Design Of Heat Exchanger Of Methanol Decomposition On Vehicle Engine

Methanol using engine exhaust heat to heat, it cracked into hydrogen and carbon monoxide mixture, cracking after this mixture into the engine combustion chamber for combustion.This form can be overcome by burning methanol toxicity, corrosion and low temperature properties of cold start and other adverse effects and can be used to achieve a high percentage of methanol, it has broad market prospects. Automotive heat exchanger methanol cracker in the whole critical components, It is thus related to the exhaust heat utilization efficiency of the decomposition of methanol, the catalyst must work within a specific temperature, ambient temperature is too low then the low rate of methanol decomposition, the catalyst for high temperature failure,must ensure that the methanol steam heated to between 260-390℃, the catalyst can play a real role. As a heat transfer device, more types of heat exchangers, but for the heat exchanger methanol cracker, need to consider the cost of production, easy to clean, the selection and use of the range, work safety, durability, etc., so the need for methanol Cracker designed to achieve the above purpose a heat exchanger.In this paper, the heat exchanger as the research object, with its performance in line with the conditions for the study of methanol cracking goal, made of heat exchanger thermal analysis, structural design and simulation, has some practical value and theoretical significance.This mainly includes the following:1) This article studies the structure of the heat exchanger to determine the fixed tube shell and tube heat exchanger plate of this paper to design the heat exchanger. To BN492 gasoline engine designed for supporting the related parts of the structure of heat exchanger size, and use empirical formula for the methanol cracker and other heat exchanger and thermal analysis of the strength check; the average temperature of the heat exchanger, heat transfer coefficient , Methanol consumption, heat transfer film coefficient, total heat transfer area, overall heat transfer coefficient and other parameters were computed and the results show that the size of the structure of the national standards are met and the heat exchanger design requirements.2) The use of GAMBIT software to establish a heat exchanger and related parts (tube sheets, flanges, etc.) of the three-dimensional model for the thermal convection after the simulation can proceed smoothly, the structural details of the components were properly Simplification; using GAMBIT software and related components for heat exchangers mesh and boundary conditions; describes the natural convection heat transfer model, while J. Bous sinesq hypothesis model assumptions are described And assumptions derived according J. Bous sinesq hypothesis model assumptions the basic natural convection boundary layer equations. Of the heat exchanger shell Distance established turbulence model, choose the standard k ~ ? turbulence model; pressure-velocity coupling equation ~ SIMPLEC methods used; flow equations and heat transfer equations are second-order upwind difference scheme, the fluid inlet and outlet by pressure into , outlet boundary conditions; heat the entire outer wall adiabatic boundary conditions.3) Based on computational fluid dynamics analysis software FLUENT6.0 temperature of heat exchanger, the internal flow field simulation, and the heat exchanger section of the pressure field analysis, the final software for use FLUENT6.0 Thermal efficiency of thermal simulation were carried out. In this paper, FLUENT6.0 software simulation results show: the thermal efficiency of the heat exchanger simulation shows that the heat exchanger can meet the vehicle needs of cracker on the heat, ie, after the heat exchanger after the shell fell within the atmosphere from eight to four Atmospheric pressure, exhaust gas temperature inside the tube pass the time from the entrance down to about 600℃200 ~ 250℃, exhaust heat released is mainly used for methanol...