scholarly journals RESEARCH OF THE INFLUENCE OF EXTERNAL VERTICAL ENVIRONMENTAL STRUCTURES ON THE SPREAD OF FIRE ON THE SURFACE OF WALLS

Fire Safety ◽  
2021 ◽  
Vol 38 ◽  
pp. 38-48
Author(s):  
R. Yakovchuk

Purpose. Using FDS modelling to investigate the influence of external vertical enclosing structures on the spread of fire on the surface of external wall structures with facade insulation with combustible insulation.Methods. Using the software package Pyrosim performed тumerical modelling of the dynamics of development and spread of fire on the surface of the thermal insulation and finishing system, which serves as a user shell for the program Fire Dynamics Simulator (FDS). To visualize the results of calculations, the software module of the PyroSim Smoke view system was used, which allows building appropriate graphical representations of temperature distributions. This system also allows you to monitor the dynamics of temperature fields and reproduce the heating process with animation.Results. With the help of computer modelling of fire test parameters of facade insulation system for fire propagation in FDS environment, numerical and graphical indicators were obtained by computer simulation of the fire test parameters of the facade insulation system for fire propagation in the FDS environment. They characterize the process of occurrence, spread and development of fire by the surface of the facade insulation system. Also, we established the influence of external vertical enclosing designs on a fire surface of outside walls with a warming of a facade by a combustible heater. The obtained results of numerical modelling of the parameters of the fire test of the facade insulation system for the propagation of fire in the FDS environment indicate that the overall standard deviation in the theoretical data was higher than the results of experimental stud-ies. Thus, the presence in the structure of a fragment of the building vertical wall (inner corners of the building) creates a “shielding effect”, i.e. the flame emanating from the window is reflected and the temperature on the surface of external walls with facade insulation rises significantly. Thus, for thermocouples T15-T17 the temperature rises by 140-220 °C; for thermo-couples T19-T21 – by 180-350 °C; for thermocouples T27-T29 – by 110-190 °C, respectively.In addition, the presence of external vertical enclosing structures on the facade of the building contributes to the increase in temperature and inside the structures of external walls with facade insulation, as evidenced by the readings of thermocouples T33 and T35 – an increase of 50-100 °C; thermocouples T36 and T38 – increase by 50-180 °C.Practical value. The results of numerical simulations obtained by the author are aimed at the use of design organizations in the installation of fire belts using noncombustible mineral wool boards in the inner corners of the building as insulation in the presence of window and balcony openings to prevent fire from spreading on facade systems in residential buildings.

2000 ◽  
Vol 123 (1) ◽  
pp. 84-95 ◽  
Author(s):  
C. J. Ho ◽  
F. J. Tu

An experimental and numerical investigation is presented concerning the natural convection of water near its maximum-density in a differentially heated rectangular enclosure at high Rayleigh numbers, in which an oscillatory convection regime may arise. The water in a tall enclosure of Ay=8 is initially at rest and at a uniform temperature below 4°C and then the temperature of the hot vertical wall is suddenly raised and kept at a uniform temperature above 4°C. The cold vertical wall is maintained at a constant uniform temperature equal to that of the initial temperature of the water. The top and bottom walls are insulated. Using thermally sensitive liquid crystal particles as tracers, flow and temperature fields of a temporally oscillatory convection was documented experimentally for RaW=3.454×105 with the density inversion parameter θm=0.5. The oscillatory convection features a cyclic sequence of onset at the lower quarter-height region, growth, and decay of the upward-drifting secondary vortices within counter-rotating bicellular flows in the enclosure. Two and three-dimensional numerical simulations corresponding to the visualization experiments are undertaken. Comparison of experimental with numerical results reveals that two-dimensional numerical simulation captures the main features of the observed convection flow.


2016 ◽  
Vol 20 (5) ◽  
pp. 1407-1420 ◽  
Author(s):  
Jaime Sieres ◽  
Antonio Campo ◽  
José Martínez-Súarez

This paper presents an analytical and numerical computation of laminar natural convection in a collection of vertical upright-angled triangular cavities filled with air. The vertical wall is heated with a uniform heat flux; the inclined wall is cooled with a uniform temperature; while the upper horizontal wall is assumed thermally insulated. The defining aperture angle ? is located at the lower vertex between the vertical and inclined walls. The finite element method is implemented to perform the computational analysis of the conservation equations for three aperture angles ? (= 15?, 30? and 45?) and height-based modified Rayleigh numbers ranging from a low Ra = 0 (pure conduction) to a high 109. Numerical results are reported for the velocity and temperature fields as well as the Nusselt numbers at the heated vertical wall. The numerical computations are also focused on the determination of the value of the maximum or critical temperature along the hot vertical wall and its dependence with the modified Rayleigh number and the aperture angle.


2014 ◽  
Vol 627 ◽  
pp. 93-96 ◽  
Author(s):  
Raffaele Sepe ◽  
Enrico Armentani ◽  
Giuseppe Lamanna ◽  
Francesco Caputo

During the last few years various experimental destructive and non-destructive methods were developed to evaluate residual stresses. However it is impossible to obtain a full residual stress distribution in welded structures by means of experimental methods. This disadvantage can be solved by means of computational analysis which allows to determine the whole stress and strain fields in complex structures. In this paper the temperature distribution and residual stresses were determined in a single-pass butt joint welded by GMAW (Gas Metal Arc Welding) process by finite element model (FEM). A 3D finite parametric element model has been carried out to analyze temperature distribution in butt weld joints and thermo-mechanical analyses were performed to evaluate resulting residual stresses. Temperature fields have been investigated by varying an initial preheating treatment. Moreover the technique of “element birth and death” was adopted to simulate the process of filler metal addition The high stresses were evaluated, with particular regard to fusion zone and heat affected zone. The influence of preheating and post-heating treatment on residual stresses was investigated. The residual stresses decrease when preheating temperature increases. The maximum value of longitudinal residual stresses without pre-heating can be reduced about 12% and 38% by using the preheating and post-heating process respectively.


2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Abdullatif Ben-Nakhi ◽  
M. M. Eftekhari ◽  
D. I. Loveday

A computational study of steady, laminar, natural convective fluid flow in a partially open square enclosure with a highly conductive thin fin of arbitrary length attached to the hot wall at various levels is considered. The horizontal walls and the partially open vertical wall are adiabatic while the vertical wall facing the partial opening is isothermally hot. The current work investigates the flow modification due to the (a) attachment of a highly conductive thin fin of length equal to 20%, 35%, or 50% of the enclosure width, attached to the hot wall at different heights, and (b) variation of the size and height of the aperture located on the vertical wall facing the hot wall. Furthermore, the study examines the impact of Rayleigh number (104⩽Ra⩽107) and inclination of the enclosure. The problem is put into dimensionless formulation and solved numerically by means of the finite-volume method. The results show that the presence of the fin has counteracting effects on flow and temperature fields. These effects are dependent, in a complex way, on the fin level and length, aperture altitude and size, cavity inclination angle, and Rayleigh number. In general, Nusselt number is directly related to aperture altitude and size. However, after reaching a peak Nusselt number, Nusselt number may decrease slightly if the aperture’s size increases further. The impact of aperture altitude diminishes for large aperture sizes because the geometrical differences decrease. Furthermore, a longer fin causes higher rate of heat transfer to the fluid, although the equivalent finless cavity may have higher heat transfer rate. In general, the volumetric flow rate and the rate of heat loss from the hot surfaces are interrelated and are increasing functions of Rayleigh number. The relationship between Nusselt number and the inclination angle is nonlinear.


Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Paolo Mesolella ◽  
Sergio Nardini

A numerical analysis of mixed convection in gas saturated metal foam in a horizontal channel with an open cavity heated at uniform heat flux on a vertical wall is studied numerically. Non-local thermal equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 PPI and ε = 0.909, the fluid is air and for the assisting case. Results, for different Peclet and Rayleigh numbers, are given in terms of solid and fluid wall temperatures and local Nusselt numbers and stream function and temperature fields. Results show that diffusive effect determined lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. The interaction between the forced flow in the channel and the buoyancy due to the heated wall determines different thermal and fluid dynamic behaviors.


2012 ◽  
Vol 450-451 ◽  
pp. 1118-1122
Author(s):  
Xiu Yun Chen ◽  
Jian Hao Lin

The foam concrete used as surface materials and polyurethane used as core material for the development of new composite heat-insulated board of exterior insulation system. The research and applications showed that the thermal insulation system with excellent constructability, significant environmental benefits, economic and social benefits have been obtained. The implementation of 65% energy saving for residential buildings is the key of further work of energy efficiency in hot summer and cold winter zone, with huge market potential and the good application prospect.


Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Gianluca Tartaglione

Solar chimney is a new method to produce electrical power. It employs solar radiation to raise the temperature of the air and the buoyancy of warm air to accelerate the air stream flowing through the system. By converting thermal energy into the kinetic energy of air movement, solar chimneys have a number of different applications such as ventilation, passive solar heating and cooling of buildings, solar-energy drying, and power generation. Moreover, it can be employed as an energy conversion system from solar to mechanical. A component, such as a turbine or piezoelectric component, set in the path of the air current, converts the kinetic energy of the flowing air into electricity. In this paper, a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0.20 m for the vertical parallel walls configuration and at the inlet 0.34 m and at the outlet 0.20 m for convergent configuration. The chimney consists of a converging channel with one vertical wall and one inclined of 2°. The analysis is carried out on a three-dimensional model in airflow and the governing equations are given in terms of k-ε turbulence model. The problem is solved by means of the commercial code Ansys-Fluent. The numerical analysis was intended to examine the effect of the solar chimney’s height and spacing. Further, comparison between radiative and non-radiative model is examined and discussed. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles for a uniform wall heat flux on the vertical wall equal to 300 W/m2. Thermal and fluid dynamics behaviors are evaluated in order to have some indications to improve the energy efficiency of the system.


2014 ◽  
Vol 1073-1076 ◽  
pp. 1263-1270 ◽  
Author(s):  
Feng Qian

The text elaborates on the significance and profile of insulation system for external wall of residential buildings in our country, makes comprehensive comparison among the external wall's self-insulation system, external wall's internal insulation system, sandwich composite insulation system and external wall's external insulation system, and reveals that the external wall's external insulation system has the advantage of strong feasibility, law cost, effective heat insulation break bridge and protective structure, which offers great potential for existing buildings in energy-saving rebuilding, thus finding a widest application and enjoying a promising market prospects.


2012 ◽  
Vol 185 ◽  
pp. 90-93 ◽  
Author(s):  
Sami Ullah ◽  
Faiz Ahmad

In the intumescent fire retardant (IFR) coating char thickness and its strength play a vital role to protect the base steel structure from the fire. The IFR coating contains expandable graphite (EG), ammonium polyphosphate (APP), melamine, boric acid, bisphenol, epoxy resin BE-188 (BPA) which is used as a binder with ACR hardener H-2310 polyamide amine and multi wall carbon nanotubes (MWCNTs). A range of different formations were prepared to study the heat shielding effect and char expansion after fire test. The intumescent coating was tested at 800°C for one hour in the furnace and found to be very stable and well bonded with the steel substrate. The characterization was done by using Thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM) after fire test. The results confirmed that MWCNTs enhanced the char resistant of IFR coating on steel substrate after fire test. Keywords: Intumescent fire retardant coating, Expandable Graphite, Multiwall Carbonnano tubes, FESEM and TGA.


Author(s):  
Mehdi Boghrati ◽  
Ehsan Ebrahimnia Bajestan ◽  
Vahid Etminan

According to the importance of cooling and heating process of a solid object, entropy generation in confined flow around a block is studied. In the current study, numerical simulation of laminar flow and heat transfer of nanofluids with nanoparticles of different shapes is considered. The nanofluids are water mixture with either Al2O3 nanoshperes or carbon nanotubes (CNTs). The incompressible Navier-Stokes and energy equations are solved numerically in a body fitted coordinates system using a control volume technique. The flow patterns and temperature fields for different values of the particles concentrations are examined in detail. Furthermore, the effects of nanoparticles shape and concentration on the heat transfer are studied. Furthermore the influences of nanofluids on pressure drop and pump power is examined. On the other hand, the entropy generation minimization is considered as the optimization criterion. The results indicate that in most cases the nanofluids enhance the heat transfer as well as pressure drop. It is interesting to note that the shape of nanoparticles is critical in determining the key mechanism of heat transport in nanofluids. Nanofluids with cylindrical nanoparticles exhibit a greater increase in heat transfer compared with nanofluids having spherical shape nanoparticles.


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