SU1695055A1 - Recuperator - Google Patents

Abstract

The invention relates to heat exchange technology and can be. used on heating and thermal furnaces of metallurgy and mechanical engineering. The purpose of the invention is to intensify heat exchange by means of turbulence in the flow of heat exchanging media. The pipes 12 and 15 of heat exchange elements are provided with annular grooves 13 and 16 on the outer surface and annular protrusions 14 and 17 on the inner surface, respectively. Grooves 13 Cold fosiyx 1 g 4 rasters h h 0,6) set heat tempered 23 for stage a year You are given a stream of mbiKbi fnit gas siyx displaced d (0, 4-0.6) 5 with respect to the projections 17, where S is the pitch between the projections 16. The bottom 18 is hemispherical with the central projection 20 inside the heat exchanging element. The gap h between the exit end of the inner tube 12 and the protrusion 20 is h (0.5-0.6) d, where d is the diameter of the inner tubes. When the heat exchanger is installed in the vertical flue duct, it can be equipped with a tube plate 21 perpendicular to the heat exchange elements and perforated holes 22, the diameter of which decreases towards the hole 23 in the smoke channel intended to exit the flue gases. The air from the near-wall layer and from the middle of the flow, the passage through the pipes 12 and 15 of the heat exchange element, is intensively mixed due to the displacement of the grooves 13 and the protrusions 17. Making the bottom hemispherical at a given distance allows to intensify the heat exchange with the air stream and bottom that flows from the pipe. 1 hp f-ly, 4 ill. A 5 8, S oo ate about ate

Description

The invention relates to the design of heat exchangers designed to preheat the air entering the burners with the heat of the exhaust flue gases of industrial furnaces in order to save fuel,

Intensification of the process of heat transfer from the metal wall of the heat exchanger to the heated air allows to increase the air heating temperature, and hence the efficiency of the heat exchanger.

In order to intensify heat exchange in the near-wall (boundary) air layer, various types of turbulators are used, including those made in the form of periodic protrusions or depressions of the non-heat exchange surface. Periodically located protrusions or depressions lead to the formation of vortex zones near the surface, due to which heat transfer is intensified with a moderate increase in aerodynamic drag.

A heat exchange tube is known with annular grooves on the outer surface and corresponding protrusions on the inner surface, and in the longitudinal direction it is divided into sections with the same height of protrusions in each of them and different height of the protrusions in the adjacent stepwise region of Hc. di / D 0.97-0.88, where di is the minimum internal diameter of the pipe in the area of the projections; D is the internal diameter of the smooth part of the pipe. In addition, the protrusions are made with different pitch, incrementally increasing from site to site in the direction of increasing height of the protrusions in the range

,

where t is the step of the protrusions, d is the thickness of the pipe stem.

A disadvantage of the known heat exchange tube is the relatively low values of the temperature of the air preheating when used as a heat exchange element of the heat exchanger. This is due to the fact that with the help of turbulization only of the near-wall layer, it is difficult to provide a significant increase in the temperature of air preheating, since there is no intensive mixing of air volumes from the thin near-wall zone and from a much larger flow core.

In addition, the manufacture of a heat exchange pipe with different heights of protrusions along the length and with different pitch is difficult, non-technological and practically impossible at

industrial production of heat exchangers.

A recuperative air preheater is known, comprising an air intake and an air intake manifold, heat exchange elements connected to it. The latter are located in a gas duct equipped with a gas supply and gas outlet nozzles. Heat exchange elements

made of inner and outer tubes, with the outer tube plugged from the end using the bottom. The bottom is located from the outlet end of the inner tube with a gap, the value of which is 0.5-0.75

on the diameter of the inner tube. Besides,

the bottom is wound up in the cavity of the outer pipe

for a distance of 0.5-1.0 times its diameter.

The disadvantage of the famous recuperator

The heat exchange rate is low due to the absence of flow turbulization on smooth pipes.

The aim of the invention is to intensify heat transfer.

The goal is achieved by the fact that

in the heat exchanger, which includes the air supplying and air exhausting collectors and heat exchange elements attached to them, which contain an external and internal damped from one end of the bottom

tubes made with annular grooves on the outer surfaces with the formation of corresponding protrusions on the inner surfaces, annular grooves on the inner pipes are located

with displacement d relative to the annular protrusions on the outer pipes equal to d (0.4–0.6) 5, and the bottom is made hemispherical with a central protrusion inside the heat exchanger element, with the gap h

between the outlet end of the inner tube and the bore is h (0, ..., 6) d, where S is the pitch between the annular projections on the outer tubes. d, is the diameter of the inner tube.

In addition, to intensify heat transfer when installing the heat exchanger in the vertical section of the smoke channel, it can be equipped with a tube plate perpendicular to the heat exchange elements

and perforated holes arranged coaxially with heat exchange elements 1, with the diameters of the holes in the tube plate decreasing towards the hole in the smoke channel intended for the exit of the flue gases,

Figure 1 shows the heat exchanger, longitudinal section; figure 2 - heat exchanger in the vertical section of the smoke channel, a longitudinal section; FIG. 3 is a plot of the average heat transfer coefficient to air; 5 Going displacement d / S with an initial air speed in the inner tube W 10 m / s: Fig. 4 shows a plot of the heat transfer coefficient to air flowing out of the inner tube, “d from hemispheric the bottom with a protrusion on the size of the gap h between the protrusion and the output end of the inner tube (W 10 m / s).

The recuperator contains an air-retaining manifold A, an air exhaust manifold B and heat exchange elements C. The air supply collector 1A is formed by a cap 1 with a connecting pipe 2 attached to it along the central axis, side walls 3-6 with a separating wall 7 with openings 8. The air outlet manifold B is formed by side walls 3-6 with a side wall 9 attached to the latter, a bottom wall 10 with openings 11.

Each heat exchanger element C contains an inner pipe 12 fixed in the opening 8 of the dividing wall 7 of the air inlet manifold A, and it is provided with annular grooves 13 on the outer surface forming the annular projections 14 on the inner surface. The outer tube 15 is located coaxially with the inner tube 12. The upper end is fixed in the opening 11 of the lower wall 0 by the air of the water collector 8. It is made with annular grooves 13 on the outer surface forming the annular projections 14 on the inner surface. Coaxially with the inner tube 12, the outer tube 15 is located. The upper end is fixed in the hole 1 -. the bottom wall 10 of the outgoing health of the colleagues / mount B; It is made with lug grooves 16 on the outer surface forming the annular projections V; on the inner surface, made with a step S. Pr /.chem protrusions 17 are offset from the grooves 13, is equal to d (0.4-0.6) 5. The outer tube 15 is plugged from the lower end of the hemispherical bottom 1B.

In the center of the outer surface of the bottom 18, a depression 19 is formed, forming a protrusion 20 on the inner surface of the bottom, and the gap h between the outlet end of the inner pipe 12 and the protrusion 20 is h (0.5-0.6) d, where d is the diameter of the inner pipe.

The heat exchanger can be equipped with a tube plate 2 with holes 22 placed coaxially with heat-cooling elements C, and the diameters of the holes 22 are made

decreasing towards the opening in the flue channel 23 intended to exit the flue gases.

Making annular grooves and corresponding annular protrusions on the tubes of the heat exchanging element leads to the turbulence of the near-wall air layer on the inner walls of both the inner and outer pipes due to the turbulizing effect of the annular protrusions, contributing to the periodic emission into the main stream of air from the near-wall layer. The presence of annular grooves on the outer surface of the inner tube contributes to the formation of microvortices in the grooves and the periodic release of portions of air into the near-wall layer located on the outer tube. By placing the annular grooves on the outer surface of the inner tube with displacement d (0.5-0.6) 3 relative to the protrusions of the outer tube, intensive mixing of the main air flow with air located in the near-wall layer occurs. This leads to the intensification of heat exchange and an increase in the temperature of air heating.

Performing the bottom in the form of a hemisphere with a protrusion in the center, located with a gap relative to the output end of the inner tube equal to h (05-0.6) d, allows to intensify the heat exchange between the roeduh and the bottom flowing from the inner tube. Intensification of heat exchange in this area of the heat exchange element is caused by the installation of a protrusion in the center of the hemispherical bottom, which leads to a decrease in the zone of inhibited flow, which is formed when the jet hits the bottom.

The obtained ratios are determined by the experimental put. During the experiments, the claimed ranges of optimal values of 5 and h were obtained, and a comparison of the performance indicators of the proposed processor with the prototype was also carried out.

Studies have been carried out on the effect of the relative position of the annular grooves in the inner tube of the proposed heat exchanger and the annular projections on the outer tube on the average heat transfer coefficient to air. The initial air velocity in the inner tube varied. The B range is W - 5–20 m / s, which corresponds to the speed range used in industrial recuperators. In the recuperator model, the values of the average heat-traction coefficient for the rex air velocities are obtained. The resulting data on dependency

, F - f Г (5/0) d / in the break of air W 10 m / s are presented in the form of a diagram of the RE fig.Z,

Anapiz of data poedstavleyny n phi 3 shakes that the maximum heat exchange rate is achieved in the range of the G-shift - d- (0.5-0.6) 3, 4iO corresponds to the stated ratio. At the same time, the average rate of the hematopoietic v of the proposed river is / rati on 25-35%, blizzard, whose prototype at the same speed.

Gropedrpy experimental study of the pyi.i and the magnitude of the input end of the internal coarse and onset of IR semiaceo 1 ohm day,; y) pa the coefficient of heat transfer from the bottom to the air. The magnitude of the flow rate of air from the internal TP / O1 mg change B within V / 5-UO m / s The heat recovery model nporoinna get-1-i value i coefficients of heat transfer from the bottom to the air for the same air speed from h; (morning pipe The data of r, on the dependence of 5g f (n / u) for the speed of the outflow of air W 10 m / s, is presented in the form of a graph in

An analysis of the data presented in Fig. 4 shows that the maximum intensification of the winding zone in the range has been increased by a gap of h (0.5–0, & J) i C OUT of the ground coheToieieii kio. r rn 3njM the value of the heat transfer coefficient oi the bottom to the air at the extension of 12–4%, at the prototype at the same speed of the arc.

Thus, the claimed ranges of the ratio zS- (O / O 6) S t /. h (0.5–0.6) d allows the maximum heat buildup to be maximized by the thermal beam that is provided. dos-h, post-hardened goals

When; / .., Ta, -. RvKe rock / peratoa into the mantle - with a D11moy - mantle of rough goploobmennoe unevenly bathed in dash izami basics due to one-sided detachment and others. Heat and coarseness of the gas field located in the walls of the smoke channel, POOTMLO. Complicated hole for the exit of the flue gases, lower than TeiincoT-dach to tubular and heat exchange elements, and more close to the hole. The nepnef-dicl-rns tube tube board equipment and heat exchange is a hole that is perforated with holes placed by C.DOCI on hepatoblasts and having diameters, v / o1y1aya.aa.es according to the direction Y rejection to exit dim / 1-zzav, p-with vol st strznizlosl b

0

0

five

0

five

ABOUT

uniform flushing of tubular heat exchange elements with flue gases and thereby intensify heat transfer

The heat exchanger works as follows

Cold air through the cuttings 2 is fed into the air intake manifold A, from where it, through the openings 9 of the separation wall 1, enters the inner pipes 12 of the tyuobmechnyh elements C, equipped with annular grooves 13 with the formation of a curved surface of the annular projections And, From the inner pipe 12 the air flows on a hemispherical bottom 18 with a protrusion 20, turns smoothly through 180 ° and moves along an annular gap between the inner tube 12 and the outer 1b, which is provided with annular grooves 16, which form a collar on the inner surface of the tube Straight protrusions 7 Due to the inherent displacement between the annular grooves 13 and the protrusions 17, there is an intensive mixing of air from the near-wall layer and the flow core. From the pipe 9 of the suction collector. The air is withdrawn from the heat exchanger.

The economic effect in comparison with pilot is achieved due to the intensification of heat transfer, as a result of which the temperature of the air heating increases by 20-30% under other equal conditions. This leads to an increase in fuel economy by an average of 7%. When the air flow rate at the proposed recuperator is 1000 m / h, which corresponds to burning 100 m / h of natural gas, the three-shift heat exchanger operation (i.e. 7500 h per year) annual economic benefit from the use of the proposed recuperator compared to the prototype will be

- - - 1000

| 470 rub.

1000

 one rekug | Srator.

In addition, the proposed recuperator

5 in contrast to the analogue, it is easy to manufacture, since the same genuine pipe lugs the pitch and height of the knurling

Claims (2)

1. The heat exchanger in the supply air and supply air vents and connected to them, installed in an ia water inlet equipped in its side windows with inlet and outlet nozzles, heat exchange elements s, made in the form of 5 internal and external pipes, the last of which is plugged from the end with the help of a bottom placed at a given distance - -) and 1 from the end of the internal pipe, about tl and h a-o and ti and so that intensified heat transfer, the tubes are made with annular grooves on the outer surfaces with the formation of corresponding protrusions on the inner surfaces, and the annular grooves on the inner pipes are arranged with displacement d relative to the annular protrusions on the outer tubes equal to d (0.4-0, 6) S, and the bottom is hemispherical from the center with a protrusion inside the heat-exchange element, and the gap h between the end of the inner tube and the protrusion is h (0.5-0.6) d where S is the spacing between the annular protrusions on the outer tubes; d is the diameter of the inner tube. 2. The recuperator according to claim 1, that is, in order to intensify heat transfer when installing heat exchanging elements in a vertical duct equipped with an inlet pipe in the lower section and an outlet pipe in the side the wall, it is additionally provided with a partition with openings placed across the gas duct, and heat exchange elements are inserted into these openings, the latter being made with a diameter decreasing towards the outlet nozzle. Hungry Air  BUT 77777 ///////// 7 // 7 /////: 777 77777777 bottom one  A 1 58 that /// / / -b Naeretyi Vozuh Fiyo.1 a, 8t / A 40 ABOUT 0.2 Ohm 0.8 0/5 FigZ elg, # r / w% 50 50 ABOUT 02 01 Figh 0,8 hid