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Patent Searching and Data


Title:
CONDENSING HEAT EXCHANGER
Document Type and Number:
WIPO Patent Application WO/2017/007353
Kind Code:
A1
Abstract:
Condensing heat exchanger having in its upper part a combustion chamber equipped with a hole for a burner pipe, flue tubes mounted in a tube sheets, encircled by an outer shell, inside of which is created a chamber for the liquid being heated, and equipped with a heated liquid inlet port and outlet port, a condensate tank equipped with a condensate drain discharge and an exhaust outlet into the chimney, characterised in that the ratio of the length (L) of the flue tube (1) to its cross-sectional circumference washed by flue gas is between 2.5 and 6.5, while the flue tubes (1) have embossed pits (2) directed toward the centre of the tube (1), facing each other and forming a section in which the distance between the tips of the pits (2) inside the flue tube (1) is 1.0 mm at most.

Inventors:
SZCZEPAŃSKI KRZYSZTOF (PL)
BERNACIAK MACIEJ (PL)
Application Number:
PCT/PL2016/000072
Publication Date:
January 12, 2017
Filing Date:
June 30, 2016
Export Citation:
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Assignee:
AIC SPŐŁKA AKCYJNA (PL)
International Classes:
F24H1/28; F24H8/00; F24H9/00; F28F1/40; F28F1/42
Domestic Patent References:
WO2013141728A22013-09-26
Foreign References:
US20080029243A12008-02-07
US20110146594A12011-06-23
DE2408886A11975-09-04
Attorney, Agent or Firm:
POMIANEK, Grażyna (PL)
Download PDF:
Claims:
Claims

1. A condensing heat exchanger having in its upper part a combustion chamber equipped with a hole for a burner pipe, flue tubes mounted in the tube sheets, encircled by an outer shell, inside of which is created a chamber for the liquid being heated, and equipped with a heated liquid inlet port and outlet port, a condensate tank equipped with a condensate drain discharge and an exhaust outlet into the chimney, characterised in that the ratio of the length (L) of the flue tube (1) to its cross-sectional circumference washed by flue gas is between 2.5 and 6.5, and the flue tubes feature embossed pits (2) formed along the length of the tube (1) and pointing towards the centre of the tube (1), and said pits (2) are positioned opposite each other, and two opposite pits (2) mark out a section, where the distance between the lowest points in the pits (2) measured inside the tube (1) in the section is 1.0 mm at most.

2. The exchanger according to Claim 1, characterised in that the height (S) of the combustion chamber (3) corresponds, at most, to three times the dimension of the cross-sectional circumference of the flue tube (1), washed by flue gas.

3. The exchanger according to Claims 1 or 2, characterised in that the height (H) of the heat exchanger, covering the height (S) of the

combustion chamber (3) and the distance between tube sheets (4, 5) with flue tubes (1) installed, is six to eight times the dimension of the cross- sectional circumference of flue tube (1), washed by flue gas.

4. A method of heat exchange in the exchanger according to Claims 1 to 3, characterised in that for a flue gas temperature of 1 450°C to 1 550°C, at the inlet to the flue tube (1) and with flow rate of 0.83 - 0.89 kg/h of flue gas in the flue tube (1) (for natural gas, C02 = 9%) and for an initial temperature of 30°C and dT = 20 of heated liquid, with a counterflow of 22 - 26 1/h for the flue tube (1), , the flue gas at a distance of 155 - 225 mm from the inlet to this tube (1) reaches the dew point, and the pressure drop is not more than 375 Pa.

Description:
Condensing heat exchanger

The invention relates to a condensing heat exchanger to be used in central heating systems and tap water systems.

There are known heat exchangers equipped with an assembly of tubular elements, with hot flue gases flowing through these elements, mounted between two tube sheets and placed in a chamber enclosed by an outer shell with heated water circulating in it, fed by an inlet port located in the lower part of the outer shell and received by a discharge port located in the upper part of the outer shell. In exchangers of this type, the combustion chamber is placed above the upper tube sheet, while below the lower tube sheet, the condensate drain pan is situated.

From patent description PL216290 B l, a heat exchanger is known that is equipped with an outer shell, inside of which there is an assembly of vertical tubular elements mounted at their both ends in tube sheets, and equipped with a gas combustion chamber located above the upper tube sheet, and equipped with walls, mounted crosswise the tubular elements, having holes with tubular elements running through them, and equipped with liquid inlet and outlet ports located in the side wall of the outer shell.

The aim of the invention is to reduce the resistance of flue gas flow through the heat exchanger.

This aim is achieved by selecting the optimum dimensional relationships between various elements of the heat exchanger, depending on the flue tube's cross sectional circumference washed by flue gas, while maintaining the condensing nature of the heat exchanger.

A condensing heat exchanger, having in its upper part a combustion chamber equipped with a hole for a burner pipe, flue tubes mounted in a tube sheets, encircled by an outer shell, inside of which is created a chamber for the liquid being heated, and equipped with a heated liquid inlet port and outlet port, a condensate tank equipped with a condensate drain discharge and an exhaust outlet into the chimney, is characterised, according to the invention, in that the ratio of the length of the flue tube to its cross-sectional circumference washed by flue gas is between 2.5 and 6.5, and the flue tubes feature embossed pits formed along the length of the tube and pointing towards the centre of the tube, and said pits are positioned opposite each other, and two opposite pits mark out a section, where the distance between the lowest points in the pits measured inside the tube in the section is 1.0 mm at most.

Preferably, the height of the combustion chamber corresponds, at most, to three times the dimension of cross-sectional circumference of the flue tube washed by flue gas.

Preferably, the height of the heat exchanger is six to eight times the dimension of cross-sectional circumference of the flue tube, washed by flue gas.

The proportions developed regarding the dimensions of the heat exchanger secure the condensing nature of the phenomena occurring in the heat exchanger while reducing the resistance of flue gas flow through the heat exchanger.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

In the drawings:

Fig. 1 shows the heat exchanger in an axial section;

Fig. 2 - the flue tube in an isometric view;

Figs. 3 and 4 - the flue tube in a side view; Fig. 5 - the flue tube in a top view, Figs. 6 and 7 - the flue tube in an axial section;

Fig. 8 - the flue tube in a cross section.

A heat exchanger in the exemplary embodiment of the invention has, in its upper part, a combustion chamber 3 equipped with a hole for a burner pipe, flue tubes 1 mounted in tube sheets 4, 5, enclosed by an outer shell 6, inside of which a heated fluid chamber 7 is formed, and equipped with a heated fluid inlet port 8 and outlet port 9. The lower part of outer shell 6 has a condensate tank 10 mounted, equipped with a condensate discharge 11 and the exhaust outlet 12 into the chimney, as shown in Figure 1. Flue tubes 1 have embossed pits 2 directed towards the centre of tube 1. At a predefined height, the flue tube 1 has two embossed pits 2 facing each other and forming together a separate section, which is shown in Figs. 2 to 8. The distance between the tips of the pits in the flue tube in the section is 0.5 mm, and the ratio of flue tube 1 length L to its cross-sectional circumference washed by flue gas is 3.5. The adjoining sections of pits 2 are located along the flue tube at an angle of 90° one to another. The height H of the heat exchanger is seven times the dimension of the cross-sectional circumference of the flue tube washed by flue gas, and the height S of the combustion chamber is double the dimension of the cross-sectional circumference of the flue tube washed by flue gas.

In other variants of the embodiment described above, the distance between the tips of embossed pits 2 in the flue tube 1 in the section cannot be more than 1.0 mm, and the ratio of flue tube 1 length L to its cross- sectional circumference washed by flue gas is between 2.5 and 6.5.

In other variants of the embodiment described above, the height S of the combustion chamber 3 is at most three times the dimension of the cross-sectional circumference of the flue tube 1 washed by flue gas, and the height H of the heat exchanger, including the height S of the combustion chamber 3 and the distance between tube sheets 4, 5 with flue tubes installed is six to eight times this dimension.

It was found that for a flue gas temperature of 1 450°C to 1 550°C, at the inlet to the flue tube and with a flow rate of 0.83 - 0.89 kg/h of flue gas in the tube (for natural gas, C0 2 = 9%) and an initial temperature of 30°C and dT = 20 K of heated liquid, with a counterflow of 22 - 26 1/h for the flue tube, , the flue gas at a distance of 155 - 225 mm from the inlet to this tube reaches the dew point, and the pressure drop is not more than 375 Pa.