AU2012202470B2

AU2012202470B2 - Fluid Heater

Info

Publication number: AU2012202470B2
Application number: AU2012202470A
Authority: AU
Inventors: George Frederick Price
Original assignee: PRIMO TECH Pty Ltd
Current assignee: PRIMO-TECH Pty Ltd
Priority date: 2005-09-08
Filing date: 2012-04-30
Publication date: 2013-08-01
Anticipated expiration: 2026-09-08
Also published as: AU2012202470A1

Abstract

-16 Abstract A gas-fired, instantaneous fluid heater (10) devised particularly for heating water. The heater (10) comprises housing (11) incorporating an integral flue (13) oriented vertically. The housing (11) accommodates a combustion chamber (21) and a blower (25) for delivering a combustible mixture of gas and air to the combustion chamber (21). The blower (25) communicates with a gas-fired burner (23) at one end of the combustion chamber (21). A heat exchanger (27) is accommodated at the other end of the combustion chamber (21). The flue (13) communicates with the combustion chamber (21) through the heat exchanger (27). A water flow line (32) extends between a water inlet (33) and a water outlet (35) and passes through the heat exchanger (27). A flow sensor (45) is incorporated in the water flow line (32) on the upstream side of the heat exchanger( 27). A temperature sensor (47) is provided in the fluid flow line (32) upstream of the heat exchanger (27) and a temperature sensor (48) is provided in the fluid flow line (32) downstream of the heat exchanger. The flow sensor (45) outputs a signal indicative of the volumetric flow rate of water along the flow line (32). The temperature sensor (47) outputs a signal representative of the temperature of water entering the water heater (10), and the temperature sensor (48) outputs a signal representative of the temperature of the water exiting the heater. The signals outputted by the flow sensor (45), the temperature sensors (47), 48 are transmitted to a controller (51) which is responsive to the inputted signals. The controller (51) regulates the speed of the blower (25), so controlling the amount of the combustible mixture of gas and air delivered to the burner (23). -' -n CD mI n-4-I-40 '/<CD 3 -x - DD D X o0 C: C 0 CD m >. CL 0 CD m CD CD . + -n4 0l CTL~ CD m( -n 01 CD) o -2o C)G M

Description

P/00/0 11 28/5/91 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Name of Applicant: Primo-Tech Pty Ltd Actual Inventor George Frederick Price Address for service is: WRAYS Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR Invention Title: Fluid Heater The following statement is a full description of this invention, including the best method of performing it known to me: 1 -2 "Fluid Heater" Field of the Invention This invention relates to heating of a fluid. More particularly, the invention relates to apparatus for, and a method of, heating a fluid. The fluid may be of any appropriate type, including a gaseous fluid or a liquid. The invention has been devised particularly, although no necessarily solely, as a gas-fired instantaneous water heater. Background Art Gas-fired instantaneous water heaters are well known. Typically such water heaters comprise a heat exchanger disposed above a gas burner accommodated within a combustion chamber. Water to be heated is passed through the heat exchanger to receive heat from a combustion process within the combustion chamber. With such water heaters there are two significant limitations affecting their performance. First, it necessary to limit the thermal efficiency of the heaters to approximately 80% to prevent condensation forming on the heat exchanger and falling onto the burner below, seriously affecting its operation. Secondly, it is difficult to achieve outlet temperature stability with sudden changes in water flow. It is against this background, and the limitations associated therewith, that the present invention has been developed. Disclosure of the Invention According to a first aspect of the invention there is provided an instantaneous fluid heater, comprising a fluid flow path having an inlet for receiving fluid for heating and an outlet for the heated fluid, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas-burner, and a blower for delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein air and gas are mixed in the blower at a predetermined ratio to provide the combustible gaseous mixture discharged at the outlet, and wherein the fluid flow path is defined by a conduit.

-3 Preferably, the instantaneous fluid heater further comprises a control means for controlling the flow rate of the combustible gaseous mixture delivered to the burner. Preferably, the instantaneous fluid heater further comprises means for sensing the fluid temperature before entry into the heat exchanger, means for sensing the fluid temperature upon or after exiting the heat exchanger, means for sensing the flow rate of fluid along the flow path, the control means being responsive to the fluid inlet and outlet temperature and the fluid flow rate for regulating the flow rate of the combustible mixture delivered to the burner. Sensing the fluid temperature upon or after exiting the heat exchanger establishing an outlet temperature reference to provide supplementary feedback, allowing the target temperature to be achieved more quickly. Tthe blower intakes both air and gas for causing mixing thereof and delivery of the resultant mixture to the burner. Typically the operational speed of the blower is regulated to control the volumetric flow rate of the combustible mixture delivered to the burner. Preferably, the blower has an air intake opening onto ambient air. The air intake may comprise a plurality of intake ports. Preferably, the blower has a gas inlet adapted for connection to a gas source and a control valve is incorporated in the gas inlet to maintain a prescribed gas to air mix ratio. The mix ratio remains constant and the amount of the combustible mixture delivered to the burner is determined by the blower speed. Preferably, the speed of the blower is regulated by the control means. Sensing the fluid temperature upon or after exiting the heat exchanger establishes an outlet temperature reference to provide supplementary feedback, allowing the target temperature to be achieved more quickly. Preferably, the instantaneous fluid heater further comprises a combustion chamber in which the burner is accommodated and a flue in communication with the combustion chamber, the heat exchanger being disposed within the combustion chamber between the burner and the flue.

-4 Preferably, the burner is orientated to direct a flame front generally horizontally into the combustion chamber in a direction towards the heat exchanger and the flue. Preferably, the heat exchanger is at one end of the combustion chamber and the burner is at the other end of the combustion chamber, and the flue communicates with the combustion chamber through the heat exchanger. Preferably, the arrangement is configured for drainage of water condensate into the flue. According to a second aspect of the invention there is provided a water heater in accordance with the instantaneous fluid heater according to the first aspect of the invention. According to a third aspect of the invention there is provided a method of instantaneously heating a fluid comprising of the steps of: passing fluid along a conduit defined fluid flow path having an inlet for receiving fluid for heating; an outlet for the heated fluid, and a heat exchanger therebetween at which the fluid is in heat exchange relationahip with a gas-fired burner; intaking air and a gas into a blower to provide a combustible mixture, and delivering the combustible mixture to the burner, and mixing the combustible mixture in the blower Preferably, the method further comprises controlling the rate of flow of the combustible mixture to the burner. Preferably, the method further comprises: sensing the fluid temperature before entry into the heat exchanger; sensing the fluid temperature upon or after exiting the heat exchanger; sensing the flow rate of fluid along the flow path and responding to the fluid temperatures and the fluid flow rate as necessary to determine the required flow rate of the combustible mixture. Where the fluid being heated is intended to be heated to a set temperature the control means is preferably responsive to the fluid inlet temperature, the fluid outlet temperature, and the fluid flow rate in controlling the flow rate of the combustible mixture, in accordance with the following algorithm: Demand = [(Tset - Tin) x Flow] + [(Tset-Tout) x Flow] -5 Demand is an expression of required power (temperature rise x flow) and Where:controls the blower speed Tset is set temperature in deg C Tin is the inlet fluid temperature in deg C Tout is outlet fluid temperature in deg C Flow is fluid flow in litres per minute In the algorithm, the expression [(Tset-Tout) x Flow] provides the supplementary feedback. According to a fourth aspect of the invention there is provided an instantaneous water heater comprising a conduit defining a fluid flow path having an inlet for receiving water for heating and an outlet for the heated water, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas burner, and a variable speed blower for mixing and delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein the operational speed of the blower regulates the volumetric flow rate of the combustible gaseous mixture delivered to the burner. According to a fifth aspect of the invention there is provided an instantaneous water heater comprising a conduit defining a fluid flow path having an inlet for receiving water for heating and an outlet for the heated water, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas burner, and a variable speed blower for mixing and delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein air and gas are mixed in the blower at a predetermined ratio to provide the combustible gaseous mixture discharged at the outlet, and wherein the operational speed of the blower regulates the volumetric flow rate of the combustible gaseous mixture delivered to the burner.

-6 Brief Description of the Drawings The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which: Figure 1 is a schematic view of a water heater according to an embodiment of the invention; Figure 2 is a front view of the water heater; Figure 3 is a side view of the water heater; Figure 4 is a view similar to Figure 2 with the exception that a front cover has been removed to reveal internal workings of the heater; and Figure 5 is a schematic elevational view of the operating components of the water heater. Best Mode(s) for Carrying Out the Invention The embodiment shown in the drawings is directed to a gas-fired, instantaneous water heater 10 intended for domestic use. The water heater 10 comprises a housing 11 of generally rectangular construction, incorporating an integral flue 13 oriented vertically. The housing 11 has a removable panel 15 providing access to the interior 17. Within the interior 17 there is accommodated a combustion chamber 21 defined within casing 22, and a blower 25 for delivering a combustible mixture of gas and air to the combustion chamber. The blower 25 communicates with a gas-fired burner 23 in the combustion chamber 21 at one end thereof. A heat exchanger 27 is accommodated within the combustion chamber 21 at the end thereof opposite to the burner 23. A water flow line 31 extends between a water inlet 33 and a water outlet 35. The water flow path 31 comprises a flow line 32 having a portion 36 thereof of circuitous configuration disposed within the combustion chamber 21. The portion 36 of the -7 water flow line 32 has fins 39 attached thereto to provide the heat exchanger 27 within the combustion chamber 21. The portion 36 of the flow line 32 comprises an inner section 37 and an outer section 38 in serial relation, with the inner section 37 being located closer to the burner 23 than the outer section 38, as shown in Figure 5. The water inlet 33 communicates with the outer section 38, and the water outlet 35 communicates with the inner section 37. With this arrangement, cold water enters a (cooler) zone of the heat exchanger 27 away from the burner 23 and progresses towards a (hotter) zone closer to burner 23. While not shown in the drawings, each section 37,38 of the flow line 32 winds back and forth within the combustion chamber 21. The windings are disposed within a generally vertical plane. Further, while also not shown in the drawings, the flow line 32 may further comprise a water jacket section between the inner and outer sections 37 and 38. The water jacket section may wind around the inner perimeter of the combustion chamber 21 for the purpose of cooling the casing 22 of the combustion chamber 21. The flue 13 communicates with the combustion chamber 21 through the heat exchanger 27. More particularly, the spacings 40 between the fins 39 provide exhaust passages opening into the flue 13. The burner 23 is located at one end of the combustion chamber 21 to direct a flame front into the combustion chamber in a generally horizontal direction. With this arrangement, combustion products contact the heat exchanger 27, passing through the spacings 40 between the fins 39 and then entering the flue 13. The bottom of the combustion chamber 21 defined by bottom wall 42 of the casing 22 is sloped downwardly towards the flue 13 such that any water condensate forming in the combustion chamber (from contact of the hot combustion products with the heat exchanger 27) can drain into the flue 13. A sump (not shown) is provided at the base of the flue 13 to collect water condensate draining into the flue. A drain line (also not shown) may be fitted to the sump for disposal of the collected condensate.

-8 A flow sensor 45 is incorporated in the water flow line32 on the upstream side of the heat exchanger 27. A temperature sensor 47 is provided in the fluid flow line 32 upstream of the heat exchanger 27 and a temperature sensor 48 is provided in the fluid flow line 32 downstream of the heat exchanger. The flow sensor 45 outputs a signal indicative of the volumetric flow rate of water along the flow line 32. The temperature sensor 47 outputs a signal representative of the temperature of water entering the water heater 10, and the temperature sensor 48 outputs a signal representative of the temperature of the water exiting the heater. The signals outputted by the flow sensor 45 and, the temperature sensors 47, 48, are transmitted to a controller 51 which is responsive to the inputted signals. As previously mentioned, the blower 25 delivers the combustible mixture to the burner 23. The combustible mixture comprises gas and combustion air. Gas and air are delivered to the blower 25 where mixing occurs for delivery via blower outlet 55 to the burner 23. The blower 25 has an air intake 57 and a gas intake means 59. The air intake 57 comprises two intake ports 61 opening onto the exterior of the blower for intake of ambient air. The gas intake means 59 communicates with a gas intake path 63 in which there is incorporated a gas valve 65. The blower 25 and the gas valve 65 are each responsive to the controller 51. In this regard, the controller processes signals received from flow sensor 45 and temperature sensors 47, 48, and determines the demand requirements for the burner, having regard to the desired temperature setting for the heated water. The controller 51 has an input 67 to receive an input signal representative of the desired temperature setting. In this embodiment, the input signal is transmitted to the controller 51 by wireless transmission from a remote control device 53. The controller 51 controls the speed of the blower 25, thus controlling the rate of delivery of the combustible fuel mixture to the burner. The controller 51 also signals the gas valve 65 to deliver gas to the blower 25. The blower 25 controls the volume of gas -9 (together with the appropriate mix of air therewith) in accordance with the gas demand as set by the speed of the blower 25. Ignition of the burner 23 is electronic, and so no pilot light is necessary. This is advantageous as there is no gas usage when there is no demand for hot water. The controller 51 comprises a microprocessor which can respond almost instantly to the monitored parameters of the incoming water; namely, the flow rate of the incoming water as determined by flow sensor 45, and also the temperature of the incoming water as determined by the temperature sensor 47 as well as the temperature of the exiting water as determined by sensor 48 This allows the controller 51 to regulate the delivery of the combustible mixture to the burner for controlling the water temperature. The air/fuel ratio is fixed by the gas valve 65, so as to deliver efficient combustion in combustion chamber 21. The heat exchange process in the combustion chamber 21 is fully condensing, so providing a highly efficient transfer of energy. More particularly, water generated as part of the combustion process is allowed to condense when the hot products of the combustion contact the heat exchanger 27. This optimises energy transfer from the hot products of combustion to the heat exchanger 27 (and thus to the water flow therethrough). Indeed, it is believed that such an arrangement can deliver a thermal efficiency of at least 90%. Control of the heater 10 by the controller 51 is responsive to the water inlet and outlet temperatures, and the water flow rate, in accordance with the following algorithm: Demand = [(Tset - Tin) x Flow] + [(Tset-Tout) x Flow] Demand is an expression of required power (temperature rise x Where: flow) and controls the blower speed Tset is set temperature in deg C Tin is the inlet water temperature in deg C -10 Tout is outlet water temperature in deg C Flow is water flow in litres per minute The supplementary feedback regarding outlet water temperature allows the heater to reach the set temperature more quickly and respond to sudden changes in flow. Because the control is pre-emptive (rather than reactive) in its operation, it can respond almost immediately to changes in water flow, thereby maintaining a relative constant water temperature at the outlet regardless of pressure disturbances in the plumbing system to which the water heater is connected. A feature of the water heater is that it can be used with several remote control devices 53. Typically, one device 53 would be placed in the kitchen area, another possibly in the laundry area, and still another in each bathroom of a home. This allows water temperature to be controlled from each of those locations within the home. Temperatures selected through each remote control device can be retained in the memory of that device for ongoing use, if desired. The remote control devices 53 are wireless and therefore require no installation. From the forgoing, it is evident that the present embodiment provides a simple yet highly efficient water heater which can rapidly respond to changes in selected parameters of water flow, thereby providing greater temperature stability. The heater according to the embodiment offers improved thermal efficiency through: * premixing the fuel gas and combustion air and delivering the mix to the burner at variable rates via variable speed blower * using an operated gas valve to maintain a constant gas/air ratio e using a heat exchanger designed to promote full condensation " arranging the burner, heat exchanger and flue to deal with the condensate produced in the heat exchange process The heater according to the embodiment offers improved stability and improved response to changes in flow through: -11 * simplifying the control system so that there is only one variable to be controlled, being the blower speed " making the flow the primary driver of the control system, rather than outlet temperature, so that a change in flow will almost immediately cause a corresponding change in blower speed * use of supplementary feedback to allow the gap between set temperature and outlet temperature to be closed very rapidly while minimising overshoot. It should be appreciated that the heating apparatus according to the invention is not necessarily limited to the embodiment described, being a instantaneous, gas-fired water heater. The heating apparatus according to the invention may find application in other areas where a fluid requires heating. Improvements and modifications may be made without departing from the scope of the invention. Throughout the specification, unless the context requires otherwise, the word ''comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. Apparatus for heating fluid, comprising a fluid flow path having an inlet for receiving fluid for heating and an outlet for the heated fluid, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas-burner, and a blower for delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein air and gas are mixed in the blower at a predetermined ratio to provide the combustible gaseous mixture discharged at the outlet.

2. Apparatus according to claim 1 further comprising a control means for controlling the flow rate of the combustible gaseous mixture delivered to the burner.

3. Apparatus according to the claim 2 further comprising means for sensing the fluid temperature before entry into the heat exchanger, means for sensing the fluid temperature upon or after exiting the heat exchanger, means for sensing the flow rate of fluid along the flow path, the control means being responsive to the fluid inlet and outlet temperature and the fluid flow rate for regulating the flow rate of the combustible mixture delivered to the burner.

4. Apparatus according to any one of the preceding claims wherein the operational speed of the blower is regulated to control the volumetric flow rate of the combustible mixture delivered to the burner.

5. Apparatus according to any one of the preceding claim wherein the blower has an air intake opening onto ambient air.

6. Apparatus according to any one of the preceding claims wherein the blower has a gas inlet adapted for connection to a gas source and a control valve is incorporated in the gas inlet to maintain a prescribed gas to air mix ratio.

7. Apparatus according to any one of claims 2 to 6 wherein the speed of the blower is regulated by the control means. -14

8. Apparatus according to any one of the preceding claims further comprising a combustion chamber in which the burner is accommodated and a flue in communication with the combustion chamber, the heat exchanger being disposed within the combustion chamber between the burner and the flue.

9. Apparatus according to claim 8 wherein, the burner is orientated to direct the flame front generally horizontally into the combustion chamber in a direction towards the heat exchanger and the flue.

10.Apparatus according to claim 8 or 9 wherein, the heat exchanger is at one end of the combustion chamber and the burner is at the other end of the combustion chamber, and the flue communicates with the combustion chamber through the heat exchanger.

11.Apparatus according to claim 8, 9 or 10 wherein the arrangement is configured for drainage of water condensate into the flue.

12.Apparatus according to any one of the preceding claims wherein the fluid comprises water.

13.A method of heating a fluid comprising of the steps of: passing fluid along fluid low path having an inlet for receiving fluid for heating; an outlet for the heated fluid, and a heat exchanger therebetween at which the fluid is in heat exchange relationship with a gas-fired burner; delivering a combustible mixture of gas and air to the burner; and controlling the rate of flow of the combustible mixture to the burner.

14.A method according to claim 13 further comprising controlling the rate of flow of the combustible mixture to the burner.

15.A method according to claim 14 further comprising: sensing the fluid temperature before entry into the heat exchanger; sensing the flow rate of fluid along the flow path; and responding to the fluid temperatures and the fluid flow rate as necessary to determine the required flow rate of the combustible mixture. -15

16.A method according to claim 13, 14 or 15 wherein the fluid is intended to be heated to a set temperature and wherein the control means is responsive to the fluid inlet temperature, the fluid outlet temperature, and the fluid flow rate in controlling the flow rate of the combustible mixture, in accordance with the following algorithm: Demand = [(Tset - Tin) x Flow] + [(Tset-Tout) x Flow] where: Demand is an expression of required power (temperature rise x flow) and controls the blower speed Teat is set temperature in deg C Tin is the Inlet water temperature In deg C Tout is outlet water temperature in deg C Flow is water flow in litres per minute

17.An instantaneous water heater comprising a fluid flow path having an inlet for receiving water for heating and an outlet for the heated water, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas-burner, and a variable speed blower for delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein the operational speed of the blower regulates the volumetric flow rate of the combustible gaseous mixture delivered to the burner.

18.An instantaneous water heater comprising a fluid flow path having an inlet for receiving water for heating and an outlet for the heated water, a gas-fired burner, a heat exchanger at which the fluid path is in heat exchange relationship with the gas-burner, and a variable speed blower for delivering a combustible gaseous mixture to the burner, the blower having a gas intake, an air intake and an outlet communicating with the burner, wherein air and gas are mixed in the blower at a predetermined ratio to provide the combustible gaseous mixture discharged at the outlet, and wherein the operational speed of the blower regulates the volumetric flow rate of the combustible gaseous mixture delivered to the burner.

19.Apparatus for heating a fluid substantially as herein described with reference to the accompanying drawings.

20.A method for heating a fluid substantially as herein described.