Effect Of The Structured Surfaces On The Fluid Flow And Heat Transfer Of Falling Evaporator

Absorption heat transformer(AHT) has no environmental hazards, it is recognized as environment protection device. In industrial applications, AHT takes thermal energy from a low-level to a higher-temperature process. The recycled thermal energy will therefore reduce the prime energy needed in the process. Based on the heat transfer performance for falling film evaporation on the exterior wall of a vertical tube. A vertical evaporative test platform was adopted to measure the temperature and flow rate under various spray densities.During the experiment we used both circular tube and corrugated tube to test. The experimental results show that with the increase of spray density in a certain range, the total heat transfer coefficient and the heat transfer coefficient of water-film are both increase, also with the increase of flux in the tube, the total heat transfer coefficient and the heat transfer coefficient of water-film are both increase, and the total heat transfer coefficient of corrugated tube is better than that of circular tube. Because the corrugated tube increased the heat transfer face and enhanced the turbulence of the flow, so the total heat transfer coefficient increased.In the same time, based on the experiment condition, simulated the flow in the corrugated and circular tube, with the help of CFD software. The results show that the appearance of the swirl is determined by the angle and the wavelength influence the boundary development. The method was also used to analyze the mechanism for enhancing heat transfer and can be used to study how apply the field harmony theory to corrugated tube enhance heat transfer.In the end, we design a new corrugated tube. In order to check the performance of the new tube, we need the help of CFD software. A two phase flow CFD model using the VOF (volume of fluid) method was presented for predicting the hydrodynamics of the falling film on the vertical wavy pipes. Using the proposed CFD model, the flow behaviors of liquid on various wavy pipes were investigated. The simulated results showed that changing the microstructures of wavy pipes would improve the heat transfer efficiency between liquid and gas.