RU1776969C - Heat exchanger - Google Patents

Abstract

Usage: as convective heating surfaces of boiler units, water economizers. SUMMARY OF THE INVENTION: a heat exchanger comprises inlet and outlet manifolds, in which even and odd coil tubes having the same length and forming a checkerboard bundle are included in parallel. The degree of finning for even and odd coils is different, and the inner diameters of the pipes of coils with different degrees of finning are selected in accordance with a given ratio. 3 ill. next to

Description

The invention relates to boiler equipment and can be used as convective heating surfaces of boiler units, for example, water economizers.

As the analysis of domestic and foreign scientific, technical and patent literature shows, at present, the development of silver heating surfaces and their introduction as convective elements of various heat exchange devices are intensively underway. In particular, the use of such surfaces in boilers allows one to intensify heat transfer, significantly reduce the consumption of metal under pressure,

reduce dimensions, reduce power costs for overcoming hydraulic and aerodynamic drags and, ultimately, get cost savings on power equipment as a whole.

Of the many silver heat exchangers used in boiler units, two main types can be distinguished - heat exchangers from pipes with longitudinal and transverse fins. Such heat exchangers are described in the book Finned heating surfaces of steam boilers / G.I. Levchenko, I.D. Liseikin, A.M. Kopeliovich and others. - M.: Energoatomiedat. 1986, - 168s.

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A disadvantage of longitudinally finned tube heat exchangers is the low degree of finning. Increasing it by increasing the height of the fin leads to an increase in the longitudinal steps of the pipes in the bundle, which, in addition to reducing the thermal efficiency of the ribs, negatively affects the efficiency of the heat exchanger as a whole.

In heat exchangers from tubes with transverse fins, it is possible to obtain a higher finning coefficient both by increasing the height of the fins and by reducing the pitch between the fins. In this case, an increase in the degree of finning does not lead to a decrease in the efficiency of the ribs, as in a heat exchanger made of pipes with longitudinal finning. But reducing the pitch between the ribs increases the likelihood of contamination, which significantly reduces the benefits of such heat exchangers.

An example of a heat exchanger that combines, to one degree or another, the advantages of heat exchangers with longitudinal and transverse fins is the heat exchanger described in the article by Zoz V.N., Demp E.P., Medvedev V.A. Industrial testing of convective heating surfaces from alternating coils with longitudinal and transverse finning // Combined heat power plants: Interuniversity. scientific Sat Sarat. Polytechnics, Institute, 1989. p. 61-63. executed by a. with. No. 846982 (USSR), which in this case is taken as a prototype. This heat exchanger contains inlet and outlet collectors, in which even and odd coils from pipes having the same length are included, which form a staggered bundle, moreover, the degree of finning for different and odd coils is different. Such a heat exchanger is less contaminated by external deposits, compact, and convenient to use, since it is possible to freely extend emergency coils in the horizontal direction during repair work. However, it also has a significant drawback. The heat exchanger exhibits uneven heat sinks of even and odd coils connected in parallel, having different finning degrees / heating surface / with equal internal cross sections, i.e. at the same flow rate. The reason for the thermal sweep between coils with varying degrees of finning is their structural non-identity. It is known that thermal scans under operating conditions of the heat exchanger lead to undesirable temperature

reamers and voltages in its structural elements, decrease in reliability indicators / 4 /.

The purpose of the invention is to increase operational reliability by reducing the temperature scans between the even and odd coils of the heat exchanger.

This goal is achieved in that in a heat exchanger containing inlet and outlet collectors, in which even and odd coils from pipes having the same length and forming a staggered bundle are included, and the degree of finning is even and odd

the coils are different, and the inner diameters of the pipes of the coils with different degrees of finning are selected in accordance with the ratio

0.97

. (s

d2)

0.5

1.03,

(1)

0

5

0

5

where di and d2, p and p2 are, respectively, the internal diameters of the pipes and the degree / coefficient / fins of different types of coils.

A distinctive feature of the claimed technical solution from the prototype is the ratio of the inner diameters of the pipes of the coils with varying degrees of finning. This feature determines the compliance of the proposed technical solution with the novelty criterion.

As a result of the analysis of known solutions, the inventors of the applications did not find a technical solution with the above distinguishing feature from the prototype. At the same time, the use of this distinguishing feature allows one to reduce the temperature scans between alternating structurally non-identical coils in the heat exchanger and thus increase the operational reliability of the heat exchanger as a whole. The foregoing allows us to conclude that the proposed solution meets the criterion of significant differences as a new set of features.

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Under actual operating conditions of the proposed heat exchanger, in connection with different pass-through sections of even and odd coils, the flow rate of the heat carrier in these coils is also different. This leads (in accordance with the heat balance equation) to an increase in the temperature increment in coils with a smaller flow area. The temperature pattern between structurally non-identical coils will be reduced.

In FIG. 1 shows the proposed heat exchanger; in FIG. 2 - section BB in FIG. 1; in FIG. 3 is a view along arrow B in FIG. 2.

As can be seen in FIG. 1 and in FIG. 2, the proposed heat exchanger contains inlet 1 and outlet 2 collectors, which evenly include parallel 3 with longitudinal finning and odd 4 with transverse finning coils from pipes having the same length and forming a chess bundle 5, the degree of finning for even and odd the coils are different, and the inner diameters of the pipes of the coils with varying degrees of finning in accordance with the ratio / 1 /.

The proof of the existence of the maximum positive effect in the proposed range of changes in the ratio of the internal diameters of structurally non-identical coils and the absence of such an effect outside this range is given in the appendix to the description of the invention. Calculations showed that in the proposed heat exchanger, the temperature sweep can be reduced only by performing various flow sections of structurally non-identical coils.

Thus, the proposed heat exchanger fully retains all the structural and thermotechnical advantages of the prototype, and also allows to increase operational reliability by reducing the temperature scans between the heat exchanger coils. The implementation of the cross sections of even and odd coils in the proposed ratio is possible in several ways:

-application of pipes with different internal diameters, with constant outside / i.e. pipes with different wall thickness /;

-application of pipes with various external diameters with a constant pipe wall thickness.

In operating condition, the flow of heating fluid (e.g., flue gas) will wash the heat exchanger in the direction perpendicular to the tube bundle. The heated medium (e.g. water) will move inside the pipes of structurally non-identical even 1 and odd 2 coils. The implementation of the inner diameters of the pipes of even coils smaller than that of the pipes of odd coils, respectively leads to a decrease in water flow in even coils, i.e. to increase in them the increment of water temperature. As a result of this, the temperature of the water at the outlet of the structurally non-identical coils 1 and 2 is equalized, which, in turn, leads to a decrease in the temperature scan between the heat exchanger coils.

Claims (1)

SUMMARY OF THE INVENTION A heat exchanger comprising inlet and outlet collectors and flat coil pipes of the same length, arranged alternately to form a checkerboard bundle, the adjacent coil pipes having different degrees of finning, characterized in that, in order to increase operational reliability, inner diameters of adjacent coil pipes are made in accordance with the ratio 0.97 §§) 1.03, d2 pi) where ch is the inner diameter of one serpentine pipe; p is the degree of finning of this series pipe; da inner diameter of adjacent serpentine pipe: pi is the degree of finning of the adjacent serpentine tube.