ES2384776B1 - Internal insulation for exhaust gas heat exchanger - Google Patents

Abstract

Internal insulation for exhaust gas heat exchanger, being of the type of casing exchanger and engine tubes, where the exhaust gas circulates through pipes inside a housing bathed by a coolant so that the internal insulation is based on a medium insulator of the hot gas inlet speaker (5) to the heat exchanger (1). This execution allows to reduce the temperature of the hot gas inlet loudspeaker 5, and reduce the tensions, increasing its useful life.

Description

Internal insulation for exhaust gas heat exchanger.

OBJECT OF THE INVENTION

The following invention, as expressed in the statement of the present specification, refers to an internal insulation for exhaust gas heat exchanger, having as its object the incorporation of an internal insulating means of the hot gas inlet baffle to the Heat exchanger providing a series of advantages, such as reducing the temperature of the inlet loudspeaker in contact with the refrigerant, reducing its tensions and thereby increasing its useful life.

SCOPE.

An internal insulation for exhaust gas heat exchanger, whose exchangers are especially applicable in engines, is described herein.

BACKGROUND OF THE INVENTION

Referring to a generic arrangement of an exhaust gas heat exchanger of the casing and tube type, it is one that has a hot gas inlet, an inlet and outlet of coolant and a cold gas outlet.

In this way, the exchanger is formed by an external housing, an expansion tank, an inlet loudspeaker and gas passage tubes bathed in the coolant, whose gas passage tubes can have various arrangements and, thus, the tubes can have a circular or square section or be tubes with a disturbance, so that the exhaust gases can enter at a temperature higher than 500 ° C and exit at a temperature below 300 ° C, depending on the application. The coolant is usually pure water or mixed with ethylene glycol, but in some applications it can be seawater, salts that change phase or oil.

Exhaust gas heat exchangers are generally made of stainless steel type 304L or 316L, although ferritic steel, titanium or aluminum can also be used, so that the process of

manufacturing consists of joining the subcomponents by welding or by brazing copper or nickel.

On the other hand, it can be indicated that the inlet zone of the exchanger is subject to very high temperatures, so that, in some applications, these temperatures can exceed 900 ° C. In addition, generally, the flow and temperature of the gas entering the exchanger vary sharply according to the required power, the engine temperature, the external temperature, etc. These sudden changes in temperature generate contractions and dilations of the material, subjecting it to high tensions, so that the area of the exchanger that suffers the greatest tensions is the entrance area, where the gas collides with the baffle at high temperature.

In many cases, if the exchanger is not properly designed or if it has been operating for many hours, fatigue breakage of the metal in the inlet loudspeaker or even the inlet area of the gas pipes occurs.

The problem of overheating is usually solved with the following recommendations:

•

Increase the flow of refrigerant, in order to cool the entrance area. This has as a disadvantage that a larger water pump is needed, the engine consume more fuel, and increase costs.

•

Increase the distance between the gas pipes in order to favor the flow of refrigerant and reduce tensions. This makes the exchanger less compact, occupy more Space and be more expensive.

•

Reduce the amount of gas or the maximum temperature of the gas circulating in the exchanger This has the disadvantage that it can make consumption worse or Increase the amount of contaminants that the engine generates.

•

Design a conduit that increases the speed of the refrigerant in the area of entry, this being the best option. This can increase costs, or be unfeasible due to lack of space.

•

Change the material in the entrance area, although this may increase costs or worsen corrosion resistance.

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On the other hand, we can indicate that the exhaust heat exchangers are used in engine applications with the following objectives:

•

Cool the exhaust gas to reintroduce it into the intake of the engine, thereby reducing nitrogen oxides emissions (what is known in the industry by Exhaust Gas Recirculation, EGR).

•

Recover heat from the exhaust gas to increase engine warm-up speed.

•

Cool the exhaust gas to protect elements of the exhaust system.

•

Steam production for power generation in stationary vehicles or engines.

•

In the case of stationary generator engines, recover the heat lost in the exhaust gas to

heating a water circuit, which can be used for heating, industrial processes or even cold generation, in what is known as cogeneration.

DESCRIPTION OF THE INVENTION

An internal insulation for exhaust gas heat exchanger is described herein, being of the type of casing and engine tube heat exchanger, where the exhaust gas circulates through pipes within a housing bathed by a coolant, so that the internal insulation is based on an insulating means of the hot gas inlet baffle to the heat exchanger.

The insulating means of the hot gas inlet baffle to the heat exchanger is based on the incorporation of at least one insulating layer of ceramic material on the outer surface of the gas inlet baffle to the heat exchanger.

Likewise, the insulating means of the hot gas inlet baffle to the heat exchanger can be based on the incorporation of at least one insulating layer of plastic material on the outer surface of the gas inlet baffle to the heat exchanger.

Likewise, the insulating means of the hot gas inlet loudspeaker to the heat exchanger can be based on the incorporation of at least a second input baffle separated by an air chamber.

By incorporating the insulating means of the hot gas inlet loudspeaker into the heat exchanger based on the incorporation of at least one insulating layer on its outer surface where the gases meet at its inlet, it is protected from high temperatures that suffer, allowing to reduce the tensions that occur in it and increase its life.

In the practical execution of internal insulation of the heat exchanger based on the incorporation of at least a second loudspeaker, being separated by an air chamber, the innermost baffle is protected and although the outermost baffle, devoid of cooling, suffers cracks not They would affect the exchanger.

Likewise, a layer of insulating material can be incorporated over internal areas of the heat exchanger and / or the gas passage pipes, allowing it to be protected from corrosion.

To complement the description that is going to be carried out below, and in order to help a better understanding of the characteristics of the invention, this descriptive report is accompanied by a set of drawings, whose figures are illustrative and not limiting , the most characteristic details of the invention are represented.

BRIEF DESCRIPTION OF THE DESIGNS.

Figure 1. Shows an elevation view of a conventional type exhaust gas heat exchanger, where the hot gas inlet and outlet of the cold gas can be observed, as well as the inlet and outlet of the coolant.

Figure 2. It shows a view, according to a longitudinal section, of a conventional heat exchanger, being able to observe the gas passage tubes bathed by the coolant.

Figure 3. It shows a view, according to the previous section in detail, of the inlet loudspeaker on which the gases in its inlet enter the heat exchanger, which is fixed perimetrically to the housings thereof and to which the pipes are fixed

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gas flow

Figure 4. Shows a view, according to the section of the previous figure, of an inlet loudspeaker provided with an insulating layer on the external surface on which the gases in the inlet to the exhaust gas heat exchanger come into contact.

Figure 5. It shows a view, according to the section of the previous figure, with the incorporation of a second loudspeaker that acts as a protector for the input loudspeaker and which are separated by an air chamber.

DESCRIPTION OF A PREFERRED EMBODIMENT.

In view of the aforementioned figures and in accordance with the numbering adopted, we can observe how an exhaust gas heat exchanger 1 of the conventional type is constituted by a housing 2 with a hot gas inlet 3 and a cold gas outlet 4, as well as with an inlet loudspeaker 5 on which the hot gases meet at its entrance to the heat exchanger 1 and an outlet baffle 6 among which are a series of gas passage tubes 7, whose passage tubes 7 they are bathed in a coolant 8, which penetrates into the casing 2 of the heat exchanger 1 through the coolant inlet 10 and exits through the coolant outlet 11.

The gas passage tubes 7 may have different sections, such as circular or square, or they may be disturbed tubes. Thus, in any of the applications the heat exchanger 1 would be of the type of casing and gas passage tubes bathed in a coolant 8 as pure water or mixed with ethylene glycol, although in some applications it may be seawater, salts that change phase or oil.

Heat exchangers are generally made of 304L or 316L stainless steel, although ferritic, titanium or aluminum steel can also be used, so that the manufacturing process consists of joining the subcomponents by welding or by brazing copper or nickel and gases usually enter at a temperature higher than 900 ° C and exit at a temperature below 300 ° C, so that the heat exchanger inlet zone is subject to very high temperatures, and, in addition, the flow rate and The temperature of the gas entering the heat exchanger varies sharply according to the required power, the engine temperature, the external temperature, etc. These sudden changes in temperature generate contractions and dilation of the material, subjecting it to high tensions, so that the zone of the heat exchanger that undergoes greater tensions is the entrance zone, where the gas collides with the entrance baffle at very high t emperature

In this way, in many cases, in heat exchangers, either by design or by many hours of operation, metal fatigue breaks in the inlet loudspeaker or even in the inlet zone of the gas pipes , places where higher temperatures occur which is a serious inconvenience.

In order to be able to solve these drawbacks the object of the present invention is the incorporation of an internal insulating means of the hot gas inlet baffle to the heat exchanger.

In this way, the insulating means of the input loudspeaker is based on the incorporation of at least one insulating layer 9 on the external surface of the input baffle of the hot gases 5 to the heat exchanger 1 and whose insulating layer 9, preferably , will be of ceramic or plastic material.

Likewise, a layer of insulating material can be incorporated on internal areas of the heat exchanger and / or the gas passage pipes allowing:

•

protect the metal from corrosion and the use of materials less resistant to corrosion, that is, cheaper, and;

•

avoid over-cooling of the exhaust gas in the outlet area of the exchanger. In this case, the ceramic material would prevent the gas from exchanging heat with the outside.

On the other hand, the layer of insulating material 9 may be applied to the input baffle before the manufacturing process of the entire heat exchanger 1. One possibility is the use of plasma spray. The material must be stable against the temperature and corrosion of the exhaust gas medium.

The proposed solution provides the following advantages:

•

Reduction of the temperature of the hot gas inlet loudspeaker 5, and consequent reduction of tensions and increase of their useful life.

•

Lower coolant flow requirement, therefore facilitating the reduction of

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Water pump or engine oil requirement.

•

Reduction of the amount of boiling on the front face of the heat exchanger 1, reducing the risk that the accumulation of water vapor entails for the heat exchanger, the water pump and the other components of the cooling circuit.

•

It protects the hot gas inlet loudspeaker 5 from corrosion of the exhaust gases, thus being able to facilitate the use of cheaper and less corrosion resistant materials.

•

It allows to reduce the distance between the gas passage tubes 7, reducing the total size of the heat exchanger.

•

It allows reducing the complexity of the refrigerant pipes in the hot zone of the exchanger.

•

Increases the resistance of the heat exchanger to the accumulation of lime and deposits in the refrigerant circuit, which usually occur in the hot zone.

Likewise, in a variant of practical implementation of the invention, the insulating means of the hot gas inlet loudspeaker 5, in contact with the coolant 8, to the heat exchanger 1, may be based on the incorporation of a second baffle 12, leaving an air chamber between both speakers 5 and 12.

In this way, the innermost loudspeaker 5 and in contact with the coolant 8 will be protected by the second inlet baffle 12, the air chamber 13 remaining between them collaborating in isolation.

On the other hand, even if cracks appear on the second loudspeaker 12, more external and uncooled, in which the hot gases come into its entrance to the heat exchanger, due to overheating, it would not represent any problem since it does not exert sealing functions.

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Claims (2)

1st.- INTERNAL INSULATION FOR EXHAUST GAS HEAT EXCHANGER, being of the type of casing exchanger and engine tubes, where the exhaust gas circulates through pipes inside a housing bathed by a coolant, characterized in that the internal insulation is based on an insulating means of the hot gas inlet baffle (5) to the exchanger of heat (1). 2nd.- INTERNAL INSULATION FOR EXHAUST GAS HEAT EXCHANGER, according to claim 1, characterized in that the insulating means of the hot gas inlet baffle (5) to the heat exchanger

(one)

it is based on the incorporation of at least one insulating layer (9) of ceramic material on the external surface of the gas inlet baffle (5) of the heat exchanger (1).

3rd.- INTERNAL INSULATION FOR EXHAUST GAS HEAT EXCHANGER, according to claim 1, characterized in that the insulating means of the hot gas inlet baffle (5) to the heat exchanger

(one)

 It is based on the incorporation of at least one insulating layer (9) of plastic material on the external surface of the gas inlet baffle (5) of the heat exchanger (1).

4th.- INTERNAL INSULATION FOR EXHAUST GAS HEAT EXCHANGER, according to claim 2, characterized in that the insulating means of the hot gas inlet baffle (5) to the heat exchanger

(one)

 It is based on the incorporation of at least one second input speaker (12) separated by an air chamber (13).

5th.- INTERNAL INSULATION FOR EXHAUST GAS HEAT EXCHANGER, according to claim 1, characterized in that a layer of material is incorporated over internal areas of the heat exchanger (1) and / or the pipes of (7) of the gas passage insulating. ES 2 384 776 Al ES 2 384 776 Al SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 201230458 SPAIN Date of submission of the application: 28.03.2012 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: F28D9 / 00 (2006.01) F28F9 / 02 (2006.01) RELEVANT DOCUMENTS

Category

56 Documents cited Claims Affected

X

WO 9854529 A1 (SANDVIK AB et al.) 03.12.1998, 1,2,5

page 4, lines 25-30; figure 3.

X

CA 2107397 A1 (WAGNER WILLIAM W) 31.03.1995 1,3,5

X

DE 102010005216 A1 (GAB NEUMANN GMBH) 28.07.2011, 1,4,5

summary; Figure 1.

X

WO 2009066260 A1 (PETROLEUM OIL AND GAS CORP OF et al.) 05.28.2009, 1.5

pages 5-6.

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 29.06.2012

Examiner J. A. Celemín Ortiz-Villajos Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 201230458 Minimum documentation sought (classification system followed by classification symbols) F28D, F28F Electronic databases consulted during the search (name of the database and, if possible, terms of search used) INVENES, EPODOC State of the Art Report Page 2/4  WRITTEN OPINION Application number: 201230458 Date of Written Opinion: 29.06.2012 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 1-5 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1-5 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 201230458  1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

WO 9854529 A1 (SANDVIK AB et al.) 03.12.1998

D02

CA 2107397 A1 (WAGNER WILLIAM W) 31.03.1995

D03

DE 102010005216 A1 (GAB NEUMANN GMBH) 07/28/2011

 2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement In the state of the art several documents have been found that affect the inventive activity of the submitted application. They then go on to explain these documents, and how they affect the request submitted. A shell and tube heat exchanger for the production of black coal is diffused in D01, which contains the essential technical characteristics of claims 1 and 2 of the submitted application, namely (references correspond to D01): internal material insulations ceramic (25 and 27) of the end plates (baffles) (26 and 29) of the heat exchanger. In D02 a shell and tube heat exchanger is also diffused, the end plate of which is made of plastic material (14), thus anticipating the essential technical characteristic of claim 3 of the submitted application. In D03 a casing and tube heat exchanger is diffused with two input baffles (3), separated by an intermediate plate (4). It is considered obvious to a person skilled in the art, to replace said intermediate plate (4) with an air chamber, thus obtaining the technical characteristic of claim 4 of the submitted application. Although neither in D01, nor in D02, nor in D03, the heat exchangers are specific for exhaust gases, as in the requested invention, it is considered that this does not affect the inventive activity of the application, since the object of the The invention is the thermal insulation of the input loudspeakers, and said thermal insulation is valid, in principle, for other types of heat exchangers. Likewise, claim 5 of the application is considered to be evident to a person skilled in the art in the field of heat exchangers, by disseminating a common technical characteristic in said field. For all the above, it can be affirmed that all the essential technical characteristics of the requested invention are either found as such in the state of the art, or they are deduced in an evident way for a person skilled in the art, in view of said state of the art, so that the application presented, does not possess inventive activity, according to article 8 of the Law 11/1986 of Patents. State of the Art Report Page 4/4