KR20050039729A - Improved water heater - Google Patents

Abstract

This invention relates to a water heater comprising a water tank (1) having a wall (2) formed from material having heat transfer properties and a cold water inlet (5) adjacent one end of the tank. A tube (8), adapted to carry a refrigerant fluid, is secured externally about the tank wall (2). Heat-conductive material is provided along the length of the tube, with the tube and the heat-conductive material in heat-conductive contact with the external surface of the wall of the tank to transfer heat from condensation of the refrigerant fluid in the tube through the wall to the water contained in the tank (1). An evaporator (15) is positioned so as to be exposed to ambient conditions for absorbing heat energy from the ambient conditions. The evaporator is provided with a passage for carrying the refrigerant fluid whereby the fluid may be heated by the ambient conditions. A compressor (12) is connected to the passage and to the tube (8) so as to circulate the refrigerant fluid through the tube and to the evaporator (15).

Description

Improved Water Heater {IMPROVED WATER HEATER}

The present invention relates to improved construction and manufacture of water heaters, and more particularly, to the construction and manufacture of heat pump water heaters.

The discussion of the prior art throughout this specification should never be appreciated that such prior art is widely known or to be accepted as forming part of the general knowledge common in the art.

Australian patent 603510 discloses a water heater and a method of manufacturing a heat exchanger for a water heater, wherein a tube installed to carry a refrigerant is wound around the water tank and joined to the wall of the water tank by a thermally conductive binder. The tube is wound around the tank under tension to reduce the likelihood of breakage of the thermally conductive binder during expansion and contraction of the tube and tank during use. The tank is baked in an oven to cure the binder. The binder performs two functions; That is, firstly, a coil is coupled onto the tank, and secondly, to improve the heat transfer performance between the tube and the tank.

However, a problem associated with this process is the use of expensive, specially prepared binders, which are required to cure the paste in an oven or kiln at elevated temperatures of about 250 ° C. for a time interval of about 2 hours. Should be baked in. The need to use an oven to cure the paste also adds manufacturing time and cost.

Preferred embodiments of the present invention are now described in more detail with reference to the accompanying drawings.

1 is a fragmentary front sectional view of a water tank with a heat exchanger suitable for use with the water heater embodying the present invention;

FIG. 1A is a fragmentary yellow cross sectional front view of the tank portion showing a tube attached to the tank; FIG.

2A is a schematic front view of an apparatus for applying the tube to the tank;

FIG. 2B is a schematic enlarged front view of the tube deformation roller shown in FIG. 2A; FIG.

3 is a schematic diagram illustrating the design of a heat pump water heating system operated by solar heat embodying the present invention;

4 is a schematic diagram illustrating an apparatus for cooling the compressor used in the system of FIG. 3;

FIG. 5 is a schematic diagram illustrating one structure of a refrigerant passage in a solar collector used in the system of FIG. 3; FIG.

FIG. 6 shows a cross-sectional side view of one of the solar evaporators / collectors used in the system of FIG. 3.

It is therefore an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

To this end, a first embodiment of the present invention provides a water heater comprising:

A water heater having a wall formed of a material having heat exchanger characteristics;

A cold water inlet adjacent one end of the tank;

A tube delivering a refrigerant externally fixed relative to the tank wall;

The tube and a thermally conductive material in thermally conductive contact with the wall outer surface of the tank for transferring heat from the condensation of refrigerant within the tube to the water contained in the tank through the wall. Thermally conductive materials arranged over;

An evaporator, positioned to be exposed to ambient conditions for absorbing thermal energy from ambient conditions, having a passage for delivering said refrigerant, said refrigerant being heated by said ambient conditions; And

A compressor connected to the passage and tube for circulating refrigerant through the tube and to the evaporator.

Unless expressly required in the context, throughout the description and claims, the terms 'comprise', 'comprising' and similar terms are to be construed as concepts of inclusion as opposed to concepts of exclusion or consumable concepts. That is to say, including but not limited to.

Preferably, the tube is wound around the tank.

Preferably, the thermally conductive material extends substantially equal to the length of the tube.

Preferably, the tube is formed from copper or a copper based alloy.

Preferably, the tube is mechanically fixed at one or more positions to the wall of the tank.

In one preferred embodiment, two or more tubes are wound around the tank and carry the refrigerant.

A second embodiment of the present invention provides a method of manufacturing a heat exchanger for a water heater, which comprises attaching one end of a tube to an outer surface of a metal water tank, placing the tube around an outer surface of the tank. And injecting a heat transfer seal between the tube and the wall of the tank.

Preferably, the tube is wound around the outer surface of the tank. More preferably, the tube is wound around the outer surface of the tank under a predetermined tension.

In a preferred embodiment, the pitch of the winding of the tube around the tank varies. More preferably, the winding of the tube is located closer to the bottom of the tank and the adjacent winding is gradually increased towards the top of the tank.

Advantageously, in comparison with conventional water heaters known from Australian patent 603510, the present invention alleviates the requirements required to cure the binder at elevated temperatures. Compared with the water heater known from Australian patent 603510, the heat transfer material acts to improve heat transfer between the tube and the tank, and unlike the binder known from the prior art, the tube is connected to the water tank. It does not act to keep it on the wall. According to the invention, the tube is mechanically attached on the wall of the tank.

Referring to the drawings, the water tank 1 is cold water adjacent to the bottom surface 3, which has a cylindrical wall 2, a bottom surface 3, a convex top wall 4, a diffuser or a diverter 6. It is provided with an inlet (5) and a hot water outlet (7) adjacent the upper wall (4). Although the bottom surface 3 is shown concave, it may be convex if desired. A tube 8 carrying a coolant such as coolant R22 is surrounded around the outer surface of the tank wall 2. The tube 8 is made from copper or a copper base alloy. The tube 8 is preferably constructed flat as shown in FIG. 1A, thus having a flat surface of the tube, which is positioned against the wall of the tank, and having a generally D-shaped cross section. A heat seal paste 9 is located between the adjacent surface of the tube 8 and the wall of the tank, which provides heat transfer between them. Preferably, the heat seal paste is located over the entire length of the interface between the tube 8 and the tank wall 2. However, it is typically appreciated that the heat seal paste may be located intermittently across the interface, even with an increase in heat transfer efficiency. In order to ensure the best possible contact during expansion and contraction of the tube and tank wall 2 between uses, the tube 8 is wound around the tank 1 under tension and mechanically fixed to the tank 10 under tension. This can be accomplished in the manner shown schematically in Fig. 2A.

It is to be appreciated that while the tube 8 is preferably wound spirally around the outer surface of the tank wall 2, an alternative to positioning the tube 8 on the outer wall of the tank may also be possible. For example, the tube may be formed in a concertina manner and is located on the outer wall of the tank so that the tube extends above and below the outer wall of the tank. However, it should be noted that this configuration may add additional complexity to the manufacture of the system and is therefore less desirable than spiral tube winding.

According to the invention, the heat transfer material 9 in paste form is inserted or injected between the tube 8 and the tank wall 2. Preferably, the paste does not need to be cured, or if curing is desired, it can be cured under ambient conditions and thus alleviates what is required to cure to elevated temperatures in an oven or kiln. A suitable heat transfer paste is "HTSP Silicone Heat Transfer Compounds Plus", commercially available from Australia at ElectroLube. This is a silicone oil based heat transfer paste having a thermal conductivity of about 3.0 W / mK. Other suitable types of heat transfer paste may also be used, such as "Bostick 1128 Heat Transfer Sealant" sold in Australia by Bostick Corporation. There are a number of advantages associated with the use of the heat transfer sealant, including eliminating the requirement for the curing step, which results in cost savings for the product and significant shortening in manufacturing time. Preliminary experiments also show that the heat transfer performance of the system is improved.

As shown in FIG. 2A, the tank 1 is supported on a turntable 20, which is rotatably driven by a motor 21 via a gearbox 22 and a chain drive 23. An appropriate length of tube 8 is supplied by feed roller 24 and deformed by the deformation roller 25 into the D-shape shown in FIG. 1A. The feed roller 24 and the deformation roller 25 form an assembly comprising a nut that engages the feed screw 26, the feed screw being assembled at the rate required for rotation of the table 20. Is rotatably driven by a motor 270 to move it over the tank 1, so that the tube 8 is wound around the tank at the required spacing between adjacent outer bodies. .

As shown in more detail in FIG. 2B, the deformation roller 25 includes a knurled roller 28 and a grooved support roller 29. The rollers 28 and 29 are driven by gears 30 and 31, which are driven at the same speed as the pitch roller 24 to ensure that the tube 8 is fed and deformed at the same speed. do. The pitch roller 24 and the rollers 28 and 29 are compressed by the brake pad 32 to suppress free rotation, as shown in FIG. 2B. The tension applied to the tube can be adjusted by clamping the brake pad 32 to engage the roller 29 and the gear 30 under the influence of a spring 33 which is controllably compressed by the tension nut 34. Can be.

In the present embodiment, the parts of the tank 1 and the copper flash on which the tube 8 is fixed are applied in a known manner. Then, the tube 8 is fixed to the bottom of the tank wall 2 by spot welding, and the tube 8 is then wound around the tank using the apparatus shown in FIG. 2A. When the tube is wound completely over the length of the tank, its upper end is fixed to the wall 2 of the tank 1 by spot welding to keep the tube 8 under tension.

The tube 8 extends from a position adjacent the bottom surface 3 to a suitable height on the tank 1 and forms a heat exchange surface S on the wall 2. The lowest winding 8A of the tube 8 is located below the cold water inlet 5, which is usually cold, and this causes sub-cooling of the refrigerant and thus it is stabilized enough to deliver. Although it is mentioned that modifications to the system are carried out in the system described further below, the tube 8 is a heat pump operated by a solar heat of the general type described in Australian patent 509901 (Fig. 3 as described below). ) Other types of heat pumps can also be used and the heat exchange medium carried by the tube 8 can be changed as desired.

By attaching the coolant conveying tube 8 to the outer surface of the tank 1, a double wall effect is automatically achieved and required by the relevant water authority, and the coolant conveying tube is connected to water to form a double walled tube. It is recognized that the protection measures required by the conditions are met. It is preferable that both the tube 8 and the tank 1 are made of a similar material, or at least made of a material having a similar coefficient of thermal expansion.

In this case, the tank 1 is made of steel or stainless steel, while the tube 8 is made from copper or a copper-based alloy. If materials with different coefficients of thermal expansion are used, the different rates of expansion and contraction of the materials can be compensated by increasing the winding tension of the tube 8 in the manner described above. In any case, the winding of the tube under tension ensures that the thermal bond is maintained despite the bending of the materials caused by expansion and contraction between uses.

The heat exchanger described above is also well suited for use with fluids A such as water, which are likely to contain sedimentable contaminants, since the main part of the heat exchanger surface S is vertical so that the heat exchanger This impedes the accumulation of deposits on the surface. In addition, the heat exchanger surface S is sufficiently extended for the application of a coating such as glass enamel, while maintaining the product of the heat exchange coefficient and the surface area at an effective level, and the fluid A to be heated and the surface of the heat exchanger Minimize the temperature difference between (S).

The heat exchange surface (S) region is chosen to provide the best compromise between the following conflicting requirements:

(a) a requirement such that the heat exchanger surface is generally vertical and slopes downwards or downwards as discussed above;

(b) the flow density of the heat in the fluid (A) to be heated should be low enough to prevent destabilization of unstable components in the fluid, the maximum between the heat exchanger surface (S) and the fluid (A) The temperature difference is a requirement that the fluids in contact with the surface be limited so as not to locally heat the fluid A to a point where it reaches some extreme destabilization temperature;

(c) The requirement that the heat exchanger surface S be as broad as possible.

Requirement (c) minimizes the irreversibility of the system, wherein the heat exchanger of the system has the coldest sink of fluid A at which temperature is transferred between the refrigerant B and the fluid A to be heated. (sink) A part that tries to get as close to the temperature as possible. By making the heat exchanger densely, the passive volume of the conduit is increased. This volume acts as a stored volume of fluid ready for delivery to the last user of fluid A.

In order to make the heat exchanger dense and efficient, the spacing between the windings of the tube 8 and the flow rate of the refrigerant or other heat exchange fluid (B) are suitable for the fluid side surface area (S), the heat transfer medium side surface. The area T, heat transfer coefficient, heat exchange fin efficiency and, if required, should be optimized to give adequate manual storage.

In general terms, the design process for the preferred embodiment described above can be summarized as follows:

Taking into account the manual storage volume requirements and the stratification of the fluid A, the above is due to an increase in the heat transfer temperature difference across the surface S caused by a decrease in the area available for delivering the required total heat flow. The surface area S is made wider but as compact as possible, until the advantages outlined above are negated.

The spacing arrangement and dimensions of the tubes on the outer surface of the heat exchanger surface S are then subjected to engineering design procedures performed taking into account internal tube heat transfer, tube-to-wall coupling conduction and, where applicable, fin efficiency. Is determined by

Reconsideration of the determined surface area S may be necessary if the spacing arrangement of the tube indicates that further optimization of the structure is possible through some compromise with the surface area S.

In order to avoid lowering the stored volume of the fluid through mixing with a fluid that is not yet fully heated or cooled, the stratification of the fluids at different temperatures should be promoted as much as possible. For this purpose, the inlet and outlet conduits are arranged so as not to promote mixing by stirring the fluid A. In addition, the cold water inlet 5 is located at the bottom of the tank and the hot water outlet 7 is located at the top of the tank. In order to achieve a reduction in agitation, it will be appreciated that the axis of the cold water inlet 5 is perpendicular to the axis of the layers. Also, a diffuser-deflector 6 facing the bottom is used for the cold water inlet 5, while a diffuser-current transformer 6a facing upwards is used to further reduce mixing and stirring. Used in (7).

The heat exchanger is preferably embodied in counterflow principle so that it is additionally arranged to improve heat transfer. In the illustrated embodiment, it is recognized that the refrigerant B flows from the top to the bottom of the wound tube 8.

A heat pump water heating system operating by solar heat will be schematically shown in FIG. 3 and will be shown to include a heat exchange system embodying the invention, wherein the tank 1 and the refrigerant conveying tube 8 are insulated. It is housed in a housing 10 that includes a foam 11. For convenience, the compressor 12 and the receiver / filter / dryer 13 of the heat pump system are mounted on a cooling chassis 14 located above the tank housing 10. This arrangement eliminates the need for the housing 10 to be supported in an elevated position to position the compressor and receiver under the tank housing as usual, thus reducing manufacturing costs.

Although other types of refrigerant compressors can be used without substantial deterioration of the system efficiency, the compressor 12 is preferably a rotary compressor. Rotary compressors are preferred for their relatively soft soundproofing. In addition, rotary compressors can accommodate liquid slugs on the suction side of the compressor, while other types of compressors are very difficult to accommodate such slugs. Such slugs can occur due to rapid changes in temperature as a result of changes in weather conditions in heat pumps powered by solar heat.

In order to minimize the heat loss from the system, the compressor 12 is preferably externally insulated. In order to compensate for the accumulation of heat partially caused by this external insulation, the refrigerant is preferably passed through a bypass, capillary tube or fixed orifice (not shown) controlled by a control valve. The compressor is cooled by flowing directly from the outlet of the condenser or receiver to the "suction side" of the inlet suction tube or cylinder. One apparatus for accomplishing this is shown schematically in FIG. 4 and appears to include a cylinder 12A embedded in an insulating casing 12B and comprising a rolling piston 12C and a vane 12D. Liquid injection tube 12E is connected to the suction conduit 12G from the refrigerant conduit into the compressor 12. By this arrangement, the heat normally consumed in the air is transferred to the water in the tank via the condenser. The arrangement shown in FIG. 4 operates more reliably than being injected directly into the cylinder as used in commercially available compressors.

The system includes a thermostatic control system comprising a thermostat (T). More complex thermostat variables are possible, including:

a) setting a variable or double thermostat depending on the level of sunlight, or

b) sensing the evaporation temperature when the unit is operating and using it as an indication of the potential performance which in turn increases or decreases the thermoset set point.

The overall purpose of the system described above is to operate the system during the day by raising the water to a higher temperature during daylight hours than during the night. Even if control "intelligence" is required in this case so that a suitable water temperature is reached during the winter, another complication is possible by making the set point of the thermostat the action of solar radiation and the ambient air temperature. Similarly, it is possible to allow the system to operate primarily during off-peak periods.

The compressor 12 and receiver 13 are connected to a series of solar evaporator plates 15 located at sun-exposed positions. Each evaporator plate includes a number of refrigerant passages 16, which are preferably arranged in the structure shown in FIG. Each evaporator plate 15 is made from two metal sheets bonded together by a so-called Roll-Bond ™ process, except for the passage 16 region, which is well known in the art. Since the evaporator plates are formed from thin metal sheets, each evaporator plate is supported in an outwardly curved profile as shown in the front sectional view of FIG. 6. The outwardly curved profile is maintained by positioning a molded insulating foam former 17 behind each plate 15, the assembly being supported by two supports as shown in FIGS. 3 and 6. . Each evaporation plate 15 is further strengthened by forming an angle portion 18 along each longitudinal edge of the plate 15. The evaporator plate apparatus described above has been shown to work well in a winding test performed to evaluate the ability to withstand the winding forces received when the evaporator plate is mounted to the roof of the dwelling.

As can be seen from FIG. 5, each evaporator plate is connected to three independent parallel refrigerant passages 16 connected to all ends by a manifold 19 to which said refrigerant conduits (not shown) are connected. Is formed. The plates 15 are connected in series, as shown in FIG. 3, so that the outlet manifold of the first plate is connected to the inlet manifold of the second plate and so on. As further shown in FIG. 5, a first passage connected to one manifold at one end of the plate, the other end of the plate which helps to equalize the flow of the refrigerant within the parallel passage 16. Is the last passage connected to the manifold. The cross-sectional area of the manifold is reduced (2) to further assist in equalizing the flow after each junction. The device minimizes the cross-sectional area of the manifold and its junction for a given design pressure drop across the manifold. This results in an improved burst pressure for a given refrigerant pressure drop when the typical "waffle" type used in other "Roll Bond" evaporators compared to the performance of the distributor.

As a result of these features, the evaporator plate can be used with a high evaporation pressure refrigerant, such as R22, without causing a high pressure drop across the evaporator. In addition, as is typically required, the evaporator may be installed with an angle that slopes downwards, which means that the flow uniformity between passages 16 is typically influenced by gravity to give the lowest passage. Because I do not receive. Refrigerant is delivered to the top rather than the bottom of each plate 15 as in the usual case, which makes it possible to use a smaller amount of refrigerant since the plate does not have to overflow as in the case of bottom inflow. . An additional advantage is that advantageous oil return is achieved, since the oil does not tend to accumulate on the bottom as in the case of bottom entry. The upper entry of the refrigerant combined with the high velocity refrigerant circulation causes an annular flow of wet fluid within the passage 16, which improves heat transfer from the plate to the fluid. In this operating state, refrigerant gas flows in the wet fluid annular ring.

A liquid trap is provided before returning the refrigerant to the compressor inlet to prevent accumulation of liquid in the plate 15, while the system is turned off by gravity flowing down into the compressor inlet. do. The tram must be sized such that oil is delivered with the refrigerant gas between operations.

It can be seen from FIG. 3 that the TX valve in the liquid conduit is located in the cooling chassis 14 rather than the evaporator plate 15 as is usual. Although compensation should be allowed for the position of the TX valve at this position, the valve is performed in a good manner at this position and the manufacture of the system is simplified by the position of the valve at this point. The TX valve is inclined by setting to give a suitable superheat condition to a suitable superheat device.

While the evaporator plate is shown in the above-described embodiment as installed in the sun-exposed position, the plate has a high ambient temperature or the tank, as shown by the broken line in FIG. 3. Can be installed outside of the housing 10 in a wrap around the structure of the region so that it can be installed at a roof or another location at least partially exposed to the sun. In this situation, the heat pump at least partially operates as an air sourse heat pump.

Although the present invention has been described with reference to specific embodiments, it is recognized by those skilled in the art that the present invention may be embodied in various other forms.

As described above, the present invention can be used in the construction and manufacture of water heaters, in particular heat pump water heaters.

Claims (13)

A water tank having a wall formed from a material having heat transfer characteristics; A cold water inlet adjacent one end of the tank; A tube for carrying a refrigerant fluid externally fixed relative to the tank wall, and a thermally conductive material over the length of the tube, wherein the tube and the thermally conductive material contain refrigerant fluid from the condensation within the tube. Thermally contact the outer surface of the tank wall to transfer heat through the wall to water contained in the tank; An evaporator exposed to ambient conditions for absorbing thermal energy from said ambient conditions, said evaporator having a passage for carrying said refrigerant fluid, said fluid being heated by said ambient conditions; And And a compressor coupled to the passageway and the tube for circulating a refrigerant fluid through the tube and to the evaporator. The method of claim 1, Wherein said heat transfer material comprises a paste located between said tube and tank wall. The method according to claim 1 or 2, And the tube is wound spirally around the tank. The method according to any one of claims 1 to 3, And the tube is generally D-shaped in cross section. The method according to any one of claims 1 to 4, Wherein the thermally conductive material extends generally in coordination with the length of the tube. The method according to any one of claims 1 to 5, And the tube is formed from copper or a copper-based alloy. The method according to any one of claims 1 to 6, And the tube is mechanically fixed at one or more positions to the wall of the tank. The method according to any one of claims 1 to 7, A water heater, characterized in that two or more tubes are wound around the tank to carry the refrigerant fluid. Attaching one end of the tube to an outer surface of the metal water tank, winding the tube around the outer surface of the tank, and injecting a heat transfer sealant between the tube and the wall of the tank. Manufacturing method. The method of claim 9, And the tube is wound around an outer surface of the tank. The method of claim 10, And the tube is wound around an outer surface of the tank under a predetermined tension. The method according to any one of claims 9 to 11, And a pitch of the winding portion of the tube around the tank is changed. The method of claim 12, And the winding portion of the tube is arranged closer to the bottom of the tank and the spacing between adjacent winding portions is gradually increased toward the top of the tank.