权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study of High Efficiency Micro Heat Exchanger and Refrigerant Distribution using Throttle Mechanism

高效微型换热器及节流机构制冷剂分配研究

基本信息

批准号：
16560173
负责人：
SAITOH Shizuo
金额：
$ 2.3万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16560173/
关键词：
two-phase flow T-type distribution boiling heat transfer coefficient distributor compact heat exchanger refrigerant flow distribution oscillating flow

项目摘要

For the multi-path heat exchanger using small diameter tubes, a distributor supplies refrigerant to each passage of heat exchanger tubes. No evenness of refrigerant decreases the efficiency of the heat exchanger. In the present study, the distribution of refrigerant to parallel small tubes and the boiling heat transfer for refrigerant R-134a were investigated to provide useful data for the design of compact heat exchangers using small tubes. The distributor, which is connected to the parallel evaporator tubes, supplies refrigerant to each evaporator. Two orifice plates, which are three kinds of nozzle diameters(0.1mm, 0.15mm and 0.2mm), are installed in the distributor connected the front ends of the evaporator tubes. The experimental investigation was performed under the mass flux 100 to 250kg/m^2s, heat flux from 4.8 to 11.8kW/m^2 and inlet refrigerant vapor quality of the evaporator < 0. Results showed that 1) the distribution of refrigerant was not affected by nozzle diameter. 2) the refrigerant flow was steady with decreasing the nozzle diameter, which meant that the fluctuation of refrigerant flow decreased by throttle. 3) two-phase oscillating flow occurred in the evaporator was suppressed by throttle. For the effect of throttle for the boiling heat transfer, when mass fluxes were 100 and 150kg/m^2s, the boiling heat transfer coefficient for the nozzle diameter 0.1mm was better than for the diameter 0.2mm. But, in the case of the mass flux 250kg/m^2s, both the boiling heat transfer coefficients for the diameter 0.1mm and for 0.2mm were almost same values. The boiling heat transfer coefficient was improved at low mass flux. In previous study, it was known that the oscillating flow in the evaporator decreased the heat transfer coefficient. Throat on the entrance of evaporator suppressed flow instability and as a result, the boiling heat transfer coefficient was improved.

对于采用小管径的多路换热器，由分配器将制冷剂输送到换热器的每一通道。制冷剂不均匀会降低换热器的效率。本文研究了冷媒在平行小管中的分布和冷媒R-134a的沸腾换热特性，为小型管换热器的设计提供参考。分配器连接在平行的蒸发器管上，为每个蒸发器提供制冷剂。在连接蒸发器管前端的分配器上安装有两个孔板，分别为0.1mm、0.15mm和0.2mm三种喷嘴直径。实验研究在质量通量100 ~ 250kg/m^2s，热流密度4.8 ~ 11.8kW/m^2，蒸发器进口制冷剂蒸气质量< 0的条件下进行。结果表明：1)制冷剂的分布不受喷嘴直径的影响。2)随着喷嘴直径的减小，制冷剂流量趋于稳定，即节流减小了制冷剂流量的波动。3)通过节流抑制蒸发器内的两相振荡流。对于节流对沸腾传热的影响，当质量通量为100和150kg/m^2s时，直径为0.1mm的喷嘴沸腾传热系数优于直径为0.2mm的喷嘴。但在质量通量为250kg/m^2s的情况下，直径为0.1mm和直径为0.2mm的沸腾换热系数几乎相同。在低质量通量条件下，沸腾换热系数有所提高。在之前的研究中，我们知道蒸发器内的振荡流动降低了换热系数。蒸发器入口喉部抑制了流动不稳定性，从而提高了沸腾换热系数。