| 摘要: |
| 气液两相流体板内均匀流动分配是影响制冷用钎焊板式换热器性能的重要因素。本文通过计算流体力学数值模拟软件对两相制冷剂R410A在人字波和点波板内流动分配特性进行了研究，对比分析了两种板型压力分布、速度分布和液相体积比分布，发现人字波板压力、速度和液相分布相对均匀，板中心速度和液相分布略高于两侧，而点波板呈现进出口近侧流速显著高于远端而液相分布显著低于远端的分布特点。提出了用当量断面平均两相流量偏差和平均液相流量偏差对板内流动分配均匀性进行评价。结果表明：人字波板较点波板，气液两相侧向流动和分配较好，二者平均两相流量偏差分别为14.2%和39.6%，平均液相流量偏差分别为15.6%和41.3%。分析表明圆型点波结构流动方向上存在直通截面，侧向流动弱化，因气液流速差异导致两相过早分离，造成气相短路。能够控制直通截面大小和产生二次涡阶结构的“鱼鳞”点波结构可有效增强侧向扰动，改善点波板的气液两相表面流动和分配均匀性，其平均两相流量偏差和平均液相流量偏差分别为7.6和8.9%。 |
| 关键词: 均匀分配 数值模拟 板式换热器 蒸发器 制冷剂 |
| DOI： |
| 投稿时间：2022-11-14 修订日期：2023-04-20
录用日期：2023-05-12 |
| 基金项目:浙江省“ 尖兵”“ 领雁”重大研发攻关计划项目(2022C01159)资助。 |
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| Flow Characteristics and Optimization of Two-phase Flow Distribution over Plate Surface of Brazed-Plate Heat Exchanger |
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Wei Wenjian1,2, Xu Guaoliang1, Zhang Zhifeng3, Ding Ergang2, Wang Yanfeng2
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| (1.Institute of Advanced Heat Transfer and Energy Application, Zhejiang University of Water Resources and Electric Power;2.Zhejiang DuanAn Thermo-tech Co. Ltd.;3.Danfoss Plate Heat Exchanger Co. Ltd.) |
| Abstract: |
| The homogenous distribution of liquid and vapor over a plate surface is a key factor affecting the performance of brazed-plate heat exchangers in refrigeration and air-conditioning units. The two-phase flow and distribution over the plate surface were investigated with R410A fluid using computational fluid dynamics (CFD) simulation software. The distributions of pressure, velocity, and liquid volumetric fraction were comparatively analyzed. It was observed that the pressure, velocity, and liquid phase were distributed comparatively evenly for the herringbone plate. The velocity and liquid volumetric fraction along the plate centerline were slightly higher than those along the edges. However, for the dimpled plate, the velocities in the proximal zone were significantly higher than those in the distal zone, which is opposite to the distribution of liquid volumetric fraction. New methods called the mean two-phase flow deviation (MTFD) and mean liquid flow deviation (MLFD) at the nominal section were proposed to evaluate the maldistribution of fluid flow over the plate surface. The results indicated that the distribution and sideways flow were better for the herringbone plate than for the dimple plate. The MTFD values were 14.2% and 39.6%, and the MLFD values were 15.6% and 41.3% for the herringbone and dimple plates, respectively. It was determined that the bypass section existed in the flow direction for the round dimple plate, which led to poor sideways flow and earlier separation between the vapor and liquid. The proposed boomerang dimple plate pattern, similar to fish skin, can improve the two-phase flow distribution over the plate surface because it can reduce the size of the bypass section and generate vortices under a concave shape. The new geometry can enhance turbulence and promote the two-phase fluid to move sideways effectively. The MTFD and MLFD values were 7.6% and 8.9%, respectively. |
| Key words: even distribution numerical simulation plate heat exchanger evaporator refrigerant |
