EP2508834A2

EP2508834A2 - Heat exchanger

Info

Publication number: EP2508834A2
Application number: EP11460027A
Authority: EP
Inventors: Adam Pacholski
Original assignee: AIC SA
Current assignee: AIC SA
Priority date: 2011-04-07
Filing date: 2011-05-19
Publication date: 2012-10-10
Also published as: EP2508834A3; PL219104B1; PL394478A1

Abstract

A heat exchanger comprising an outer jacket, which encases a set of vertically running pipe elements anchored in sieve walls on both ends, a gas combustion chamber positioned over the upper sieve wall, and baffles mounted crosswise to the pipe elements, with openings through which the pipe elements run, plus water, gas, and fume inlet and outlet pipe stubs, wherein the outer jacket (9) is conical in shape gaining in diameter towards the top, and the top baffle (5) below the upper sieve wall (2) is conical in shape, its apex pointing down.

Description

The invention concerns a heat exchanger of the pipe exchanger group, designed for exchanging heat between gas and liquid. It is applied in heat engineering, particularly in domestic central heating installations.
There are many known types of pipe heat exchangers. Their structure depends on the place of their application, the circulating agent used, and the specific demands and needs. All pipe heat exchangers of the liquid-gas type share a common feature, namely they all have a system of pipe elements transferring hot gas or liquid, fitted in between two sieve walls of a chamber enclosed in an outer jacket, where the heated water or gas circulates. In domestic central heating installations, where the heat is generated by burning gas, heat exchangers are provided with a combustion chamber mounted above the upper sieve wall, and have water inlet and outlet pipe stubs, a gas inlet pipe stub, and a gas exhaust pipe stub. In such exchangers the pipe sets are positioned vertically. Also known, are heat exchangers used in heat engineering, called condensers or liquefiers, composed of a number of pipe sets installed in a chamber enclosed in an outer jacket. In such exchangers, the pipes are fitted in between the perforated bottom, with the water chamber underneath, from where the water is transferred into the pipes to serve as a cooling agent for the steam coming out of the turbine outlets and transferred to the chamber where the pipes are installed. Depending on the type of the pipe heat exchanger, the pipe elements used in the piping systems differ in their diameters and shapes, and may be equipped with different auxiliary elements, such as baffles or additional pipes etc., so as to enhance efficiency of the heat exchange.
Known from Polish patent specification No. 186723 , is a liquid-gas pipe heat exchanger, in which hot gas is introduced into a chamber enclosed in an outer jacket cooling down while circulating around the pipes fitted in between the flat perforated bottom. The pipes are filled with the cooling agent flowing into the chamber and leaving it through the pipe stubs fitted in the perforated bottom cover. The gas condensates are drained off from the exchanger through the outlet pipe stub in the outer jacket encasing the heat exchange chamber. The chamber is also fitted with additional perforated pipes, whose end sections going through the perforated bottom are connected to the collecting pipe linked to the vapour exhaust pipe. The perforated pipes are used to suck out the air from the gas-filled space of the exchanger and discharge it outside. Moreover, the exchange chamber is divided with baffles positioned perpendicular to the pipe elements.
Moreover, the heat exchanger known from the patent application published under No. W02008/131616 consists of a cylindrical jacket with inlet and outlet pipe stubs, enclosing a set of pipe elements, where the pipes go through a spiral baffle and are connected to sieve walls shaped into flat discs fitting the cylindrical outer jacket. Inside the exchanger tie rods are installed, one of which runs along the central axis of the cylindrical outer jacket. The tie rods are anchored in the sieve wall on the one end, and in the spiral baffle on the other. They are divided into segments and equipped with distance pipes. The described exchanger may also feature additional pipes running through the spiral baffle, though not anchored in the sieve walls, to improve the rigidity, protect against deformations, and facilitate matching the openings in the spiral baffle to the exchanger pipes. The specification discloses the structure of the spiral baffle in detail.
Known from the international patent application published under No. W02009/078577 is a boiler comprising a cylindrical casing, vertically positioned liquid-gas exchanger, burner installed in the combustion chamber of the exchanger, inlet and outlet of the heated water, fume exhaust duct, gas inlet, fittings which supply the air and appropriately mix it with the gas, as well as control devices. This embodiment of the heat exchanger contains a set of pipe elements rectangular in cross section, regularly distributed between the walls of the outer jacket forming the chamber, through which the heated water flows. The top ends of the pipes are anchored in the flat upper sieve wall under the combustion chamber. The pipes, piercing through the flat bottom sieve wall and crossing the exhaust gas recirculation chamber, are linked with the fume exhaust duct. The water chamber is fitted with flat disc-shaped baffles, through which the pipe elements run. These separating baffles disturb water circulation and thus improve heat exchange. They are positioned perpendicular to the pipe elements, and their diameter is smaller than the inner diameter of the heat exchanger jacket to leave some space between the baffles and the jacket for the water to flow. The said specification discusses the correlation between the width of this space and water circulation, as well as the pressure of the water on the baffles. In the described embodiment it is proposed to equip the baffles with circulation pipes to prevent increased pressure of water on the baffles. These pipes are anchored in the top baffle on the one end , and the bottom on the opposite end. The structural variant of the embodiment described in the application envisages leaving some space between the pipe element walls and the openings in the baffles, through which the pipes run to increase water circulation disturbance and improve heat exchange efficiency. The described boiler is equipped with an auxiliary independent water circuit consisting of spiral pipes installed in the water chamber and coiled around the combustion chamber.
The heat exchanger according to the invention, comprising an outer jacket, which encases a set of vertically running pipe elements anchored in sieve walls on both ends, a gas combustion chamber positioned over the upper sieve wall, and baffles mounted crosswise to the pipe elements, with openings through which the pipe elements run, plus water, gas, and fume inlet and outlet pipe stubs, is characterised in that the outer jacket is conical in shape gaining in diameter towards the top, and the top baffle below the upper sieve wall is conical in shape, its apex pointing down.
Preferably, the top baffle has a central opening in the middle and its outer diameter corresponds with the diameter of the outer jacket.
The flare angle of the conically shaped top baffle falls within the range of 90° < β < 180°.
The outer diameters of the subsequent baffles are, interchangeably, equal to or smaller than the diameter of the outer jacket, where the baffles of the diameter equal to that of the outer jacket have a centrally located opening.
The top baffle of the exchanger is additionally perforated with regularly distributed openings.
In the preferable variant of the exchanger those additional openings are arranged in a single circle, or in a number of concentric circles.
The advantage of the solution according to the invention consists in substantially increased effectiveness of the heat exchange processes, both along the whole length of the exchanger pipe elements, and in the area of the upper sieve wall and the combustion chamber.
The exemplary embodiment of the heat exchanger according to the invention is illustrated on the drawing, where fig. 1 presents the interior of the heat exchanger, and fig. 2 visualises the exchanger in the longitudinal section.
The heat exchanger consists of a vertically positioned set of pipe elements 1 rectangular in cross-section and arranged spokewise, whose ends are welded to the upper sieve wall 2 at the top and the bottom sieve wall 3 at the bottom. Above the upper sieve wall 2 is the cylindrical steel-sheet combustion chamber 4 permanently welded to the said wall. Fitted perpendicular to the pipe element set are three horizontally positioned baffles 5, 6, and 7 made of steel sheets. Baffles 5, 6, and 7 have a number of openings, the diameters of which correspond with the diameters of the pipe elements 1 running through them. The top baffle 5 is conical in shape, its apex pointing down. The cone flare angle β is approximately 130°. The central baffle 6 and bottom baffle 7 are shaped into flat discs. A large, centrally positioned opening 8 is cut in each of the top 5 and bottom 7 baffles. The set of the pipe elements 1, the sieve walls 2 and 3, the baffles 5, 6, and 7, and the cylinder of the combustion chamber 4, are encased in the outer jacket 9 shaped into a truncated cone gaining in diameter towards the top. The outer diameters of top baffle 5 and bottom baffle 7 correspond with the inner diameters of the outer jacket 9, whereas the diameter of the central baffle 6 is smaller than the inner diameter of the outer jacket 9 at the said baffle level. The exchanger is closed from the top with a cover 10 fitted with a gas inlet pipe stub, an opening for the burner with its ventilation valve system, and other mounting elements necessary for the installation of the equipment and the boiler casing, which houses the described heat exchanger. The bottom sieve wall 3 is permanently welded to the outer jacket at their contact point. The cover 10 is severably connected to the outer jacket 9 and the combustion chamber 4 with bolts. Water inlet 11 and water outlet 12 stub pipes are installed respectively in the top and bottom section of the outer jacket 9, and the bottom tank 13 formed under the bottom sieve wall is fitted with condensate drain pipe stub 14 and gas fume exhaust pipe stub 15. In the preferable embodiment of the heat exchanger the top baffle 5 has a number of additional openings 16 regularly arranged in a circle in between the pipe element set 1.
The heat exchanger is designed for burning natural gas and propane and thus obtain heat used to heat the water circulating in the central heating installation. The gas burns in the combustion chamber 4 in the top section of the exchanger, then the fumes flow down through vertical pipe elements 1 passing heat on their way to the water circulating inside the outer jacket 9, between the water inlet 11 and the water outlet 12. When flowing down, the fumes cool down below the dewpoint temperature and accumulate in the bottom container 13, from where they are drained off together with the accumulated condensate through the condensate drain pipe stub 14 and the gas fume exhaust 15. The heated water circulates outside and around the pipe elements 1, in the direction opposite to the flow of the fumes, i.e. the water is introduced through the water inlet pipe stub 11 at the bottom of the exchanger and flows upwards around the pipe elements 1 and the combustion chamber 4, whereupon it is removed from the heat exchanger through the water outlet pipe stub 12 in the upper section of the exchanger. The desired water flow around the pipe elements 1 and the combustion chamber 4 is forced by the set of baffles, where the flow is directed through the central opening 8 in the bottom baffle 7 to the central section of the exchanger, then towards the walls of the outer jacket 9, around the outer edges of the central baffle 6, and then again towards the centre, from where the stream of water is directed through the central opening 8 in the top baffle 5 to the central point of the top sieve wall 2, thanks to which the flow of water around the said wall and the combustion chamber 4 is even in all directions. The water lingering in the dead zones under the top baffle 5 flows through the additional openings 16, which perforate the baffle.
In the exemplary variant of the invention embodiment the heat exchanger contains 20 pipe elements, its height is ~ 600 mm, top diameter ~ 350 mm, bottom diameter ~300 mm, and the diameter of the combustion chamber is ~300 mm too. The maximum temperature guaranteed at the outlet is ~90 ⁰ C.
In other embodiments variants, the heat exchanger may have a conically-shaped top sieve wall, a conical bottom sieve wall, and a conical baffle, and different numbers of the other baffles subsequently alternating in outer diameters, every other baffle having a large, centrally-located opening. Preferably, the cone shape of the bottom sieve wall is identical to the conical shape of top sieve wall, though other embodiments of the exchanger are possible, where their cone flare angles may differ, or the top and bottom sieve walls may be flat, or given any other shape. The pipe elements of the exchanger may also differ in their cross-sections and arrangement.
The shape of the top baffle 5, as well as the interchangeably varying outer diameters of the baffles and the corresponding large central openings 8 in the baffles force the preferable water flow in the exchanger, which increases heat exchange efficiency. Pertaining particularly to increased heat exchange efficiency in the area of the combustion chamber is the higher speed flow of the liquid washing around the combustion chamber due to the new shape of the top baffle. The additional openings 16 in the top baffle 5 prevent the formation of the so-called dead zones under the baffle, where the water tends to come to a standstill, by permitting its controlled flow, that is the seeping of the fluid between the zones under and over the baffle at specific points.

Claims

A heat exchanger comprising an outer jacket, which encases a set of vertically running pipe elements anchored in sieve walls on both ends, a gas combustion chamber positioned over the upper sieve wall, and baffles mounted crosswise to the pipe elements, with openings through which the pipe elements run, plus water, gas, and fume inlet and outlet pipe stubs, is characterised in that the outer jacket (9) is conical in shape gaining in diameter towards the top, and the top baffle (5) below the upper sieve wall (2) is conical in shape, its apex pointing down.
The heat exchanger according to Claim 1, wherein the top baffle (5) has a central opening (8) in the middle and its outer diameter corresponds with the diameter of the outer jacket (9).
The heat exchanger according to Claim 1 or 2, wherein the flare angle (β) of the conically shaped top baffle (5) falls within the range of 90° < β < 180°.
The heat exchanger according to Claim 1, wherein the outer diameters of the subsequent baffles (5,6,7) are, interchangeably, equal to or smaller than the diameter of the outer jacket (9), where the baffles of the diameter equal to that of the outer jacket (9) have a centrally located opening (8).
The heat exchanger according to Claims 1-4, wherein the top baffle (5) is additionally perforated with regularly distributed openings (16).
The heat exchanger according to Claim 5, wherein those additional openings(16) are arranged in a single circle, or in a number of concentric circles.