Research On The Influence Of Air Duct Structure On Air Distribution In Artificial Environment Laboratory

With the implementation of national energy-saving emission reduction policies,the energy efficiency requirements of air-conditioning and refrigeration equipment are getting higher and higher,so the performance test accuracy of air-conditioning and refrigeration equipment is particularly important.As a test device for testing various types of air conditioning and refrigeration equipment,the artificial environment laboratory shall provide uniform and stable working environment for the sample to be tested when collecting the performance data of the prototype of the tested air conditioning and refrigeration equipment.Both national and international standards made a detailed description for the corresponding prototype test conditions and allowable amplitude,such as the national standard GB/T17758-2010 allows cold-type unitary air-conditioning mechanism for maximum dry-bulb temperature changing amplitude value is 1?,and the average change of amplitude is 0.3 ? under the cold test condition.The better the homogeneity of the flow field in the artificial environment laboratory is,the smaller the gradient of the flow field around the prototype and the more stable the experimental conditions will be,so it is very necessary to study the uniformity of the flow field inside the artificial environment laboratory.At the same time,the internal flow field of the artificial environment laboratory is closely related to the supply air duct structure,the return air duct structure and the static pressure space structure.In this paper,the influence of geometric structure design on the distribution of airflow structure from the three dimensions of return air static pressure space,supply air duct structure and return air duct structure is studied.The structural dimensions of the supply air duct structure have been calculated by the theoretical calculation of its square air supply duct,30° slope air supply duct,45°slope air supply duct,60°slope air supply duct,highly continuous slope air supply duct and constant air volume continuous with the same air supply under the same blast condition and is verified by the test results.The maximum relative error between measured and calculated is 16.35%and the recommended air supply speed is 2?6m/s.Three ways as the uniformity index,the air supply efficiency index and the comprehensive index to evaluate the air supply duct is put forward,and when using the comprehensive index to evaluate the thermal performance of the air supply duct structure,the 60°slope air supply duct is recommended.Further,this article sent back to the artificial environment laboratory for six air supply duct structure of three return air static pressure space structure of no air supply static pressure space,single supply air static pressure space and double return air static pressure space;the square air supply duct,30°slope air supply duct,45°slope air supply duct,60°slope air supply duct,highly continuous slope air supply duct and constant air volume continuous slope air supply duct;three return air duct structure of flat roof,triangular roof and trapezoidal top,with a total of 10 kinds of structural design to a detailed numerical simulation,and its three structures were verified.The following conclusion is obtained:(1)The supply air static pressure space is beneficial to the stability and uniformity of the flow field in indoor the test area.The structural design of the double return air static pressure space has little effect on the flow field in the test area of the laboratory.(2)The influence of the cross-section blast air duct on the temperature field in the laboratory is small,and the main influence is on the velocity field.The slope inside the square pipe is beneficial to the uniform air flow of the four air vents and the constant air volume continuous slope air supply duct works best.(3)The slope return air duct design has a more stable temperature field in the test area of the laboratory,and the triangular and trapezoidal roof designs allow the wind speed fluctuations in the test area to be smaller and more stable.(4)It is recommended to use the single return draft static pressure space/60°slope air supply duct/flat roof return air duct design,and the recommended air supply speed under this structure is 2?6m/s.