王士存 田丽亭 刘阳 刘联胜

摘要 在常压冻结塔内进行了水经过喷嘴雾化后的冻结实验，研究冷空气入口温度、喷雾水温和成核添加剂对冻结效率和空气温升的影响。结果表明：冷空气入口温度越低，液滴的冻结效率越大，空气温升越高，液滴冻结后的形态越接近干雪，液滴冻结越完全;即使冷空气入口温度为-8 ℃时，液滴的冻结效率和空气温升已分别达到61.7%和4.95 ℃，表明常压下喷雾冻结提取凝固潜热的方法具有冻结效率高和空气温升大的优点;喷雾水温升高，液滴的显热换热时间增加，导致冻结时间缩短，液滴冻结效率下降，但冷空气入口温度越低，喷雾水温对液滴的冻结效率影响越小;硼砂作为水溶液的成核剂，质量分数为1.5%硼砂溶液的导热系数相对于水提高了9.5%，硼砂溶液浓度越高，液滴的导热系数越大，液滴冻结成核能力越强，冻结效率和空气温升越大。当冷空气入口温度为-17 ℃时，质量分数为1.5%硼砂溶液的冻结效率和空气温升相对于水分别提高了13.6%和1 ℃。

关 键 词 喷雾冻结;冻结效率;空气温升;成核添加剂

中图分类号 TK124     文献标志码 A

文章编号：1007-2373（2021）06-0077-07

Abstract The freezing experiment of water atomized by nozzle was carried out in atmospheric pressure freezing tower. The effects of inlet air temperature， spray water temperature and nucleating additives on the freezing efficiency and the air temperature rise were studied. The results show that the lower the inlet temperature of cold air is， the higher the freezing efficiency of droplets is， the higher the temperature rise of air is， and the better the freezing effect is. When inlet temperature of cold air is -8 ℃， the freezing efficiency and air temperature rise are 61.7% and 4.95 ℃， respectively， which show that spraying to extract the latent heat of solidification under atmospheric pressure has higher freezing efficiency and air temperature rise. With the increase of spray water temperature， the time of sensible heat transfer for droplets increases， which results in the reduction of freezing time and the drop of freezing efficiency for droplets; however， when the inlet temperature of cold air is too low， the spray water temperature has little effect on the freezing efficiency of droplets. When borax was used as nucleating additive， the thermal conductivity of 1.5% borax solution increased by 9.5% compared with that of water. Meanwhile the concentration of borax solution increases， which leads to the rise in thermal conductivity of the droplet， the enhancement of nucleating ability， and the growth of freezing efficiency and air temperature rise. When the inlet temperature of cold air is -17 ℃， the freezing efficiency and air temperature rise of 1.5% borax solution are 13.6% and 1℃ higher than that of water， respectively.

Key words spray freezing; freezing efficiency; air temperature rise; nucleation additive

0 引言

最新統计，全球建筑物能耗约占总能耗的40%左右，中国建筑能源消费总量为9.47 亿t标准煤[1-2]，全国建筑总面积达到 642.47 亿m2，其中暖通空调的能耗在逐年增加，占据举足轻重的地位。空气源热泵以其高效、节能、环保的特点被广泛应用[3-4]，但在低温工况运行时，系统面临蒸发温度过低、压缩比大、运行不稳定、制热效率明显下降等问题[5-6]，当机组排气温度过高时，甚至出现非正常停机现象。……