多支管分液聯(lián)箱結(jié)構(gòu)優(yōu)化研究
發(fā)布時間：2018-07-23 16:57
【摘要】：本文采用數(shù)值模擬的方法,利用Fluent中的VOF模型,通過研究工質(zhì)為R134a的多支管分液聯(lián)箱氣液分離流動性能,對多支管分液聯(lián)箱進行了結(jié)構(gòu)優(yōu)化研究。多支管分液聯(lián)箱是分液冷凝器實現(xiàn)高效傳熱的關(guān)鍵部件,其主要作用是在換熱器各管程間實現(xiàn)氣液分離和排出冷凝液體,其工作原理是利用氣液兩相密度差,使得液相在多孔隔板上沉積,通過分布于多孔隔板上的各分液孔將液相排出進入下一管程,同時在隔板上部形成阻汽液膜,使氣相由出口支管排出進入到下游換熱管中,形成高干度傳熱,提高分液冷凝器的整體換熱性能。分液聯(lián)箱作為其中的關(guān)鍵部件,既要實現(xiàn)有效排液,又要實現(xiàn)有效阻汽作用,兩者都需要通過結(jié)構(gòu)設(shè)計自動實現(xiàn)。本文研究選定典型的換熱器工況,首先研究了實驗聯(lián)箱結(jié)構(gòu)下多支管分液聯(lián)箱內(nèi)部的氣液分離流動特征,對兩相工質(zhì)的分布特點、聯(lián)箱出口支管干度的分布特點、聯(lián)箱內(nèi)的壓力分布和波動特點以及聯(lián)箱出口支管和分液孔的流量分布均勻性進行了分析；然后研究了分液孔孔徑對分液聯(lián)箱各性能參數(shù)的影響,最后研究采用聯(lián)箱壁面開槽結(jié)構(gòu)時,槽深對分液聯(lián)箱各性能參數(shù)的影響。模擬結(jié)果表明：孔徑主要影響聯(lián)箱的排液流動,壁面開槽主要影響聯(lián)箱底部液膜的沉積。排液流動隨孔徑的增大而增強,壁面開槽能夠顯著增加聯(lián)箱底部液膜的沉積。在給定工況下,孔徑和槽深的變化對聯(lián)箱內(nèi)的壓力分布基本沒有影響。在給定工況下,出口支管的氣相流量分配均勻性不會因孔徑的變化發(fā)生明顯改變,而液相流量分配的均勻性則會隨著孔徑的增大而變好,當孔徑為0.4mm時均勻性最好；當流動達到穩(wěn)定后,各出口支管的氣相流量相對平均值的波動幅度隨著孔徑的增大保持不變,各出口支管液相流量相對平均值的波動幅度則隨著孔徑的增大略有減小或保持不變；在給定工況下,各分液孔的氣相和流量分配均勻性均隨分液孔孔徑的增大而變差。當流動達到穩(wěn)定后,各分液孔的氣相流量相對平均值的波動幅度隨著孔徑的增大而減小,液相流量相對平均值的波動幅度隨著孔徑的增大略有減小,基本保持不變；對于開槽聯(lián)箱結(jié)構(gòu),在給定工況下,出口支管的氣相流量分配均勻性隨槽深的變化基本保持不變,而液相流量分配的均勻性則會隨著槽深的增大而變差。當槽深過小,液膜容易被氣相從聯(lián)箱壁面剝離,槽深過大,聯(lián)箱底部的液膜容易在槽頂區(qū)域被氣流沖擊形成分散液滴。當槽深為0.2mm時,聯(lián)箱底部沉積液膜的連續(xù)性最好,當槽深增大,各出口支管流量相對平均值的波動幅度增大。
[Abstract]:In this paper, the method of numerical simulation and the VOF model in Fluent are used to study the structure optimization of multi-branch tube separation header by studying the gas-liquid separation flowability of multi-branch tube separation header with working fluid R134a. The multi-branch tube separated liquid header is the key component of the condenser to achieve high efficiency heat transfer. Its main function is to realize gas-liquid separation and discharge of condensate liquid among the tubes of the heat exchanger. The working principle is to utilize the gas-liquid two-phase density difference. The liquid phase is deposited on the porous separator, and the liquid phase is expelled into the next tube through the holes distributed in the porous partition. At the same time, the vapor blocking liquid film is formed on the upper part of the partition, so that the gas phase is discharged from the outlet branch tube into the downstream heat transfer pipe. High dryness heat transfer is formed to improve the overall heat transfer performance of the condenser. As one of the key components, the separated liquid header is not only effective to drain liquid, but also effective to prevent steam, both of which need to be realized automatically through structural design. In this paper, the typical operating conditions of heat exchangers are studied. Firstly, the characteristics of gas-liquid separation flow in the multi-branch tube separation header under the experimental header structure are studied. The distribution characteristics of the two-phase working fluid and the dry degree of the branch pipe at the outlet of the header are studied. The characteristics of pressure distribution and fluctuation in the container and the uniformity of the flow distribution of the outlet branch pipe and the separation hole of the header are analyzed, and the influence of the pore diameter of the separate liquid hole on the performance parameters of the header is studied. Finally, the influence of groove depth on the performance parameters of liquid header was studied when the header wall was slotted. The simulation results show that the pore diameter mainly affects the discharge flow of the header, and the slotted wall mainly affects the deposition of liquid film at the bottom of the header. The efflux flow increases with the increase of pore size, and the slotted wall can increase the deposition of liquid film at the bottom of the header. Under given working conditions, the variation of aperture and groove depth has little effect on the pressure distribution in the box. Under given conditions, the gas phase flow distribution uniformity of outlet branch tubes will not change obviously because of the change of pore diameter, but the uniformity of liquid phase flow distribution will become better with the increase of pore size, and the uniformity is the best when the pore diameter is 0.4mm. When the flow reaches a stable level, the fluctuation range of the gas phase flow relative to the mean value of each outlet branch pipe remains constant with the increase of the pore size. The fluctuation range of the relative average liquid flow rate of each outlet branch pipe decreases slightly or remains unchanged with the increase of pore diameter, and the gas phase and flow distribution uniformity of each pore becomes worse with the increase of pore diameter under given operating conditions. When the flow reaches stability, the fluctuation amplitude of the relative average gas phase flow rate decreases with the increase of pore size, while the fluctuation amplitude of the relative average flow rate of liquid phase decreases slightly with the increase of pore size. For the slotted header structure, the gas phase flow distribution uniformity of the outlet branch tube remains basically unchanged with the change of the groove depth under given working conditions, but the uniformity of the liquid phase flow distribution will become worse with the increase of the groove depth. When the tank depth is too small, the liquid film is easily stripped from the header wall by the gas phase, and the tank depth is too large. The liquid film at the bottom of the tank is easily impacted by the air flow at the top of the tank to form dispersed droplets. When the channel depth is 0.2mm, the continuity of the deposition liquid film at the bottom of the header is the best, and when the channel depth increases, the relative average flow rate of each outlet branch pipe increases.
【學(xué)位授予單位】：廣東工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TK172
本文編號：2140048
[Abstract]:In this paper, the method of numerical simulation and the VOF model in Fluent are used to study the structure optimization of multi-branch tube separation header by studying the gas-liquid separation flowability of multi-branch tube separation header with working fluid R134a. The multi-branch tube separated liquid header is the key component of the condenser to achieve high efficiency heat transfer. Its main function is to realize gas-liquid separation and discharge of condensate liquid among the tubes of the heat exchanger. The working principle is to utilize the gas-liquid two-phase density difference. The liquid phase is deposited on the porous separator, and the liquid phase is expelled into the next tube through the holes distributed in the porous partition. At the same time, the vapor blocking liquid film is formed on the upper part of the partition, so that the gas phase is discharged from the outlet branch tube into the downstream heat transfer pipe. High dryness heat transfer is formed to improve the overall heat transfer performance of the condenser. As one of the key components, the separated liquid header is not only effective to drain liquid, but also effective to prevent steam, both of which need to be realized automatically through structural design. In this paper, the typical operating conditions of heat exchangers are studied. Firstly, the characteristics of gas-liquid separation flow in the multi-branch tube separation header under the experimental header structure are studied. The distribution characteristics of the two-phase working fluid and the dry degree of the branch pipe at the outlet of the header are studied. The characteristics of pressure distribution and fluctuation in the container and the uniformity of the flow distribution of the outlet branch pipe and the separation hole of the header are analyzed, and the influence of the pore diameter of the separate liquid hole on the performance parameters of the header is studied. Finally, the influence of groove depth on the performance parameters of liquid header was studied when the header wall was slotted. The simulation results show that the pore diameter mainly affects the discharge flow of the header, and the slotted wall mainly affects the deposition of liquid film at the bottom of the header. The efflux flow increases with the increase of pore size, and the slotted wall can increase the deposition of liquid film at the bottom of the header. Under given working conditions, the variation of aperture and groove depth has little effect on the pressure distribution in the box. Under given conditions, the gas phase flow distribution uniformity of outlet branch tubes will not change obviously because of the change of pore diameter, but the uniformity of liquid phase flow distribution will become better with the increase of pore size, and the uniformity is the best when the pore diameter is 0.4mm. When the flow reaches a stable level, the fluctuation range of the gas phase flow relative to the mean value of each outlet branch pipe remains constant with the increase of the pore size. The fluctuation range of the relative average liquid flow rate of each outlet branch pipe decreases slightly or remains unchanged with the increase of pore diameter, and the gas phase and flow distribution uniformity of each pore becomes worse with the increase of pore diameter under given operating conditions. When the flow reaches stability, the fluctuation amplitude of the relative average gas phase flow rate decreases with the increase of pore size, while the fluctuation amplitude of the relative average flow rate of liquid phase decreases slightly with the increase of pore size. For the slotted header structure, the gas phase flow distribution uniformity of the outlet branch tube remains basically unchanged with the change of the groove depth under given working conditions, but the uniformity of the liquid phase flow distribution will become worse with the increase of the groove depth. When the tank depth is too small, the liquid film is easily stripped from the header wall by the gas phase, and the tank depth is too large. The liquid film at the bottom of the tank is easily impacted by the air flow at the top of the tank to form dispersed droplets. When the channel depth is 0.2mm, the continuity of the deposition liquid film at the bottom of the header is the best, and when the channel depth increases, the relative average flow rate of each outlet branch pipe increases.
【學(xué)位授予單位】：廣東工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TK172
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