Fluid flow control device

Abstract: A space heater has an elongate combustion tune (12) and a burner device (52) for supplying a combustible mixture into an inlet (34) of the tube through which the mixture and combustion products are caused to flow by a fan (58). An air conduit means has a part (36) which receives the heated gas and distributes it for heating purposes and an air duct (44) which extends longitudinally of and adjacent the tube in heat flow communication with a first region of the tube. The tube is arranged so that it emits radiant heat from a radiation region circumferentially spaced from the first region.

Description: The present invention relates to a space heater, particularly of the type useful for heating large spaces, such as factory interiors. Radiant heaters can be of simple construction but need to be suspended at a predetermined height above the location to be heated in order to provide the required heating effect. They are also relatively inefficient, since only a minor proportion of the heat is radiated to the desired location. Air heaters are potentially more controllable, but the propensity of hot air to rise can lead to an excessive amount of the available heated air accumulating in a region above the heater. US-A-4727854 describes a space heater comprising an elongate combustion tube; a burner device for supplying a combustible mixture into an inlet of the tube adjacent one end thereof; means for urging the combustible mixture and its combustion products to flow through the tube; and air conduit means including an air duct extending longitudinally of and adjacent the tube in heat flow communication with a first region of the tube and wherein the tube is arranged so that in use it emits radiant heat over at least a portion of its length from a radiation region circumferentially spaced from said first region. The heater of the invention is characterised in that the air conduit means is arranged to receive heated gas from an outlet of the combustion tube remote from the inlet and serves to distribute it for heating purposes. Preferably the air conduit means comprises, in addition to said air duct, a distribution duct having outlets along its length for distributing heated air. Preferably means are provided to vary the proportion of air flowing respectively through the air and distribution ducts. Conveniently, the combustion tube comprises two parallel elongate tube portions communicating at one pair of their ends by way of a joint element, the other ends providing said inlet and outlet. The distribution duct may then extend generally centrally of the tube portions, whereas the air duct may extend generally above each tube portion. Thus the tube portions can radiate heat downwardly, whereas heat which passes upwardly and would otherwise be lost is used to warm the air in the duct above. The invention will now be described, by way of example, with reference to the accompanying drawings in which:- Fig. 1 is a view in side elevation of one embodiment of the space heater of the invention; Fig. 2 is a front elevation (seen in the direction of the arrow A in fig. 1) of the heater on a larger scale; Figs. 3 and 4 are more detailed schematic views of the heater from rear and front respectively, showing the arrangement of the components, and Figs. 5 and 6 are respectively a side elevation and plan view of alternative form of combustion tube. The heater 10 employs a burner tube 12 which is generally U-shaped, having a pair of long parallel straight arm portions 14 connected together at one end by a curved portion 16 forming a bend. The tube 12 which is desirably of superhelix spirally wound construction, may have a total length of about 10 metres for example, and two arm portions 14 each having a length of 4.7 metres with the length of the bend at about 40 cm. The tube outside diameter is typically 10 cm, but it will be understood that the aforesaid typical dimensions can be varied according to the desired output and other operational requirements. The tube 12 extends within a housing, within which it is suitably suspended on chains 18 which accommodate normal thermal expansion and contraction during operation of the heater. The housing has an outer casing 20 of aluminium or mild steel for example, in the form of an inverted trough with a base 22, angled side portions 24, and downwardly extending lower wall portions 26 which extend beneath the rest of the assembly to serve as low level reflectors. The lower wall portions have spaced apertures to receive bolts or similar fasteners securing associated external fixtures 28 to said portions. An inner casing 30, conveniently of aluminium or mild steel, extends within the outer casing, slightly spaced from the base 22 and angled side walls 24 thereof, except in a central region where it defines a downwardly extending channel 32. At the sides, the inner casing 30 extends to the outer casing 20 and is connected to it, suitably by riveting at 30A. The central channel 32 is closed at the top by a plate 34, in order to form a longitudinally extending central distribution duct 36 which has openings 38 in its underside at intervals along its length. The space between the outer and inner casings (apart from the duct 36) is filled with insulating material 37 such as compressed fibreglass. Generally above each arm portion 14 of the tube 12 and adjacent the central warm air distribution duct 36, there is a space constituting a respective arm of a secondary air duct 44 containing air which will be heated because of the close proximity of the duct to the upper surface of the burner tube 12. At the end of the tube 12 remote from the U-bend 16, there is a burner/fan assembly 46. As can be seen in Figs. 3 and 4, the ends of the tube 12 are connected respectively to a pair of plenum chambers, of which one is an inlet chamber 48 and the other an outlet chamber 50. A burner unit 52 and an air inlet 54 are associated with the inlet chamber 48 and a hot air outlet 55 with the chamber 50. The burner may be adapted to burn any convenient fuel, such as natural gas, and serves to direct a burning mixture of gas and air into the tube 12. The inlet chamber 48 extends at 48A partly across the central region between and beneath the arms of the tube, where the air taken in by the burner unit 52 will tend to be preheated by the heater. The outlet plenum chamber 50 communicates with a restricted throat 50A which creates a Venturi effect, and thence with a duct 56 leading to a fan unit 58 forming part of the assembly 46 and suitably of pull-push type, driven by a motor 60. The fan unit 58 serves to draw air and combustion products through the tube 12, from the inlet 54 to the outlet 55, and thence through the duct 56 via the throat 50A. The air mixture entering the chamber 50 may be typically at about 200°C. The fan 58 may also be arranged to draw in air heated by the heater from the immediate surroundings. The output of the fan is divided between the central distribution duct 36 and the arms of the secondary air duct 44 by adjustable flow control means such as shutters or baffles, illustrated at 44A, adjacent the fan outlet. The output air is directed primarily into the central duct 36, whence it escapes through the apertures 38, to provide a downward flow of heated air from the heater into the space to be heated. The secondary flow from the fan via the flow control means 44A into the secondary duct 44 travels along the arms thereof generally above the tube 12, picking up more heat from the tube (and thus tending to expand) until it is blown downwards by the pressure, creating a further down draught of heated air. The air passing along the secondary duct 44 tends to cool the tube 12 and hence lessen its ability to radiate heat. Thus the amount of radiant heating is variable by adjusting the positions of the flow control means 44A which control the amount of air that passes along the secondary duct. It is thus possible to operate the heater to give a wide range of different ratios of convective to radiant heat outputs. In the alternative embodiment illustrated in Figures 5 and 6, each arm of the burner tube includes an inner tube portion 70, 71 respectively surrounded by a corresponding outer tube portion 72, 73. The ends of the outer tubes at one end of the assembly are closed by an end plate 74 and the ends of the inner tubes adjacent the plate 74 are spaced inwardly from the plate to leave a space 75 within the outer tube 72, 73 which communicates with the adjacent end of the inner tube 70, 71. The other ends of both the inner and outer tubes open into an end chamber 76 with the inner tube ends projecting some way into the chamber and being joined to connectors 78 which extend through an adjacent end plate 79 and into a burner/fan assembly indicated generally at 80. The assembly 80 contains a burner 81, the outlet of which is arranged to inject hot air and combustion products into the adjacent end portion 77 of the inner tube 70. The assembly 80 also includes a fan unit 82 which communicates with an outlet chamber 83 equivalent to the chamber 50 in the previous embodiment. An outlet of the chamber 83 communicates with a central duct 84 extending longitudinally of and above the combustion tubes and arranged generally centrally thereof. In operation, hot gases injected into the inner tube 70 travel along this tube, the flow thereof being enhanced by actuation of the fan 82 which draws air and combustion products through the interconnected inner and outer tube from the end 77 of the inner tube 71 to which it is connected. The flow of gases through the tubes is indicated by arrows and it will be seen that gases flow along the inner tube 70 into the chamber 75 and thence in the reverse direction along the space 75A between the inner and outer tubes into the chamber 76. From here, the gases enter the space 76A between the tubes 71 and 73 and once again reach the chamber 75 from which they reverse and flow back along the inner tube 71 and through the connection 78 into the outlet chamber 83. Pressure build-up in this chamber forces the gases along the air duct 84 and through openings in the latter (not shown) downwardly out of the apparatus into an external space to be heated. It will be seen that the convoluted gas flow path provided by the telescoped inner and outer tubes provides a sufficiently long path for heat exchange purposes and enables the overall length of the apparatus to be significantly decreased, as compared with the embodiment of Figures 1 to 4.

Claims: A space heater comprising an elongate combustion tube (12); a burner device (52) for supplying a combustible mixture into an inlet (54) of the tube adjacent one end thereof; means (58) for urging the combustible mixture and its combustion products to flow through the tube; and air conduit means including an air duct (44) extending longitudinally of and adjacent the tube in heat flow communication with a first region of the tube and wherein the tube (12) is arranged so that in use it emits radiant heat over at least a portion of its length from a radiation region circumferentially spaced from said first region, characterised in that the air conduit means (36, 44) is arranged to receive heated gas from an outlet (55) of the combustion tube remote from the inlet and serves to distribute it for heating purposes. A space heater according to Claim 1, characterised in that a distribution duct (36) is provided in addition to the air duct (44) and has outlets (38) along its length for distributing heated air. A space heater according to Claim 1 or Claim 2, characterised in that adjustable means (44A) are provided to vary the proportion of air flowing respectively through the air (44) and distribution (36) ducts. A space heater according to any one of the preceding claims, characterised in that the combustion tube has two parallel elongate tube portions (14) communicating at one pair of their ends by way of a joint element (16), the other ends providing said inlet and outlet. A space heater according to Claim 1, characterised in that a distribution duct (36) is provided in addition to the air duct (44) and the combustion tube has two parallel elongate tube portions (14), the distribution duct (36) extending generally centrally of the tube portions and the air duct (44) having portions extending respectively above the tube portions. A space heater according to any one of the preceding claims, characterised in that the tube outlet (55) communicates via a restricted throat (50A) with a duct (56) through which heated air is drawn by a fan (58) and fed to the air conduit means. A space heater according to Claim 3, characterised in that the tube outlet (55) communicates via a restricted throat (50A) with a duct (56) through which heated air is drawn by a fan (58), the outflow from which is supplied to the air (44) and distribution (36) ducts in a proportion determined by said adjustable means (44A). A space heater according to any one of the preceding claims, characterised in that said air duct (44) extends adjacent the upper region of the combustion tube (12) and a lower region of the tube emits radiant heat. A space heater according to any one of Claims 1 to 3 and 6 to 8, characterised in that the combustion tube has a pair of branches, each of which includes an inner tube (70, 71) arranged generally co-axially within an outer tube (72, 73), the outer tubes (72, 73) being closed at one pair of adjacent ends and their other ends communicating with an end chamber (76), one end (77) of one of the inner tubes remote from said outer tube closed ends being arranged to receive heated gas from the burner device (81) and the corresponding end (77) of the other inner tube being associated with means (82) for promoting the flow of heated gas through the assembly, the arrangement being such that heated gas from the burner device is caused to flow from the burner along one inner tube (70) and in the reverse direction along the surrounding outer tube(72), prior to flowing along the other outer tube (73) and thence in the reverse direction along the other inner tube (71) prior to entering the air conduit means.

Inventors: JONES DAVID MERVIN, MAUND JOHN KEITH, JONES, DAVID MERVIN, MAUND, JOHN KEITH
Applicants: ADVENTEC LTD, ADVENTEC LIMITED
Application year: 1990
Main classification: F24H3
IPC codes: F24D5