EP0359306A2 - Heizkessel - Google Patents

Heizkessel Download PDF

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Publication number
EP0359306A2
EP0359306A2 EP89202169A EP89202169A EP0359306A2 EP 0359306 A2 EP0359306 A2 EP 0359306A2 EP 89202169 A EP89202169 A EP 89202169A EP 89202169 A EP89202169 A EP 89202169A EP 0359306 A2 EP0359306 A2 EP 0359306A2
Authority
EP
European Patent Office
Prior art keywords
fins
heat
heat exchanger
boiler
heat source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89202169A
Other languages
English (en)
French (fr)
Other versions
EP0359306A3 (de
Inventor
Marcel Castermans
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
"STELRAD IDEAL"
Original Assignee
"STELRAD IDEAL"
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by "STELRAD IDEAL" filed Critical "STELRAD IDEAL"
Publication of EP0359306A2 publication Critical patent/EP0359306A2/de
Publication of EP0359306A3 publication Critical patent/EP0359306A3/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/0005—Details for water heaters
    • F24H9/001—Guiding means
    • F24H9/0026—Guiding means in combustion gas channels

Definitions

  • the invention relates to a boiler with heat trans­fer by convection between a heat source and a profiled heat exchanger.
  • Such boilers are generally used in central heating installations.
  • the heat source usually a gas or oil burner, generates heat which warms up a transfer medium, generally the flue gases of the burned gas or oil. That transfer medium then transfers its absorbed heat to a liquid, usually water, by means of a heat exchanger.
  • the flue gases flow along the outer surface of the heat exchanger and transfer their heat by convection to the metal, usually cast iron, of the heat exchanger which transfers then, on its turn, the absorbed heat by convection to the water.
  • the surface of the heat exchanger is usually profiled, for instance provided with fins if the boiler is made of cast iron, in order to increase the effective surface of the heat exchanger.
  • a drawback of the known boilers consists in that the profiling of the heat exchanger is substantially identical over its whole surface.
  • the temperature gradient of the transfer medium over the heat exchanger forms an exponentially decreasing function as a result of which the part of the heat exchanger, which is first brought into contact with the transfer medium, will absorb the largest quantity of heat whereas the part the furthest remote from the heat source, will absorb the least quantity of heat. All this results in an unequal heat transfer over the whole surface of the heat ex­changer. That unequal heat transfer on its turn causes stresses in the material of the heat exchanger. Furthermore, there also arise larger losses in the heat exchange as a result of said unequal heat transfer.
  • the object of the invention is to realize a boiler wherein a substantially equal heat transfer takes place over the surface of the heat exchanger.
  • a boiler according to the invention is characterized in that the surface of the profile applied to the heat exchanger and over which the heat transfer takes place, in­creases with increasing distance from the heat source. Since the temperature of the transfer medium is higher in the vicinity of the heat source then remote from the heat source, the smaller surface near the heat source will absorb less heat at a higher temperature and the larger transfer surface remote from the heat source will absorb more heat at a lower temperature. As a result thereof, the heat transfer per surface unit is substantially constant when further parameters, such as for example the speed of the transfer medium, remain constant and no stresses are created in the material of the heat exchanger. Due to the equal heat transfer, the maximum thermal load of the heat exchanger is lowered and a smaller heat exchanger can be used for a transfer of an equal amount of heat which con­stitutes an economic value.
  • a first preferred embodiment of a boiler according to the invention wherein the surface of the heat exchanger is provided with fins is characterized in that the surface of the fins increases the further the fins are remote from the heat source.
  • the fins which are situated nearby the heat source have a smaller surface than the ones which are situated further from the heat source and the heat transfer per fin is substantially constant if other parameters remain of course constant.
  • a second preferred embodiment of a boiler according to the invention is characterized in that the surface increase of the fins is mainly realized by an increase in length of the fins. In this way, the increase in surface can be realized easily.
  • a third preferred embodiment of a boiler according to the invention is characterized in that the fins are serially disposed in series each time of substantially parallel fins,wherein each of the fins of a same series has substantially a same surface, and in that the surface of the fins of successive series increases with increasing distance from the heat source.
  • the heat transfer is hereby optimized.
  • the increase in length between two successive fins in a direction away from the heat source is mainly determined by the total number of fins of a different length on the same heat exchanger.
  • constructional limitations are taken into account and manufacturing costs are reduced.
  • a further preferred embodiment of a boiler according to the invention is characterized in that the profile of the fin is mainly determined by the length of the fin. This results in a simple determination of the profile taking into account the length of the fin.
  • the boiler shown in Figure 1 comprises a connection 1 for supplying a fuel, in the chosen example natural gas, which connection is connected to an atmospheric burner 2 operating as a heat source.
  • the boiler is further provided with a heat exchanger 3 the outer surface of which is provided with series of fins (4-10).
  • a liquid for example water, circulates along the inner surface of the heat exchanger.
  • the cold water is supplied through a pipe coupling 11 and the heated water is outputted through a pipe coupling 12.
  • the heat capacity of a fin that is the amount of heat which can be absorbed by a fin, is mainly determined by the dimension of the fin and the material of which the fin is made at least if other parameters of the transfer medium remain constant. The larger the surface of the fin, the more heat the fin can absorb, respectively supply, at least within certain limits.
  • the fins 4 of the first series which is situated the nearest to the heat source have the smallest surface.
  • the surface of the further series of fins (5-10) increases the further the fins are remote from the heat source.
  • the fins which are situated more closely to the heat source thus have a smaller heat capacity than the ones which are remotely situated since they have a smaller surface.
  • the temperature of the flue gases is however the highest near the heat source and this temperature decreases due to heat transfer to the fins and due to further losses the more the flue gases are remote from the heat source.
  • the curve 14, shown in Figure 2 illustrates the decrease in temperature of the flue gases as a function of the distance over the heat exchanger (vertical y-direc­tion: temperature of flue gas; horizontal x-direction : distance over the heat exchanger).
  • the curve shows for example that, at the height of the first series of fins 4, the temperature is 1400°C whereas the temperature is for example 270°C at the height of the last series of fins 10.
  • the geometry of the heat exchanger is as such that its cross-section decreases with increasing distance from the heat source. This geometry is thus chosen because a volume change caused by the temperature decrease of the transfer medium, occurs in the transfer medium. The density of the transfer medium increases as the temperature and the volume of the latter decreases. However, since the cross-section of the heat exchanger decreases with increa­sing distance from the heat source, the speed of the transfer medium remains substantially the same as a result of which no disturbing of the heat transfer is caused.
  • the heat exchanger is now submitted to a tempe­rature gradient the absolute value of which is, on the one hand, much smaller than the maximum temperature gradient in a conven­tional heat exchanger and which remains, on the other hand, approxi­mately constant over the whole length of the heat exchanger. Stresses in the material of the heat exchanger are thereby avoided. Even if there are some changes over the surface, the fluctuations remain nevertheless limited. The fact that stresses in the material are avoided results in that less material is needed since it is no longer necessary to compensate those stresses with additional material.
  • the fin length as well as the total number of dif­ferent fin lengths is mainly determined by : - the temperature difference between the flue gases on the hot and on the cold side of the heat exchanger. - the length of the heat exchanger as determined in the flow direction of the flue gases. - the desired optimalization degree. - the constructional limitations.
  • the temperature belonging to this point A corresponds then approximately to the average temperature of the flue gases over the part OV of the heat exchanger.
  • the length of the fin is now given by the distance OV.
  • An analogous procedure is now followed to determine the points B, C and D and in this way to determine the length of the fins WL, MN and EF.
  • the surfaces OVTR, WLZK, MNJI and EFHG are all approximately equal to each other so that the heat transfer for each of the fins is approximately the same.
  • Figure 3 shows an example of a profile of a fin.
  • the length (c) is indicated in the x-direction whereas the y-direction indicates the height.
  • the fins from the successive series are disposed shifted with respect to each other so that an optimal heat transfer between flue gases and fins is realized at a minimum aerodynamic resistance.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Details Of Fluid Heaters (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
EP19890202169 1988-09-13 1989-08-28 Heizkessel Withdrawn EP0359306A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BE8801050A BE1002487A6 (nl) 1988-09-13 1988-09-13 Verwarmingsketel.
BE8801050 1988-09-13

Publications (2)

Publication Number Publication Date
EP0359306A2 true EP0359306A2 (de) 1990-03-21
EP0359306A3 EP0359306A3 (de) 1991-02-06

Family

ID=3883626

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890202169 Withdrawn EP0359306A3 (de) 1988-09-13 1989-08-28 Heizkessel

Country Status (2)

Country Link
EP (1) EP0359306A3 (de)
BE (1) BE1002487A6 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0533271A1 (de) * 1991-09-19 1993-03-24 PENSOTTI S.p.A. Wärmetauscherelement für einen Kessel

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1524520A (en) * 1924-06-07 1925-01-27 Junkers Hugo Heat-exchange apparatus
FR957533A (de) * 1950-02-23
DE1082724B (de) * 1954-08-16 1960-06-02 Gerhard Goebel Dipl Ing Heizkessel fuer Sammelheizungsanlagen
DE3327354A1 (de) * 1983-07-29 1985-02-14 Hans Dr.h.c. 3559 Battenberg Vießmann Heizungskessel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR957533A (de) * 1950-02-23
US1524520A (en) * 1924-06-07 1925-01-27 Junkers Hugo Heat-exchange apparatus
DE1082724B (de) * 1954-08-16 1960-06-02 Gerhard Goebel Dipl Ing Heizkessel fuer Sammelheizungsanlagen
DE3327354A1 (de) * 1983-07-29 1985-02-14 Hans Dr.h.c. 3559 Battenberg Vießmann Heizungskessel

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0533271A1 (de) * 1991-09-19 1993-03-24 PENSOTTI S.p.A. Wärmetauscherelement für einen Kessel
TR26317A (tr) * 1991-09-19 1995-03-15 Pensotti S P A Kazan isi esanjör birimi

Also Published As

Publication number Publication date
EP0359306A3 (de) 1991-02-06
BE1002487A6 (nl) 1991-02-26

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