RU2241935C2 - Heat-exchanger - Google Patents

Abstract

FIELD: heat-exchanging equipment, particularly for refrigeration, cryogenic and other industries.

SUBSTANCE: heat-exchanger comprises body, inlet and outlet manifolds, tubes grouped in packet. Inlet and outlet manifolds are provided with partitions, tubes have cross-sections of elongated droplet shape and arranged in staggered rows. Tube rows are divided one from another by netted plates welded to tubes. Tubes are blown by air in which fine water spray is injected. Each tube is connected to netted plate located in front of the tube by outer tube side. Opposite tube side is secured to next netted plate. Fine water spray is injected in air flow passing in tube space by atomizers.

EFFECT: improved ability to heat transfer without flow resistance growth.

2 dwg

Description

The invention relates to heat exchangers for refrigeration, cryogenic and other heat transfer equipment.

In many modern plants, low-temperature heat is released in large quantities, which is difficult to dispose of and therefore must be removed to the environment.

The use of air cooling seems promising.

The main task in the design of air-cooled heat exchangers is to obtain high heat transfer coefficients from heat-exchange surfaces to air with a minimum aerodynamic drag of the devices.

One of the main directions of increasing the intensity of heat transfer to air can be considered an increase in the heat transfer surface.

The intensification of heat transfer processes, increasing the compactness of heat exchangers are possible by using porous and mesh materials with a developed inner surface as fins.

The main task is to ensure air circulation through porous fins with the least hydraulic resistance.

In this connection, the problem arose of creating fundamentally new heat exchangers for cooling and condensation of various media upon contact of heat carriers through a separating wall, in which porous plates would be used as fins, and the cooling medium would circulate through them.

Known package heat exchanger "Plastan" [1], where the plates are collected in a package and fixed at the ends of the distribution plates. Moreover, the plates are collected in a package through the sealing elements. On the plates at a distance equal to 5-10% of the package length, ledges are made, the depth of which is equal to 1.0-1.5 of the width of the o-ring. The plates are interconnected in pairs in separate boxes through the sealing elements, which on the ledge section repeat the shape of the plates.

The disadvantages of this design include its low efficiency due to the dissipation of vortex structures formed behind the ledges, while the flow core leads to turbulization of the entire flow and an outstripping increase in hydraulic resistance compared to an increase in heat transfer.

Also known is a package of plates for a heat exchanger and a heat exchanger containing this set of plates [2].

The package for heat transfer plates contains a set of parallel metal heat exchange plates and a wavy central part, so that the adjacent adjacent plates form a double countercurrent circuit of two different media. On the longitudinal edges of each of the heat transfer plates there is a coupling element for connecting two adjacent plates. Moreover, a packet of alternating open and closed ends is formed, and at the corners there are connecting elements for connecting the heat exchange plates to the elements.

Each coupling element of the longitudinal edges of the heat plates is a T-profile, the edge of which is connected to the longitudinal edge of the corresponding heat plate by a continuous sealed weld.

This design, providing a compact heat exchanger, does not solve the problem of reducing hydraulic resistance.

Back in 1995, to increase the heat transfer coefficient without a significant increase in hydraulic resistance (description of the invention [3]), the use of a corrugated heat exchange surface in the form of alternating protrusions and depressions was proposed. They have the same dimensions with respect to the center line. Adjacent surfaces form diffuser-confuser channels. The protrusions are made with a sharp edge.

The disadvantages include the difficulty of using a heat exchanger in the presence of a significant difference in the pressures of the coolants, low reliability.

Also of interest is the invention [4], in which the design of a heat exchanger containing collectors and channels for at least two coolants is given, organized by a package of heat-conducting plates with rows of holes and spacers between rows of holes that separate the coolants. Moreover, the spacers are made hollow, with inclined jumper-turbulators in the area of each hole of the plates and superimposed on the holes of the plates with rotation through an angle of 180 ° through each plate. There are also turbulent elements in the form of protrusions.

Known heat exchanger, selected as a prototype [5].

The heat exchanger contains a bag in the form of pairwise assembled vertical corrugated metal plates and porous plate inserts.

The inserts have a length greater than the length of the plates. The sections of the inserts extending at both ends of the plates are interconnected in a checkerboard pattern by means of covers.

The plate assembly forms channels for a cooled working environment. At the ends of each of the pairs of plates, covers are installed that cover the channels and are equipped with nozzles for supplying and discharging cooled media.

The cooled medium from above through the nozzles (for supply) enters the channels, from where it is discharged from the heat exchanger through the branch pipes.

The cooled medium from below enters the channels between the inserts that are not connected by covers, and through these inserts the covers are removed from the channels, exchanging heat with the cooled medium through the walls of the plates and inserts.

The disadvantages of this design of the heat exchanger include the presence of blank covers connecting staggered ends of the porous inserts. The coolant flowing from below into the channels of the heat exchanger completely passes through these inserts into adjacent channels between the inserts, which leads to a decrease in the efficiency of porous fins, an increase in the cost of overcoming the resistances during movement of the cooling medium.

The purpose of the present invention is to increase heat transfer without a significant increase in hydraulic resistance.

The goal is achieved by the fact that the collectors are equipped with partitions that provide movement of the cooled fluid from the intake manifold along a series of pipes up to the exhaust manifold; then through another row of pipes down to the intake manifold, after which the medium along the third row of pipes is fed up to the exhaust manifold with exit from the heat exchanger.

The pipes in cross section are elongated droplets, staggered and stacked in rows in a bag, and the rows are separated by mesh plates. The pipes are attached to the mesh plates. A fine-dispersed spray of water, for example, using nozzles, is injected into the stream of air entering the annulus.

The invention is illustrated by drawings, where figure 1 shows a diagram of a heat exchanger; figure 2 is a diagram of the flows of water, air and fine spray of water.

The heat exchanger consists of a housing 1, an intake manifold 2, pipes 4, an exhaust manifold 3, mesh plates 5, partition walls of the collectors 6, the annulus 7, nozzles 8.

The pipes 4 in cross section are made in the form of an elongated drop. The elongated cross section of the pipes 4 allows to increase the heat transfer surface and reduce air turbulization.

To improve heat transfer, the pipes 4 are staggered. Moreover, the pipe 4 with a convex outer side is welded to the mesh plate 5 located in front, and the opposite side of the pipe 4 is attached to the subsequent mesh plate 5.

To increase heat transfer, a finely dispersed spray of water is injected into the air stream, for example, using nozzles 8.

The heat exchanger operates as follows.

The cooled medium enters the intake manifold 2, then, under pressure, flows upward through a series of pipes 4 to the exhaust manifold 3. Due to the partition 6 of the exhaust manifold 3, the medium is directed downward along another row of pipes 4 to the intake manifold 2, then the partition 6 of the intake manifold 2 is directed upward the next row of pipes 4 in the exhaust manifold 3 and is removed from the heat exchanger.

Before air is supplied to the annular space 7 of the heat exchanger, a finely dispersed spray of water is injected into the air stream, for example, using nozzles 8.

Air passing through the mesh plates 5, rows of pipes 4, takes the heat of the cooled medium passing through the pipes 4, and goes to the other side of the heat exchanger.

At a high air supply rate, heat transfer occurs mainly through the outer hemisphere of the surface of the pipe 4, the other inner hemisphere of the pipe 4 works with less intensity, since it has little contact with air.

If the cross section of the pipe 4 has the shape of an elongated drop, then the air continues to come into contact with the second half of the surface of the pipe 4, taking heat. This increases the effect of the heat exchanger.

When a finely dispersed spray of water is injected into the flow of injected air, moisture evaporates on the surface of the heat exchanger, lowering the wall temperature.

Studies were conducted to determine the effectiveness of the proposed design of the heat exchanger. Two types of heat exchange elements were studied. The first element was made in the form of a steel pipe of circular cross section with a diameter of 15 mm, and the second in the form of an elongated drop of the same diameter. The length of the pipes was 450 mm. To increase heat transfer, a finely dispersed spray of water is injected into the air using a nozzle.

Experimental studies have shown that the use of droplet-shaped pipes in air heat exchangers instead of round pipes, the use of mesh plates, and the injection of finely divided liquid into a cooled medium gave positive results.

The duration of cooling water from 90 to 40 ° C is reduced by 25-30%.

Literature

1. The invention of the Russian Federation No. 2137998, claimed 13.05.1998.

2. Application for the invention of the Russian Federation No. 98107316/06, stated on 04/20/1998.

3. The invention of the Russian Federation No. 2031348, claimed 20.03.1995.

4. The invention of the Russian Federation No. 2039921, claimed July 20, 1995.

5. Auth. testimonial. USSR No. 892177, declared 19.10.1979

Claims (3)

1. A heat exchanger comprising a housing, intake and exhaust manifolds, pipes connected in a package, characterized in that the intake and exhaust manifolds are provided with baffles, the pipes in the cross section are elongated droplets, staggered in rows, the rows of pipes are divided by mesh plates and welded to them, the pipes are blown with air into which a finely dispersed spray of water is pumped. 2. The heat exchanger according to claim 1, characterized in that the outer side of the pipe is attached to a mesh plate located in front, and the opposite side of the pipe is attached to a subsequent mesh plate. 3. The heat exchanger according to claim 1, characterized in that a finely dispersed spray of water is injected into the air entering the annulus, for example, using nozzles.

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