GB2253031A

GB2253031A - A water storage and heating vessel

Info

Publication number: GB2253031A
Application number: GB9201545A
Authority: GB
Inventors: Ottomar Kampfenkel
Original assignee: Joh Vaillant GmbH and Co
Current assignee: Vaillant GmbH
Priority date: 1991-01-25
Filing date: 1992-01-24
Publication date: 1992-08-26
Anticipated expiration: 2012-01-24
Also published as: FR2672113A1; DE4201972C2; IT1263177B; GB2253031B; ITMI920105A0; GB9201545D0; ITMI920105A1; DE4201972A1; FR2672113B1

Abstract

A water storage vessel 8 is heated by a burner 1 communicating with a flame tube 3 extending through the vessel 8 which is provided with a pipe coil 7 in its interior for heating water for room-heating 46 and communicating with a heat exchanger 6, accommodated in the interior of the flame tube 3. The water storage vessel 8 is provided with both heat insulation 20 adjacent to the flame tube 3 and 21 on its outside surfaces. A second water condensing coil 30 may be in series with the coil 6 but in the flue 22 which includes a fan 23 and a split funnel 32/35 for collecting condensate, an S-bend preventing condensate from falling into the tube 6. To minimise the emission of pollutants, the burner may be supplied by a mixing chamber (26), which is connected to gas and air supply lines (27, 25), which may contain independent throttle valves (28, 29), controlled by a common control device (18) (Fig 1, not shown). <IMAGE>

Description

2 2 5 3, i.- 1 1 - Water storage vessel The present invention relates to a

water storage vessel which is heated by a burner when in use, through which vessel a flame tube extends and which is provided on its outside surfaces with heat insulation and is provided in its interior with a pipe coil for preparing roomheating water.

Such a water storage vessel has been previously proposed for example in DE-U-82 08 266. In that design the flame tube is made of a highly heat-conductive material and is surrounded by a pipe coil having a lead which increases with the distance from the burner disposed underneath.

The above-mentioned design has the disadvantage that the contents of the water storage vessel are cooled by means of the flame tube while the burner is not operating. This results in considerable losses of heat. Another problem is that merely as a result of the cooling of the contents of the water storage vessel thus caused, the burner must frequently be started even when hot tap water and room-heating water are not required. Such frequent starting of the burner results in a considerable energy requirement and in higher emissions of pollutants.

It is an aim of the present invention to obviate' these disadvantages and to provide a burner-heated water storage vessel which is of the construction described 2 - hereinbefore, which can be heated up quickly, and in which cooling losses are substantially avoided or reduced.

Accordingly the present invention is directed to a water storage vessel as described in the opening paragraph of the present specification, in which a heat exchanger which communicates with the pipe coil in the interior of the water storage vessel is accommodated in the interior of the f lame tube, and the water storage vessel is provided with heat insulation adjacent to the flame tube.

As a result of these measures the water can be heated up very quickly by means of the heat exchanger which is accommodated in the flame tube. At the same time, the provision of heat insulation, also adjacent to the flame tube, will substantially reduce the cooling of the water in the water storage vessel while the burner is not-operating. As a result, operation of the burner will generally not be required when hot tap water or roomheating water is not needed so that the number of starting phases of the burner, when more pollutants are emitted, will be minimised throughout the operating time. Only the relatively small volume of water in the heat exchanger disposed in the flame tube will be subjected to an appreciable cooling. But the heat insulation provided adjacent to the flame tube will cause the convection' forces to be relatively high during operation of the burner so that the resistance of the gas path of the heat exchanger and of the draught control device may be high and therefore air flow will be low when the burner is not in use and thus the cooling of the contents of the heat exchanger so affected will be slowed down correspondingly.

The heat exchanger provided inside the flame tube also affords the advantage that the contents of the water storage vessel will be heated up quickly so that water can be tapped at a high rate when the burner is in use.

Besides, the storage of heat permits a relatively high heat demand to be met by relatively low burner powers and the burner power need not be modulated. This is significant also from the ecological aspect because a burner which is operated with only one combustion setting can be adjusted, as a rule, so as to minimise the emission of pollutants. The measures adopted in accordance with the present invention result also in a relatively high annual utilisation ratio.

Preferably, the heat exchanger which is accommodated in the flame tube is constituted by a pipe coil.

Desirably, the flame tube at its bottom end, which faces the burner, comprises an enlarged portion, which serves as a combustion chamber and accommodates the burner and has wall surfaces which are free of the heatinsulating layer.

In that case the contents of the water storage vessel are heated by the heat exchanger and the water storage vessel is also directly heated up by the surfaces which define the enlarged portion although said surfaces are relatively small. As a result, the contents of the 5 heat storage vessel will be heated more quickly.

The emission of pollutants can be reduced further in an embodiment in which the burner comprises a premixing burner having a preceding mixing chamber, which is connected to a gas supply line and an air supply line, and said lines contain throttle valves, which are controlled by a common control device. Emission of pollutants may be yet further reduced if an additional air supply pipe leading to the outside of a building is provided for a supply of additional air and surrounds a flue gas pipe, which extends downstream of the flame tube and also leads to the outside, the burner is connected to the additional air supply pipe by a communicating line, and an exhaust gas fan is accommodated in the exhaust gas pipe. 20 These measures permit greater control of the burner and, as a result, a substantial decrease of the emission of pollutants. The efficiency can be increased if a flue gas pipe, which extends downstream of the flame tube and leads to the outside, accommodates a flue gas heat exchanger, which precedes the heat exchanger accommodated in the flame tube in the water path and is connected to a return line of the room-heating system. In that case, flue gases can be utilised to preheat the room-heating water which flows in the heat exchanger that is accommodated in the flame tube so that the efficiency of the water storage vessel is improved.

Preferably, a frusto-conical drain ring is provided, which defines an annular gap with a line which extends therethrough and connects the flue gas heat exchanger and the heat exchanger accommodated in the flame tube, said drain ring tapers downwardly, a funnel connected to a drain line is disposed below the said drain ring, and the line is formed like a siphon over the opening of the said funnel.

As a result, the condensate formed in response to a very substantial cooling of the combustion gases can be drained in a simple manner and an ingress of such water into the flame tube can be avoided.

Advantageously, an exhaust gas pipe is provided downstream of the flame tube, which exhaust gas pipe at least in part is surrounded by an additional air supply pipe leading to the outside of a building, in which that portion of the flue gas pipe which is surrounded by the -additional air supply pipe is provided with fins, and in which the additional air supply pipe is connected by a communicating line, to ventilating passages serving to' ventilate rooms, preferably through an interposed fresh air fan, and to exhaust air passageways.

As a result, the air-conducting system of the water storage vessel can also be used for room heating and the inflowing additional air will be heated by the fins of the flue gas pipe.

Preferably the communicating line contains an adjustable throttle valve.

It is also possible to provide a common controller for controlling the throttle valve which is disposed in the communicating line connected to the exhaust air passageways and a flue gas fan accommodated in the flue gas line.

This will permit a greater control of the ventilation of the room.

Preferably, the heat exchanger which is accommodated in the interior of the flame tube is provided with a catalytic coating at least in that portion in which its tube temperature is in an intermediate range.

In a preferred embodiment a valve is contained in a communicating line, which connects the outlet of the heat exchanger that is accommodated in the flame tube and the inlet of the pipe coil that is disposed in the heat storage vesself the outlet of the pipe coil is connected by an additional valve to the outlet of the heat exchanger accommodated in the flame tube and the two valves are controlled by the control device.

These measures permit improved operation of the burner-heated storage vessel. For instance, when there is 7 no demand f or hot tap water the room-heating circuit may be heated only by the heat exchanger which is accommodated in the flame tube so that heat losses will substantially be avoided. Besides, tap water can be heated in that case without any problems even when the heating system flow temperature must be maintained at a value which exceeds the upper temperature limit for the heating of the tap water. In that case the valves may be adjusted to supply heat to the room-heating circuit only through the heat exchanger accommodated in the flame tube. Besides, when the flow temperature of the room-heating system is below the upper limit of the temperature in the storage vessel the heat demand for the room- heating water can be met by the storage vessel so that the number of burner cycles may be kept low and the emission of pollutants will thus be decreased. Examples of water storage vessels made in accordance with the present invention are shown in the accompanying drawings, in which: 20 Figure 1 is a vertical sectional view of such a water storage vessel; Figure 2 is a vertical sectional view of a modified construction of the water storage vessel shown in Figure 1; 25 Figure 3 is a vertical sectional view of part of a further modified water storage vessel; and Figure 4 is a vertical sectional view of a further modified water storage vessel.

A water storage vessel 8 shown in Figure 1 contains a centrally disposed flame tube 3, the bottom end of which provides a combustion chamber 2 constituted by an enlarged portion of the flame tube 3. The combustion chamber 2 contains a burner 1, which is controlled by a control device 18 via a control line 42.

The water storage vessel 8 is provided with a heat-insulating layer 21 on its outside peripheral surfaces and on both outside end faces.

In its interior, the water storage vessel 8 contains a pipe coil 7, which surrounds the flame tube 3 and is connected to a heat exchanger. The latter is constituted by another pipe coil 6 which is accommodated in an upper portion of the f lane tube 3 and which is provided with a catalytic coating at least on a portion thereof where the tube temperature is in an intermediate range.

Adjacent to the flame tube 3, the water storage vessel 8 is also provided with a heat-insulating layer 20, by which a heat transfer towards the interior of the flame tube 3 will be substantially prevented whilst the burner 1 is not being used. As a result, only the surfaces defining the combustion chamber 2 are free of a heatinsulating layer, although that region may also be' insulated.

A flue gas pipe 22 is disposed above the flame tube 3 and extends through the top end face 43 to the outside of a building (not shown) through a wall 44. The pipe 22 contains a flue gas fan 23. The flue gas pipe 22 is surrounded by an additional air supply pipe 24, which also extends to the outside of the building (not shown) through a wall 44. The additional air supply pipe 24 communicates through a communicating line 25 with a mixing chamber 26 of the burner 1. A gas line 27 also opens into said mixing chamber 26.

The communicating line 25 contains a throttle valve 28 and the gas line 27 contains a throttle valve 29. The said throttle valves 28 and 29 are adjustable by actuators 62, which are connected to the control device 18 by a line 42.

is The heat exchanger 6 is connected to the return line 45 of a room-heating system 46, which comprises a circulating pump 14 and a conventional by-pass 13, which is connected to a three-way valve 15. The valve 15 is incorporated in the flow line 11 leading to the radiators 12 of the room-heating system 46 and is connected to the pipe coil 7 disposed in the heat storage vessel 8. The three-way valve 15 may be replaced by two solenoid valves.

Tap water is supplied to the water storage vessel 8 through an inlet 9 and leaves the said vessel through an outlet 10, which is provided with a tap 47. The tap water is heated in the interior of the water storage vessel 8 by the water which has been heated by the - heat exchanger 6 and flows in the pipe coil 7.

The burner 1 is controlled in dependence upon the temperature of the tap water in the water storage vessel 8. That temperature is detected by a temperature sensor 16. When a demand f or hot tap water has resulted in a drop of the temperature in the water storage vessel 8, the three-way valve 15 is actuated to short-circuit the heating circuit that includes the by-pass 13. The circulating pump 14 and the three-way valve 15 are controlled by the control device 18, which is connected to said components by control lines 19.

The embodiment shown in Figure 2 dif f ers from that of Figure 1 in that combustion air is supplied from the room in which the equipment is installed. The flue gas pipe 22 contains an additional heat exchanger 30, which is provided with fins and is connected to the return line 45 of the room-heating system.

Upstream of the pipe coil 6 which acts as a first flue gas heat exchanger the water path of the flue gas heat exchanger 30 is connected by a communicating line 31 to the heat exchanger 6 that is accommodated in the flame tube 3. The communicating line 31 extends through and defines the inner periphery of an annular gap 33, the outer periphery of which is defined by a downwardly tapering frusto-conical drain ring 32. Below that drain' ring 32 the communicating line 31 constitutes a siphon and extends laterally past a funnel 35. The latter is positioned directly underneath the gap 33, and which is connected to a drain line 36, which extends out of the flue gas pipe 22 and leads to collecting means 48, which receive the condensate that has been formed. The opening of the drain ring 32 is smaller than the opening of the funnel 35 to ensure that the condensate formed can be collected and drained.

In the embodiment shown in Figure 3 an additional air supply pipe 24 is also provided, which surrounds the flue gas pipe 22. The flue gas pipe 22 is provided on its inside and outside with fins 40, 401, which permit a transfer of heat from the f lue gas to the incoming additional air.

The additional air supply pipe 24 is connected by a communicating line 36, which contains an additional air fan 38, to ventilating passages for air-conditioning a room 48. The corresponding exhaust air passages of that room 48 communicate through a communicating line 37 with the flue gas pipe 22. The communicating line 37 contains a throttle valve 39.

A controller 41 is provided, which is controlled by a sensor 49 for detecting the temperature in the room 48 which is to be air-conditioned. The controller 41 controls the drive means 231 of the flue gas fan 23 and the actuator 42 of the throttle valve 39 through lines 51 and 52 respectively. The sensor 49 is connected by a line to the controller 41, which constitutes a part of the - 12 control device 18.

In the embodiment shown in Figure 4 a draught control device 4 is provided above the flame tube 3 and precedes a flue gas pipe 5, which merges into the flue gas 5 pipe 22 (not shown).

In that embodiment the outlet of the pipe coil 7 is connected to the flow line of the room-heating system, which flow line includes the three-way valve 15. The outlet of the pipe coil 7 is connected by a line 53 to the outlet of the heat exchanger 6, which is accommodated in the flame tube 3. That line 53 contains a solenoid valve 54, which is controlled by the control device 18 via a line 55. The inlet of the pipe coil 7 is connected by a line 56 to a directly preceding further solenoid valve 57, which is also controlled by the control device 18. Upstream of the solenoid valve 57 the line 58 opens into the line 53, by which the outlet of the heat exchanger 6 disposed in the flame tube 3 is connected to the inlet of the pipe coil 7.

The two solenoid valves 54 and 57 permit an optimum adaptation to the current operational requirements. For instance, when the temperature tSp in the storage vessel is below a predetermined lower limit tugr for the temperature in the storage vessel, the burner 1 can be operated by a precedence circuit for heating up the storage vessel. In that case the room-heating system 46 will be short-circuited by the three-way valve 15.

That mode of operation may be continued until the temperature in the storage vessel has reached an upper limit togr. Then the solenoid valve 54 is opened whereas the solenoid valve 57 is kept closed.

In that case a water circuit is established, which leads through the heat exchanger 6 accommodated in the flame tube 3, the solenoid valve 57, the pipe coil 7, the three-way valve 15, the circulating pump 14 and back to the heat exchanger 6 so that the contents of the storage vessel 8 can be heated up quickly.

When there is no heat demand for room heating or for tap water, the burner 1 will not start until the temperature tSp has dropped below the lower limit for the temperature in the storage vessel.

Two modes of operation may be adopted during the room-heating period, in which heat is required for room heating:

1. The flow temperature tv which is required in the line 11 in accordance with the heating curve exceeds the upper limit togri which is adjusted at the set point adjuster 61 for the temperature in the storage vessel.

In that case the solenoid valve 57 is opened by the control device 18 and the solenoid valve 54 is kept closed so that the storage vessel 8 and specifically the pipe coil 7 is short-circuited and the heating circuit is supplied only by the heat exchanger 6, which is accommodated in the flame tube 3.

2. The flow temperature tv is lower than the upper limit togr of the temperature in the storage vessel.

In that case the solenoid valve 57 is kept closed and the solenoid valve 54 is kept open so that a water circuit is established, which leads through the heat exchanger 6, the pipe coil 7, the three-way valve 15, the room-heating system 46 and the circulating pump 14. The heat required for room heating is initially supplied by the storage vessel 8. The water in the storage vessel 8 will cool as a result. In low-temperature roomheating systems the burner 1 will not be started until the temperature tSp in the storage vessel is below the lower limit tugr,, which is also adjusted by the set point adjuster 61. In case of higher set points for the f low temperature a signal or a function (e.g., for the lower limit tugr) of the temperature in the storage vessel is required for the premature reheating of the storage vessel.

Claims

1. A water storage vessel which is heated by a burner when in use, through which vessel a f lame tube extends and which is provided on its outside surfaces with heat insulation and is provided in its interior with a pipe coil f or preparing room-heating water, in which a heat exchanger which communicates with the pipe coil in the interior of the water storage vessel is accommodated in the interior of the f lame tube, and the water storage vessel is provided with heat insulation adjacent to the flame tube.

2. A water storage vessel according to claim 1, in which the heat exchanger which is accommodated in the flame tube is constituted by a pipe coil.

3. A water storage vessel according to claim 1 or claim 2, in which the flame tube at its bottom end, which faces the burner, comprises an enlarged portion, which serves as a combustion chamber and accommodates the burner and has wall surfaces which are free of the heatinsulating layer.

4. A water storage vessel according to any preceding claim, in which the burner comprises a premixing burner having a preceding mixing chamber, which is connected to a gas supply line and an air supply line, and said lines contain throttle valves, which are controlled by a common control device.

- 16

5. A water storage vessel according to any preceding claim, in which an additional air supply pipe leading to the outside of a building is provided for a supply of additional air and surrounds a flue gas pipe, which extends downstream of the flame tube and also leads to the outside, the burner is connected to the additional air supply pipe by a communicating line, and an exhaust gas fan is accommodated in the exhaust gas pipe.

6. A water storage vessel according to any 10 preceding claim in which a flue gas pipe, which extends downstream of the flame tube and leads to the outside, accommodates a flue gas heat exchanger, which precedes the heat exchanger accommodated in the flame tube in the water path and is connected to a return line of the room-heating system.

7. A water storage vessel according to claim 6, in which a frusto-conical drain ring is provided, which defines an annular gap with a line which extends therethrough and connects the flue gas heat exchanger and the heat exchanger accommodated in the flame tube, said drain ring tapers downwardly, a funnel connected to a drain line is disposed below the said drain ring, and the line is formed like a siphon over the opening of the said funnel.

8. A water storage vessel according to any preceding claim in which an exhaust gas pipe is provided downstream of the flame tube, which exhaust gas pipe at least in part is surrounded by an additional air supply pipe leading to the outside of a building, in which that portion of the flue gas pipe which is surrounded by the additional air supply pipe is provided with fins, and in which the additional air supply pipe is connected by a communicating line, to ventilating passages serving to ventilate rooms, preferably through an interposed fresh air fan. and to exhaust air passageways.

9. A water storage vessel according to claim 8 in 10 which the communicating line contains an adjustable throttle valve.

10. A water storage vessel according to claim 9, in which a common controller is provided for controlling the throttle valve which is disposed in the communicating line connected to the exhaust air passageways and a flue gas fan accommodated in the flue gas line.

11. A water storage vessel according to any preceding claim, in which the heat exchanger which is accommodated in the interior of the flame tube is provided with a catalytic coating at least in that portion in which its tube temperature is in an intermediate range.

12. A water storage vessel according to any preceding claim, in which a valve is contained in a communicating line, which connects the outlet of the heat exchanger that is accommodated in the flame tube and the inlet of the pipe coil that is disposed in the heat storage vessel, the outlet of the pipe coil is connected by an additional valve to the outlet of the heat exchanger accommodated in the f lame tube and the two valves are controlled by the control device.

13. A water storage vessel substantially as described herein with reference to and as shown in any one of Figures 1 to 4 of the accompanying drawings.