RU151351U1 - FIRE BOILER - Google Patents

Abstract

A fire tube boiler containing a cylindrical water supply body, in the cavity of which a furnace is coaxial to it and a burner is installed in it, the furnace having an ellipse in cross section, characterized in that the furnace has transverse ribs with a finning coefficient φ: φ = F / F≈ ? 1.32, F is the area of the finned surface of the furnace; F is the area of the inner smooth surface of the finned tube.

Description

The utility model relates to a power system and can be used in heating and hot water supply systems, including household appliances, as well as a heater for liquids and gases.

A fire tube boiler is known, comprising a burner with a firebox, a reversing chamber, and a bundle of convection tubes in a water supply housing. (See “Handbook of heat exchangers: In 2 vols. T2 / Transl. From English under the editorship of OG Martynenko et al. - M .: Energoatomizdat, 1987. - 352 p.).

The disadvantages of this boiler is its low efficiency, due to the low heat transfer coefficient in the furnace.

The closest to the claimed utility model in terms of technical nature and the effect achieved is a fire tube boiler, which contains a cylindrical body with a cooling chamber for exhaust gases, a heat chamber with a furnace coaxial with it, having an elliptical cross-sectional shape. Smoke tubes are placed around the flame chamber. Inlet and outlet of water into the housing is carried out by means of nozzles, and its heating is carried out using a burner fixed in the front of the housing (Patent RU 121350 U1 of 10.20.2012).

The disadvantages of the known boiler is its low efficiency due to the low heat transfer coefficient in the furnace and the undeveloped heat transfer surface.

The technical problem solved in the proposed device is the creation of a boiler design that provides the highest efficiency of the furnace as a result of increasing the heat transfer area and increasing the heat transfer coefficient in the furnace due to the location of the transverse fins inside the furnace space, the ribs of which are made as a result of knurling, without changing the characteristics of the burner.

This technical result is achieved by the fact that in a fire-tube boiler containing a cylindrical water supply body, in the cavity of which a coaxial fire chamber is placed, having an ellipse in cross section with a burner installed in it, the fire chamber communicates with a convective tube bundle, and according to the proposed technical solution in the firebox made transverse ribs with a finning coefficient φ:

φ = F _op / F≈1.32, where

F _op - the area of the finned surface of the furnace;

F is the area of the inner smooth surface of the finned tube.

The essence of the technical solution is illustrated by drawings, where:

in FIG. 1 schematically shows a longitudinal section of the proposed fire tube boiler;

in FIG. 2 schematically shows a cross section of the proposed fire tube boiler;

in FIG. 2 is a graph of the dependences of the ratios of the heat transfer coefficient of the finned φ _finned to the non- _finned α _{ellipse of} the furnace surfaces on the finning coefficient φ, which shows the section with the maximum α _finned / α _ellipse for different numbers of Re;

in FIG. 3 is a graph of the relationships between the amount of heat transferred from the gas to the wall due to molecular heat conduction, convection, and radiation, finned Q _finned to non- _finned Q _{ellipse of} the furnace surface versus finning coefficient φ, which shows a section with maximal _finned Q / Q _ellipse for different numbers Re;

in FIG. 4 is a plot of the relationship between the efficiency coefficient of a finned tibial and non-finned η _{ellipse of} the furnace surface versus the finning coefficient φ, which shows a section with maximum η _finned / η _ellipse for different numbers of Re;

The fire tube tube contains a housing 1 filled with liquid, a burner 2 with a furnace 3, having an elliptical cross-sectional shape inside the furnace space, which has transverse ribs 4 with a finning coefficient φ, a reversing chamber 5 and a bundle of convection tubes 6. The ribs 4 are obtained by rolling (the process of plastic deformation of bodies on a rolling mill between rotating drive rolls) or casting (the technological process of manufacturing blanks, which consists in filling a prefabricated mold liquid material followed by solidification).

The boiler works as follows:

In the furnace 3 from the burner 2 direct the flow of flame. Combustion processes occur in the furnace. Next, the flow of combustion products enters the reversing chamber 5 and then into the convective bundle of pipes 6. A part of the heat of combustion and the heat of the exhaust gases is transmitted through the finned dividing wall to the coolant in the housing 1.

A turbulence model with two equations is used to describe turbulent flows of reacting gases. This turbulence model is called k-ε (Mikhailov, A.G. Numerical modeling of heat and mass transfer processes during combustion of gaseous fuel in the furnace volume / A.G. Mikhailov, P.A. Batrakov, S.V. Terebilov. - Natural and Technical Sciences . - 2011 - No. 5 (55). - P. 354-358), where k is the turbulent kinetic energy, ε is the dispersion value of the kinetic energy.

When describing the finning coefficient for a furnace in the form of an ellipse cross-section, the following literature source “Determination of the heat transfer coefficient through a smooth and finned pipe” was used by V.V. Bukhmirov D.V. Rakutin. - Ivanovo: UIUNL IGEU, 2010. - From 11-12, in addition, the concept of the equivalent diameter of the cross section of a furnace in the form of an ellipse was calculated by the formula:

d _e = l, 55S ^0.625 / P ^0.2 ,

where S is the cross-sectional area of the furnace in the form of an ellipse;

P is the perimeter of the cross section of the furnace in the form of an ellipse.

S = πab,

P = 2π (( a ² + b ² ) / 2) ^1/2 ,

where π = 3.1415 rad

a - semimajor axis;

b - minor axis.

The finning coefficient φ is equal to:

F _op is the area of the fin surface of the furnace;

F is the area of the inner smooth surface of the finned tube.

,

,

F = πd _e L

where d _E is the internal equivalent diameter of the finned tube (where a = a _D is the inner major axis of the finned pipe (Fig. 2.), b = b _D is the inner minor axis of the finned pipe (Fig. 2.) [Determination of heat transfer coefficient through a smooth and finned tubes / VV Bukhmirov, DV Rakutina. - Ivanovo: UIUNL IGEU, 2010. - C 11-12.]);

d _Er is the equivalent diameter of the rib (where a - a _d is the semimajor axis of the rib (Fig. 2.), b = b _d is the semiminor axis of the rib (Fig. 2.));

n is the number of edges;

δ _ρ is the thickness of the ribs (δ _p = τ / 2, τ is the step of the ribs (Fig. 1));

L is the length of the furnace (Fig. 1),

The fins increase the heat transfer surface area and thus, at the same heat transfer coefficient, contribute to an increase in the amount of heat transferred. Thus, increasing the efficiency η of the furnace is achieved by increasing the heat transfer area (to compare the surface area of the finned furnace with a smooth one, we use the finning coefficient), heat transfer coefficient when installing transverse ribs.

The efficiency η of the furnace is determined by the formula:

where Q ₁ is the heat used to heat the cold liquid.

Q _C - heat transferred by convection.

where, ΔT = T ₁ -T ₂ ,

T ₁ - gas temperature in the furnace,

T ₂ is the temperature of the furnace wall;

Q _R - heat transferred by radiation (determined by the Monte Carlo probabilistic method (Mikhailov, A.G. Numerical modeling of heat and mass transfer processes during combustion of gaseous fuel in a furnace volume) / A.G. Mikhailov, P.A. Batrakov, S.V. Terebilov . - Natural and technical sciences. - 2011. - No. 5 (55). - S. 354-358);

Q _calc - the amount of heat (dry gas) emitted during the combustion of fuel is determined by the volume composition,%, and the known heat of combustion of the components (lower heat of combustion):

Q _calc = 358CH ₄ + 640C ₂ H ₆ + 915C ₃ H ₈ + 1190C ₄ H ₁₀ + 1465C ₅ H ₁₂ + 126.5CO + 107.5H ₂ + 234H ₂ S.

In case of finned surface:

Q _ribbed = Q ₁ , α _ribbed = α, η _ribbed = η, where

Q _finned - heat used to heat a cold liquid in a furnace with a cross-sectional shape of an ellipse and transverse finning;

α _finned - heat transfer coefficient, determined by the conditions of gas movement in the furnace with a cross-sectional shape of an ellipse and internal transverse finning;

η _ribbed - the efficiency of the efficiency of the furnace with the shape in the cross section of an ellipse and transverse ribbing.

In the case of a non-finned surface Q, _ellipse = Q ₁ , α _ellipse = α, η _ellipse = η, where

Q _ellipse is the heat used to heat a cold liquid in a furnace with a cross-sectional shape of an ellipse without fins;

α _ellipse is the heat transfer coefficient determined by the conditions of gas movement in the furnace with a cross-sectional shape of an ellipse without fins;

η _ellipse - coefficient of efficiency of the efficiency of the furnace with the shape in cross section of an ellipse without fins.

As a result of the analysis of numerical solutions using the above formulas, it was determined that for n = 6, τ = 167 mm, a _D · = 520 mm b _D = 400 mm a _d · = 440 mm, b _d = 320 mm, the finning coefficient φ≈ 1.32 corresponds to points with the maximum values of α _finned / α _ellipse , Q _ribbed / Q _ellipse , η _ribbed / η _ellipse for different Re.

at Re = 10000 and a finning coefficient φ≈1.32, the maximum value of the value of α _finned / α _ellipse = 1.08 (Fig. 2), the maximum value of the value of Q _finned / Q _ellipse = 1.1 (Fig. 3), and the maximum value of η _ribbed / η _ellipse = 1,055 (Fig. 4).

Thus, the calculated data confirm that an increase in the efficiency η of a furnace with a shape in the cross section of an ellipse with transverse ribs installed inside the furnace space at a finning coefficient φ≈1.32 leads to an increase in the efficiency of the furnace η in comparison with a furnace with a shape in the cross section of an ellipse with a non-ribbed inside the combustion surface within 5.5%.

Claims (1)

A fire tube boiler containing a cylindrical water supply housing, in the cavity of which there is a furnace coaxial to it and a burner installed in it, the furnace having an ellipse in cross section, characterized in that the furnace has transverse ribs with a finning coefficient φ: φ = F _op / F≈? 1.32, F _op is the area of the fin surface of the furnace; F is the area of the inner smooth surface of the finned tube.

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