【摘要】：滿液式蒸發(fā)器具有比干式蒸發(fā)器更好的換熱性能,因此被大中型工業(yè)制冷系統(tǒng)所采用。針對(duì)傳統(tǒng)的滿液式制冷系統(tǒng)中存在循環(huán)泵大量電能消耗的問(wèn)題,有人提出了滿液式噴射泵制冷系統(tǒng)。在該系統(tǒng)中使用氣液兩相噴射器來(lái)取代循環(huán)泵的使用。并且氣液兩相噴射器的性能直接影響滿液式蒸發(fā)器的浸液率和蒸發(fā)換熱性能,因此研究和優(yōu)化氣液兩相噴射器具有重要意義,本文以數(shù)值計(jì)算為主要方法對(duì)氣液兩相噴射器進(jìn)行了分析研究,主要內(nèi)容如下： (1)通過(guò)研究調(diào)查,簡(jiǎn)要分析了滿液式噴射泵制冷系統(tǒng)相對(duì)傳統(tǒng)的滿液式制冷系統(tǒng)所能產(chǎn)生的節(jié)能效益和節(jié)能意義。 (2)假設(shè)拉瓦爾噴嘴內(nèi)為完全平衡兩相流,提出通過(guò)兩相流完全平衡的聲速方程對(duì)氣液兩相噴射器拉瓦爾噴嘴的設(shè)計(jì)提出改進(jìn)方法,并且結(jié)合經(jīng)驗(yàn)方法,完成了氣液兩相噴射器的整體結(jié)構(gòu)的基本設(shè)計(jì)。通過(guò)對(duì)比模擬結(jié)果得到的聲速值與拉瓦爾噴嘴設(shè)計(jì)聲速值,得到偏差在14.94%-24.42%,相對(duì)單相流聲速計(jì)算方法,提出的拉瓦爾噴嘴改進(jìn)方法已經(jīng)大幅接近實(shí)際聲速情況。 (3)通過(guò)加入R22的熱力學(xué)參數(shù),結(jié)合氣液兩相噴射器的設(shè)計(jì)方法,得出本文氣液兩相噴射器的基本物理模型。通過(guò)CFD方法分析了以R22為工作介質(zhì)的氣液兩相噴射器的內(nèi)部流動(dòng),通過(guò)對(duì)比模擬結(jié)果中兩相流的主要參數(shù)空隙率值與經(jīng)驗(yàn)值,得到兩者偏差在11.65%以內(nèi),變化趨勢(shì)的一致性,驗(yàn)證了兩相流計(jì)算模型的準(zhǔn)確性。 (4)分析了R22為工作介質(zhì)的氣液兩相噴射器內(nèi)部的壓力、溫度、密度和速度等參數(shù)的基本情況,分析兩相之間的相變傳質(zhì)情況,捕捉到了該氣液兩相噴射器內(nèi)部由于相變引起的噴嘴出口激波和擴(kuò)散室入口凝結(jié)激波,并對(duì)其基本特性進(jìn)行了分析和經(jīng)驗(yàn)驗(yàn)證。 (5)得到了多組結(jié)構(gòu)變化、工況變動(dòng)時(shí)的氣液兩相噴射器的模擬結(jié)果,得到的氣液兩相噴射器的噴射系數(shù)范圍為0.16～1.1,模擬結(jié)果表明噴射系數(shù)受凝結(jié)激波的影響顯著。調(diào)整混合室長(zhǎng)徑比可以改變凝結(jié)激波的發(fā)生位置,在保證凝結(jié)激波存在的前提下,凝結(jié)激波發(fā)生位置到混合室出口的距離影響噴射系數(shù)的大小,在一定范圍內(nèi),越接近混合室出口,噴射系數(shù)值越大,但到一定程度之后,噴射系數(shù)受凝結(jié)激波發(fā)生位置的影響變?nèi)�。隨著氣液兩相噴射器的背壓提高,凝結(jié)激波消失,噴射系數(shù)急劇減小。
[Abstract]:Full-liquid evaporator has better heat transfer performance than dry evaporator, so it is used in large and medium industrial refrigeration system. Aiming at the problem of high power consumption of circulating pump in traditional full liquid refrigeration system, a full liquid jet pump refrigeration system is proposed. A gas-liquid two-phase injector is used in the system to replace the circulating pump. And the performance of gas-liquid two-phase ejector directly affects the leaching rate and evaporative heat transfer performance of the full-liquid evaporator, so it is of great significance to study and optimize the gas-liquid two-phase ejector. In this paper, the gas-liquid two-phase ejector is analyzed and studied by numerical calculation. The main contents are as follows: (1) through investigation, The energy saving benefits and significance of the full liquid jet pump refrigeration system compared with the traditional one are briefly analyzed. (2) assuming that the Laval nozzle is a completely equilibrium two-phase flow, an improved design method of the gas-liquid two-phase injector Laval nozzle is proposed by the sound velocity equation of the two-phase flow, and the empirical method is combined. The basic design of the whole structure of the gas-liquid two-phase ejector is completed. By comparing the sound velocity values obtained from the simulation results with the designed sound velocities of the Laval nozzles, the method of calculating the sound velocities of the single phase flow with a deviation of 14.94 to 24.422 is obtained. The improved method of Laval nozzle is close to the actual sound speed. (3) by adding the thermodynamic parameters of R22 and combining the design method of gas-liquid two-phase ejector, the basic physical model of gas-liquid two-phase injector is obtained. The internal flow of gas-liquid two-phase injector with R22 as working medium is analyzed by CFD method. By comparing the main parameters of the two-phase flow in the simulation results with the experimental results, the deviation between them is within 11.65%. The accuracy of the two-phase flow calculation model is verified by the consistency of the variation trend. (4) the internal pressure, temperature, density and velocity of the gas-liquid two-phase injector with R22 as the working medium are analyzed, and the phase transition mass transfer between the two phases is analyzed. The shock waves at the nozzle exit caused by phase transformation and the condensation shock at the inlet of the diffusion chamber are captured in the gas-liquid two-phase ejector. The basic characteristics of the shock wave are analyzed and verified by experience. (5) the simulation results of gas-liquid two-phase ejector with different structure and working conditions are obtained. The jet coefficient of gas-liquid two-phase injector is 0.16 ~ 1.1. The simulation results show that the jet coefficient is significantly affected by the condensation shock wave. Adjusting the ratio of length to diameter of mixing chamber can change the location of condensate shock wave. Under the premise of ensuring the existence of condensation shock wave, the distance from the location of condensation shock wave to the outlet of mixing chamber affects the size of jet coefficient, and within a certain range, The closer it is to the outlet of the mixing chamber, the greater the jet coefficient is, but after a certain degree, the effect of the condensation shock on the jet coefficient becomes weaker. With the increase of the back pressure of the gas-liquid two-phase injector, the condensation shock wave disappears and the ejection coefficient decreases sharply.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB657

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