WO1996024021A1

WO1996024021A1 - Heat exchanger

Info

Publication number: WO1996024021A1
Application number: PCT/FI1996/000060
Authority: WO
Inventors: Christer Ekman
Original assignee: Abb Installaatiot Oy
Priority date: 1995-02-03
Filing date: 1996-01-31
Publication date: 1996-08-08
Also published as: SE9702844L; SE513547C2; SE9702844D0; DK90197A; FI950491A0; CA2212051A1; FI950491A; NO973552L; RU2157960C2; DE19681200T1; NO973552D0

Abstract

The invention relates to a heat exchanger, whereupon the heat exchanger comprises a pipe section for liquid circulation and fin parts that are attached to the outer surfaces of the pipe section in order to enlarge the heat-exchange surface. In order to make the heat transfer more efficient, the fin parts are divided into at least two zones (5, 6). The pipe sections (8, 9) of the fin zones can be connected to collecting pipes (16) and to distributor pipes (18), so that after the liquid has passed through one fin zone (5) it is arranged to be mixed at least in one collecting pipe (16) before it is supplied to the distributor pipe (18) of the next zone (6), or to the distributor pipes of the following zones.

Description

Heat exchanger

The invention relates to a heat exchanger, especially for regulating the temperature of air by means of a liquid supplied into the heat exchanger, or vice versa, whereupon the heat exchanger comprises a pipe section for liquid circulation and fins that are attached to the outer surfaces of the pipe section in order to enlarge the heat-exchange surface. This kind of heat exchangers are presently well known in different fields of technology. An example of technical fields utilizing such heat exchangers is ventilation technology. Ventilation installations are often provided with heat exchangers of the aforementioned type, situated in connection with either air treatment apparatuses or ducts. In the most common situation, liquid flows inside the pipes and air outside the pipes. In order to provide better heat transfer, fins that extend the heat-exchange surface are attached to the outer surface of the pipes. The fins are often wavy and mutually very closely positioned in order to provide a good heat-transfer ratio.

The air is warmed in a supply air device in the winter and possibly cooled in the summer in order to obtain the desired state for the supply air. The heating stage often consists of two or three steps. The first step is the process of heat recovery wherein, in case of a liquid heat exchanger, the liquid is a liquid protected from freezing. The next step is the actual heating radiator which is used to increase the heat, or if there is no step of heat recovery, to supply heat so that the desired air temperature is obtained either as a final or intermediate state. The third step, which is the after-heating step, occurs in an after-heating radiator that is usually required after a humidifying part, after a dehumidification process performed by cooling, or for the purpose of zone-specific heating.

The cooling process takes place not only in the supply air heat exchanger in the summer, but also in the heat recovery radiator of the exhaust air device in the winter, in which case the liquid is a liquid prevented from freezing. In other respects, the process corresponds to the above-described process.

If liquid radiators are added to the process circuit, the purpose is to provide the liquid circuit with the desired temperature either partly or entirely, at the same time as the air system usually also benefits from this. There are also such liquid radiators that are used for both heating and cooling in series or at different times.

The structure of fin-type heat exchangers is conventionally unchanging. The structure consists of the following components: a radiator supply water connection that is attached to a distributor pipe from which pipe sections, or so-called tube pipes, diverge and circulate in depth through the radiator fins according to a specific geometry that is recurrent and that is determined by apertures provided in the fins. The tube pipes form water routes through the radiator and end in a collecting pipe from which the water exits via a connecting pipe for water leaving the radiator. Such radiators comprise one distributor pipe, or bypass manifold, and one collecting pipe, or collecting manifold, for the discharge of water. In all the above-described cases, the radiators conventionally operate in such a way that a change in the temperature occurs in a radiator that is homogenous in the direction of motion of air. A case wherein the fin is extended by means of manufacturing technique may constitute an exception, but in such a case the operation of the radiators remains the same, however. The capacity of the radiator is usually controlled by adjusting the liquid flow or its temperature, or by regulating the temperature of the air, depending on the direction of flow of energy.

Efficient energy exploitation often leads to very small temperature differences. In the fin area of the radiator, there occur in the air side temperature stratifications that can be considerable and that deteriorate the total heat-transfer coefficient, depending on the pipe routes. The temperature of the liquid varies between the different water routes depending on how evenly the liquid flow divides. Small temperature differences result in deep radiators. In practice, the number of pipe rows in the flow direction of air can be as high as twelve. Together with the small fin pitch, wavy fins and a possible production-technical fin extension, this makes the efficient cleaning of the radiator impossible. Since the radiator cannot be cleaned, a contamination layer forming on its surface deteriorates the heat transfer, wherefore the radiator capacity decreases. In order to obtain the desired capacity, the radiator has to be overdesigned utilizing a so-called contamination coefficient which can be about 1.3 for example in industrial applications. In addition to a consequent increase in the investment costs, the drag of the radiator and the resultant consumption of the electrical power of the blower increase. Since the contamination layer also makes the flow ducts between the fins narrower, the flow resistance and the consumption of electrical power increase as a result. The total effect can increase the flow resistance of the radiator and the electrical power consumption that is directly proportionate with the flow resistance more than 50% for the radiator. This leads to a need to overdesign also the driving motor, belt drives, contactors, cables etc. This results in a considerable increase in both running and investment costs.

According to studies, in some cases the increasing flow resistance decreases the air flow as much as 30% when the radiator becomes dirty. Especially in industrial processes, but also in normal ventilation installations, the whole system must be readjusted in such a case by increasing the rotational velocity of the blower with special dampers or the like. This naturally produces considerable costs.

Due to the greater flow resistance, the noise level of the blower increases. The noise suppression system must also be overdesigned, or an additional suppression mechanism must be constructed afterwards.

The contamination of radiators used for heat recovery is particularly harmful. In addition to the aforementioned drawbacks, the efficiency of heat recovery decreases. This means that in addition to the consumption of electrical power, the consumption of thermal energy also increases, in some cases it is even doubled.

A very serious drawback is the health hazard associated with contamination. The contamination layer forms a substrate for bacterial and fungal populations which comprise spores that may get into the air flow and cause allergic reactions, at worst a fever known as a "printer's disease" in printing houses and in textile industry. Another known problem is an unpleasant odour, which spreads from some plants at the beginning of the heating season and which is caused by the fact that populations which were generated on the cool radiator surfaces during the summer start secreting evaporable substances when the temperature of the radiators increases. The purpose of the invention is to provide a heat exchanger by means of which the prior art drawbacks can be eliminated. This is achieved with the heat exchanger according to the invention, the first embodiment thereof being characterized in that the fin parts are divided into at least two zones, and that the pipe sections of the fin zones are connected to collecting pipes and to distributor pipes, so that after the liquid has passed through one fin zone it is arranged to be mixed at least in one collecting pipe before it is supplied to the distributor pipe of the next zone, or to the distributor pipes of the following zones. The second embodiment of the heat exchanger according to the invention is characterized in that the fin parts are divided into at least two zones in such a way that there remains between the zones an intermediate space where the air is arranged to be mixed before it flows into the next zone. The blending of air can be made more efficient for example with special turbulence sheets, air sprays, guide plates or with some other device known per se.

The primary advantage of the invention is its flexibility since, if desired, it benefits both the liquid side and the liquid and air sides, depending on the requirements of the overall situation. It also provides production-technical advantages, since it is possible to select the fin zone according to the manufacturing technique so that there is no need to use extended fins. The extended fins tend to cause additional resistances in the air side and to increase the gathering of dirt and dust. Additional advantage is provided by the fact that the heat exchanger according to the invention can be cleaned in two or more stages depending on the number of spaces remaining between the fin zones. The cleaning method can be for example vacuuming, a cleaning gun, a combination of a vacuum cleaner and a cleaning gun, or some other cleaning method known per se that is either fixed or installed temporarily for the cleaning stage. In the following, the invention will be described in greater detail by means of preferred embodiments described in the accompanying drawing, in which

Figure 1 shows the coupling end in the first embodiment of the heat exchanger according to the invention,

Figure 2 is a view of the heat exchanger of Figure 1 taken along arrows II-II of Figure 1,

Figure 3 shows another alternative implementation of the embodiment of Figure 1 in a similar manner as Figure 2,

Figure 4 is a top profile of a second embodiment of the heat exchanger according to the invention, Figure 5 is an end view of the cleanout arrangement of the embodiment of Figure 1,

Figures 6a and 6b show the different implementations of a detail in the heat exchanger according to the invention, and Figure 7 shows a modification of the embodiment of Figure 1.

In Figure 1, a bypass manifold for incoming water is denoted by reference numeral 1, and a collecting manifold for the water leaving the heat exchanger by reference numeral 2. A connecting pipe from the bypass manifold 1 to the network is denoted by reference numeral 3, and a connecting pipe for the collecting manifold 2 in turn by reference numeral 4. A roof element of a possible housing in the heat exchanger is denoted by reference numeral 12, and a bottom element correspondingly by reference numeral 13. According to an essential basic idea of the invention, the fin parts of the heat exchanger are divided into at least two zones 6, 5 in such a way that there remains between the zones an intermediate space

7 where the air is arranged to be mixed before it flows into the next zone. This is clearly apparent in Figure

1 which shows the direction of the air flow by means of an arrow. In the example of the figure, the first fin zone in the direction of travel of the air is denoted by reference numeral 6, and the second fin zone correspondingly by reference numeral 5. The intermediate space where the air is mixed either mechanically or thermally is denoted by reference numeral 7, as noted above.

Figure 2 is a top view of the heat exchanger according to Figure 1. In Figure 2, reference numeral

8 denotes a pipe section, a so-called tube pipe, which begins from the water distributor pipe 1 and circulates through the fin zone 5, turning back to the fin zone 5 by means of a bent pipe 10. The fins of the fin zone are clearly visible in the enlarged partial view of Figure 2. A bent pipe 11 transfers the liquid to the next fin zone 6 past an intermediate space 7 after which a pipe section 9, a so-called tube pipe, guides the liquid through the fin zone. The liquid finally arrives at a collecting manifold 2 for exhaust liquid. It should be noted that even though the liquid circulation is described above by means of one pipe section, in reality there are several pipe sections, i.e. tube pipes. Figure

2 also shows possible end plates of the heat exchanger by means of reference numerals 14 and 15.

As described above, the invention can be applied both in the air and the liquid side. According to the basic idea of the invention, the fin parts are divided into at least two zones 6, 5, and the pipe sections 8, 9 of the fin zones are connected to collecting pipes 16 and distributor pipes 18 so that when the liquid has passed through one fin zone 5, it is arranged to be mixed at least in one collecting pipe 16 before it is fed into the distributor pipe 18 of the next zone 6, or into the distributor pipes of the following zones. This kind of implementation is described in Figure 3 which shows two separate fin zones 5 and 6, an intermediate space 7, and tube pipes 8 and 9 that pass through the fin zones 5 and 6. Reference numeral 16 shows a collecting pipe that is situated after the fin zone 5 and that is joined by a tube pipe, or in practice tube pipes 8. The liquid that has flowed through the fin zone 5 is mixed in the collecting pipe 16 before it moves via an interconnector 17 to a distributor pipe 18 from which tube pipes 9 of the fin zone 6 divide the liquid further to the fin zone 6. In the embodiment of Figure 3, the fin zones

5, 6 are separate zones. However, this is not the only alternative. If the basic idea of the invention is only applied to the liquid side, the fin zones can also be implemented as fictitious zones. Figure 4 shows such an embodiment. The fictitious fin zones are denoted by reference numerals 19 and 20. The tube pipes of the fin zone 19 are connected to a collecting pipe 21 from which the liquid moves after mixing via an interconnector 22 to a distributor pipe 23 where the tube pipes branch into the fin zone 20.

It should thus be noted that the term used in the claims covers both separate fin zones and the fictitious fin zones of Figure 4. The fictitious fin zones can be produced quite freely without any intermediate spaces. The basic idea is that the temperature differences that have occurred in the liquid in a fin zone are evened out before the liquid is supplied into the next fin zone.

Figure 5 in turn shows the cleanout arrangement of the embodiment of Figure 1. Reference numeral 24 shows a cover part by means of which a cleanout is provided at the intermediate space 7. The heat exchanger can be advantageously cleaned through this cleanout by means of a suitable cleaning device or cleaning agent. Figures 6a and 6b show two versions of a liquid receiver basin to be attached to the bottom section of the heat exchanger according to the invention. Reference numeral 25 shows a basin alternative containing no drain connection, and reference numeral 26 shows a basin alternative with a drain connection.

Figure 7 shows a modification of the embodiment of Figure 1. Figure 7, as Figure 1, shows the coupling end of the heat exchanger according to the invention. Like reference numerals are used in corresponding points as in Figure 1. The bypass manifold for incoming water is denoted in Figure 7 by reference numeral 27, and the collecting manifold for the water leaving the heat exchanger in turn by reference numeral 28. In this modification, the bypass manifold and the collecting manifold are provided with connecting pipes 29 and 30 that are parallel with the manifolds. The connecting pipes 29 and 30 can be oriented in parallel, as in Figure 7, or in opposite directions.

The above-described embodiments are not intended to limit the invention in any way, but the invention can be modified quite freely within the scope of the claims. Therefore, it is clear that the heat exchanger according to the invention, or the details thereof, do not necessarily have to correspond exactly to those shown in the figures, but other kinds of arrangements are also possible. For example, the invention is not in any way limited to two fin zones, even though the examples of the figures show such embodiments. The invention can also be applied in connection with two, three or more fin zones. The invention can also be utilized for both heating and cooling purposes, as noted above.

Claims

1. A heat exchanger, especially for regulating the temperature of air by means of a liquid supplied into the heat exchanger, or vice versa, whereupon the heat exchanger comprises a pipe section for liquid circulation and fin parts that are attached to the outer surfaces of the pipe section in order to enlarge the heat-exchange surface, c h a r a c t e r i z e d in that the fin parts are divided into at least two zones (5, 6; 19, 20), and that the pipe sections (8, 9) of the fin zones are connected to collecting pipes (16; 21) and to distributor pipes (18, 23), so that after the liquid has passed through one fin zone (5; 19) it is arranged to be mixed at least in one collecting pipe (16; 21) before it is supplied to the distributor pipe (18; 23) of the next zone (6; 20), or to the distributor pipes of the following zones.

2. A heat exchanger according to claim 1, c h a r a c t e r i z e d in that the fin parts are divided into zones (5, 6) in such a way that there remains between the zones an intermediate space (7) where the air is arranged to be mixed before it flows into the next zone.

3. A heat exchanger, especially for regulating the temperature of air by means of a liquid supplied into the heat exchanger, or vice versa, whereupon the heat exchanger comprises a pipe section for liquid circulation and fin parts that are attached to the outer surfaces of the pipe section in order to enlarge the heat-exchange surface, c h a r a c t e r i z e d in that the fin parts are divided into at least two zones (5, 6) in such a way that there remains between the zones an intermediate space (7 ) where the air is arranged to be mixed before it flows into the next zone.

4. A heat exchanger according to claim 2 or 3, c h a r a c t e r i z e d in that a cleanout is placed on the outer surface of the heat exchanger at the intermediate space (7 ) .

5. A heat exchanger according to any one of the preceding claims, c h a r a c t e r i z e d in that a liquid receiver basin (25, 26) is positioned in connection with the lower part of the heat exchanger.

6. A heat exchanger according to claim 5, c h a r a c t e r i z e d in that the receiver basin (26) is provided with a drain connection.

7. A heat exchanger according to any one of the preceding claims, c h a r a c t e r i z e d in that the connecting pipes ( 29, 30) are attached to the ends of the bypass manifold and the collecting manifold (27, 28) parallel to the manifolds.