Optimization And Control Of Indoor Air Flow Based On CFD And Adjoint Method

The indoor air flow is responsible for heat and pollutant transport,which embrace the thermally comfortable and healthy indoor environment.As the traditional method of building indoor air distribution cannot meet the needs of individualized demand and energy saving at the same time,this work developed state-of-the-art methods for inverse design of an enclosed environment.Contrary to the traditional parametric research,this optimization and control method of indoor air flow,starting from the objective demand,based on adjoint method and CFD,provide a theoretical basis for creating an efficient,safe,sustainable and individualized indoor air flow.This paper takes into account the characteristics of indoor air flow and indoor heat and pollutant source,conducts quantitative analyses about the formation process of temperature,velocity and pollutant field in different regions,and then propose a multi-variable and multi-objective inverse optimization algorithm according to the influence mechanism of each parameter on indoor environment.This algorithm,verified by experiments thereafter,couples the multi-parameter and multi-physical field of indoor environment,designs the environment parameters,thus effectively reducing building energy consumption and ensuring reasonable indoor environment.Specific innovative work is as follows,(1)The mechanism of fluid convection in building ventilation and conjugate heat and mass transfer process is investigated firstly.And then the governing equations are derived from the spatial position variable function.Without any prior flow field information,multiple boundary heating fluxes of the enclosed environment are identified by inverse identification algorithm,which is based on the auxiliary equations of sensitivity problem and adjoint problem.Many factors including measure points' location,number and noise(e.g.,measurement error)are discussed about the influence on the inverse flow simulation and its calculation accuracy.(2)For the spatial distribution of multiple discrete heating sources in natural convection enclosed rooms,a theoretical analysis of the relationship between global heat conduction performance and discrete heat sources is established based on the constructal theory.Based on the sensitivity derivative of the global heat conduction,the adjoint method is employed to optimize the spatial locations of discrete heating sources with specific sizes.According to the linear regression,the functional relationship between the optimal global heat conduction and the control parameters is established.(3)A double air channel solar chimney has been thoroughly studied on ventilation characteristics by analyzing its temperature distribution and outlet velocity under different sets of length-width ratio,heat flux density and inclination angle.And then the computational fluid dynamic coupled with adjoint method is established for the double air channel solar chimney.Furthermore,the effectiveness and reliability of the inverse algorithm is verified by identifying and optimizing the optimal configurations of double air channel solar chimney.(4)The removal and control of indoor pollutants by mechanical ventilation and multi-component buoyancy are studied.For the direct problem,considering the multi-component buoyancy effect,the transport mechanism of indoor heat and pollutants is studied.For the inverse problem,the single-objective optimization is conducted firstly,and the optimized value is taken as the dimensionless scale of the multi-objective optimization function.Then,the multi-objective function is established by combining the spatial average concentration and the average diffusion radius.The contaminants in different flow patterns are effectively controlled by the gradient-based adjoint method.(5)Computational fluid dynamic(CFD)is exploited to investigate and explore the heat and mass transfer process which is driven by natural convection and forced convection about its flow mechanism,multiple-steady region and inducing condition,thus providing the theoretical basis for ventilation strategy,heat and pollutant removal in industrial production processes.The streamlines,heatlines and masslines are used to describe and analyzed the fluid flow,heat and mass transfer.