EP0431446B1 - Heat exchange assembly for unit heaters - Google Patents

Heat exchange assembly for unit heaters Download PDF

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Publication number
EP0431446B1
EP0431446B1 EP90122666A EP90122666A EP0431446B1 EP 0431446 B1 EP0431446 B1 EP 0431446B1 EP 90122666 A EP90122666 A EP 90122666A EP 90122666 A EP90122666 A EP 90122666A EP 0431446 B1 EP0431446 B1 EP 0431446B1
Authority
EP
European Patent Office
Prior art keywords
air tubes
flues
air
heat exchange
impressions
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.)
Expired - Lifetime
Application number
EP90122666A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0431446A1 (en
Inventor
Alfonso Vescovi
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.)
TECNOCLIMA SpA
Original Assignee
TECNOCLIMA SpA
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 TECNOCLIMA SpA filed Critical TECNOCLIMA SpA
Priority to AT90122666T priority Critical patent/ATE95298T1/de
Publication of EP0431446A1 publication Critical patent/EP0431446A1/en
Application granted granted Critical
Publication of EP0431446B1 publication Critical patent/EP0431446B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • F24H3/00—Air heaters
    • F24H3/02—Air heaters with forced circulation
    • F24H3/06—Air heaters with forced circulation the air being kept separate from the heating medium, e.g. using forced circulation of air over radiators
    • F24H3/10—Air heaters with forced circulation the air being kept separate from the heating medium, e.g. using forced circulation of air over radiators by plates
    • F24H3/105—Air heaters with forced circulation the air being kept separate from the heating medium, e.g. using forced circulation of air over radiators by plates using fluid fuel

Definitions

  • This invention generally relates to unit heaters and like apparatus for the treatment of hot air and, more particularly, an improved heat exchange assembly therefor.
  • the unit heater is an apparatus used for quickly heating industrial rooms and generally comprises a radiator, frequently with finned tubes, through which an electric fan blows air in the room to be heated.
  • a conventional heat exchanger is also used, in which the heat exchange fluid is the flue gas generated in a chamber directly communicating with said heat exchanger and by the air moved by the electric fan and passing therethrough generally in a cross flow.
  • conventional heat sources can be used, such as gas or gas oil burners.
  • the first system causes a substantial resistance to the flue gas flow which causes a pressurization condition in the combustion chamber and therefore it is not suitable.
  • the second system resorts for example to the vacuum created by the stack draught and this is almost impossible for the low levels of vacuum so obtainable.
  • US-A-2,613,920 discloses a heat exchange assembly for unit heaters and like apparatus for the treatment of hot air comprising a heat exchanger formed of flues and air tubes and a combustion chamber.
  • the air tubes have in cross-section the shape of a trapezoid with the small base placed at the bottom.
  • the air tubes are arranged side by side in such a manner as to form therebetween a flue.
  • the lower portion of the air tubes forms the roof of said combustion chamber.
  • the flues have in cross-section the shape of a trapezoid with the small base placed at the top and the side walls of said air tubes are provided with impressions for avoiding the laminar flow of the flue gas and imparting thereto the necessary turbolence.
  • the present invention aims at improving a heat exchange assembly of this type.
  • a gas operated unit heater comprising a housing 1 provided with a bottom 2 and a top panel 3, as well as a front panel 4 having an outlet 5 (Fig. 3) for the hot air.
  • the hot air stream can be oriented by means of baffles 6.
  • an electric fan 7 is arranged, which blows in the air from the outside through the heat exchanger 8.
  • a combustion chamber 9 is arranged provided with an extractor 10 of the flue gas flowing from the combustion chamber 9.
  • a set of burners 11 are provided above the burners 11 a conventional ignition device 12 is arranged, which is connected to a control panel 13 and a valve 14 is provided for controlling the feeding of the combustible gas to the burners.
  • the unit heater till now described is of a conventional design.
  • this unit heater is given by the configuration of its heat exchanger 8.
  • This comprises a set of air tubes 15 arranged side by side and supported at both the ends, i.e. the air inlet and outlet ends, by conventional support elements.
  • the air tubes 15 are arranged in spaced relationship so as to provide therebetween hollow spaces 16 forming the flues 17.
  • the lower portion of the air tubes 15 forms the roof of the combustion chamber 9.
  • the side walls 21 of the air tubes 15 are provided with a set of impressions 18 having a circular shape in plan view and forming concavities or convexities. These impressions 18 are arranged in rows offset to each other in such a manner that in each air tube formed of two side walls 21 a concave impression of each row of one side wall 21 lies in front to a convex impression of the other side wall 21 (Fig. 3).
  • the function of the impressions 18 is to impart to the flue gas passing through the flues 17 so formed the required turbulence in order to avoid the laminar flow which would negatively affect the heat exchanger operation.
  • the upper row of the impressions 18 is made so as to assure the correct spacing of the outlet portion of the flues and the possibility to comfortably carrying out the cleaning thereof.
  • each air tube 15 is formed from a single blank B of steel sheet comprising a center portion C of rectangular shape from the small sides of which rectangular flanges 24 terminating in tabs 25 extend and from the large sides of which trapezoidal flanges 22 terminating in tabs 23 extend.
  • This blank is then subjected to a press-forming operation in which the center portion C is bent over, the flanges 22 are outwardly bent by 90° and the flanges 24 are inwardly bent by 90°, whereas the tabs 23 and 25 are 90°-bent with the respect to the relative flanges so as to form a tube having a cross-section in the shape of a trapezoid with the small base forming the bottom wall 19 and the large base forming the top wall 20.
  • the inclined sides of the trapezoid are formed by the side walls 21 of the so press-formed tube.
  • the bottom wall 19 is then slightly curved, as can be seen from the drawings and this is obtained by a drawing operation.
  • each of the tab 23 is welded, as indicated by S, to a corresponding tab 23 of an adjacent air tube formed from another blank, and the pair of tabs 25 are welded together, also indicated by S, so as to form the top wall 20 of the air tube. Therefore, the side walls 21 are inclined by an angle ⁇ with respect to the vertical and this inclination of the side walls 21 allows the flues 17 formed between two air tubes 15 to have a cross-section decreasing from the bottom to the top so as to impart to the flue gas flowing therein a venturi effect increasing their flow velocity.
  • the so formed heat exchanger has therefore air tubes 15 having in cross-section the shape of a trapezoid with the small base placed at the bottom and flues 17 formed between each pair of air tubes 15 having in cross-section the shape of a trapezoid with the small base placed at the top.
  • the curved bottom walls 19 of the assembled air tubes 15 form the roof of the combustion chamber 9 and this due to the above described construction of the heat exchanger.
  • This construction avoids also the requirement to provide the conventional tube plates to be welded to the tubes and therefore the costs of this welding operation. Furthermore, this construction avoids also a discontinuity zone and weak points.
  • the curved shaping of the bottom walls 19 of the air tubes 15 promotes the flow of the flue gas therein, minimizes the resistance to the flow and gives a preferential direction which better reacts to the expansion.
  • the air tubes 15 obtained according to the invention from a single blank of metal sheet allow them to be assembled by carrying out a straightline and simple welding operation of the tabs 25 and the tabs 23.
  • the flue gas produced by the gas burnt in the burners 11 move upwardly through the flues 17 formed by the hollow spaces 16 between each pair of air tubes 15 (Fig. 1).
  • the velocity of the flue gas increases due to the venturi effect provided by the inclination of the side walls 21 and contact the impressions 18 in such a manner as to be deflected alternatively in opposite directions, thereby following a sinuous path imparting thereto the necessary turbulence.
  • the focus of the invention is formed by the flues 17 obtained by arranging side by side the air tubes 15 and then welding this air tubes to each other, as above described.
  • a further feature of these flues is the shape, the dimension and the arrangement of the impressions 18, the main function of which is to avoid the occurrence of a laminar flow therethrough and the provision therein of a turbulence that continuously mixes them, by eliminating at the same time the pressure drop.
  • a second feature of the flues according to the invention is the trapezoidal shape thereof.
  • the main purpose of this trapezoidal shape is to maintain by venturi effect to a high level the flow velocity of the flue gas which, because of their cooling, decrease in volume.
  • the heat exchanger according to the present invention has also the advantage of being of easy construction because it is sufficient to carry out a blanking operation only for obtaining the starting blank of the air tube, a subsequent press-forming operation for forming the air tube with the flanges 22 and 24 terminating in 90°-bent tabs 23 and 25, respectively and a final continuous welding operation for welding to each other the tabs 25 of the air tubes and the tabs 23 of the air tube to an associated tab 23 of an adjacent air tube.
  • This type of heat exchanger having a high efficiency which is promoted by the low resistance to the flue gas passage can be of course used, besides with the unit heaters provided with extractor and sealed chamber as those herein described, also with apparatus provided with natural draught.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Thermal Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Direct Air Heating By Heater Or Combustion Gas (AREA)
  • Devices For Blowing Cold Air, Devices For Blowing Warm Air, And Means For Preventing Water Condensation In Air Conditioning Units (AREA)
  • Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
  • Inorganic Insulating Materials (AREA)
  • Steering-Linkage Mechanisms And Four-Wheel Steering (AREA)
  • Domestic Hot-Water Supply Systems And Details Of Heating Systems (AREA)
EP90122666A 1989-12-06 1990-11-27 Heat exchange assembly for unit heaters Expired - Lifetime EP0431446B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90122666T ATE95298T1 (de) 1989-12-06 1990-11-27 Waermetauscheinheit fuer lufterhitzer.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT22201U IT219055Z2 (it) 1989-12-06 1989-12-06 Gruppo di scambio termico per aerotermi e per apparecchi similari per trattamento dell'aria calda
IT2220189U 1989-12-06

Publications (2)

Publication Number Publication Date
EP0431446A1 EP0431446A1 (en) 1991-06-12
EP0431446B1 true EP0431446B1 (en) 1993-09-29

Family

ID=11192974

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90122666A Expired - Lifetime EP0431446B1 (en) 1989-12-06 1990-11-27 Heat exchange assembly for unit heaters

Country Status (5)

Country Link
EP (1) EP0431446B1 (it)
AT (1) ATE95298T1 (it)
DE (1) DE69003657T2 (it)
ES (1) ES2045728T3 (it)
IT (1) IT219055Z2 (it)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITMI20022081A1 (it) * 2002-10-02 2004-04-03 Tecnoclima Spa Generatore d'aria calda.

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2613920A (en) * 1949-12-14 1952-10-14 Borg Warner Heat exchanger
US3236454A (en) * 1963-11-06 1966-02-22 Peerless Corp Sealed combustion central heating system

Also Published As

Publication number Publication date
ES2045728T3 (es) 1994-01-16
EP0431446A1 (en) 1991-06-12
IT8922201U1 (it) 1991-06-06
IT219055Z2 (it) 1992-11-27
DE69003657T2 (de) 1994-02-10
IT8922201V0 (it) 1989-12-06
ATE95298T1 (de) 1993-10-15
DE69003657D1 (de) 1993-11-04

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