Research On The Flow Characteristics And Distributor Equipment Of Falling Liquid Film Down A Vertical Tube

In industrial fields, there is usually a lot of low-temperature waste heat. In the recovery of industrial waste heat, absorption heat pump units have the advantage in environmental protection and low power consumption. The process of falling film is that spraying the solution onto the surface of the tube in absorption heat pump unit. The liquid appears as film flow down outside of heat exchanger tubes due to gravity. The condition of filming affects the heat and mass transfer of absorption unit significantly. Small temperature difference, small flow, high heat and mass transfer coefficients, simple structure and small power consumption are the significant advantages for the process of falling film. It has been widely used in multiphase convective heat-mass transfer of industrial equipment as a high efficient enhanced heat and mass transfer. The falling film process and key parameters of distributing film uniformly is carried on the experimental research and numerical simulation in this paper.Setting the film experiment platform with lithium bromide solution as cyclic working substance, choosing smooth tube as falling film pipe fittings, the experimental results show that the film annular gap size should be1.3-2.Omm based on the previous experimental research. After the theoretical analysis on liquid film flow characteristics of the falling film outside the vertical tube, the relation of the falling film liquid physical parameters ρ,μ, and the volume flow rate Q are obtained, Later, comparing with other experimental researches with lithium bromide solution of different concentration, the correctness of the theoretical analysis is proved. According to the falling film experiments, it is also concluded that the falling film configuration’s flow coefficient increases with the rise of temperature of lithium bromide solution in the same concentration; flow coefficient decreases with the increase of concentration of lithium bromide solution in the same temperature. A new tape falling liquid film down the outside of a vertical tube was put forward, and had the experimental research and theoretical analysis. Key parameters such as the inner diameter annulus gap of liquid distributor device, the number of spiral grooved channel, the structural parameters of spiral grooved channels, and spiral angel are determined to eliminate the stocks of effusion of liquid film and to make sure the liquid film covers the entire wall better.Based on VOF method, a gas-liquid two phase flow model which vertical tube falling film flow is established with the use of Fluent software. Through numerical simulation analysis of the liquid film flow patterns and velocity distribution, the results show that with the development of fluid down the tube wall, the average thickness of liquid film from the distributing film of annulus gap outlet in large thickness values decrease quickly, and then decreases trend slowing, finally tends to a constant value. As the inner diameter of the annulus gap, the liquid inlet velocity, lithium bromide solution concentration increases, the average film thickness values are also increasing.