During heat waves, spraying heat exchanger helps to prevent overheating thermal processes like air conditioning systems. Spraying efficiency is studied to get the best performance enhancement ratio and avoid pressure drop related to water films. In this paper, we studied the effectiveness and local heat transfer coefficient for an exchanger which is partially sprayed. Thermography is used to describe wet section locations and areas for assessing incoming water flux. Results show an increase between 10 up to 30% of the local heat transfer coefficient in wet passes. On the opposite, global exchanger effectiveness is lowered to about 3% in wet conditions. This effect is related to the increase of the heat capacity on the air-side which reduces the calorific ratio in most cases. Spray cooling impact is most of the time limited by evaporation in the experiment. A formula is proposed to diagnose evaporation rate according to wall temperature, air humidity, and incoming water flux. It is also shown that effective evaporative cooling is shared between air and working fluid. Cooling transfer to working fluid depends on the calorific ratio between fluids. Hence, this latest affects spraying efficiency and has to be considered in optimizing spray cooling of heat exchangers.

在热浪期间，喷洒热交换器有助于防止过热的过程（如空调系统）过热。研究喷雾效率以获得最佳的性能增强比并避免与水膜有关的压降。在本文中，我们研究了部分喷涂的交换器的有效性和局部传热系数。热像仪用于描述潮湿区域的位置和区域，以评估传入的水通量。结果表明，在湿通道中，局部传热系数增加了10％至30％。相反，在潮湿条件下，整体交换器效率降低到约3％。该效果与空气侧的热容量的增加有关，这在大多数情况下降低了发热量。喷雾冷却的影响大部分时间受实验中蒸发的限制。提出了根据壁温，空气湿度和进水通量来诊断蒸发速率的公式。还显示出有效的蒸发冷却在空气和工作流体之间共享。冷却液向工作流体的转移取决于流体之间的热量比率。因此，这种最新情况会影响喷涂效率，因此必须在优化热交换器的喷涂冷却时加以考虑。