Studies On Fluid Mechanics Performance And Heat Transfer Characteristics Of Fatty Acid Methyl Ester(FAME)in Falling Film Evaporator

Fatty acid methyl ester is also known as biodiesel, which can be produced by the transesterification reaction of animal fats and methanol. FAME has been considered new type green energy with vast development potential because of its variety of excellent performance. The industrial production of biodiesel mainly uses waste oil as raw materials, catalyzes that and methanol reaction in the presence of acids or bases to make the crude FAME, then obtains pure FAME through vacuum distillation and rectification.Using conventional line-tube heat exchanger for evaporation of the high-viscosity and easy-to-scaling mixture, this can easily block liquid distributor and make the cleaning of foul tube impossible. Depending on the nature of liquid model,this paper designed a new type of evaporator and conducted experimental study on its falling film flow and heat transfer performance,which can provide reference for engineering design.Firstly, according to experimental process and predetermined evaporation capacity, the main experiment equipment such as the shell of evaporator, liquid distributor, electric heating module, condenser and storage tank et al, were designed specifically. Besides, test device was installed and debugged carefully.Then, we used debugged test device to carry on the falling film evaporation heat transfer experiment. First, under normal pressure, at different feed rate and temperature, the forming-film effect of liquid distributor and liquid film flow condition on evaporator shell wall with different taper angle were observed to determine the best volume flow rate range(1.3 ~ 3.0m3/h) that can ensure liquid forming film well. Afterwards, The influence of heating power on heat transfer process were determined to acquire optimum input voltage(300V), and found that heat transfer coefficient firstly increased shortly then decreased gradually with the increase of heat flux under turbulence state. Then, under the determined input power and volume flow rate range, the variation of evaporation heat transfer coefficientswith half taper angle of evaporator shell and liquid film Reynolds was studied, the result shown that evaporator shell’s taper angle can intensify heat transfer process and improve heat transfer coefficient, but large Reynolds number increased liquid film thickness to waken heat transfer process.Finally, based on the method of volume of fluid(VOF), numerical simulation of liquid film flow on inclined wall was simulated by CFD software. And the influence of wall’s taper angle, feed flow rate, contact angle and surface tension on liquid film forming process, liquid film thickness and velocity were researched.