Study On Ventilation System Of Cable Cabin In Underground Integrated Pipe Gallery

The integrated pipe gallery is the corridor of the pipeline,also known as the common trench.Mainly through the comprehensive planning layout,a variety of municipal pipelines are laid in large pipe corridors.The cable compartment is one of the important compartments in the integrated pipe gallery.It is a closed underground building.Cable heating and wall moisture will deteriorate the indoor temperature and humidity environment,so that bacteria and other microorganisms can breed,and various harmful gases will also be in the cable compartment.Internal accumulation.Therefore,the integrated duct cable compartment is usually provided with a ventilation system to remove residual heat,residual moisture and harmful toxic gases in the cabin.At present,the calculation method of indoor ventilation volume of cable cabins adopts the method of gas exchange times,but all of them are empirical data,and the results are not accurate enough to meet the requirements of high efficiency ventilation of modern integrated pipe corridors.This paper first studies the factors affecting the ventilation of the cable compartment: waste heat,residual moisture and harmful toxic gases.Among them,the common insulating layer materials of 10 kV and 110 kV are cross-linked polyethylene,which decomposes under high temperature to produce three by-products of cumyl alcohol,acetophenone and methane.Among them,both cumyl alcohol and acetophenone are liquid,so the harmful toxic gases in the cable compartment are mainly methane.Secondly,the calculation method of ventilation amount corresponding to each factor is analyzed.It can be seen that the amount of ventilation required for exhaust heat is greater than the amount of ventilation for draining moisture and discharging harmful toxic gases.When the ventilation is 3.28m3/s,that is,the number of air changes is 7.56 times/h,it can meet the ventilation requirements of the actual engineering case.Several common cable cabin ventilation forms are listed in the article.Firstly,the characteristics of the temperature field,humidity field and velocity field of the cable compartment under different mechanical ventilation modes are explored.It can be seen that the high temperature air gathers at the exhaust vent and the temperature is significantly higher than the cabin.In other areas,the air temperature at the top of the cabin is higher than the bottom.The humidity exchange in the cabin is distributed at the air inlet.The relative humidity distribution in the cabin is relatively stable and low in the middle.Secondly,the characteristics of the temperature field and humidity field of the cable cabin under the number of air changes of 2,4,6,8,10,12 times per hour are explored.The common one-to-one row ventilation form is taken as an example,and the section temperature(40 °C)is adopted.The non-guaranteed rate is used as the criterion.It can be seen that the temperature non-guarantee rate on the cross section is 35.42% when the number of air changes is 2 times/h,and the temperature on the cross section is not increased when the number of air changes is increased to 8 times/h or more.The guarantee rate is 0%,so the optimal number of air changes is 8 times/h.On the basis of numerical simulation,the paper evaluates several mechanical ventilation systems based on the evaluation indexes of heat removal efficiency,temperature non-guarantee rate,moisture discharge efficiency and humidity nonguarantee rate.It can be seen that the ventilation pattern of one row and one row is optimal under the indexes of heat removal efficiency and moisture discharge efficiency,and the two-in-one row ventilation form is optimal under the evaluation index of humidity nonguarantee rate.The induced ventilation form is optimal under the evaluation index of temperature non-guarantee rate.In order to evaluate the four types of ventilation more comprehensively,the AHP-fuzzy comprehensive evaluation method is used to quantitatively analyze various mechanical ventilation methods.The results show that the comprehensive scores of induced ventilation and one-to-one mechanical ventilation are 82.25 and 81.25,both of which are Better ventilation.The cable cabin ventilation was studied.Firstly,the factors affecting the average temperature of the exhaust air were analyzed.The results showed that the outside air temperature,the soil temperature around the cabin and the heat generation of the cable were positively correlated with the average temperature of the exhaust air.The remaining factors and the average temperature of the exhaust air were Negative correlation.Secondly,the seven factors are set as independent variables.The orthogonal analysis method makes significant analysis.The external air temperature,the perimeter of the cabin section,the number of air changes and the heat generation of the cable have the most significant effect on the ventilation effect.Finally,the multi-linear regression model is used to fit the cable cabin ventilation calculation formula,which provides a theoretical reference for the selection of the cable cabin ventilation system and the calculation of the ventilation volume.