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Title:
HOT-WATER HEATER WITH INTEGRATED AUTOMATIC MIXING OF WATER FOR LOW-TEMPERATURE CORROSION PROTECTION
Document Type and Number:
WIPO Patent Application WO/2017/190716
Kind Code:
A2
Abstract:
A hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection, comprising a water inlet (15) opening into the heater manifold (18) wherein the manifold contains at least one mixing opening (14), which opens into the heater water space (2). The heater water space (2) is reduced between the water inlet (15) and the water outlet (10) to at least one flow-through opening (16) with a water flow regulator (17). The water space may also contain a partition with at least one flow-through opening and a water flow regulator.

Inventors:
HALADA MICHAL (CZ)
Application Number:
PCT/CZ2017/000035
Publication Date:
November 09, 2017
Filing Date:
May 04, 2017
Export Citation:
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Assignee:
BLAZE HARMONY S R O (CZ)
HALADA MICHAL (CZ)
International Classes:
F24H1/24; F24H9/40
Attorney, Agent or Firm:
PRIKRYL, Jaromir (CZ)
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Claims:
Hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection.

CLAIMS

1. A hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection, comprising a water inlet (15) opening into the manifold (18), wherein the manifold (18) contains at least one mixing opening (14) which opens into the heater water space (2) characterized in that the water space (2) of the heater is reduced between the water inlet (15) and the water outlet (10) to at least one flow-through opening (16) with a water flow regulator (17).

2. The hot-water heater according to claim 1, characterized in that the water space (2) of the heater contains a partition (6) containing at least one flow-through opening (16) with a water flow regulator (17).

3. The hot-water heater according to claim 1 or 2, characterized in that the flow regulator (17) consists of a paraffin bottle (24), in which a piston (23) linked with a flap (22) is placed, wherein the paraffin bottle (24) is placed in the heater water space (2).

Description:
Hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection.

Field of the invention

The present invention relates to the hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection, where the heat-carrying water is mixed automatically inside the heater so that the heat-transfer surfaces have a higher temperature than the dew point of flue gases, which provides protection against low- temperature corrosion. The invention principally relates to hot-water solid-fuel heaters connected with a storage tank (accumulating tank)

Background of the invention

The operation of hot-water heaters, in particular boilers or stoves with a water heat exchanger, is associated with an undesirable phenomenon, low-temperature corrosion of heat-transfer surfaces. During this chemical reaction, the heater wall material reacts with oxygen, which causes gradual thinning of the heater walls. In fact, heat-transfer surface corrosion determines the service life of the heater. The ability to resist low-temperature corrosion is therefore an essential feature of the heater.

Flue gases produced during common fuel combustion (wood, coal, oil, gas, etc.) contain water vapour. If water vapour condensates on heat-transfer surfaces of the heater, the intensity of corrosion is many times higher.

Water steam condensation occurs if the temperature of heat-transfer surfaces is lower than the dew point of flue gases. The value of the dew point of flue gases is 40-60°C depending on the type of fuel. To avoid vapour condensation on heat-transfer surfaces of the heater and thereby low-temperature corrosion, hot-water heaters or hot-water heater connections contain various measures and methods ensuring that the heat-transfer surface temperature is higher than the dew point of flue gases.

One of the known solutions is to connect a forced short-circuit heater with water temperature regulation. This solution is used for a vast majority of today's solid fuel heaters. The solution essentially consists in that the inlet and the outlet pipes of the heater are interconnected by a short-circuit pipe. This pipe removes a part of water leaving the heater, which is mixed with the water entering the heater. The water flow in the short- circuit pipe is ensured by a pump. The amount of water in the short-circuit pipe is usually controlled by an automatic three-way mixing valve to have the temperature of water entering the heater higher than the dew point of flue gases. The most commonly used automatic mixing valve employs the so-called paraffin thermostat consisting of a paraffin bottle and a piston. When the required temperature such as 60°C is reached, paraffin melts, expands and pushes the piston out. The piston is connected with a flap controlling the amount of flowing water. The backward movement is ensured by a spring.

One drawback of the described solution is the necessity to connect a short-circuit pipe, install a pump and a mixing valve, which brings about investment and operating costs, complex installation, and increases the risk of failures. Another drawback is the space required and the heat loss from the installed equipment surface.

This solution has additional drawbacks for heaters connected with a storage tank (accumulating tank). In the event of power failure, the automatic mixing valve closes the water supply to the heater thus preventing the transfer of heater's residual output by force of gravity circulation to the tank. To avoid the risk of heater overheating, another device should be installed. For example, it is a mixing valve by-pass pipe with electrically operated valve, or a cooling loop connected in the heater through a special thermostatic valve to an independent source of pressure water, or a backup power source to drive the pump. The necessity for another device increases the acquisition cost even more, makes the installation more complicated and increases the risk of failures.

A heater solution with optimized inlet water supply is also known. This solution essentially consists in that the water is supplied to the central or the upper part rather than to the lowest part of the heater water space. The inlet water is therefore mixed with the already heated water in the heater, so the heat-transfer surfaces do not come into contact with the coolest inlet water. Many heaters also have rectifying channels or rails in their water spaces so that the heat-transfer surfaces most exposed to corrosion are in contact with preheated water. Some variant of the solution mentioned above is used in 10-20% of current heaters. One drawback of this solution is that it is not always able to provide sufficient water temperature in the heater, and is therefore not able to ensure full protection against low-temperature corrosion. In addition, the ability of gravity circulation is more or less limited, especially when connected with the storage tank at the same height level as the heater.

Therefore, this solution is used solely as a supporting measure, which is combined with another measure.

Another known solution is a heater with optimized inlet water distribution. According to EP 0693 661, for example. In this solution, the water inlet opens into the manifold containing one or more mixing openings, wherein the mixing openings open into the heater water space. The water flowing through these openings mixes with water in the water space of the boiler. Cooling of the heat-transfer surfaces of the heater is thus minimal. One drawback of this solution is that this method of protection does not work for every flow-rate and temperature of water. It is adequate in combination with another measure for gas or oil heaters. It is insufficient for solid fuel boilers and it is not known to have been used in such heaters.

Another known solution is to increase the inlet water temperature through external measures. This method essentially consists in that the heater is not connected with a short circuit and a mixing device, but a measure is used to ensure that the temperature of water entering the heater does not drop below the dew point of flue gases. For example, the circulator pump is switched on by the switching thermostat only when the temperature of water leaving the heater reaches 60°C, or heater elements are sized and the output is maintained so that the temperature of return water is above 40-50°C during operation. One common drawback of these solutions is that they do not ensure sufficient heat-transfer surface temperature in all modes of operation and for all heater surfaces. Therefore, these methods provide only partial protection against low-temperature corrosion.

Another known solution is to use a heater with multiple-layer heat-transfer surfaces. This solution essentially consists in that the water-cooled heat-transfer surfaces of the heater are protected by another wall, usually of steel sheet, so that they are not in direct contact with flue gases. During operation, the additional wall is heated by the flue gases or flame to a considerably higher temperature than the dew point of flue gases. The additional wall transfers heat to the water-cooled walls mostly by radiation. The space between the walls is usually primed with combustion air. Multiple-layer heat-transfer surfaces are used by most gasification boilers to protect the stoking chamber (the so-called hot-chamber system). It is not used for other heat-transfer surfaces because it greatly reduces the ability to cool the flue gases. Therefore, it does not provide a comprehensive heater protection, which is a major drawback of this method.

Each of the known solutions has its advantages and drawbacks. A solution that would meet all of the following requirements is not known, though:

- To work at every temperature and flow-rate of return water;

- To allow for the gravity circulation of water with a storage tank located at the same height level as the heater;

- Not to require an electrical power supply;

- Not to require the installation of a short circuit with a mixing valve, etc.

- To be simple, cheap to manufacture and reliable.

Object of the invention

The drawbacks of the known solutions described above are eliminated completely or to a considerable extent by the hot-water heater with integrated automatic mixing of water for low-temperature corrosion protection, comprising a water inlet opening into the heater manifold, wherein the manifold contains at least one mixing opening, which opens into the heater water space. The invention essentially consists in that the heater water space is reduced between the water inlet and the water outlet to at least one flow-through opening with a water flow regulator on the basis of water temperature.

According to the first preferred embodiment, the heater water space contains a partition containing at least one flow-through opening with a water flow regulator on the basis of water temperature.

It is preferred that the flow regulator consists of a paraffin bottle, in which a piston linked with a flap is placed, wherein the paraffin bottle is placed in the heater water space.

The advantage of the heater according to the invention is that the heater heat- transfer surfaces, which are in contact with flue gases, have a temperature higher than the dew point of flue gases, which prevents low-temperature corrosion. At the same time, it has the following advantages:

- It works at every temperature and flow-rate of return water; - It allows for the gravity circulation of water with a storage tank located at the same height level as the heater;

- It does not require an electrical power supply;

- It does not require the installation of a short circuit with a mixing valve, etc.

-The solution is simple, cheap to manufacture and reliable.

Summary of figures in drawings

The invention is illustrated in the attached drawings which represent:

FIG. 1 - Side view of the heater section with a partition in the water space and a flow regulator in this partition

FIG.2 - Front view of the heater section with a partition in the water space and a flow regulator in this partition

FIG.3 - Detail of the regulator from FIG. 1

FIG.4 - Side view of the heater section with the flow regulator at the heater inlet

FIG.5 - Front view of the heater section with the flow regulator at the heater inlet

FIG.6 - Detail of the regulator from FIG.4

Description of embodiments

A description of hot-water heater embodiment - lump wood-fire gasification boiler with a partition in the water space and a water flow regulator in this partition, Figs. 1 to 3.

In its upper part, the boiler contains a stoking chamber L whose walls are surfaced with an inner shell 12, which is lined in the lower part by ceramic lining 19. Between the inner shell 12 and the heat-transfer surfaces there is an air gap 13. In the lower part of the boiler there is an afterburner chamber 9 enclosed in ceramic lining 19. The stoking chamber 11 and the afterburner chamber 9 are connected by an opening - a nozzle3. The afterburner chamber 9 is connected with the flue-gas heat exchanger 5 comprised of several vertical channels, which open into the flue gas outlet 1 in the upper part. In about 114 of the boiler height, the water space 2 of the boiler contains a manifold 18, which is a rectangle-based space, bordered by the bottom sheet 8 in the lower part, the bottom 4 of the stoking chamber 1 in the upper part, and the side walls 7 in the vertical direction. One of the side walls 7 of the manifold 18 includes the water inlet 15. The side walls 7 and the bottom sheet 8 of the manifold 18 contain mixing openings 14 which open into the water chamber 2 of the boiler. In the described embodiment, all mixing openings 14 are the same and have a round shape with a diameter of 7 mm, and are about 100 in total. The layout of individual mixing openings 14 is proportional to the heat input intensity distribution - most of the mixing openings 14 are located in the bottom sheet 8 of the manifold 18 around the opening - nozzle 3, because they open into the part of the water space 2 with heat-transfer surfaces of the afterburner chamber 9, where the heat input is the most intense.

In about 114 of the height, just above the manifold 18, the water space 2 is divided by the partition 6. The water space 2 under the partition 6 is surrounded by heat-transfer surfaces of the afterburner chamber 9 and the first part of the flue-gas heat exchanger 5^ which are heat-transfer surfaces with a high input intensity. The water space 2 above the partition 6 is, conversely, surrounded by heat-transfer surfaces of the stoking chamber H and the central and the upper part of the flue-gas heat exchanger 5, which are heat-transfer surfaces with low output intensity. In the front boiler wall, the partition 6 has a flow-through opening 16 equipped with a water flow regulator 17 on the basis of water temperature in the water space under the partition 6. In the present embodiment, the flow regulator 17 is a paraffin thermostat with the opening temperature 60°C, consisting of a paraffin bottle 24, in which there is a piston 23 connected with a flap 22. The flap 22 is pushed (downwards) by a return spring 21. The paraffin bottle 24 is located in the water space 2 under the partition 6 in the bed 25.

The function of the described embodiment is as follows:

Combustion air is fed to the boiler, and the combustion air flows through the air gap 13 and enters the fuel layer in the stoking chamber 11, where primary combustion (gasification) takes place. The produced gases flow through the opening - nozzle 3, where combustion air firing the gases is fed to the gases. The gases flow to the afterburner chamber 9, where they burn down. The flue gas produced flows behind the ceramic lining 19 to the flue-gas heat exchanger 5, and from there to the flue gas outlet 1 The primary combustion in the stoking chamber 1 releases heat that heats the inner shell 12, which further heats, mostly by radiation, the heat-transfer surfaces surrounding the stoking chamber 11 The flame and flue gases transfer the heat to the heat-transfer surfaces surrounding the afterburner chamber 9 and the flue-gas heat exchanger 5, and the heat-transfer surfaces transfer the heat to the water in the water space 2 of the boiler.

The heat-transfer fluid - water at 20°C, for example, flows through the water inlet 15 to the manifold 18, and from there, through the mixing openings 14^ it enters the water space 2 under the partition 6 where water at about 60°C is found. As the mixing openings 14 are small, the water jet coming from them quickly mixes with the water in the water space 2 under the partition 6. As the layout density of mixing openings 14 corresponds with the input intensity of individual parts of the water space 2 under the partition 6, the temperature of water in the entire volume of the water space 2 under the partition 6 is about the same. The water then flows through the flow-through opening and washes the paraffin bottle 24 of the water flow regulator 17. If, for example, the combustion output grows, thus also increasing the input to the heat-transfer surfaces, the temperature of water in the water space 2 of the boiler increases, and the temperature of water washing the water flow regulator 17 rises above 60°C. As a result, the paraffin melts, increases its volume and pushes out the piston 23, which opens the flap 22 by its upward movement. This increases the water flow through the flow-through opening 16, thus also increasing the cold inlet water supply from the manifold 18 to the water space 2 under the partition 6^ which decreases the temperature of water in the boiler. In the opposite situation, when the combustion output is decreased, the temperature of water in the water space 2 of the boiler drops, the paraffin solidifies, the piston 23, under the return spring 21 pressure, is retracted to the paraffin bottle 24 and closes the flap 22 by its downward movement. This decreases the water flow through the flow-through opening 16, thus also decreasing the cold water supply from the manifold 18 to the water space which increases the temperature of water in the boiler. In the manner described above, the water flow regulator 17 maintains a temperature of 60°C at the flow-through opening 16 and thereby also in the water space 2 under the partition 6.

The water flowing through the flow-through opening 16 then moves through the water space 2 of the boiler above the partition 6, and the heat-transfer surfaces of the stoking chamber 11 and of the central and the upper part of the flue-gas heat exchanger 5 heat it to 75°C, for example. The water heated in this way then flows through the water outlet 10 from the boiler.

The water space 2 under the partition 6 surrounds the heat-transfer surfaces, which transfer about 70% of the overall heat input to the water, which is why the water here heats from 20°C, for example, to 60°C, which is by 40°C. While the water space 2 above the partition 6 is surrounded by the heat-transfer surfaces with a lower input intensity, which transfer about 30% of the overall input to the water, which is why the water here heats by 15°C, for example, which is from 60°C to 75°C. If water at 40°C, for example, flows to the boiler, it heats in the water space 2 under the partition 6 to 60°C again, which is by 20°C. In the water space 2 above the partition 6, it then heats by about 5°C, which is to 65°C.

One advantage of this embodiment is that thanks to the partition 6, it allows using a simple water flow regulator 17 with a temperature sensor (paraffin bottle 24) at the same place where the flow-through opening 16 is located. Another advantage of this embodiment is that it may have two water inlets 15 with a simple design, on the right-hand side and the left-hand side of the boiler, for example, which increases the variability of connection.

A description of hot-water heater embodiment - lump wood-fire gasification boiler with a water flow regulator at the boiler inlet, Figs. 4 to 6.

This embodiment is the same as the preceding one except that the water space 2 of the boiler does not contain any partition 6, and the flow-through opening 16 with the water flow regulator 17 is behind the water inlet 15. In the present embodiment, the paraffin thermostat is also used as a water flow regulator 17, except that the paraffin bottle 24 is placed in the water space 2 under the manifold 18 so that the piston 23 goes through the bottom sheet 8 of the manifold 18.

The function of the second embodiment is practically identical to the first embodiment.

One advantage of this embodiment is that it does not have to have any partition 6. However, it requires a flow regulator 17 with temperature sensor 24 - a paraffin bottle located elsewhere than the flow-through opening 16. The piston 23 must therefore move through the wall, which makes the water flow regulator 17 technically more demanding. Another limitation of this embodiment is that the boiler has only one water inlet 15.

The heater embodiments may vary in the type of the heater used - the design can be used practically in any type of heater that heats water - boilers, stoves or fireplace inserts with hot-water heat exchanger, etc.

The shape and location of the manifold 18 may also be different. It may take the form, for example, of a toroid, arc, etc., depending on the heater design type.

Also the mixing openings 14 may be different; they may take the form of a rectangle or an elongated slot.

There may be multiple flow-through openings 16 in different heater designs, wherein not all of them have to contain the water flow regulator 17 - openings with the water flow regulator 17 may provide a minimal constant flow to remove residual heat from the heater when the fuel bums down (when there is no risk of corrosion any more), for example, etc.

The water flow regulator 17 may also vary, for example, by using an oil or bimetallic thermostat, or otherwise automatically controlled valve or flap instead of the paraffin thermostat.

The partition 6 may be in a different part of the water space 2 of the heater, depending on the heater design.

A design without the partition 6 is also possible, wherein the water outlet 10 or the water inlet 15 may be used as a flow-through opening 16.

The regulator may have a separate detection element (sensor) and an active element (flap actuator), a remote-bulb thermostat, for example.

List of reference signs

1. Flue gas outlet

2. Water spacer

3. Opening - nozzle

4. Bottom

5. Rue-gas heat exchanger

6. Partition

7. Side wall

8. Bottom sheet

9. Afterburner chamber

10. Water outlet

11. Stoking chamber

12. Inner shell

13. Air gap

14. Mixing opening

15. Water inlet

16. Flow-through opening

17. Water flow regulator

18. Manifold

19. Ceramic lining

20. Heat insulation

21. Return spring

22. Flap

23. Piston

24. Paraffin bottle

25. Bed