Study On Uncertainty Of Fluid Flow And Heat Transfer Performance Of Heat Exchanger Based On Stochastic Collocation Method

Shell and tube heat exchanger plays a leading role in today’s heat exchange equipment by virtue of its economy and reliability.At present,most of the numerical simulation research on shell and tube heat exchanger adopts certain geometric model and boundary conditions.However,there are many uncertain factors in the operation condition of shell and tube heat exchanger,such as geometric model uncertainty,operation condition uncertainty and so on.These uncertainties are one of the important reasons for the complexity of fluid flow in heat exchanger.Therefore,it is of great practical significance to further study the uncertainty in the process of flow and heat transfer.In this paper,the uncertainty analysis method of stochastic collocation method is used to simulate and analyze the two-dimensional staggered plate and shell and tube heat exchanger.The specific work contents are as follows:(1)The influence of uncertainty on the flow and heat transfer performance of two-dimensional staggered heat exchanger was studied when the inlet temperature,inlet velocity,viscosity and thermal conductivity were random variables.The random variables are sampled according to the uniform distribution function,and each group of random boundary conditions is substituted into the deterministic simulation program for calculation.The coefficients of the polynomial are calculated to obtain the statistical value of the concerned response,and the influence of each random variable on the system is quantified.The results show that the uncertainty of fluid inlet temperature has the greatest influence on the temperature distribution of the heat exchange plate,followed by the thermal conductivity of the fluid.The inlet temperature of the fluid has the greatest influence on the velocity distribution of the heat exchanger plate.(2)A numerical simulation program framework is built to quantify the uncertainty of fluid flow and heat transfer in shell and tube heat exchanger under random boundary conditions and physical parameters.Considering the fluid inlet temperature,fluid inlet velocity,fluid viscosity and fluid thermal conductivity in shell and tube heat exchanger as random variables with uniform distribution,this method uses non embedded polynomial chaotic expansion to express the output random field response,selects the appropriate collocation,solves the deterministic equations by coupling,and finally obtains the statistical characteristics of the random output field,By using Sobol global sensitivity analysis method,the relative contribution of each uncertain boundary condition to the total output variance is quantified.The results show that the inlet temperature uncertainty of shell and tube heat exchanger has an important influence on the temperature distribution.Secondly,the influence of the uncertainty of air thermal conductivity on the temperature distribution gradually increases along the flow direction.The uncertainty of fluid thermal conductivity has the greatest influence on the convective heat transfer capacity of shell and tube heat exchanger.This paper provides an efficient research method for quantifying the uncertainty of fluid flow and heat transfer in shell and tube heat exchanger,and the analysis conclusion has guiding significance for the comprehensive evaluation of heat exchanger performance.