Field of the Invention

The invention relates to a deaerator device for removing gasses from liquids, particularly for removing dissolved gasses, such as air, from water in a water heating system.

Background to the Invention

Water heating systems are employed in both domestic and industrial environments for both supplying hot water and for heating purposes. Water heating systems normally employ a primary heater, often in the form of a gas-fired or oil-fired boiler. Where the water heating system is used for heating a building, water is heated at the boiler and is then dispersed to radiators or other heat emitting elements, which are normally fed with water on a closed loop system.

The water used in such heating systems often contains a significant proportion of air dissolved therein, which can have a detrimental effect on the performance and efficiency of the heating system. Dissolved oxygen in feedwater will cause serious corrosion damage in a boiler by attaching to the walls of metal piping and other equipment and forming oxides, such as rust. Additionally, dissolved carbon dioxide combines with water to form carbonic acid that may cause further corrosion. Therefore, it is desirable to reduce the amount of air dissolved in the water to ensure a more efficient heating system, thereby reducing the amount of fuel required to provide heat to a building.

Previous arrangements have been proposed, such as that disclosed in EP2589885 (Whetstone et al), which describes a deaeration device comprising a vessel having a water-receiving chamber, wherein the chamber has an inlet, and outlet and a vent. The vent in that document is a conduit having an inlet located within the chamber and that is submerged in the water of the deaeration device, when in use. The vent outlet is located externally of the chamber. Summary of the Invention

Accordingly, the present invention is directed to a deaerator device comprising a main chamber having a top surface and arcuate walls tapering inwardly to a narrower bottom surface, the main chamber being provided with a water inlet in fluid communication with a water outlet, wherein: the water inlet is substantially tangential to the main chamber; and the water outlet is arranged at the lower end of the main chamber; wherein the top surface of the main chamber has at least one air outlet aperture; wherein water flow through the main body is unencumbered by obstacles; and wherein the internal top surface of the main chamber is substantially flat.

Thus, the present invention differs from the prior art by removing the vent conduit, or “dip tube”, of previously proposed devices from the flow path of the water, which, in turn, allows for a more efficient release of air and other gasses from the water passing therethrough. This goes against conventional teaching. The use of a dip tube in the flow path of the water results in the water flow being impeded, thereby reducing the speed of flow of the water and delaying or preventing the formation of an internal vortex within the deaeration device.

The deaerator device of the present invention comprises an air outlet aperture, or vent, to allow the release of air that is removed from the water passing through the deaerator device; however, it is preferable to remove the dip tube completely from the device. Alternatively, it may be preferred to shorten the dip tube to a length at which it does not interfere with the flow of the water through the deaeration device.

The present invention is provided with a substantially flat internal top surface. It has been observed that use of a domed, or ‘egg-shaped’ internal top surface can lead to the expulsion of water from within the main chamber, through the air outlet; however, where a flat internal top surface is provided, whilst air is vented through the air outlet, the risk of water passing therethrough is significantly reduced and, in some arrangements, prevented. Whilst there might be a slight increase in the space between the water inlet and the top of the main chamber, the majority of the top of the main chamber should, preferably, be substantially flat. The gap between the inlet and the top of the main chamber should be less than half of the diameter of the inlet and, preferably, less than a quarter of the diameter of the inlet, with a particularly advantageous size of less than an eighth of the diameter of the inlet.

In one arrangement, the air outlet comprises an air outlet conduit. The air outlet may be in the form of an air outlet conduit that extends from, or through, the top surface of the main chamber.

In a preferred arrangement, a first end of the air outlet is substantially flush with the internal surface of the top surface of the main chamber. Therefore, the air outlet does not extend a significant length into the main chamber, but stops at, or adjacent to, the internal surface of the top of the main chamber. This ensures that the flow of water through the device is not slowed or impeded by the air outlet conduit.

It has been observed that the use of a parallel-walled dip tube causes turbulence within the flow of water through the deaerator device, which reduces its efficiency. Therefore, where an air outlet conduit, or ventilation conduit, does extend into the main chamber and towards the water outlet thereof, it is advantageous that the diameter of the conduit increases in the direction towards the water outlet, preferably in a non-linear manner.

Thus, the conduit may be flared, preferably with curved walls, so that the end distal from the top surface of the main chamber has a larger diameter than the end proximal the top surface of the main chamber. The flared conduit reduces the risk of the conduit from disrupting the formation of a vortex in the water, during operation. Whilst one might consider making the diameter of the deaeration device larger to accommodate an air outlet conduit with parallel walls, the present invention may, instead, employ a flared conduit. This allows a smaller diameter device to be employed, which accelerates the water passing therethrough faster, thereby creating a bigger pressure drop in the centre of the vortex.

It is preferable that the air outlet is provided with a one-way valve. This reduces the risk of the back-flow of air into the device. It is particularly advantageous that the water outlet is substantially linear, although it will be appreciated that a slight curve therein. Furthermore, the water outlet is, preferably, at least 200mm long and, more preferably around 300mm long, although it may extend to 600mm, which provides a sufficiently long outlet to ensure that the vortex that is created in the main chamber has sufficient length to extend down the outlet. Having a substantially linear water outlet that leads from the deaerating device to the heating system to which it is connected, and preferably a water outlet that is at least 200mm long, provides sufficient space for the vortex to form and to degas the water effectively. In many installations the water outlet is curved or connected to a curved element, such as an elbow, which reduces the efficiency of the device, particularly as the curve causes turbulence, destabilises the vortex and increases the working pressure. For clarity, it will be appreciated that the water outlet may be integrally formed with the deaerator device, or it may be attached thereto. Hitherto, it has been the case that installers have not appreciated that a 90 degree elbow raised the operating pressure in that locality and that erodes the difference in the respective pressures at the centre and the outside circumference of the vortex. Furthermore, it is preferable to have a maximum of one elbow joint of around 90 degrees between the heat source and the deaerator device.

Having a maximum of one elbow therein makes the arrangement more efficient.

In a preferred embodiment, the deaerator device comprises steel and it may be that the device is cast in steel. The use of steel allows the device to metabolise dissolved oxygen, thereby reducing the amount of oxygen in the deaerated water and allowing nitrogen to float freely from the deaerator device by passing the water through the vortex. Whilst it is common practice to simply position an automatic air vent at the highest point in a system, it is more efficient and results in less corrosion to employ the deaerator device of the present invention. Thus, by passing the water through the aerator device of the present invention, the decrease in pressure at the centre of the vortex makes the bubbles of nitrogen to sufficiently large enough to gain buoyancy and therefore to float free against the flow of water. Such a system as set out in the present invention has been shown to achieve a very low level of dissolved air.

It is advantageous that the air outlet is substantially coaxial with the water outlet. It should be noted that, unlike present devices, the deaerator device of the present invention does not require annual maintenance.

It is preferable that the inlet to the main chamber is positioned wholly in the top third of the main chamber, and, in some arrangements, it may be arranged wholly in the top quarter of the main chamber. Positioning the inlet at such a position increases the speed with which the water passes around the internal surface of the main chamber. By arranging the inlet to the main chamber in this manner, the space available for the above the inlet is significantly reduced, thereby reducing the likelihood of the water moving away from the water outlet at the base of the main chamber. The result of this is that the water moves downwards through the main chamber more quickly, thereby speeding up the deaeration process. This improvement over the existing technology increases the efficiency of the device. Additionally, where the main chamber has a substantially flat top, the space available above the inlet in the main chamber is reduced. The water entering the device flows around the internal surface of the main chamber and creates a vortex. Thus, the water is driven towards the outlet and gas is removed from the water during the process.

The air outlet, which may be in the form of a tube that extends from the top of the main chamber into the main chamber and towards the outlet. The tube may extend to a position that is less than a third down the main chamber and, preferably, the tube extends to a position less than half of the axial length of the main chamber. This allows the tube to extend to a position to which it does not interfere with the flow of the water passing through the device, during normal operation. Thus, the water flow is unencumbered by the tube.

Hitherto, engineers in the field have been of the thinking, and are taught, that an automatic air vent placed at the highest point in the system will effectively de-aerate the system and prevent corrosion; however, in such an arrangement, heating systems still corrode, due to the action of nitrogen within the system, which, when precipitated out of solution form bubbles that are too small to have natural buoyancy. Thus, in the present invention, by creating a natural pressure drop within the main chamber, or body, of the device, the nitrogen bubbles are able to form in a size that is large enough to float free against the flow of water and thus deaerate in a very effective way from within the centre of the vortex created by the device. Therefore, the present invention is more efficient and reduce the risk of corrosion when compared with existing devices.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a first arrangement in accordance with the present invention; Figure 2 shows a second arrangement in accordance with the present invention; Figure 3 is a graph showing temperature and dissolved oxygen in a deaeration device; and

Figure 4 is a further embodiment of the present invention.

Detailed Description of Exemplary Embodiments

Figures 1 and 2 show an aeration device 10 that comprises an internal main chamber 12 that is provided with an inlet 14 that is arranged substantially perpendicularly to the main chamber 12 and at the top thereof. At the lower end of the main chamber 12, there is a water outlet 16 and the water outlet 16 is in fluid communication with the inlet 14 via the main chamber 12.

At the upper end of the main chamber 12, there is a top surface 18 having an internal face 20 and an external face 22. The internal face 20 of the top surface 18 is substantially flat. An air outlet 24 is located in the top surface 18 and extends therethrough, thereby allowing air to flow from the inside of the main chamber 12 to the outside thereof.

The main chamber 12 is shaped so that its internal surface is contoured to the shape of a lower half of a prolate spheroid, or part ovoid shape, which is to say that it narrows from the inlet 14 to the outlet 16 in an arcuate fashion. In this manner, the curved internal wall of the main chamber 12 has a non-constant radius of curvature which progressively decreases in a direction from the inlet towards the outlet, the vessel having radii of curvature which are positive, taken with reference to a central axis of the deaerator device 10 located within the chamber main chamber 12.

In the embodiment shown in the accompanying figures, the deaerator device 10 may have a maximum outer diameter of 240mm and the thickness of the sidewall 26 may be between 0.75mm and 4mm, but preferably around 1.5mm to 3mm, so the maximum internal diameter of the vessel 16 (and thus the maximum diameter of the main chamber 12) is around 117mm. In the deaerator device 10 shown in the figures, the main chamber 12 has into six sections in planes that are perpendicular to a main longitudinal axis of the device 10. The deaerator device 10 may have a length L between the inlet 14 and the outlet 16 of 110mm, and so lengths LI to L5 would be, 18.33mm; 36.67mm; 55mm; 73.33mm; and 91.67mm, respectively.

When installed, water enters the main chamber 12 through the inlet 14 and, due to the inlet 14 being substantially tangential to the main chamber 12, the water is directed onto the internal wall of the main chamber 12. Due to the shape of the internal surface of the main chamber 12 and under the force of gravity, the water is directed towards the outlet 16 whilst being accelerated. As the water is rotating around the outside of the main chamber 12, and as the diameter of the chamber decreases towards the outlet 16, a vortex is formed in the water. Due to the water being unencumbered by a dip tube or other obstacles, the vortex is able to form more readily. Thus, as the water rotates and gasses are released therefrom, due to the pressure differential created, and they pass upwards to the air outlet 24. Because the vortex forms quicker than when a dip tube encumbers the flow of water, the present invention results in more efficient degassing of the water and reduces the lag time between starting the water flow and the degassing taking effect, compared with existing systems.

In one arrangement, the volume of the deaerator device 10 is provided as a proportion of the total volume of water in the system in which it is fitted is around 1%, and, preferably, about 0.5%. Such a percentage of the overall water in the system may be beneficial in respect of the performance of the deaerator device 10. Thus, the volume of the main chamber 12 of the deaerator device 10 may be around 400ml. In the arrangement shown in Figure 2, a ventilation conduit 30 that extends through the top surface 18 of the main chamber 12, thereby providing a ventilation passage for the gasses that are removed from the water. The ventilation conduit 30 extends from the top surface 18 of the main chamber 12 towards the outlet 16; however, it extends to a position within the main chamber 12 wherein it does not interfere with the passage of water through the deaerator device 10.

The ventilation conduit 30 of the deaerator device 10 is shaped so that its internal diameter, through which the gasses pass, increases in a direction towards the outlet 16, thereby having a diameter adjacent the top surface 18 of the main chamber 12 that is less than the diameter of the end of the ventilation conduit 30 that is distal therefrom. In the arrangement in Figure 2, this increase in internal diameter is non-linear, thereby resulting in a flared conduit. One purpose of the non-linear curvature of the internal surface of the ventilation conduit 30 is to prevent the disruption of the forming of the vortex.

The ventilation conduit 30 is fitted to the top surface 18 of the main chamber 12 by way of a threaded connector 32 positioned on the ventilation conduit 30 that engages with a corresponding connection in the top surface 18. An internal threaded connection 34 may be provided within the ventilation conduit 30 to receive a further air outlet conduit (not shown).

Figure 3 shows the temperature and dissolved oxygen in a deaeration device constructed from steel. Although no heat source was provided, the temperature gradually increased from 20 degrees Celsius to 31 degrees Celsius over 150 minutes. The level of dissolved oxygen decreased from 8.6ppm to lOppb in 75 minutes, which is considered to be deaerated water, and the dissolved oxygen concentration was undetectable (less than lppb) after 150 minutes, thereby indicating that the dissolved oxygen was effectively removed completely. The corrosion of metals and steel in deaerated water is negligible. Thus, where the deaeration device is constructed from steel, it can remove dissolved oxygen from the water. As the device heats the water as the water passes therethrough, the gas more readily released due to the increase in temperature. Figure 4 shows a further example of a deaerator device 10’ according to the present invention. In the device of Figure 4, the inlet 14 is positioned in the top third of the main chamber 12. The outlet 16 is sufficiently long, for example, more than half of the length of the main chamber 12, to allow space for the vortex to extend through the outlet. Again, the diameter of the main chamber 12 decreases over its axial length in a non-linear manner. The outlet 16 may comprise two parts that are connected together via respective threaded portions. Similarly, the inlet 14 may be connected to a water supply using a threaded connection. The removal of air, particularly nitrogen, from the water passing through the deaerator device is especially useful in creating a more efficient heating system.

The deaerator device may also be used in air-conditioning systems. One or more features of the described embodiments may, where not otherwise precluded by the claims, be incorporated into another of the described embodiments.