چكيده به لاتين
Boiling is a process of heat transfer that, with only a slight temperature difference by changing the liquid phase to steam, increases the amount of energy. It dissipates heat from the surface. Boiling in the industry affects the performance of boilers and many industrial devices. For this reason, researchers have always been looking for ways to increase the boiling rate, especially in the field of nucleate boiling.
Two methods of affecting boiling are the use of suspended particles and dissolved gas. In case of temperature rise or pressure decreases, the solubility of the dissolved gas decreases, and micron gas bubbles form, and with turbulence, they accelerate the formation of primary boiling nuclei. Experiments have also shown that type and the size of suspended and deposited particles also affect the boiling performance. Numerous researchers on the effects of these particles on the evaporation did, and it was concluded that the particles affect the boiling performance. It directly affects the formation of boiling nuclei, increases the critical heat flux, and improves boiling. Studies show that these particles increase the viscosity of the fluid and the thermal conductivity of the fluid, or by Increased roughness and contact angle of the surface, boiling and evaporation improves. Therefore, the presence of stimulus particles is the change of liquid phase to vapor.
In this project, first, a suitable laboratory system was designed and built according to the goals and demands of the issue that suspended particles were hydrophobic. After design and construction, pure water evaporation flow was measured first. The resulting model, The evaporation of pure water, is well in line with the physics of the problem, which is a linear regression decrease with evaporation flow rate and increase in temperature. Then the Hydrophilic and hydrophobic aluminum particles, phlogopite, and silica were injected into the test water with mass percentages of 0.05, 0.01, and 0.1. The results show that the evaporation rate is directly related to the number of hydrophilic particles injected and their thermal conductivity, but Hydrophobic particles do not affect boiling performance and evaporation flow. Hydrophobic particles, due to their non-polar nature, after Injections from the bottom of the fluid, reach the water's surface after a short time and become ineffective.
