AU2001100015A4 - Space heater - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

SPECIFICATION

INNOVATION

PATENT

Invention Title: Space Heater The following statement is a full description of this invention, including the best method of performing it known to us: Freehills Carter Smith BeadleMELC601144010.6 CD/01141001.0 1 A SPACE HEATER Field of the Invention This invention relates to a space heater in which heat is extracted from combustion gases with high efficiency.

Background to the Invention It is known to heat room air by passing it through the body of a space heater. In the majority of cases, the result is highly inefficient with little heat being supplied to the room air and most of the combustion heat escaping with the combustion gases through a flue or chimney depending on the location of the heater.

The present invention aims to improve the efficiency of heat exchange within a gas fuelled space heater. It is desirable that the efficiency of heat exchange is improved to levels of 90-96% plus combustion efficiency of gas input.

Summary of the Invention The invention accordingly provides a gas space heater comprising a metal box structure located within an outer casing which has a transparent or semitransparent front section, the structure housing: at least a primary heat exchanger, a secondary heat exchanger, and a tertiary heat exchanger, each of the heat exchangers subject to combustion gases; and a convection fan; wherein the convection fan draws external air into the heater and passes it over and around the heat exchangers, in order to heat the external air, which is then blown out of the heater.

CD/01141001.0 2 The heat exchangers preferably include, as a primary heat exchanger, a fire box subject to gas heating; as a secondary heat exchanger there is preferably provided a tubular member leading from the fire box of the primary heat exchanger and connecting to one end of a tertiary heat exchanger comprising an array of tubes which are connected at their other end to the atmosphere through the combustion fan so as to extract and expel the combustion products from within the fire box, the tubular member and the array of tubes. The combustion products may be expelled to atmosphere through a horizontal flue located through a wall part of the building being heated or upwards through the roof or an existing chimney, both with a cowl on the outer or the upper outer end of the flue.

It is also preferred that the convection fan is positioned centrally within and at the bottom of the heater box structure so as to draw cool air from the space to be heated through an opening at the lower end of the outer casing which is heated by heat transfer through contact with the outer surfaces of the primary, secondary and tertiary heat exchangers and finally expelled into the space to be heated. The convection fan is so situated that it provides a cooling effect on the combustion fan and adjacent electronic control mechanisms.

Brief Description of the Drawings The invention will now be described by way of non-limiting example with reference to the accompanying drawings in which: Figure 1 is a perspective view from the front of the heater according to the invention; Figure 2 is a sectional cross-section taken along the line 2-2 of Figure 1 in the direction of the arrows shown; Figure 3 is a sectional side view taken along the line 3-3 of Figure 2; Figure 4 is a part sectional plan view from above taken along the line 4-4 of Figure 3; CD/01141001.0 3 Figure 5 is a part sectional plan view from above taken along the line 5-5 of Figure 3; and Figure 6 is a part sectional plan view from above taken along the line 6-6 of Figure 3.

List of features shown in the drawings Space Heater 6 Outer casing 7 Glass door 8 Fire box 9 Ceramic logs Ceramic gate 11 Grate apertures 12 Burners 13 Air inlet manifold 14 Rear of casing Air inlet rear connection 16 Baffle chamber 17 Secondary heat exchanger 18 Flexible steel tube 19 Tertiary heat exchanger Ends of flexible steel tube 21 Helical tape 22 Header 23 Finned tubes 24 Header Condensate sump 26 Combustion fan 27 Flue pipe 28 Helical fins 29 Helical insert tape Convection fan 31 Condensate pump CD/01141001.0 4 32 Lower louvred opening 33 Gas connection Description of Preferred Embodiments Referring to Figure 1 of the drawings, the space heater 5 of the invention is illustrated as seen from inside the space in a building to be heated and there is shown the outer casing 6 of the heater with its large neo-ceramic door glass 7, which may have a safety screen (not shown) fitted thereon as a security measure for young children.

Referring to the cross-section of Figure 2, there is illustrated the fire box 8 comprising a primary heat exchanger in accordance with the invention within which are located ceramic logs 9 supported on ceramic grate 10 having apertures 11 therein to allow passage of gas flames from burners 12 located on an air inlet manifold 13 extending through the rear 14 of the casing 6 at 15. At the upper part of the fire box 8 there is located a baffle chamber 16 which allows combustion products from the fire box 8 to pass around the edges thereof (Figure 4) into a secondary heat exchanger 17. The baffle chamber 16 acts to ensure even distribution and balanced extraction of final combustion gases.

The ceramic grate 10 acts as an insulator medium for gas and electronic components beside and below the burners 12, and logs 9 at the same time acting as an agent in improving the combustion process in fire box 8 by keeping a high temperature after the gas flames have issued from burners 12 and thereby producing a clean total combustion. The ceramic logs 9 absorb heat from the gas flames whereby thermal energy from logs 9 radiates as infra-red heat through the transparent or semi-transparent door glass 7 at the front of the heater The secondary heat exchanger 17 in this exemplary embodiment of the invention, comprises a corrugated flexible stainless steel tube 18 with 150% more exposed heat surface area than a standard plain tube of the same diameter. This form of tube also relieves thermal expansion stresses between connections of the primary heat exchanger 8 and a tertiary heat exchanger 19. The ends 20 of the CD/01141001.0 tube 18 are provided with connectors allowing quick connection, detachment and rotation of the tube 18 and which reliably ensure a tight gas sealing without the need for a welding process during assembly of the heater.

Inside tube 18 and engaging against the inside thereof there is located a helical aluminium strip or tape 21 which acts as a turbulator to the combustion gases travelling through tube 18 of the secondary heat exchanger 17 consequentially increasing the heat exchange capacity of tube 18 as compared with a standard straight through flow of a pipe or tube of the same diameter.

At the outflow end of tube 18 it is attached to a header 22 of the tertiary heat exchanger 19 which, in this embodiment of the invention, comprises a plurality of externally finned tubes 23 attached at their other end to another header 24 which in turn is connected to a condensate sump 25 and a suction combustion fan 26 (which is adapted to extract the combustion gases from the fire box 8 through the secondary heat exchanger 17 and the tertiary heat exchanger 19 and discharge these gases through a flue pipe 27 to the outer atmospheric air through either a co-axial cowl in the case of a vertical flue pipe, such as that installed in an existing chimney or in an upstanding metal tube).

Tubes 23 are secured to headers 22 and 24 expanding the ends of the tubes 23 in their attachment to the headers to expand both surface sides of the header plates thus creating a very strong crimp fixture which is reliably gas tight with no requirement for welding.

The finned tubes 23 preferably comprise stainless steel tubes with attached helical corrugated fins 28 on the external surfaces thereof to increase the thermal energy transfer to the outer surface of tubes 23. To increase the heat transfer rate within each tube, a helical twisted insert tape 29 is also located in the inside of each tube 23.

The combustion fan 26 is preferably located adjacent a convection fan located inside and at the bottom of the heater structure 5 to ensure that the cooler room air drawn through a louvred opening 32 at the lower front of the heater is CD/01141001.0 6 continually moving past the combustion fan thereby extending the reliability and life of the combustion fan motor and other parts of the combustion fan 26.

The condensate sump is attached to header 24 and is of a novel design utilising a chlorinated PVC rectangular pipe and elbow forming a goose neck shaped water seal for condensate passing through the heater with the combustion gases and collected in the condensate sump 25 and the goose neck seal is used for draining the condensate when it reaches a preset level in the sump. This water seal system avoids air leakages or pressure losses while continually draining down the condensate.

In order to maintain humidity in the space being heated (and most known room heaters dry out the air in the heated space), the heater may be provided with a condensate pump 31 drawing condensate from the sump and pumping it to the top of the heater where it is sprayed into the hot air before it exits from the top of the heater and evaporates in the hot air, so that air humidity is automatically restored.

A gas control valve 33 is located at the back of the heater and connected to a gas supply and to the burners 12 located in air manifold 13.

Automatic thermostat controls may be used with the space heater 5 of the invention and computer controlled solid state electronic controls may be built into the heater to provide safety and efficiency of the heater in use.

In use, the heater heats the ceramic logs 9 in the fire box 8 and the products of combustion are drawn through the secondary exchanger 17 and the tertiary exchanger 19 by combustion fan 26 through the condensate sump The convection fan 30 draws air through the lower front opening 32 of the heater casing and passes it over and around the tertiary and secondary heat exchanger and the fire box and blows it into the space to be heated at the front thereof. Gas and fan controls ensure that the desired room or space temperature is maintained.

The space heater of the present invention has been shown to achieve 78% CD/01141001.0 7 minimum overall heat output, which means that more than 78% of the useful available heat energy of the gas is put into the space being heated, whereas other comparable gas heaters put only around 60% of available energy into the space being heated.

It will be understood that the invention disclosed and defined herein extends to all novel features and all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these features and different combinations constitute various alternative aspects of the invention.