本文選題：自復(fù)疊熱泵系統(tǒng) + 數(shù)值模擬�。� 參考：《青島大學(xué)》2017年碩士論文

【摘要】：本文主要研究自復(fù)疊熱泵系統(tǒng)結(jié)構(gòu)改進(jìn)。研究內(nèi)容包括:自復(fù)疊熱泵系統(tǒng)(火用)分析及循環(huán)熱力計(jì)算;蒸發(fā)管數(shù)值模擬;冷凝器改進(jìn)改進(jìn);自復(fù)疊熱泵系統(tǒng)的實(shí)驗(yàn)研究。首先對實(shí)驗(yàn)系統(tǒng)做了(火用)分析及循環(huán)計(jì)算,計(jì)算結(jié)果表明,對于自復(fù)疊熱泵系統(tǒng)而言,其(火用)損失主要集中在壓縮機(jī)、節(jié)流機(jī)構(gòu)、蒸發(fā)器及冷凝器上�？紤]到對壓縮機(jī)降低(火用)損失的困難,提出使用電子膨脹閥代替熱力膨脹閥及增加回?zé)崞饕蕴岣吖?jié)流機(jī)構(gòu)的(火用)效率的節(jié)流機(jī)構(gòu)改進(jìn)方案。其次,對單根U型管內(nèi)的蒸發(fā)問題進(jìn)行了模擬。根據(jù)實(shí)際蒸發(fā)器內(nèi)可能發(fā)生的問題,對純R23制冷劑的管內(nèi)蒸發(fā)及含有質(zhì)量分?jǐn)?shù)為8%R134a的R23混合制冷劑進(jìn)行了數(shù)值模擬。模擬結(jié)果表明:純R23制冷劑在管內(nèi)蒸發(fā)時(shí),管內(nèi)的流型發(fā)展依次出現(xiàn)了泡狀流、彈狀流及環(huán)狀流。對于含有8%R134a的R23混合制冷劑的模擬結(jié)果發(fā)現(xiàn),其管內(nèi)的蒸發(fā)速度明顯低于純R23制冷劑的管內(nèi)蒸發(fā)速度。產(chǎn)生這種現(xiàn)象的原因是:混合制冷劑比純制冷劑易于達(dá)到核態(tài)沸騰完全抑制狀態(tài),分界面上易揮發(fā)組分的蒸發(fā),使得分界面飽和溫度上升,減少了給汽泡生長提供熱量的有效溫差,同時(shí)混合物的傳質(zhì)阻力減緩了汽泡的生長率,削弱了核態(tài)沸騰,導(dǎo)致了混合物的抑制狀態(tài)更容易達(dá)到,造成傳熱惡化。決定使用精餾器來代替汽液分離器以改善蒸發(fā)器的換熱效果。根據(jù)非共沸混合工質(zhì)在換熱時(shí)其換熱系數(shù)要低于純組分工質(zhì)的換熱效果這一現(xiàn)象,本文提出在冷凝器上增加一個(gè)分離器來提高冷凝器的換熱效果并使混合制冷劑充分分離的實(shí)驗(yàn)方案,在此實(shí)驗(yàn)方案的基礎(chǔ)上,搭建了實(shí)驗(yàn)臺。最后,對負(fù)載及空載時(shí)有無分離器及不同制冷劑充注比例時(shí)不同測量點(diǎn)的溫度進(jìn)行了實(shí)驗(yàn)測量,并對自復(fù)疊系統(tǒng)與兩級壓縮、噴氣增焓系統(tǒng)進(jìn)行了對比并觀察了冷凝器內(nèi)的流型變化。得到主要結(jié)論:經(jīng)過分離后的非共沸工質(zhì)所具有的最大傳熱溫差及傳熱窄點(diǎn)現(xiàn)象得到了有效抑制,影響其換熱的傳質(zhì)熱阻也大大減小,同時(shí)經(jīng)過分離器分離后的制冷劑與冷凝器的換熱重新回到了換熱開始階段,制冷劑蒸汽能夠與管壁直接接觸提高了換熱系數(shù),并結(jié)合實(shí)際觀測到的流型進(jìn)行了驗(yàn)證。通過自復(fù)疊系統(tǒng)與其它幾種系統(tǒng)的比較發(fā)現(xiàn),自復(fù)疊系統(tǒng)在制冷量、功率、制冷系數(shù)等方面都優(yōu)于其它幾種系統(tǒng)。
[Abstract]:In this paper, the structure improvement of self-stack heat pump system is studied. The research contents include: exergy analysis and cycle thermodynamic calculation of self-stack heat pump system; numerical simulation of evaporator tube; improvement of condenser; experimental study of self-stack heat pump system. The exergy analysis and cyclic calculation of the experimental system show that the exergy loss is mainly concentrated on compressor, throttle mechanism, evaporator and condenser for the self-stack heat pump system. Considering the difficulty of reducing exergy loss of compressor, a scheme of improving throttling mechanism by using electronic expansion valve instead of thermal expansion valve and adding regenerator to improve the exergy efficiency of throttle mechanism is put forward. Secondly, the evaporation problem in a single U-tube is simulated. According to the possible problems in the actual evaporator, the evaporation of pure R23 refrigerant and the mixture of R23 refrigerant with mass fraction of 8%R134a are numerically simulated. The simulation results show that when pure R23 refrigerant evaporates in the tube, bubbly flow, slug flow and annular flow occur in turn. The simulation results of R23 refrigerant containing 8%R134a show that the evaporation rate in the tube is obviously lower than that in the pure R23 refrigerant. The reason for this phenomenon is that the mixed refrigerant is easier than the pure refrigerant to achieve the completely suppressed state of nucleate boiling, and the evaporation of volatile components on the boundary surface increases the saturation temperature of the interface. The effective temperature difference of heat supply for bubble growth is reduced, and the mass transfer resistance of the mixture slows down the growth rate of the bubble, weakens the nucleate boiling, and makes the inhibition state of the mixture easier to achieve, resulting in the deterioration of heat transfer. It was decided to replace the steam-liquid separator with a rectifier to improve the heat transfer efficiency of the evaporator. According to the phenomenon that the heat transfer coefficient of non-azeotropic working fluids is lower than that of pure working fluids, In this paper, an experimental scheme of adding a separator to the condenser to improve the heat transfer effect of the condenser and make the mixture refrigerant fully separate is proposed. On the basis of the experimental scheme, an experimental bench is built. Finally, the temperature of different measuring points under load and no-load with or without separators and different refrigerant filling ratios are measured experimentally, and the self-stacking system and two-stage compression are also studied. The jet enthalpy system was compared and the flow patterns in the condenser were observed. The main conclusions are as follows: the maximum heat transfer temperature difference and the heat transfer narrow point phenomenon of the separated non-azeotropic working fluid have been effectively restrained, and the heat transfer resistance affecting the heat transfer of the non-azeotropic working fluid has been greatly reduced. At the same time, the heat transfer of refrigerant and condenser after separating from the separator has returned to the initial stage of heat transfer, and the heat transfer coefficient of refrigerant steam can be increased by direct contact with the tube wall, which is verified by the actual observed flow pattern. It is found that the self-stacking system is superior to other systems in refrigeration capacity, power, refrigeration coefficient and so on.
【學(xué)位授予單位】：青島大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU83

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本文編號：1985419