GB2130677A

GB2130677A - Recuperative heat exchanger

Info

Publication number: GB2130677A
Application number: GB08327014A
Authority: GB
Inventors: Heinrich Landgraf; Knut Brockmeier
Original assignee: Kombinat Textima VEB
Current assignee: Kombinat Textima VEB
Priority date: 1982-10-08
Filing date: 1983-10-10
Publication date: 1984-06-06
Also published as: GB8327014D0; DD210966A1; FR2534363A1; DE3336367A1

Abstract

Recuperative heat exchangers such for example as pipe bundle heat exchangers or plate-type heat exchangers with vertical or oblique plate arrangement upon which gaseous heat-carrier media act, has a distributor (12) for causing a cleaning fluid to act upon them, and beneath the heat transmission elements (2; 20) a collecting vessel (7) for the cleaning fluid is arranged. <IMAGE>

Description

SPECIFICATION Recuperative heat exchanger The invention relates to recuperative heat exchangers such for example as pipe bundle heat exchangers or plate-type heat exchangers with vertical or oblique plate arrangement upon which gaseous heat-carrier media act, between which heat is to be exchanged.

When gaseous media act upon heat exchangers, usually soiling of the heat transmission surfaces must be expected. Mention may be made by way of example of air discharge currents out of driers and heat treatment machines in the textile industry, which currents are cooled in heat recuperation installations for the purpose of recovery of the waste heat. In this operation textile aids, preparations and the like mixed with dust condense on the heat transmission surfaces as a thickly liquid, usually oiiy deposit which gradually encrusts, thus reduces the heat transmission and the air throughput and can finally lead to complete stoppage of the heat exchanger.

It has hitherto been usual to remove heat exchangers from their installed position for the purpose of cleaning. The physical labour necessary in the transport of the soiled heat exchangers to the cleaning apparatus is here disadvantageous. In the case of glass, which is increasingly in use as material for heat exchangers, in addition to the stated difficulty there is also the risk of breakage in transport.

Furthermore in order to achieve optimum cleaning effects, cleaning baths are commonly used with which it is possible to operate manually only when using protective gloves and observing precautionary measures. By reason of this situation the cleaning intervals are made as long as possible, which reduces the effectiveness of the heat recuperation.

From Fed. Ger. Pub. Sp. No. 30 09 889 an indirect heat exchanger has become known which comprises a series or parallel arrangement of a plurality of component heat exchangers, of which at least one at any time is cleanable while the other component heat exchangers are in operation, these in each case, as a whole, being designed for at least the total heat exchange. The component heat exchangers are arranged in a frame which is mobile in a non-displaceable chassis between two positions, a working position and a cleaning position.

Thus it is in fact possible to clean the component heat exchangers in sequence while the heat exchanger is still in operation, without having to hait the latter completely; this however is not necessary in every case, since the machine containing the heat exchanger mostly is in any case subject to specific cleaning cycles and has to be halted.

This apparent advantage is however gained at the cost of the disadvantage that the heat exchanger as a whole must be considerably overdimensioned, both as regards capacity and as regards overall space, in order to be constantly adequate for the total heat exchange.

A further usual practice in the cleaning of heat exchangers, namely with steam lances, for example in accordance with GDR Patents Nos.

131,964,146,407, 147,096,147,097 and 150,408, is not always effective as heat exchangers have inter alia too great an overail depth in the direction of flow, so that cleaning right into the innermost part of the heat recuperation plant is not successful.

It is the aim of the invention, in the cleaning of heat exchangers, to minimise the expenditure of labour and the stoppage times of the equipment comprising the heat exchanger.

The invention is based upon the problem of producing a recuperative heat exchanger the freeing of which from deposits on the heat transmission surfaces inhibiting the heat transmission is possible without removing the heat exchanger from the heat recuperation plant.

In accordance with the invention this problem is solved in that above the heat transmission surfaces there are arranged means for causing a cleaning fluid to act upon them, and beneath the heat transmission surfaces a collecting vessel for the cleaning fluid is arranged, as fixed components of the heat exchanger.

The invention is carried out especially advantageously if the means for the action of the cleaning fluid upon the heat transmission surfaces and the collecting vessel are connected both with one another and also, each independently, with a reservoir for the cleaning fluid. This renders it possible to conduct the cleaning fluid in a cycle, that is to use it repeatedly, and to store it after the conclusion of a cleaning operation until the next cleaning operation. For this purpose it is simplest to connect the reservoir by means of a three-way cock into the conduit connecting the collecting vessel and the means for action upon the heat transmission surfaces.

According to further features of the invention a pump and a filter for the cleaning fluid are connected into the conduit for the connection of the collecting vessel with the means for action of the cleaning fluid upon the heat transmission surfaces.

According to the invention the collecting vessel for the cleaning fluid can serve, during operation of the heat exchanger, as reception vessel for condensate coming from the heat carrier medium to be cooled. For this purpose it is connected with a condensate vessel.

According to further features of the invention the means for causing the cleaning fluid to act upon the heat transmission surfaces can be formed as spray pipes provided with distributor openings or as distributors in the form of a box having a plurality of distributor openings.

If the heat transmission surfaces are formed as a bundle of pipes, in the former case the spray pipes are arranged in the same geometry and configuration as the pipes serving as heat transmission surfaces; in the latter case the distributor openings of the distributor of box form are arranged over the axes of the pipes serving as heat transmission surfaces.

The invention has the advantage that the heat exchanger can be subjected to cleaning without change of location, so that all risks in transport and dismantlement are avoided.

A cleaning operation can be initiated at minimum notice and with slight expenditure of labour, so that any foreseeably lengthy halt, especially maintenance periods, of the machine to which the heat exchanger is allocated can be utilised for this purpose.

For this reason cleaning operations can also be carried out at relatively short intervals, so that heavy soiling of the heat transmission surfaces and thus unnecessarily lengthy time consumption of the cleaning operations can be avoided.

As a further essential advantage of the invention there is the fact that cleaning of the heat exchanger can be carried out without operating personnel coming into direct contact with the cleaning fluid. Danger of harm to health and the consequently necessary expense for labour protection measures are eliminated.

The invention is to be explained below in greater detail by reference to an example of embodiment. In the drawings:- FIGURE 1 shows a representation of a pipe bundle heat exchanger in accordance with the invention, FIGURE 2 shows a section along the section line Il-Il in Figure 1, FIGURE 3 shows a section along the section line Ill-Ill in Figure 1, FIGURE 4 shows an alternative view analogous with Figure 3, FIGURE 5 shows a diagrammatic representation of a section analogous with Figure 2, through a plate-type heat exchanger in accordance with the invention, and FIGURE 6 shows a detail VI from Figure 1 in different operative positions.

In Figure 1 there is represented a heat exchanger 1 in the form of construction as a pipebundle heat exchanger. It consists essentially of heat transmission surfaces in the form of smooth or finned pipes 2 arranged one above and one beside the other. The interior spaces of the pipes 2, as a totality, constitute a first flow chamber while a second flow chamber consists of the space surrounding the pipes 2 and defined by a housing 1 9. A heat-carrier medium, for example the air supply 5 for a textile drier, to be heated in the heat exchanger 1, flows through the first flow chamber A filter 6 frees the air supply 5 from impurities and thus prevents soiling of the interior surfaces of the pipes 2.

A heat carrier medium which is to be cooled in the heat exchanger, for example the hot exhaust air 3 from the textile drier, is fed to the second flow chamber. Coarse impurities such for example as fluff, contained in this exhaust air are held back by a filter 4. Other impurities such as textile aids, preparations, etc. condense out however as a result of the cooling of the exhaust air 3 on the pipes 2 of the heat exchanger 1 and thus reduce the heat transmission.

The conditions on a plate-type heat exchanger according to Figure 5 are to be considered analogously. The heat transmission surfaces in this case are formed as flat plates 20.

In accordance with the invention, above the heat transmission surfaces there are arranged means for action of a cleaning fluid upon these surfaces, in the form of a distributor 12 provided with distributor openings 16, and a collecting vessel 7 is arranged beneath the heat transmission surfaces, as integrated components of the heat exchanger 1 (see Figure 1).

The distributor 12 can consist according to Figure 3 of a box having a plurality of distributor openings 16, which can be made as bores or slots.

Such a distributor 1 2 wili be used for preference for pipe-bundle heat exchangers. The distributor openings 1 6 are then advantageously arranged above the longitudinal axes of the pipes 2.

It is also possible, as represented in Figure 4, to assemble the distributor 12 from spray pipes 1 7 provided with distributor openings 1 6 and connected by a distributor pipe 1 8. For pipe bundle heat exchangers, especially those with rectangular pipe bundle cross-section, it is also possible to use as spray pipes 1 7 an additional row of pipes with the same geometry and configuration as the pipes 2.

For the purpose of cleaning the heat transmission surfaces the distributor 12 is charged with a cleaning fluid. For this purpose it can advantageously be connected with a fixedly installed reservoir 10 for the cleaning fluid. By means of the distributor openings 1 6 provided in the distributor 12 the cleaning fluid is caused to act upon the heat transmission surfaces, that is the pipes 2 or plates 20 as the case may be, and to flow around them as a result of the action of gravity. The impurities deposited on the heat transmission surfaces are than taken up and transported away by the cleaning fluid. This collects in the collecting vessel 7 beneath the heat transmission surfaces. It is especially favourable if the cleaning fluid can be conducted in a cycle and thus flows continuously around the heat transmission surfaces. A special embodiment of a heat exchanger 1 in accordance with the invention which is suitable for this purpose, as also represented in Figure 1, is to be described in greater detail below.

The collecting vessel 7 is connected on the outflow side through a conduit 14 with the distributor 12. Into this conduit 14 there are connected a filter 21 for the cleaning fluid, a pump 13, a drain with a valve 1 5 and a three-way cock 11. The collecting vessel 7 is also connected through a valve 8 with a condensate vessel 9.

Moreover the reservoir 10 is connected to the three-way cock 11.

In this case the cleaning operation proceeds as follows: In the "fill" position (Figure 6a) the three-way cock 11 permits the cleaning fluid to flow out of the reservoir 10 in the direction of the distributor 12. When a sufficient quantity of cleaning fluid has been introduced into the cycle, the three-way cock 11 is set into the "clean" position (Figure 6b). With the valve 8 closed the cleaning fluid which has collected in the collecting vessel 7 after flowing around the heat transmission surfaces is fed afresh to the distributor 1 2 by means of the pump 13. To do so it passes through the filter 21 and is there freed from coarse impurities.

When the process of cleaning the heat transmission surfaces has advanced sufficiently far the cleaning fluid, provided it is reusable, can be conveyed back into the reservoir 10 again by means of the pump 13. For this purpose the threeway cock 11 is to be set into the "pump away" position (Figure 6c). Otherwise the soiled cleaning fluid is removed from the heat exchanger 1 with the valve 1 5 opened.

It is especially advantageous if at the beginning of the cleaning process only a small quantity of cleaning fluid is fed to the distributor 12 and firstly frees the heat transmission surfaces and the collecting vessel 7 of coarse impurities. Then this quantity of cleaning fluid can be removed, with the valve 8 opened, into the condensate vessel 9. This precludes premature soiling of the whole of the cleaning fluid.

The cleaning process can be shortened if one works with heated cleaning fluid. This can be achieved in a simple manner in that the reservoir 10 is arranged so that the waste heat of the machine of which the heat recuperation plant containing the heat exchanger 1 is a component can be used for the heating of the cleaning fluid.

The possibility exists especially that the still warm exhaust air 3 issuing from the heat exchanger 1 flows around the reservoir 10.

Claims

1. Recuperative heat exchanger with heat transmission surfaces in the form of pipe bundles or of vertically or obliquely arranged plates, characterised in that above the heat transmission surfaces (2; 20) there are arranged means (12; 17; 18) for causing a cleaning fluid to act upon them, and beneath the heat transmission surfaces (2; 20) a collecting vessel (7) for the cleaning fluid is arranged, as fixed components of the heat exchanger (1).

2. Recuperative heat exchanger according to Claim 1, characterised in that the means (12, 17; 18) for action upon the heat transmission surfaces (2; 20) and the collecting vessel (7) are connected both with one another and each with a reservoir (10) for the cleaning fluid.

3. Recuperative heat exchanger according to Claims 1 and 2, characterised in that the reservoir (10) is connected by means of a three-way cock (11) into the conduit which connects the means (12; 17; 18) for action upon the heat transmission surfaces (2, 20) and the collecting vessel (7).

4. Recuperative heat exchanger according to Claims 1 to 3, characterised in that a pump (13) is interposed into the conduit (14) for the connection of the collecting vessel (7) with the means (12; 17; 18) for acting upon the heat transmission surfaces (2; 20).

5. Recuperative heat exchanger according to Claims 1 to 4, characterised in that a filter (21) for the cleaning fluid is interposed in the conduit (14) for the connection of the collecting vessel (7) with the means (12; 17; 18) for action upon the heat transmission surfaces (2; 20).

6. Recuperative heat exchanger according to Claim 1, characterised in that the collecting vessel (7) for the cleaning fluid serves, while the heat exchanger (1) is in operation, as reception vessel for condensates separated out of the heat-carrier medium to be cooled.

7. Recuperative heat exchanger according to Claim 6, characterised in that the collecting vessel (7) is connected with a condensate vessel (9).

8. Recuperative heat exchanger according to Claim 1, characterised in that spray pipes (17) provided with distributor openings (16) are provided as means for the action of the cleaning fluid upon the heat transmission surfaces (2; 20).

9. Recuperative heat exchanger according to Claim 1, characterised in that when the heat transmission surfaces are formed as bundles of pipes (2), the spray pipes (1 7) are arranged in the same geometry and configuration as the pipes (2) serving as heat transmission surfaces.

10. Recuperative heat exchanger according to Claim 1, characterised in that a distributor (12) in the form of a box having a plurality of distributor openings (16) is arranged above the heat transmission surfaces (2; 20) as means for action upon them by the cleaning fluid.

11. Recuperative heat exchanger according to 10, characterised in that when the heat transmission surfaces are formed as bundles of pipes (2), the distributor openings (16) are arranged above the axes of the pipes (2).

1 2. Recuperative heat exchanger substantially as described with reference to Figures 1-3, 5 and 6 and Figure 4 of the accompanying drawings.