WO2011064804A2

WO2011064804A2 - Double tubing condensation exchanger for heating water and/or for producing sanitary hot water

Info

Publication number: WO2011064804A2
Application number: PCT/IT2010/000459
Authority: WO
Inventors: Marco De Nardis
Original assignee: Fontecal SpA
Current assignee: Fontecal SpA
Priority date: 2009-11-24
Filing date: 2010-11-17
Publication date: 2011-06-03
Anticipated expiration: 2012-05-24
Also published as: IT1396729B1; EP2504632A2; IT1403750B1; ITRM20100599A1; ITRM20090614A1; WO2011064804A3; CN102713453B; CN102713453A; EP2504632B1; PL2504632T3; HK1176394A1; ES2538392T3

Abstract

The present invention concerns a double tubing condensation exchanger (1) for heating water and/or for producing sanitary hot water, characterized in that it provides a first coil (2) with a plain surface and a second coil (3) with a corrugated surface, provided in parallel each other, said first (2) and second (3) coils being spiral wound, a thermal carrier fluid circulating, independently, inside said first and second coil, said first (2) coil exchanging heat with combustion fumes mainly by irradiation and convection, and said second coil (3) exchanging heat with combustion fumes mainly by condensation.

Description

Double tubing condensation exchanger for heating water and/or for producing sanitary hot water

The present invention relates to a double tubing condensation exchanger for heating water and/or for producing sanitary hot water.

More specifically, the invention relates to a fumes-liquid heat exchanger, permitting obtaining very high energetic efficiency with low specific load loss both on the fumes side and on the liquid side.

Many solutions are available on the market for condensation heat exchangers providing a single coil.

One of main drawbacks of heat exchangers comprised of plain profile serpentine (without corrugation) is that caused by deposition of liquid due to condensation of combustion products within exchange interspaces for fumes passages.

Known condensation heat exchangers, with a plain surface serpentine, are limited by this problem to specific arrangements of boiler, just to permit proper evacuation of condensation, in order to prevent that the latter clogs interspaces for passage of burnt gases. Said problem practically obliges designers of thermal generators to position horizontally (with horizontal fumes flow) plain surface heat exchangers. The above obviously strongly limit architecture of thermal generators, obliging for example to limit hanging boiler sizes, their minimum depth, geometry of fumes path, ecc.

In view of the above, the Applicant has realised a condensation heat exchanger that can solve all the above problems.

These results are obtained, according to the invention, realising a condensation heat exchanger providing two separate coil tubings, respectively a plain tubing and a corrugated tubing. Coupling of these two different coils permits obtaining an optimum heat exchange, differentiating the kind of exchange surface as a function of fluid temperature with which it gets in contact. Within the combustion chamber, characterised by high temperatures caused by combined effects of thermal exchange due to irradiation and convection, is provided an exchanger comprised of a coil with plain surface, while in zones with a lower fumes temperature, where condensation phenomenon of gaseous compounds occurs, it is provided a second coil with a corrugated surface, in order to maximise heat exchange and promote proper outflow of condensate. Two coils are provided in series with respect to flow of gaseous products and in parallel with respect to thermal carrier fluid.

It is therefore specific object of the present invention a double tubing condensation exchanger for heating water and/or for producing sanitary hot water, characterized in that it provides a first coil with a plain surface and a second coil with a corrugated surface, provided in parallel each other, said first and second coils being spiral wound, a thermal carrier fluid circulating, independently, inside said first and second coil, said first coil exchanging heat with combustion fumes mainly by irradiation and convection, and said second coil exchanging heat with combustion fumes mainly by condensation.

Preferably, according to the invention, said first and second coils are spiral wound with the plain coil inside with respect to the outer coil.

Still according to the invention, said first coil has a section shake so as to conform to the profile of said second coil, particularly a pseudo-pentagonal section, or a rectangular section, or an ovoidal section, and like.

Always according to the invention, said exchanger is a vertical fume flow exchanger or a horizontal fume flow exchanger.

Furthermore, according to the invention, said first and second coils aree sized so a to make the relevant thermal carrier fluid reaching substantially the same temperature at the outlet from the exchanger.

The present invention will be now described for illustrative but not limitative purposes according to its preferred embodiments, with reference to the figures of the enclosed drawings, wherein:

figure 1 schematically shows a first embodiment of the heat exchanger according to the invention;

figure 2 shows a particular of the heat exchanger of figure 1 ; figure 3 schematically shows a second embodiment of the heat exchanger according to the invention;

figure 4 shows a first executive modification of a first particular of heat exchanger of figure 3;

figure 5 shows a second executive modification of a first particular of heat exchanger of figure 3; and

figure 6 shows a third executive modification of a first particular of heat exchanger of figure 3.

Observing first figures 1 and 2, it is shown a first embodiment of the heat exchanger according to the invention, generically indicated by reference number 1 , according to an arrangement with a mainly vertical flow of products from combustion within the same exchanger 1.

Exchanger 1 provides two coiled tubings, respectively a plain tubing 2 and a corrugated tubing 3, concentrically provided each other.

In embodiment shown in figures 1 and 2, heat exchanger 1 provides that cold thermal carrier fluid, to be heated, enters within heat exchanger from below, running hydraulically parallel with respect to the two coiled tubings 2, 3 upward.

Two tubings 2, 3 have different profiles, and particularly, the inner one 2 being comprised of a plain tubing, with profile shown in figure 4 (or one of the different arrangements shown in figures 5 and 6) suitable to be coupled with corrugated tubing 3, so as to realise an optimum thermal exchange, while the outer one 3 is comprised of a flexible corrugated tubing wound as a coil.

Two tubings 2, 3 are adjacent each other, and their profiles couple so as to realise an optimum exchange surface to transfer heat from combustion products to thermal carrier fluid.

In the first embodiment shown in figures 1 and 2, combustion fumes arriving from burner 4, go upward (arrows F), up to lick upper bottom of heat exchanger 1.

Fumes, once reached upper bottom 5, are forced to invert their direction, again going down toward lower bottom (not shown) through passages realised between corrugated tubing 3 and plain tubing 2.

Now, hot gaseous fluids lick both corrugated tubing 3 surface and plain tubing 2 surface, both with thermal carrier liquid to be heated. Coupling of the two thus overlapped surfaces is particularly efficient for heat treatment and it is optimum as far as material use (cost/advantages ratio) is concerned. Fumes, during the path, are cooled by system water up to reaching dew temperature and thus releasing condensation latent heat (which is proportional to the amount of condensate produced). Condensates, in this first arrangement of the heat exchanger, go down vertically toward lower bottom along with fumes, with a flow always according to the same direction of the fumes flow.

A direct passage does not exist in this first embodiment between interstices of plain coiled tubing 2 (horizontal passages between spire of plain coil), but all fumes are forced upward and to pass within paths indicated in figure 2.

Referring now specifically to figure 3 of the enclosed drawings, it is shown operation of heat exchanger 1 according to the invention in a second embodiment providing a horizontal fumes flow. Here, cold thermal carrier fluid to be heated enters within heat exchanger from below (WATER INLET) following a hydraulically parallel path of the two coiled tubings 2, 3 upward.

Two coiled tubings 2 have different profiles, and particularly the inner one 2 is comprised of a plain tubing, with profile shown specifically in figure 4, suitable to be coupled with corrugated tubing so as to realise an optimum heat exchange, while the outer one 3 is comprised of a coiled flexible corrugated tubing.

Said coiled tubings 2, 3 are adjacent each other, and are realised with profiles coupled so as to realise an optimum exchange surface for transferring heat from combustion product to thermal carrier fluid.

Both coiled tubings 2, 3 are continuous and have no branches all along heat exchanger length 1 , being connected at the bottom with return manifold and above to the inlet manifold (not shown).

Thermal exchange mode between gas burner 4, at the top of the combustion chamber, and the two tubings 2, 3, containing thermal carrier fluid, can be so summarised:

- heat exchange mainly by irradiation with inner surface of plain tubing 2 exposed toward the same burner 4;

- convection thermal exchange, with surfaces of plain tubing interested by passage of fumes (combustion products) between inside and outside combustion chamber according to arrow A of figure 3 and fume paths of figure 4. Fumes passages are schematically indicated by parallel arrows A in figure 3 and by lines B of particular shown in figure 4;

- by convection, with surfaces of corrugated tubing 3, lick by fumes flow both in the lower portion and in upper portion, so that tubing is fully hit by thermal flow. Particularly, the latter passage permits lowering fumes temperature under dew point of outlet fumes, thus recovering a large portion of condensation latent heat.

Plain coiled tubing 2 shown in figures 3 and 4 has a "pseudo- pentagonal" profile, but, as shown in figures 5 and 6, it can be realised with different profiles (pseudo-rectangular profile, pseudo- ovoidal profile, ecc).

Main function of plain tubing is that of lowering temperature of fumes arriving from combustion process (variable as a function of the kind of comburent employed and of air excess employed) up to a value of about 300°C-400°C, heating thermal carrier fluid circulating within "plain" hydraulic circuit. Specific "pseudo-pentagonal" shape of plain tubing 2 of figure 4 permits an optimum coupling with corrugated tubing 3, obliging warm fumes to lick exchange surfaces of both tubings, so as to obtain maximum fumes/water heat transfer.

Different geometry of two tubings 2, 3 further permits realising gas/liquid heat exchange in different phases:

- low specific surface of tubing 2 (plain tube), where fumes exchange heat at high temperature;

- high specific surface of tubing 3, where fumes exchange heat at low temperature and mainly where it occurs condensation of fumes with contemporaneous presence of gaseous and liquid phase. Particularly, corrugated tubing 3 during this phase permits an optimum outflow of condense.

In other words, it is used a plain profile surface to exchange heat with fumes at a higher temperature and a corrugated surface to exchange heat with pseudo cooled and suture fumes, with presence of the beginning of formation of liquid. In the above heat exchanger 1 , convective heat exchange surfaces of plain tubing 2 (interspaces between coils) have been studied to prevent at most formation of condensate inside, in order to prevent that deposition of liquid in these passages hinders regular path of fumes during some heat exchanger operation modes.

By the solution suggested according to the present invention, many advantages are obtained with respect to the known solutions.

Particularly, advantages are obtained both in terms of efficiency and in term of functionality and reliability.

Combination of plain and corrugated tubings permits obtaining a higher efficiency. System based on new coaxial combination of two coils with a different geometry, respectively comprised of a coil winding of a corrugated tubing 3, and the other one comprised of a coil winding of a plain tubing 2 (with an pseudo-pentagonal, - rectangular or - ovoidal shape, and like) permits an optimum exploitation of heat generated by hydrocarbon combustion. In fact, particular fumes path permits an optimum fumes/water exchange, with useful efficiencies higher than those obtained with known solutions.

It is further obtained a lower hydraulic load loss with respect to system with a single coil, since, with respect to solutions with a single coil known, system suggested according to the invention permits a lower hydraulic load loss of thermal carrier fluid. In fact, hydraulic parallel path comprised of the two coils and their particular geometry permits remarkably reducing divided and concentrated load loss of heat exchanger with respect to a single coil exchanger with the same exchange surface.

Finally, it is realised an optimum condensate evacuation system, due to original and new heat exchange system and to the specific "plain/corrugated" architecture permitting, with respect to the mainly employed solutions, a higher flexibility when positioning the heat exchanger within the thermal generator.

Particular geometry of the suggested heat exchanger makes it possible formation of condensate only close to the corrugated outer coil and not close to interspaces of plain tubing, thus preventing all problems connected to presence of liquid between said interspaces of plain tubing. As already said, advantages with respect to known exchangers are really remarkable, e.g. since this kind of products available on the market are restrained to a horizontal arrangement of the heat exchanger within the boiler (axis of heat exchanger provided horizontally), i.e. an arrangement by which fumes and condensate paths are vertical paths, in order to prevent condensate stagnation within coil interspaces, and permitting its exit outward the boiler. Present invention has been described for illustrative, but not limitative, purposes, according to its preferred embodiments, but it is to be understood that variations and/or modifications can be introduce by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.

Claims

1. Double tubing condensation exchanger for heating water and/or for producing sanitary hot water, characterized in that it provides a first coil with a plain surface and a second coil with a corrugated surface, provided in parallel each other, said first and second coils being spiral wound, a thermal carrier fluid circulating, independently, inside said first and second coil, said first coil exchanging heat with combustion fumes mainly by irradiation and convection, and said second coil exchanging heat with combustion fumes mainly by condensation.

2. Exchanger according to claim 1, characterised in that said first and second coils are spiral wound with the plain coil inside with respect to the outer coil.

3. Exchanger according to one of the preceding claims, characterised in that said first coil has a section shake so as to conform to the profile of said second coil, particularly a pseudo-pentagonal section, or a rectangular section, or an ovoidal section, and like.

4. Exchanger according to one of the preceding claims, characterised in that said exchanger is a vertical fume flow exchanger or a horizontal fume flow exchanger.

5. Exchanger according to one of the preceding claims, characterised in that said first and second coils aree sized so a to make the relevant thermal carrier fluid reaching substantially the same temperature at the outlet from the exchanger.