Research Of The Oscillation And Impact Of Glass Flat Of High Temperature Flow In Lateral Opened Restricted Space

For a small opening space which has the determined cavity volume and thedetermined size, when existing the release of heat, in a certain proportion the threematches will produce the phenomenon in which the overall heat flow emits repeatedlyaccording to certain rules. This phenomenon has been carefully studied by a numberof scholars, but in theory it has not get the recognized conclusion, and the relevantresearches is largely confined to reports and description of scattered experimentalphenomena.In recent years, various buildings tend to glass curtain wall materials because ofthe beauty, convenient and the transparent light and spacious interior. However ifthere is combustible material in the small space under a glass wall, the overall heatflow may be at the risk of oscillation. Especially the outer enclosure glass curtainwalls of high-rise building, it generally have lower installation channel and the smallspace in bottom, and in these small spaces often there are combustible materials usedin decoration. Combustible hot flue gas will rapidly reach the upper floor because ofthe chimney effect. In certain conditions, the overall heat flow oscillations are proneto make the glass curtain wall damaged, and the broken glass may injure people.In this paper, systematic study of basic experimental phenomena and engineeringtheory calculations for low-frequency oscillatory heat flow in a small space withlimited lateral opening are done, and the theory indication basic formula for typicalexperiments also are obtained. Based on this study, the basic experiments of the singleheat flow lateral swatting at the glass is taken, and the comparison between theoreticalanalysis results and simulation results is made.On the ISO9705fire standard laboratory bench, the experimentation for theoccurrence, maintenance and the strength of hot air oscillation is done, whichaccording to four typical openings, average heat release rate of650kW, and theburning time of about350s. The oscillation frequency under the experimentalconditions range of0.1~0.25Hz and the result are modified and compared to thefundamental oscillation frequency derived from mass and energy equations. It alsocompares to previous experimental results of other scholars. Recorded image showsthe basic situation of overall oscillation with the different openings sizes, different locations, different temperature difference between inside and outside, and if with theeffect of buoyant.Next in this paper, two types of mathematical models for oscillation in smallspace caused by high-temperature hot are constructed, the relationship amongoscillation frequency f, oscillation rate α and the function of oscillation responsecapability Rmis given. It also determines the characteristics lag time with the effect ofbuoyancy-driven and the characteristics lag time with the effect of pressure-driven.The relationship among oscillation frequency, average indoor temperature, dischargearea and space size of pressure-driven flow and buoyancy-driven flow in a smallspace are obtained.The paper shows the function of two-dimension distribution on the temperaturechange plane when the flame and high temperature air swatting the side of the glasssurface in typical experimental conditions. The analytical solutions of thermal stress,hot bending moments and displacement under the condition that different constraintsand changes in temperature distribution are given. It provides the basis of theoreticalcalculations for the position fracture critical stress occurring and the indicating forbroken time. According to the temperature distribution and the four kinds of typicalconstraints border around the glass plate, it gives the heat stress and displacementdistribution within the glass in different time. It can be observed in which constraintform stress and displacement is much larger, so it will determine the impact ofconstraint form to extension of glass broken time. It uses ANSYS to carry onnumerical simulation for the impact on glass plate of hot air varying with time. Andthen it gets the numerical result about the glass plate heat stress and heat bendingmoment changes in the different case of heat shocking. It also compares fourconstraints and obtained in which form the tensile stress of the glass by the minimumin order to specify the direction for construction.