In this paper, a comparative study is performed to evaluate the enhancement of spray cooling heat transfer using deionized water with a conventional surfactant (Tween 20) and two biosurfactants (Rhamnolipid and Sophorolipid). In the single-phase regime, appreciable enhancement on spray cooling heat transfer can be achieved using Rhamnolipid additive. However, the addition of Sophorolipid leads to a decrease in the single-phase spray cooling heat transfer. Meanwhile, in the nucleate boiling, spray cooling heat transfer is substantially enhanced using any of the three tested surfactants due to the decrease in surface tension and enhanced wettability. At the same concentration, the two biosurfactants lead to higher heat transfer than Tween 20 due to their lower surface tension as compared to Tween 20. The maximum spray cooling heat transfer enhancement is found to be 37%, 55%, or 41% using Tween 20, Rhamnolipid, or Sophorolipid, respectively as compared to deionized water. The surface condition after testing is also studied. Residual deposition is observed after testing when Rhamnolipid is added into deionized water whereas the addition of Sophorolipid leads to strong surface oxidation after testing. The strong surface oxidation causes the decrease in the rate of increment of the heat flux with increasing temperature difference. Comparatively, no distinction can be observed before and after testing when Tween 20 solution is used.

在本文中，进行了一项比较研究，以评估使用去离子水与常规表面活性剂（吐温20）和两种生物表面活性剂（鼠李糖脂和槐糖脂）的喷雾冷却传热效果。在单相体系中，使用鼠李糖脂添加剂可以显着提高喷雾冷却的热传递。然而，槐糖脂的添加导致单相喷雾冷却热传递的减少。同时，在成核沸腾中，由于表面张力的降低和润湿性的提高，使用三种测试表面活性剂中的任何一种都可以大大提高喷雾冷却的热传递。在相同浓度下，由于两种生物表面活性剂的表面张力比吐温20低，因此它们的传热比吐温20高。与去离子水相比，使用吐温20，鼠李糖脂或槐糖脂发现最大的喷雾冷却传热增强分别为37％，55％或41％。还研究了测试后的表面状况。当将鼠李糖脂添加到去离子水中时，在测试后观察到残留的沉积，而在测试后添加槐糖脂会导致强烈的表面氧化。强烈的表面氧化会导致热通量的增加速率随温度差的增加而降低。相比之下，在使用Tween 20溶液进行测试之前和之后都看不到任何区别。当将鼠李糖脂添加到去离子水中时，在测试后观察到残留的沉积，而在测试后添加槐糖脂会导致强烈的表面氧化。强烈的表面氧化会导致热通量的增加速率随温度差的增加而降低。相比之下，在使用Tween 20溶液进行测试之前和之后都看不到任何区别。当将鼠李糖脂添加到去离子水中时，在测试后观察到残留的沉积，而在测试后添加槐糖脂会导致强烈的表面氧化。强烈的表面氧化会导致热通量的增加速率随温度差的增加而降低。相比之下，在使用Tween 20溶液进行测试之前和之后都看不到任何区别。