Research On Optimal Design Of Thermal Insulation Performance For Vehicle Shelter

The vehicle shelter is an indispensable equipment in the field of emergency rescue.The improvement of its thermal insulation performance is of great significance to the thermal comfort of the cabin environment,the design of the environmental control system,and energy saving and emission reduction.Based on the basic theories of computational heat transfer,computational fluid dynamics and statics,this paper takes a vehicle shelter as the research object,with the help of numerical simulation,multi-objective optimization and full factor test design methods to carry out the optimization design research on the thermal insulation performance of the vehicle shelter,the main research content and conclusions are as follows.(1)The heat transfer simulation analysis of the vehicle shelter was carried out.CFD models of large slabs and heat leakage types of shelters were established according to different focuses.The heat flow,temperature distribution and heat flow density distribution of each model were obtained by simulation,and it is clarified that the weak link of shelter heat insulation is the thermal bridge effect caused by metal components such as skeleton,skin and rivets.(2)The calculation of the K value of the vehicle shelter and the experimental research on the thermal insulation performance were carried out.A method for calculating the equivalent area of the vehicle cabin K with consideration of heat leakage compensation is proposed.Based on the results of steady-state heat transfer simulation,the equivalent area method and the equivalent area correction method are used to calculate the K value of the whole cabin to be 1.6786W/(m~2·K)and 1.7759W/(m~2·K);Through the vehicle shelter heat insulation performance test,the calculated test K value is 1.8076 W/(m~2·K),it is found that the simulated K value obtained by the equivalent area correction calculation method is more consistent with the experimental K value,which verifies the correctness and feasibility of the K value correction calculation method and the heat transfer numerical simulation method.(3)Research on the factors affecting the insulation performance of the vehicle shelter.The concept of heat transfer ratio of the framework is introduced to evaluate the thermal bridge effect of the framework in the steady-state heat transfer process.Based on the controlled variable method and heat transfer numerical simulation analysis,it is concluded that the thermal insulation core and thermal insulation bridge with small thermal conductivity can effectively reduce the K value of the large plate,and the thermal conductivity of the thermal insulation core has the greatest impact on the K value;when the skeleton density is only 13.72%,the heat transfer ratio of the framework is as high as 56.65%,and there is a serious thermal bridge effect at the framework;the uniformity of the framework structure has a relatively small influence on the thermal insulation performance of the cabin slab.(4)The structural optimization design and simulation verification of the vehicle shelter are carried out for the thermal insulation performance.A new type of dual-core coated composite thermal insulation core is proposed.The thermal insulation core uses PU as the base material,aerogel and VIP as the core material;the thickness of the two core materials is selected as the design variable,and the equivalent of the dual-core thermal insulation core Thermal conductivity and areal density are the optimization goals,and the orthogonal polynomial proxy model and the NSGA-II algorithm are combined to perform multi-objective optimization of performance.Based on the optimized dual-core thermal insulation core to verify the performance of the mid-top plate,it is concluded that the heat transfer coefficient of the mid-top plate is reduced by 16.13%and the thermal insulation performance is significantly improved under the design requirement of areal density,which verified the effectiveness of the optimization plan for the thermal insulation core structure.Three structural design schemes for skeleton profiles are proposed,and the structural form with PA66 heat insulation strips is selected for optimal design.Take the width,height and the distance of the central axis from the central axis of the skeleton profile as factors,and take the maximum displacement,maximum equivalent stress,K value and surface density of the shelter slab as the target response,and a three-factor three-level design Full-factor simulation test is designed.Put forward the comprehensive evaluation index Z of slab mechanics,heat insulation and quality performance,and the optimal parameter combination of heat insulation strip is determined.It is concluded that the mechanical properties and areal density of the optimized mid-top plate meet the design requirements,the K value is reduced by 10.21%,the heat insulation performance is significantly improved,and the heat transfer ratio of the skeleton is reduced by 4.24%,which verifies the effectiveness of the optimization plan for the skeleton profile structure.