本文關鍵詞： 過冷 單級蒸氣壓縮式制冷循環(huán) 性能系數(shù) 數(shù)值計算 實驗研究　出處：《華北電力大學》2014年碩士論文　論文類型：學位論文

【摘要】：隨著城鎮(zhèn)化進程加速和居民生活水平的提高，空調(diào)系統(tǒng)的能源消耗占我國總能耗的比重也日益增加。提高空調(diào)系統(tǒng)的能效水平對于節(jié)能減排和實現(xiàn)可持續(xù)發(fā)展具有重要意義。液體過冷總是可以提高空調(diào)系統(tǒng)的性能系數(shù)，已經(jīng)被廣泛采用。因此本文結合空調(diào)系統(tǒng)的工質(zhì)替代和經(jīng)常部分負荷運行的特點，采用理論分析和實驗研究相結合的方法，研究如何運用過冷提高空調(diào)系統(tǒng)的循環(huán)性能。 以單級蒸氣壓縮式制冷循環(huán)為對象，根據(jù)GB/T18430.2-2008標準，采用EES軟件編程計算。對于R134a工質(zhì)，隨著冷凝溫度、高壓壓力的升高以及蒸發(fā)溫度的降低，單位過冷度引起的系統(tǒng)性能系數(shù)COP的增大值減小。而對于常用的制冷劑，雖然過冷總是提高循環(huán)的性能，但單位過冷度對不同制冷劑COP的提高不一致，，如對R218和R125增幅較大，而對R717和R407C提高較小。 在R134a單級蒸氣壓縮式制冷實驗臺進行了實驗，驗證在過冷條件下，冷凝溫度和蒸發(fā)溫度的變化對循環(huán)性能的影響。實驗和理論分析都表明：蒸發(fā)溫度變化所產(chǎn)生的單位過冷度的COP值變化要大于冷凝溫度。 對于單級蒸氣壓縮式制冷循環(huán)，合理設計冷凝器，可獲得過冷。通過建模和計算分析，對于R134a工質(zhì)，每增加1℃過冷度，冷凝器的換熱面積需增加6.5%。所以權衡系統(tǒng)的性能和經(jīng)濟性，過冷度需控制在一定的合理范圍內(nèi)。 采用獨立機械式過冷循環(huán)、噴射式過冷循環(huán)、回熱過冷循環(huán)和蓄冷式過冷循環(huán)也可以達到過冷效果。如對于獨立機械式過冷循環(huán)，5℃的過冷使COP提高約16%，并使最佳中間溫度明顯降低。噴射式過冷循環(huán)也提高了系統(tǒng)的制冷效果，但是當過冷度達到某一溫度時，循環(huán)的性能系數(shù)存在一個最大值�；責徇^冷與制冷劑的熱物理性質(zhì)有關，對于回熱過冷有利的制冷劑，回熱過冷度越大，單位質(zhì)量制冷量和COP增加百分比越大。對于蓄冷式過冷循環(huán)，冷量增量和增加率都隨過冷度的增加而增加。
[Abstract]:With the acceleration of urbanization and the improvement of living standards. The energy consumption of air conditioning system is increasing in our country. Improving the energy efficiency level of air conditioning system is very important for energy saving and sustainable development. Liquid undercooling can always improve air conditioning system. The performance coefficient of. It has been widely used. Therefore, this paper combines the characteristics of refrigerant substitution and regular partial load operation of air conditioning system, and adopts the method of combining theoretical analysis with experimental research. How to improve the circulation performance of air conditioning system by undercooling is studied. The single stage vapor compression refrigeration cycle is taken as the object. According to GB/T18430.2-2008 standard, the calculation is carried out by EES software. For R134a refrigerant, the condensing temperature is increased. With the increase of high pressure and the decrease of evaporation temperature, the increase of system performance coefficient (COP) caused by unit undercooling decreases, while for common refrigerants, the performance of cycle is always improved by undercooling. However, the increase of unit undercooling degree is not consistent with that of different refrigerants, such as R218 and R125, but slightly for R717 and R407C. The experiment was carried out on the R134a single stage vapor compression refrigeration test rig, and it was verified under the condition of supercooling. Experimental and theoretical analysis show that the COP value of unit undercooling caused by the change of evaporation temperature is greater than that of condensation temperature. For the single stage steam compression refrigeration cycle, the supercooling can be obtained by reasonably designing the condenser. Through modeling and calculation, the supercooling of R134a working fluid is increased by 1 鈩

本文編號：1465344