Search

Urban utility tunnels have developed rapidly in recent years. The effective ventilation system maintains the air quality of the utility tunnel. In order to improve the ventilation performance of utility tunnel, a three-dimensional model of utility tunnel was established according to the design drawings. Based on Fluent 14.0 software, a flow model was established. And numerical simulation methods were used to study the optimization of air ducts and ventilation methods. The utility tunnel used top ventilation and interlayer ventilation. The ventilation methods of different ventilation areas of urban utility tunnels are compared. The results showed that the combination of operational gain and ventilation zone length mainly affected the ventilation effect. Based on the simulation results, a comprehensive ventilation mode consisting of top ventilation, natural ventilation at 400 m long entrance and mechanical outlet exhaust was proposed. Electric valve, fire door, exhaust fan and induction fan could be opened in the urban public utility tunnel at low speed. This new combination method is considered the optimal combination method for the maximum ventilation speed of urban utility tunnels. [ABSTRACT FROM AUTHOR]

The purpose of this article is is to investigate the critical speed and back-layer length of smoke propagation during fires of lithium-ion battery vehicles in tunnels. The combustion of lithium-ion battery vehicles in tunnels is numerically simulated. This article uses heat release rate (HRR) and ventilation rate to predict the length of smoke counterflow in tunnel fires with new energy vehicles. Temperature is an important parameter for calculating smoke counterflow. The temperature in the tunnel is measured by thermocouples. The results showed that dimensionless critical velocity influences dimensionless HRR. The numerical simulation results indicated that there is a certain correlation between the HRR variable, which corresponds to the dimensionless smoke counterflow length and the critical speed in the tunnel. This article proposed a computational model for predicting the length of smoke counterflow. This paper contributes to the prevention of tunnel fires and reduction of social and economic losses. Therefore, this paper guides the propagation of smoke under the roof of lithium-ion battery vehicle fires in tunnels. [ABSTRACT FROM AUTHOR]

The accuracy of heat load calculation directly affects the effectiveness of the heating system. The design specifications for Heating, Ventilation, and Air Conditioning (HVAC) building load calculations utilized the Tianzheng HVAC software (THS) load calculations and HDY-SMAD software (HSS). A 14-story residential building in Qingdao was taken as an example. The calculation of the heat load was biased and the results were compared with those calculated by the THS and HSS. The results showed that the winter load calculated was 251.3 kW by using HSS. The heat index per unit area in winter was 49.9 W/m2. The heat index per unit area was 32.6 W/m2 in summer. [ABSTRACT FROM AUTHOR]

This paper evaluates the influence of natural ventilation on the longitudinal temperature attenuation of cable tunnel wall fires. It took into account the effects of different fuel quantities, cable types, cable layers, and the number of cables per layer. Experimental tests were carried out in a cable tunnel. Results indicated that under natural ventilation the cable burns well. The cable total mass loss rate varies under different conditions. Moreover, under natural ventilation, cable combustion was affected by many factors. This paper analyzed the effect of natural ventilation on longitudinal dimensionless temperature attenuation. A mathematical model was proposed for longitudinal dimensionless temperature attenuation under natural ventilation cases. In addition, a predictive model for maximum temperature rise below the ceiling was proposed to address the effects of heat release rate (HRR) and ventilation on cable tunnel fires. The experimental results were compared with previous research results. Finally, this paper established a calculation equation for dimensionless fire source heat release rate. This paper provides guidance for the fire prevention of cable tunnels. [ABSTRACT FROM AUTHOR]