| The rapid development of urban society makes the superiority of the integrated utility tunnel become more and more prominent.The ventilation resistance coefficient is an important parameter of the integrated utility tunnel’s ventilation system.It is extremely important for the design of the integrated utility tunnel’s ventilation system.Only by correctly grasping the heat dissipation law of the cables in the power cabin under different working conditions can we get the most economic ventilation volume required for the cabin to meet the requirements.The scale model experiment under the guidance of similarity theory has been widely used in the study of ventilation engineering in large space and long distance.In order to verify the similarity theory,the scale model is established according to the scale ratio of 5:1.Using the similarity theory,the similarity criterion numbers are derived,and under the condition of neglecting number of Gr,the proportional relationship of the physical parameters between the prototype and model in each boundary condition of the are obtained.The simulation calculation of different working conditions is carried out by Fluent software.The results show that the temperature,heat flux,velocity and resistance coefficient of each working condition are in accordance with the theoretical derivation proportional relationship,and the error of each parameter is within the range of 10%.Under the guidance of similar theory,the scaled experimental platform was established according to the scale ratio of 5:1.The cabins of six different pipeline layouts were tested under different air volume conditions.The average velocity distribution and total pressure distribution of each working condition was obtained.The experimental results of the working conditions without pipeline arrangement and the calculation results of the empirical formula are compared and verified.The integrated utility tunnel is divided into the inlet section,the exhaust section and the intermediate stability section.The resistance characteristics and local resistance characteristics of each working condition are analyzed.The polynomial regression is used to obtain the resistance coefficient and the ratio of Re and pipeline area.The fitting relationship,the error is also within 10%,which provides a theoretical basis for the optimal design of the ventilation system.The experimental results are compared with the numerical simulation results,and the reliability of the numerical simulation calculation is verified.The roughness,the size of the inlet and outlet,the ventilation form,the aspect ratio,the pipeline layout and the velocity are analyzed.The sensitivity of the factors affecting the coefficient of ventilation resistance,and the equivalent diameter,aspect ratio,Re and pipeline area ratio were selected as the influencing factors.The multivariate linear regression was performed on the calculation results of 54working conditions,and the resistance coefficients of each part were obtained.The fitting relationship of the relationship,the goodness of fit R~2 of each relationship is above 0.791.In the application analysis process of heat dissipation of power cabin,four influencing factors of heat dissipation heat flux,wall temperature,inlet air temperature and ventilation volume were selected,and the ventilation efficiency was evaluated by the ratio of heat dissipation efficiency and ventilation heat dissipation to total heat dissipation.The index analyzes the influence of different factors on the ventilation effect.The fitting relationship between the highest average air temperature and various factors is obtained by multiple linear regression,which provides a reference for the safe and energy-saving operation of the ventilation system. |
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