種，其中乙醇/水系統之質量分率為0.2、0.4、0.6，而乙二醇/水系統之質量分率則為0.1、0.2、0.3、0.4。 實驗結果顯示，純水之理論輸出功為最高，且其真空管集熱器熱傳效率亦為最高，因其相變化焓差相對於兩醇類混合系統較高，故工作流體吸熱量亦較高。而乙醇/水系統因其相變化焓差較小，沸點較低，使得加熱後工作流體的過熱度太高，造成真空管集熱器熱耗散太強，故理論輸出功與太陽能朗肯循環系統熱效率皆較低，因此該流體之表現為最差。而由於乙二醇/水系統在較高的操作壓力下皆沒有達到過熱狀態，且乙二醇/水系統之相變化焓差較高，故其理論輸出功亦比乙醇/水系統為高。欲得較高之系統輸出功率，應選用高相變化焓差之流體，且節流閥前後系統壓差應越大越好。 理論上來說，工作流體在降壓作功的過程中應維持在過熱的狀態，在滿足此條件下真空管集熱器出口過熱度不宜過高，因熱耗散與熱源輻照度隨工作流體溫度呈成長關係，故相較於乙醇/水系統，純水適用的熱源輻照度較高，而乙二醇/水系統因其飽和溫度高於純水且理論輸出功亦無純水高，故為三者中最不適合有機朗肯循環之工作流體。In this study, we use a xenon arc lamp as the artificial sunlight to construct the Rankine cycle system, and investigate the effect of the operating pressure and the working fluid on the theoretical power output, the heat transfer efficiency of the evacuated tube, and the thermal efficiency of the Rankine cycle. In addition, we employ the thermal resistance analysis to evaluate the heat dissipation of the evacuated tube. The system pressure varies from 200 kPa to 700 kPa, and three different types of working fluids are tested: pure water, ethanol/water, and ethylene glycol/water mixtures. The mass fraction of the ethanol in water are w = 0.2, 0.4 and 0.6. For ethylene glycol/water mixtures, the mass fraction are w = 0.1, 0.2, 0.3 and 0.4. The experimental results show that pure water yeilds the maximum theoretical power output and the highest heat transfer efficiency of the evacuated tube. This is because the lower latent heats and the lower boiling temperatures associated with the alcohol-water mixtures lead to higher superheat at the exit of the evacuated tube, which results in greater heat loss from the evacuated tube. Consequently, the ethanol/water of w = 0.6 mixture produces the lowest theoretical power output and the poorest thermal effciency. For the ethylene glycol/water mixtures at higher operating pressure, the superheated state is not reached due to their higher latent heat. So that the theoretical output power are higher than the ethanol/water mixtures. To obtain higher theoretical power output, fluid with larger latent heat and higher operating pressure are prefered. Theoretically, during the process of power producing, the working fluid should be maintained at superheated state, and the superheat at outlet of evacuated tube should not be too high. Due to the heat dissipation is as growing as the temperature of working fluid increasing, so that the ethanol/water system is suitable than pure water for lower irradiance, and ethylene glycol/water system is most not recommended for using as Rankine cycle working fluid. Because of its saturation temperature is higher than the pure water and the theoretical power output is the lowest among three working fluid type.3077575 bytesapplication/pdf論文公開時間: 2019/7/26論文使用權限: 同意有償授權(權利金給回饋學校)朗肯循環非共沸流體真空管威爾森參數熱阻分析氙弧燈rankine cyclenon-azeotropic fluidevacuated tubewilson parameterthermal resistance analysisxenon lightartificial lightthesis10.6342/NTU201600930http://ntur.lib.ntu.edu.tw/bitstream/246246/278274/1/ntu-105-R03522314-1.pdf