摘要
本文搭建了测试CO_2冷风机性能的实验台,在直接膨胀供液系统和泵供液系统下,通过改变传热温差、库温、循环倍率、迎面风速等参数来研究CO_2冷风机的性能。结果表明:在直接膨胀供液系统中,随着蒸发温度的降低,传热系数和制冷量均呈减小的趋势,蒸发温度从-22℃降低到-47℃时,传热系数从20.2 W/(m2·K)降低到16.6 W/(m2·K),制冷量从7.5 k W降低到6 k W;在泵供液系统中,随着循环倍率的增加,传热系数呈现先增大,达到最大值后缓慢减小的趋势,当循环倍率为3时,传热系数达到最大值,以库温为-20℃时为例,当循环倍率从1增大到3,传热系数增大约13.2%,循环倍率继续增大时,传热系数开始下降,增大到5时,换热系数下降至2%左右。当迎面风速从2.2 m/s变化至2.5 m/s时,传热系数仅增加了2.12%;但迎面风速从2.5m/s变化至3.2 m/s时,增幅为11.4%;当迎面风速从3.2 m/s变化至3.5 m/s时,传热系数增长幅度又变缓,仅增加了0.88%。
This study sets up an experimental platform to test the performance of a CO2 air cooler. The direct expansion system and the pump-driven system were examined by changing parameters such as evaporating temperature, storage temperature, circulation ratio, and face velocity. Experiments indicate that in the direct expansion system, the heat transfer coefficient and refrigerating capacity exhibit a decreasing trend as the evaporating temperature decreases. The heat transfer coefficient dropped from 20. 2 W/（ m2·K） to 16. 6 W/（ m2 · K）, and the refrigerating capacity dropped from 7. 5 kW to 6 kW as the evaporating temperature dropped from -22 ℃ to -47 ℃ during the experiment. A peak of the heat transfer coefficient exists for different circulation ratios in the pump-driven system, and the best circulation ratio is 3 in this paper. For example, when the storage temperature was at - 20 ℃, the heat transfer coefficient increased by about 13.2% as the circulation ratio increased from 1 to 3. However, the heat transfer coefficient began to decrease as the circulation ratio continued to increase. The heat transfer coefficient dropped by about 2% when the circulation ratio increased to 5. When the face velocity was changed from 2. 2 m/s to 2. 5 m/s, the heat transfer coefficient increased by just 2. 12%. However, it increased by 11.4% when the face velocity was changed from 2. 5 m/s to 3.2 m/s. Next, the increase rate of the heat transfer coefficient became slow as the face veloci- ty increased from 3. 2 m/s to 3.25 m/s, which is only 0. 88% in this case.
出处
《制冷学报》
CAS
CSCD
北大核心
2017年第3期13-18,共6页
Journal of Refrigeration
关键词
CO2冷风机
传热系数
制冷量
循环倍率
迎面风速
CO2 air-cooler
heat transfer coefficient
refrigerating capacity
circulation ratio
face velocity
