###### Abstract
[18] examined how micro-hole outlet diameter, volumetric flow rate, and spray height affected surface temperature distribution, heat flux, and spray cooling efficiency, and found that the heat flux increased as the flow rate increased, but the spray cooling efficiency decreased, and that there was an optimal orifice diameter and spray height for each nozzle. [PERSON] et al. [19] reviewed the progress of research on the heat transfer effect of spray cooling, and concluded that the variation in spray flow rate leads to the variation of other factors that result in the influence of heat transfer and need to be analyzed according to the experimental conditions. Both [PERSON] et al. [20] and [PERSON] et al. [21] concluded that the highest heat transfer efficiency occurs when the spray impingement surface is directly parallel to the heating surface. However, by analyzing the surface structure of the heating surface and spray velocity characteristics through experiments and simulations, [PERSON] et al. [22] determined that a spray coverage of less than 100% would provide the maximum heat transfer efficiency. In view of the above studies, it has been determined that parameters such as spray cooling height and coverage have impacts on the heat transfer characteristics. It is unclear how droplets are distributed on the surface and influence the heat transfer parameters, and there has been some disagreement on the optimal coverage rate for the best heat transfer performance. Some scholars worked on adding various additives, such as nanoparticles [23], alcohols [24], and surfactants [25], to water to improve the heat transfer efficiency of pure water. [PERSON] [26] firstly performed pool boiling and spray cooling experiments using ethanol-water mixtures and measured contact angles. [PERSON] et al. [27] used Tween20 and ethanol as cooling media to study the cooling rate of air atomized spray on stainless steel plates with an initial temperature of 900 \({}^{\circ}\)C. It was shown that increasing the ethanol content in pure water and surfactant-water mixture can effectively increase the heat transfer coefficient and cooling rate. [PERSON] et al. [28] investigated the heat transfer performance of AOS, CTAB and Tween20 in the low temperature range below 100 \({}^{\circ}\)C. The three surfactants had different optimal concentrations for heat transfer promotion, and heat transfer deterioration occurred at high concentrations due to bubble accumulation. The use of tilt mode sprays can effectively alleviate bubble accumulation and thus improve heat transfer. [PERSON] et al. [29; 30] investigated the heat transfer between Al2O3 nanofluid jets and horizontal circular surfaces and showed that presenting the data in Reynolds number captures the effect of nozzle height and jet diameter, and presenting the data in Pecoret number correlates the nanofluid concentration with a single criterion number. An important contribution of this paper is to examine the effect of different droplet distribution coverage on transient and steady-state heat transfer coefficients under a variety of parameter changes, including the effect of droplet coverage on heat transfer coefficients for medium flow rate changes and nozzle height changes. A combination of visualization analysis under the appropriate parameters and comprehensive consideration is used to determine the best spray coverage adjustment method for enhancing heat transfer. Based on the investigation of spray coverage rate, ethanol, water and the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) were used as additives to investigate the enhancement effect of the above fluids and their mixtures on the heat transfer performance. Combined with the visualization analysis, the optimal concentrations of several additives to enhance the surface heat transfer were synthesized.