平行流蒸发器制冷剂流量分配特性
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摘要
采用标准k-ε模型和Eulerian模型对平行流蒸发器集管内两相制冷剂分配特性进行模拟,发现在集管加入分流管后,制冷剂流量分配不均匀性得到明显改善.在此基础上,分别对扁管插入集管的深度、分流管开孔率对流量分配的影响情况展开分析.发现当扁管伸入集管深度大约在分流管下方1/2时流量分配均匀性最好;对比不同开孔率时的流量分配情况,发现随着开孔率的增大流量分配均匀性先变差后变好,之后随着开孔率进一步增大,流量分配均匀性又变差.分流管在小开孔率下,需要注意与制冷系统中节流阀的匹配.
The standard k-εturbulence model and the two phase flow Eulerian model are used to simulate the refrigerant distributions in the heads of parallel-flow evaporators,and the experimental results in literature is used to validate the numerical method.Then,the comparison of distributions between base line structure and the structure with perforated tube in heads is conducted and the reason behind the performance improvement of the structure with perforated tube is revealed.The comparison of flow distribution in heads with perforated tubes in the open ratio ranging from 0.11 to1.00 indicates that the uniformity of flow distribution decreases at first and then increases,after which it worsens with the further increase of open ratio.The matching issue of expansion valve with refrigerant systems should be concerned under the condition of small open ratio of perforated tubes.
The standard k-εturbulence model and the two phase flow Eulerian model are used to simulate the refrigerant distributions in the heads of parallel-flow evaporators,and the experimental results in literature is used to validate the numerical method.Then,the comparison of distributions between base line structure and the structure with perforated tube in heads is conducted and the reason behind the performance improvement of the structure with perforated tube is revealed.The comparison of flow distribution in heads with perforated tubes in the open ratio ranging from 0.11 to1.00 indicates that the uniformity of flow distribution decreases at first and then increases,after which it worsens with the further increase of open ratio.The matching issue of expansion valve with refrigerant systems should be concerned under the condition of small open ratio of perforated tubes.
引文
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[12]FEI P,HRNJAK P.Adiabatic developing two-phase refrigerant flow in manifolds of heat exchangers[D].Champaign-Urbana:University of Illinois at UrbanaChampaign,2004.
[13]BACHALO W D,HOUSER M J.Phase/doppler spray analyzer for simultaneous measurements of drop size and velocity distributions[J].Optical Engineering,1984,23(5):583.
[14]KULKARNI T,BULLARD C W,CHO K.Header design tradeoffs in microchannel evaporators[J].Applied Thermal Engineering,2004,24(5/6):759.
[2]ZOU Y,HRNJAK P.Effects of fluid properties on two-phase flow and refrigerant distribution in the vertical header of a reversible microchannel heat exchanger-comparing R245fa,R134a,R410A,and R32[J].Applied Thermal Engineering,2014,70(1):966.
[3]LEE J K,Lee S Y.Distribution of two-phase annular flow at header-channel junctions[J].Experimental Thermal and Fluid Science,2004,28(2):217.
[4]KIM N H,HAN S P.Distribution of air-water annular flow in a header of a parallel flow heat exchanger[J].International Journal of Heat and Mass Transfer,2008,51(5):977.下转第页(上接第268页)
[5]KIM N H,LEE E J,BYUM H W.Improvement of twophase refrigerant distribution in a parallel flow minichannel heat exchanger using insertion devices[J].Applied Thermal Engineering,2013,59(1):116.
[6]WANG C C,YANG K S,TSAI J S,et al.Characteristics of flow distribution in compact parallel flow heat exchangers.PartⅠ:typical inlet header[J].Applied Thermal Engineering,2011,31(16):3226.
[7]HUANG C H,WANG C H.The study on the improvement of system uniformity flow rate for U-type compact heat exchangers[J].International Journal of Heat and Mass Transfer,2013,63:1.
[8]RAMADEVI T,VIJAYANAND P.CFD analysis of dual phase refrigerant flow inside an evaporator tube of refrigerator[J].International Journal of Advance Induatrial Engineering,2015,3(3):111.
[9]VERSTEEG H K,MALALASEKERA W.An introduction to computational fluid dynamics:the finite volume method[[[[[檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿檿[M].London:Pearson Prentice Hall,2007.
[10]SCHEPPER S C K D,HEYNDERICKX G J,MARIN G B.CFD modeling of all gas-liquid and vapor-liquid flow regimes predicted by the Baker chart[J].Chemical Engineering Journal,2008,138(1):349.
[11]SCHWARZKOPF J D,SOMMERFELD M,CROWE C T,et al.Multiphase flows with droplets and particles[M].Boca Raton:CRC Press,2011.
[12]FEI P,HRNJAK P.Adiabatic developing two-phase refrigerant flow in manifolds of heat exchangers[D].Champaign-Urbana:University of Illinois at UrbanaChampaign,2004.
[13]BACHALO W D,HOUSER M J.Phase/doppler spray analyzer for simultaneous measurements of drop size and velocity distributions[J].Optical Engineering,1984,23(5):583.
[14]KULKARNI T,BULLARD C W,CHO K.Header design tradeoffs in microchannel evaporators[J].Applied Thermal Engineering,2004,24(5/6):759.