Optimum Design of Heat Exchanger for the Air Conditioning System with Surfactant Drag Reduction Technique

本研究对表面活性剂分子结构与传热还原之间的关系进行了基础研究。这是从化学的角度出发，给出了一种合理的方法来避免换热器的传热减少。由于阳离子表面活性剂与反离子联合使用可以有效地减少阻力，因此选择了四种阳离子表面活性剂来讨论分子结构的影响。它们是油基三甲基氯化铵、油基羟乙基二甲基氯化铵、油基二羟乙基甲基氯化铵、油基三羟乙基氯化铵。这些表面活性剂具有不同的亲水性基团，这就导致了胶束结构形成和胶束结构破裂的不同行为。本研究得出的结论总结如下。(1)减阻效果在很大程度上取决于机械破坏胶束的再形成速度。(2)当羟乙基基团数从0增加到2时，大减阻效果的有效温度范围下移。但具有三个羟基乙基的表面活性剂即使在较低温度范围内也几乎没有表现出减阻作用。这可能是由于羟基的大亲水头导致胶束重组延迟所致。(3)众所周知的减阻表面活性剂油基双羟乙基甲基氯化铵确实是一种优良的减阻表面活性剂，但从传热还原的角度来看，这种表面活性剂的韧性太大，胶束的重新形成速度太快。因此，我们提出具有三个羟乙基的表面活性剂油基三羟乙基氯化铵作为实际应用的表面活性剂减阻体系的最佳候选。目前，该表面活性剂已在实际空调系统中进行了表面活性剂减阻评价。

Basic research on the relationship between heat transfer reduction and surfactant molecular structure has been conducted in this study. This is the approach from chemical aspect to give an appropriate technique to avoid the hear transfer reduction at heat exchanger. Since the combined use of cationic surfactants with counter ion gives effective drag reduction, four cationic surfactants were selected to discuss the effect of molecular structure. These are oleyl tri-methyl ammonium chloride, oleyl hydroxyethyl di-methyl ammonium chloride, oleyl bis-hydroxyethyl methyl ammonium chloride, oleyl tri-hydroxyethyl ammonium chloride. These surfactants have different hydrophilic group, and this causes different behavior of micelle structure formation and micelle structure breakup. The concluding remarks obtained in this study are summarized as follows.(1) The drag-reducing effect depends strongly on the re-formation rate of micelles disrupted mechanically.(2) When increasing the number of hydroxyethyl groups from 0 to 2, the available temperature range of large drag reduction effect is shifted lower. But the surfactant having three hydroxyethyl groups barely exhibits the drag reduction even at the lower temperature range. This may be caused by the delayed micelle reformation by the large hydrophilic head of hydroxyethyl groups.(3) The well-known drag-reducing surfactant, oleyl bis-hydroxyethyl methyl ammonium chloride, is confirmed to be exactly excellent one, but from the view point of heat transfer reduction, this surfactant is too tough and the micelle re-formation is too rapid. Thus, we propose that the surfactant having three hydroxyethyl groups, oleyl tri-hydroxyethyl ammonium chloride, as an optimum candidate for the practical application of surfactant drag reduction system. This surfactant is now under the evaluation in practical air-conditioning system with surfactant drag reduction.