含氟丙烯酸疏水树脂强化水蒸汽冷凝传热研究

Heat transfer intensification of water steam condensation by fluoride acrylic hydrophobic resin

采用含氟丙烯酸疏水树脂在套管换热器的水蒸气冷凝表面上构建疏水冷凝表面,研究冷热流体流量、换热器放置方式、涂膜厚度等对换热器传热系数的影响。研究表明,当其他条件不变,换热器水平放置时,热流体加热温度由125℃增加到175℃,传热系数由10409.9W·m-2·K-1增加到38353.2W·m-2·K-1;冷流体流量由5mL/s增加到35mL/s,传热系数由38000.2W·m-2·K-1增加到52195.9W·m-2·K-1。无论是垂直还是水平放置时,疏水涂膜的厚度对传热系数影响均不大。含氟丙烯酸疏水树脂能降低换热管壁的表面自由能,增大冷凝水的接触角使液滴更易滑落,水蒸汽冷凝由膜状冷凝转变为滴状冷凝,从而减小了液膜热阻,强化了传热过程,滴状冷凝维持时间超过1000h。

Fluoride acrylic hydrophobic resin was used to constructe hydrophobic coating on water steam condensing surface of double-pipe heat exchanger. The effects of hot fluid flow, cold fluid flow, heat exchanger position and thickness of hydrophobic coating on heat transfer coefficient were researched. The results showed that, when the heat exchanger be laied parallelly, when the heating temperature of hot fluid was increased from 125℃ to175℃, the heat transfer coefficient was in- creased from 10409.9to 38353. 2. When the cold fluid flow was increased from 5mL/s to 35mL/s, the heat transfer coeffi- cient was increased from 38000. 24 to 52195.9. Thickness of hydrophobic coating had a little effect on heat transfer coeffi- cient whenever the heat exchanger be laid vertically and parallelly. The fluoride acrylic hydrophobic resin can reduce the surface free energy of heat exchanger tube, and increased the water contact angle, made the condensate drop easily, made water steam condensation changed from flim condensation to droplet condensation, reduced the heat resistance and intensifi- cared the heat transfer. The droplet condensation can be kept at least 1000 hours.