RU2229910C1 - Method of reducing action of energy flow, namely light, heat and convective gas flow, fire-proof screen and fire protection device based on the screen - Google Patents

Abstract

FIELD: fire-protection equipment, particularly for local fire extinguishing in industrial and civil objects with high fire risk, for increasing fire-resistance of fire screens and covers. SUBSTANCE: fire-proof screen and fire-resistant cover based on fire-proof screen have fire resistant and heat resistant layers made of silica or basalt fibers or of combination thereof. Fire-resistant layer density increases towards fire action area. Sprayed cooling liquid is used for intensifying evaporative cooling. EFFECT: simplified structure, reduced cost. 6 cl, 6 dwg

Description

The invention relates to fire fighting equipment and can be used for local fire extinguishing in industrial and civilian facilities with increased fire hazard, protection against fire penetration, fire, and also to increase the fire resistance of screens and shelters.

The fire screens used by the special shelter are subject to increased requirements for the provision or duration of fire protection and performance at high temperatures for a certain time necessary to take measures to actively combat the spread of fire and its elimination.

There is a method of attenuating the effects of an energy flow in the form of light, heat and convective gas flows, including the supply of controlled spray of coolant to the surface of a fire-resistant screen with the creation of a vapor-droplet-air medium (patent RU No. 2182024, IPC ⁷ A 62 C 2/08, 2002).

There is a method of shielding a fire flow by means of a mesh screen with a film coolant flow supplied from above (patent RU No. 2156628, IPC ⁷ A 62 C 2/08, 2000).

Also known is the shielding of heat fluxes using water-containing components in layers of fibrous material with a definite period of use (patent RU No. 2162189, IPC ⁷ F 16 L 59/02, 2001).

Known fire-resistant screen containing fire-resistant and heat-resistant layers (patent RU No. 2182024, IPC ⁷ A 62 C 2/08, 2002).

Known fire screen with fire-resistant and heat-resistant mesh layers (patent RU No. 2143634, IPC ⁶ F 16 L 59/02, 2000).

A similar fire-retardant material with external fire-resistant and intermediate heat-resistant layers of fibrous materials is known (application GB No. 2351021 A1, IPC ⁷ A 62 C 2/06, 1999).

Known fireproof shelter containing a fireproof screen with fireproof and heat-resistant layers of ceramics and a tubular frame with communicating channels nozzles for controlled supply with spraying coolant to the surface of the fire exposure of the screen with the creation of vapor-droplet-air environment (patent RU No. 2182024, IPC ⁷ A 62 C 2/08, 2002, patent RU No. 2156628, IPC ⁷ A 62 C 2/08, 2000).

Known fire barrier containing a flame retardant shell mounted on a frame frame, and fire extinguishing means (patent RU No.2014856, IPC ⁵ A 62 C 13/00, 1994).

Other devices are known for extinguishing fires in local volumes using coolant atomization means (patent RU No. 2079316, IPC ⁶ A 62 C 31/05, 1997, patent RU No. 2173193, IPC ⁷ A 62 C 31/05, 2001).

Other devices used screens with heat-resistant properties (patent RU No. 2111779, IPC ⁶ A 62 C 8/06, 1998, patent EP No. 0631515 B1, IPC ⁶ A 62 C 8/06, 1996).

The specified fire fighting equipment, their screens are created using different principles of protection against fire exposure without taking into account and development of phenomena and effects that occur in the structures of the screens themselves, their layers and materials, which does not allow to increase the effectiveness of fire fighting of the equipment itself.

The closest analogs selected from the set of common essential features adopted as prototypes are a method of attenuating the effects of an energy flow in the form of light, heat and convective gas flows according to RU patent No. 2182024, a fire-resistant screen made of fire-resistant and heat-resistant layers according to RU patent No. 2182024 and fireproof shelter according to patent RU No. 2182024. The main objective is to create a method of attenuating the effects of the energy flow in the form of light, heat and convective gas flows, a fireproof screen and a fireproof shelter based on it using a new concept to increase their efficiency with the possibility of the manifestation of a synergistically intense process of continuous physical effect of evaporative cooling when creating vapor-drop air from the coolant in the structure of the fireproofing materials.

The technical result from the use of inventions is to increase the time to counter the penetration of fires, simplifying structures, ease of maintenance and improving reliability in operation.

The problem is solved and the technical result is achieved by changing the location of the fibrous materials, based on their properties, distribution of the increase in their density in the direction of the surface of the fire exposure, using the concept of the manifestation of the synergistically intense process of continuous physical effect of evaporative cooling inside the screen structure simultaneously with the fire resistance and heat resistance of external and internal capillary-porous fibrous materials.

To this end, in a method of attenuating the effects of an energy flow in the form of light, heat and convective gas flows, including supplying a controlled spray of cooling liquid to the surface of a fire-resistant screen with the creation of a vapor-droplet-air medium, a screen is used with heat-resistant capillary-porous fibrous layers distributed between its outer fire-resistant layers material surface density with increasing density from 70 to 700 g / m ² towards the surface with the ability to fire exposure symptoms or inergicheski intensive process of physically continuous evaporative cooling effect.

In a fire-resistant screen containing fire-resistant and heat-resistant layers, the heat-resistant layers are made of needle-punched or needle-stitched material of a capillary-porous structure of silica or basalt fiber with a diameter of 2-15 μm, or a combination of them, with a distributed surface density of 70 to 700 g / m ² with an increase in surface density in the direction of the surface of the fire exposure, with external fire-resistant layers of fabric based on silica or basalt fibers with a diameter of 5-15 microns, or a combination of them, surface minutes a density of from 120 to 700 g / m ^2, with a grid with a mesh size of 5 × 5 × 25 mm to 25 mm from a steel wire with a diameter of 0.1-1 mm below the outer fire resistant layer on the surface side of fire exposure at a ratio of thicknesses heat- and fire-resistant layers from 5: 1 to 20: 1, with the possibility of their manifestation of a synergistically intense process of continuous physical effect of evaporative cooling with controlled spraying of coolant on the surface of the fire exposure with the creation of a vapor-droplet-air environment. The outer flame retardant layers of the fabric can be impregnated with a composition that reflects thermal radiation.

In a fireproof shelter containing a fireproof screen with fireproof and heat-resistant layers and a tubular frame with communicating channels and nozzles for controlled supply with a spray of coolant on the surface of the fire exposure of the screen with the creation of a vapor-droplet-air medium, the heat-resistant layers are made of needle-punched or needle-stitched capillary-porous material structure of silica or basalt fiber diameter of 2-15 microns, or a combination of them, with distributed surface density from 70 to 700 g / m ² velicheniem surface density toward the surface fire exposure, with external layers of fire resistant fabric based on silica or basalt fibers 5-15 microns in diameter, or combinations thereof, the surface density of from 120 to 700 g / m ^2, with grid cell size of from 5 × 5 mm to 25 × 25 mm from steel wire with a diameter of 0.1-1 mm under the outer flame-retardant layer on the side of the surface of the fire exposure, with a ratio of the thicknesses of the heat-resistant and fire-resistant layers from 5: 1 to 20: 1, with the possibility of a synergistically intense otsessa continuous physical effect of evaporative cooling. In a fireproof shelter, the outer fire-resistant layers of the screen fabric can also be impregnated with a composition that reflects thermal radiation. The tubular frame can be equipped with fastened with it, and the screen connected to it in its lower part by flexible connections, pointed pins for fixing in the ground.

Distinctive features of the method are the signs:

- the use of a screen with heat-resistant capillary-porous layers of fibrous material with a surface density of 70 to 700 g / m ² distributed between its outer fire-resistant layers with an increase in density in the direction of the fire surface;

- the possibility of the manifestation of heat-resistant layers of a synergistically intense process of the continuous physical effect of evaporative cooling.

Distinctive features of a fireproof screen and fireproof shelter based on it are the signs:

- the implementation of heat-resistant layers of needle-punched or needle-punched material of a capillary-porous structure of silica or basalt fibers with a diameter of 2-15 microns, or a combination of them;

- distributed surface density of heat-resistant layers from 70 to 700 g / m ² with an increase in surface density in the direction of the surface of the fire;

- the implementation of the outer fire-resistant layers of fabric based on silica or basalt fiber with a diameter of 5-15 microns, or a combination of them, with a surface density of 120 to 700 g / m ² ;

- the presence of a mesh with cells from 5 × 5 mm to 25 × 25 mm made of steel wire with a diameter of 0.1-1 mm under the outer flame-retardant layer on the side of the surface of the fire exposure;

- the ratio of the thicknesses of the heat-resistant and fire-resistant layers from 5: 1 to 20: 1;

- the possibility of the manifestation of heat-resistant layers with the indicated properties of a synergistically intensive process of continuous physical effect of evaporative cooling;

- the presence of an impregnating composition in the outer flame retardant layers, reflecting thermal radiation.

Additional distinctive features of a fireproof shelter are the signs:

- supplying the tubular frame with pointed pins fastened to it;

- the supply of a fire-resistant screen connected to it by flexible connections with pointed pins;

- the possibility of fixing the pointed pins in the ground.

The indicated distinguishing features and methods of making a fire-resistant screen and fire-retardant shelter based on it are essential, since each of them individually and jointly aims to solve the problem and achieve a new technical result. The manifestation in the method using a fireproof screen of a capillary-porous material with increasing density to the surface of the fire exposure of the intense process of continuous physical effect of evaporative cooling, synergistically arising with the creation of a vapor-droplet air medium with controlled spraying of coolant onto the fire surface of the screen, creates a fireproof barrier of increased ultimate durability and efficiency. Such results are most optimal in fibrous materials with a density of 70 to 700 g / m ² . The method is implemented in a fireproof screen and shelter from it due to the implementation of heat-resistant layers of needle-punched or needle-stitched material from silica or basalt fiber with a diameter of 2-15 microns, or a combination of them, the ratio of heat-resistant and fire-resistant layers ranging from 5: 1 to 20: 1 when performing fire-resistant layers of fabric based on silica or basalt fiber with a diameter of 5-15 microns, or a combination of them, with a surface density of 120 to 700 g / m ² . Placement under a fire-resistant layer on the side of the surface of the fire exposure of the mesh with cells 5 × 5 mm to 25 × 25 mm from steel wire with a diameter of 0.1-1 mm is intended to provide the form of stability of the fireproof shelter, the package of layers for the period of the fire exposure, eliminating their gap beyond the maximum possible temporal parameters of fire exposure.

The reflection of thermal radiation contributes to the impregnation of the appropriate composition of the outer flame-retardant fabric layer. The retention of the fireproof screen from the effects of wind loads is facilitated by the fixation of its tubular frame and screen with pointed pins in the ground.

These distinctive essential features of the method, the screen and the shelter from it are new, since their use in the prior art, analogues and prototypes were not found, which allows us to characterize the proposed technical solutions as meeting the criterion of “novelty”.

A single set of new essential features with common known essential features allows us to solve the problem of creating a method of attenuating the effects of energy flow in the form of light, heat and convective gas flows, creating a fire-resistant screen and fire-retardant shelter based on it due to the density distribution of fibrous materials with increasing them to the surface fire exposure, use with the blocking thermal properties of fibrous materials in both heat-resistant and fire-resistant layers, and x the ratio of the synergistically intense process of continuous physical effect of evaporative cooling with controlled spraying of coolant onto the surface of the fireproof screen with the creation of a vapor-droplet-air medium, which characterizes the proposed technical solutions by significant differences from the prior art, analogues and prototypes. New technical solutions are the result of development and experimental research, creative contribution, without the use of standardized developments or any recommendations in this technical field, based on the use of new principles for constructing structures of fibrous materials, the use of new physical effects, are original and non-obvious for specialists, correspond the criterion of "inventive step".

The invention is illustrated by drawings with a brief description.

Figure 1 presents a General view of the fire-resistant screen, figure 2 is a General view of the fireproof shelter, figure 3 is a cross section of the screen, figure 4 is a scan of the shelter screen in a view with an external surface, figure 5 is a scan of the screen shelter in a view with an inner surface, Fig.6 is a diagram of the mounting of the tubular frame and screen with pointed pins in the ground.

A more detailed description of the essence of the invention with showing the positions in the drawings is as follows.

Fire-resistant screen (figure 1) contains fire-resistant and heat-resistant layers 1, 2. Heat-resistant layers 2 are made of needle-punched or needle-stitched material of a capillary-porous structure of silica or basalt fiber with a diameter of 2-15 μm, or a combination of them, with a distributed surface density of 70 to 700 g / m ² with an increase in surface density in the direction of the surface of the fire exposure 3, with the outer fire-resistant layers 1 of a fabric based on silica or basalt fibers with a diameter of 5-15 microns, or a combination of them on top with a density of 120 to 700 g / m ² with mesh 4 with mesh sizes of 5 × 5 to 25 × 25 mm made of steel wire with a diameter of 0.1-1 mm under the outer flame-retardant layer 1 from the side of the fire surface 3, with a ratio of thicknesses heat-resistant and fire-resistant layers 2, 1 from 5: 1 to 20: 1, with the possibility of their manifestation of a synergistically intense process of continuous physical effect of evaporative cooling with controlled spraying of coolant on the surface of the fire 3 with the creation of a vapor-droplet-air environment. The outer flame retardant layers 1 of the fabric may be impregnated with a composition reflecting thermal radiation. Coolant can be applied to the fire-resistant layer 5 with the manifestation of a similar physical effect of evaporative cooling during fire exposure to the surface 3.

Fireproof shelter (figure 2) contains a fireproof screen with fireproof and heat-resistant layers 1, 2, made with similar structures of fibrous materials shown in figure 1, and a tubular frame 6 with communicating channels 7, 8 and nozzles 9 for controlled flow with spraying coolant to the surface of the fire exposure 3 with a fire-resistant layer 1 or to the fire-resistant layer 5 of the screen with the creation of a vapor-droplet-air environment. The outer flame retardant layers 1 of the fireproof shelter may also be impregnated with a composition reflecting thermal radiation. The tubular frame 6 can be equipped with fastened with it, and the screen is connected with it in its lower part by flexible connections 10 with pointed pins 11 for fixing in the ground. The operation of the fire-resistant screen (Fig. 1) and fire-retardant shelter (Fig. 2) based on the method includes the supply of controlled spraying of coolant through communicating channels 7, 8 and the nozzle 9 to the surface 3 of the fire-resistant screen or to the fire-resistant layer 5 with the creation of a vapor-droplet-air environment synergistically with which the screen due distributed between its outer fire resistant layers 1, 5 capillary-porous heat-resistant layer 2 of fibrous material areal density of 70 to 700 g / m ^2, increasing its behavior towards ited fire exposure 3 is shown a continuous process of intensive evaporative cooling effect.

Position 12 - traction tapes or cords for fixing the fire-resistant screen to the tubular frame 6.

The rationale for the physical nature of inventions in comparison with prototypes is as follows.

The principle of operation of the protective shield against the flow of energy in the form of light, heat and convective gas flows (prototype) is based on the creation of a curtain of atomized coolant by feeding it into the space between grids made of various materials.

The heat radiation from the flame and the convective flows of heated gas are partially reflected from the nets, from the created film of liquid flowing down the nets, and from the vapor-droplet-air medium between the grids, and are also partially absorbed by the vapor-droplet-air medium.

The heat balance in the area of the screen of this type can be represented as:

_Neg qΣ = q + q + q _{the last abs;}

where qΣ is the total (radiation-convective) heat flux incident on a unit area of the screen;

q _neg - part of the heat flux reflected from the screen;

q _past - part of the heat flux passing through the screen;

q _sweep - part of the heat flux absorbed by the cooling agent of the screen.

The principle of operation of a fireproof screen made of heat-resistant fibrous materials is based on blocking radiation-convective heat flux from a flame based on a rational combination of physical effects: reflection and absorption of heat radiation, evaporative cooling, as well as the heat-insulating effect of the screen and the air gap between the screen and the object.

The heat balance in the area of the screen of this type is represented as:

q'∑ = q ' _neg + q' _rad + q ' _isp + q'_isol;

where q _'rad - part of the heat flow of the re-heated surface of the screen to the surrounding space;

q ' _isp is the part of the heat flux absorbed during the evaporation of the liquid filling the capillary-porous layer of the screen and filtering the steam to its heated surface;

q ' _isol - part of the heat flux blocked by the thermal insulation of the screen and the air gap between the screen and the object.

From a comparison of the presented thermal balances follows:

a) heat flux density of reflected in the latter case is significantly higher than in the first (q _'Neg> q _ODA) mean reflectance larger tissue surface compared to the reflectivity of the liquid film and parokapelno-air medium;

b) in the second case, the incident heat flux is additionally reduced due to re-emission of the heated surface of the screen (in this case, the corresponding additional term is present in the balance relation - q ' _rad );

c) the density of the heat flux absorbed during evaporation is much higher in the second case than in the first (q ' _ap >> q _isp ), since liquid droplets moving with a high speed between the grids practically do not have time to evaporate;

d) in the second case, the additional part of the external heat flux is blocked by the thermal insulation of the screen and the air gap between the screen and the object (the balance ratio contains an additional term q ' _insulator on the right side, which is absent in the first case).

According to the principle of action, the proposed method and device are combined: the functions of passive and active fire protection are combined in them. Due to this, their effectiveness sharply increases, since the combination of functions enhances the effect of each of the fire protection methods, usually used individually (synergism). Passive fire protection is implemented:

a) due to the good heat-insulating ability (including at high temperatures) of the most heat-resistant material of the screen;

b) on the ability of a capillary-porous material to absorb moisture, which sharply increases its fire-retardant ability, since a strong physical effect of evaporative cooling is realized.

The role of active fire protection is performed by liquid nebulizers. Due to the fact that the liquid is supplied to and absorbed into the surface of the protective shield, its required flow rate is significantly reduced in comparison with the option of irrigating cooling of the surface of the object, since in this case the effect of evaporative cooling and the heat-insulating ability of the vapor zone formed between the screen and the subject. In addition, part of the liquid entering the zone of flame surrounding the protected object also reduces the intensity of its thermal effect on the fireproof device. Thus, active fire protection is also implemented as a multifactorial process.

The heat and mass transfer processes listed above that occur in a fireproof shelter during a fire exposure on its outer surface proceed unsteadily. Therefore, for a quantitative mathematical description of the thermal state of the irrigated fire-resistant screen, one should use the justified in the book: Strakhov V.L., Krutov A.M., Davydkin N.F. Fire protection of building structures (M .: TIMR Information and Publishing Center, 2000) the formulation of the corresponding boundary value problem, which allows one to take into account all of the listed physical effects of blocking the external radiation-convective heat flow.

The unsteady temperature field in the “fireproof shelter - protected object” system is determined from the solution of the differential equation of unsteady heat conductivity written in the OXY coordinate system, the beginning of which is associated with the heated surface of the screen:

a) for zones of the calculation area corresponding to the screen and the protected object

b) for zones of the computational domain corresponding to the cavity between the screen and the protected object

Differential equations (I), (II) are solved under the following boundary conditions:

initial condition:

conditions on heated surfaces:

conditions at the boundaries between materials with different thermophysical characteristics:

conditions on the axis (plane) of symmetry of the computational domain:

conditions on the surfaces enclosing the cavity:

conditions on the border between the condensation zone and the impermeable surface (zone of material saturated with water):

a) for the condensation period

b) for the evaporation period

deep soil condition:

In the formulas (I) - (XII) the following notation is adopted:

,

- плотность потока пара при конденсации и испарении; y_с - координата границы между зоной конденсации и непроницаемой поверхностью (зоной насыщенного водой материала); х_w, y_w - координаты границ обогреваемых поверхностей конструкции; x_гр, y_гр - координаты границ между слоями из материалов с различными теплофизическими характеристиками или границ полости; х_x, y_х - координаты необогреваемых границ.C is the volumetric heat capacity of the material, taking into account the thermal effect of evaporation; T is the temperature; t is the time; x, y - coordinates; λ _x is the effective thermal conductivity of the material in the direction of the 0X axis; λ $\genfrac{}{}{0ex}{}{\text{m, c}}{\text{y}}$ - effective thermal conductivity of the material in the direction of the 0Y axis, taking into account the heat release during condensation and heat absorption during filtration; ρ is the density; with _p is the heat capacity of steam (air); λ _e - equivalent thermal conductivity, taking into account natural convection in the cavity; qΣ ƒ is the total heat flux to the heated surface; n is the normal to the surface; q _i is the density of the resulting radiation flux on the i-th isothermal site of the surfaces enclosing the cavity; r is the thermal effect of the water-vapor phase transition;

,

- vapor flow density during condensation and evaporation; y _с - coordinate of the boundary between the condensation zone and the impermeable surface (zone of material saturated with water); x _w , y _w - coordinates of the boundaries of the heated surfaces of the structure; x _gr , y _gr - the coordinates of the boundaries between layers of materials with different thermophysical characteristics or the boundaries of the cavity; x _x , y _x - coordinates of unheated boundaries.

In equation (I), the exponent n is 1 in the case of axial symmetry of the computational domain and 0 in the case of plane symmetry of the computational domain.

The volumetric heat capacity of the material, taking into account the thermal effect of evaporation (dehydration), should be determined by the formula:

where φ is the porosity of the material; ρ 'is the density of the skeleton (skeleton); C 'is the heat capacity of the frame; ρ _about - bulk density of the material in the initial state; K is the mass fraction of the framework in the composition of the capillary-porous layer; χ - degree of completion of the process of evaporation of the cooler inside the capillary-porous layer (dehydration).

The effective thermal conductivity of the material in the direction of the 0Y axis, taking into account the heat release during condensation and heat absorption during filtration, should be determined by the formula:

where λ _y is the effective thermal conductivity of the material in the direction of the axis 0Y;

K _D is the diffusion coefficient of vapor in a porous permeable material;

p _s (T) is the saturation pressure;

- плотность потока пара;

- steam flow density;

- средняя теплоемкость пара;

- average heat capacity of steam;

y _s is the coordinate of the evaporation isotherm;

y ₀ - coordinates of the steam spreading line.

The steam flow density in the condensation zone is calculated by the formula:

One part of the steam released in the dehydration zone moves from the spreading line towards the heated surface, and the other in the opposite direction, into the condensation zone. The coordinate of the steam spreading line is determined from the ratio:

The vapor flow density in the dehydration zone is determined from the ratios:

a) for steam flow directed to the condensation zone:

b) for steam flow directed towards the heated surface:

The mass rate of vapor condensation on an impermeable surface (at the boundary of a layer saturated with water) is determined from relation (XVII) at y = y _s . The mass rate of condensate evaporation from the zone of water-saturated material after reaching this boundary by the evaporation front is determined directly from condition (XI).

The effective thermal conductivity of the material in the direction of the 0X and 0Y axes, as well as the density and heat capacity of the frame, are determined experimentally or by calculation according to the composition and properties of the components of the material.

The parameters of the process of dehydration of a capillary-porous material are determined experimentally by the method of thermogravimetry.

Equivalent thermal conductivity, taking into account the complex heat transfer through the cavity by the molecular thermal conductivity of the gas and natural convection, is determined by the formula:

λ _e = λ Nu, (XIX)

where λ is the molecular thermal conductivity of the gas filling the cavity;

Nu is the average Nusselt number, depending on the geometric characteristics of the cavity, the temperature difference between the enclosing surfaces, the average temperature of the medium, its thermophysical characteristics and viscosity.

The Nusselt number is calculated by the formula:

Nu = C (GrPr) ⁿ k (XX)

where C, n, k are empirical parameters;

Gr = gβ Δ T δ ³ / ν ² - Grashof number;

g is the acceleration of gravity;

β = 1 / T _avg ; T _cp = 0.5 · (T _max + T _min );

Δ T = T _max -T _min ;

T _max , T _min - the maximum and minimum values of the temperature of the surface elements enclosing the cavity;

ν is the kinematic viscosity of the gas filling the cavity;

δ is the characteristic size of the cavity;

Pr is the Prandtl number of gas.

The Prandtl number and the thermophysical characteristics of the gas filling the cavity are determined from the reference tables: Physical quantities: Reference book / A.P. Babichev, N.A. Babushkina, A.M. Bratkovsky and others; Ed. I.S. Grigorieva, E.Z. Meilikhova. - M .: Energoatomizdat, 1991 .-- 1232 p.

Calculations by formulas (XIX), (XX) are repeated during the numerical solution of the heat equation (II) at each time step. The need for this is due to the time dependence of the temperature of the surfaces enclosing the cavity, as well as the dependence of the thermophysical characteristics of the gas filling the cavity on temperature.

The resulting radiation fluxes at the ith isothermal sites of non-reflective surfaces enclosing the cavity are calculated by the formula:

where ε _i , ε _j are the integral coefficients of thermal radiation of the corresponding isothermal sites;

σ is the Stefan-Boltzmann constant;

φ _ij are the angular radiation coefficients between the respective sites;

T _i , T _j are the temperatures of the pads, determined by the joint numerical solution of equations (I), (II) with boundary conditions (III) - (XII).

The total heat flux to the heated surface of the shelter is defined as the sum of the radiant and convective components:

q∑ _f = q _lf + q _kf . (Xxii)

The density of the radiant flux absorbed by the surface of the structure is determined by the formula:

q _lf = ε _w (q _R -σ T $\genfrac{}{}{0ex}{}{\text{4}}{\text{w}}$ ), (XXIII)

where q _R is the density of the radiant flux incident on the surface.

The density of the incident radiant flux depends on the location of the structure with respect to the flame torch. The greatest value of q _R has when the vertical structure is located on the axis of the torch at x = 0, and when it is removed from the q axis, _R decreases to:

q _R = ε _f σ T $\genfrac{}{}{0ex}{}{\text{4}}{\text{f}}$ (at x = 0.5 D).

where σ = 5.67 · 10 ^-8 W / (m ⁴ · K) is the Stefan-Boltzmann constant.

The intermediate values of q _R at 0≤ x≤0.5 D are calculated using the relation:

q _R = 1.55 · ε _f σ T $\genfrac{}{}{0ex}{}{\text{4}}{\text{f}}$ exp (-0.88x / D), (XXIV)

where x is the distance from the axis of the torch to the surface; D is the characteristic size of the torch.

The density of the incident heat flux to the elementary areas of the enclosing surfaces, remote from the torch at various distances and arbitrarily oriented with respect to its axis, for the case of an optically transparent medium between the torch and the surface (low smoke) is calculated using the corresponding angular irradiation coefficients:

q _R = φ ε _f σ T $\genfrac{}{}{0ex}{}{\text{4}}{\text{f}}$ , (XXV)

where φ are the angular coefficients of irradiation (angular coefficients).

At the stage of a developed fire, in the case of an optically dense gas medium, the density of the resulting radiation flux to the surface of the structure, depending on the local temperature of the medium in the vicinity of the surface element under consideration, is calculated by the formula:

q _lf = A _f σ (T $\genfrac{}{}{0ex}{}{\text{4}}{\text{f}}$ -T $\genfrac{}{}{0ex}{}{\text{4}}{\text{w}}$ ), (XXVI)

where Aƒ = 1 / (1 / ε ƒ + 1 / ε _w -1) is the reduced degree of blackness of the gaseous medium and surface;

ε ƒ is the integral emissivity of the gaseous medium,

Tƒ is the local temperature in the vicinity of the considered surface element (at the outer boundary of the thermal boundary layer).

The convective component of the total heat flux to the heated surface of the structure is calculated according to Newton's law:

q _kf = α _f (T _f -T _w ), (XXVII)

where α ƒ is the coefficient of convective heat transfer between the gas medium and the heated surface of the structure; Tƒ, T _w are the temperatures of the gaseous medium and the heated surface.

At known velocities of the gaseous medium, determined by calculating the dynamics of fire development, empirical criteria formulas and formulas obtained using the integral equations of the boundary layer are used for the heat transfer coefficients.

The initial temperature distribution over the cross section of the structure is taken uniform.

For the numerical solution of differential equations (I), (II) with boundary conditions (III) - (XII), the finite difference method should be used in the version of the fractional step method.

Difference analogs of differential equations with corresponding boundary conditions are solved by the sweep method, which makes it possible to refine nonlinear parameters using the implicit four-point umbrella scheme. At each time step, an iterative process is implemented.

Difference analogues of the original heat conduction equations in each direction along the X and Y axes of a rectangular coordinate system are taken in the form:

C _i = f ₁ (T $\genfrac{}{}{0ex}{}{\text{S}}{\text{i}}$ );

λ _i = f ₃ (T $\genfrac{}{}{0ex}{}{\text{S}}{\text{i}}$ )

To increase the efficiency of the computational algorithm, an uneven difference grid is used in each of the directions.

To carry out numerical calculations of non-stationary temperature fields in the cross section of the structures under consideration, you can use the developed program package “Fire resistance” version T.1, certified according to GOST R ISO / IEC 9126-93, GOST R ISO / IEC TO 9294-93. This software package is designed for IBM-compatible computers and meets modern requirements for the accuracy and reliability of the results.

Numerical calculations make it possible to choose reasonably geometric parameters of the shelter, the material and thickness of the screen layers, as well as the flow rate of the cooler, at which the specified fire resistance of the object is ensured with minimal cost.

Advantages of new technical solutions

1. Radiant heat flux is completely absorbed in the layer of screen fabric adjacent to the heated surface. In the prototype, part of the thermal radiation passes through the water curtain of the screen.

2. The outer heat-resistant fabric with a special coating has a greater reflectivity compared with the reflectivity of the water film (in the prototype).

3. In addition to reflectivity, the heated outer surface has the ability to reradiate heat into the surrounding space, which further reduces the density of the heat flux entering the inner layer of the structure. This physical effect is absent in the prototype.

4. Used in the prototype film cooling is ineffective and requires large costs of the cooler. Therefore, in the proposed device, the supply of cooler to the surface of the screen is made with a significantly lower consumption. Moreover, most of the fluid supplied to the surface of the screen penetrates through the outer layer of tissue into the capillaries and pores of the intermediate layer, until it is almost completely saturated.

5. After termination of irrigation of the screen surface (with continued fire exposure), the physical effect of evaporative cooling becomes the main physical effect blocking the heat flux.

The intermediate capillary-porous layer of the screen is made of a material capable of absorbing coolant up to 80% by weight. In the case of a water-saturated screen with a thickness of about 10 mm, due to the evaporation of the cooler and steam filtration to the heated surface of the screen, the temperature of its unheated surface does not exceed 100 ° C with fire exposure to the heated surface of the screen for 1 hour or more.

This strong physical effect in the prototype is practically not realized.

6. After complete evaporation of the cooler from the capillary-porous layer, a fireproof screen made of heat-resistant materials and having good heat-insulating ability continues to perform a fire-retardant function for a sufficiently long time. The heat-insulating effect of the air layer located between the screen and the object also contributes to this.

7. Fireproof shelter made of heat-resistant materials, in contrast to the prototype, working on the principle of a water curtain, is able to maintain its integrity and perform fire-retardant function in strong winds. To increase the strength of the screen in the high-temperature zone, a steel mesh is introduced into its composition (under the outer layer of the fabric).

8. To ensure the stability of the shelter under the influence of wind, the fireproof screen is attached along the lower contour to the ground using pins.

9. The fireproof shelter in the initial state is compact and has a relatively small mass (not more than 30-40 kg), which makes it possible to carry it manually, including over rough terrain.

10. The design of the shelter provides for the possibility of its quick installation on the protected object in the field (including in the presence of wind). For this purpose, the screen is flexible and in the stowed position is folded into a roll. After installing the supports above the object, the screen automatically unfolds after pulling out a special pin from special loops.

Field tests of fire-resistant screens, shelters based on the proposed method of attenuating the effects of energy flow in the form of light, heat and convective gas flows with the implementation of a new physical effect according to the proposed technical solutions showed positive results, their effectiveness.

Thus, new technical solutions during implementation exhibit new properties that are reproducible under production conditions, and also meet the criterion of “industrial applicability”, i.e. level of inventions.

There may be various combinations with respect to the shape, size and arrangement of the individual elements, if all this does not go beyond the scope of the inventions set forth in the claims.

Claims (6)

1. A method of attenuating the effects of an energy flow in the form of light, heat and convective gas flows, comprising supplying a controlled spray of cooling liquid to the surface of a fire-resistant screen with the creation of a vapor-droplet-air medium, characterized in that they use a screen with heat-resistant capillary distributed between its outer fire-resistant layers porous layers of fibrous material with a surface density of 70 to 700 g / m ² with increasing density in the direction of the surface of the fire exposure with the possibility of they synergistically intense process of continuous physical effect of evaporative cooling. 2. Fire-resistant screen containing fire-resistant and heat-resistant layers, characterized in that the heat-resistant layers are made of needle-punched or needle-pierced material of a capillary-porous structure of silica or basalt fiber with a diameter of 2-15 μm or a combination of them with a distributed surface density of from 70 to 700 g / m ² with a surface density increases toward the surface fire exposure, with external layers of fire resistant fabric based on silica or basalt fibers 5-15 microns in diameter, or a combination of their surface density of 120 to 700 g / m ^2, with a mesh with mesh size of 5x5 to 25x25 mm made of steel wire with a diameter of 0.1-1 mm below the outer fire resistant layer on the surface side of fire exposure at a ratio of heat- and fire-resistant layer thicknesses from 5: 1 to 20: 1 with the possibility of their manifestation of a synergistically intensive process of continuous physical effect of evaporative cooling with controlled spraying of coolant on the surface of the fire exposure with the creation of a vapor-droplet-air environment. 3. The screen according to claim 2, characterized in that the outer flame-retardant fabric layers are impregnated with a composition that reflects thermal radiation. 4. Fireproof shelter containing a fireproof screen with fireproof and heat-resistant layers and a tubular frame with communicating channels and nozzles for controlled supply with spraying coolant onto the fire surface of the screen with the creation of a vapor-droplet-air environment, characterized in that the heat-resistant layers are made of needle-punched or needle-piercing material of a capillary-porous structure of silica or basalt fibers with a diameter of 2-15 microns or a combination of them with a distributed surface density from 70 to 700 g / m ² with an increase in surface density in the direction of the surface of the fire exposure with external fire-resistant fabric layers based on silica or basalt fibers with a diameter of 5-15 μm or a combination of them with a surface density of from 120 to 700 g / m ² , with a mesh with mesh sizes from 5x5 to 25x25 mm from steel wire with a diameter of 0.1-1 mm under the outer flame-retardant layer on the side of the surface of the fire exposure with a ratio of heat-resistant and fire-resistant layers from 5: 1 to 20: 1 with the possibility of synergistic manifestation and the intense process of continuous physical effect of evaporative cooling. 5. Shelter according to claim 4, characterized in that the outer fire-resistant layers of the screen fabric are impregnated with a composition that reflects thermal radiation. 6. Shelter according to claim 4 or 5, characterized in that the tubular frame is equipped with fastened with it, and the screen is connected to it in its lower part by flexible connections, pointed pins for fixing in the ground.

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