Technical field of the invention

This invention relates to a heat exchanger to exchange heat from a heat pump to a geyser.

Background to the invention

The use of heat exchangers to transfer adiabatic heat of compressed gas from a heat pump to heat household water in a geyser is known. Typically the water from the geyser is circulated through the heat pump and returned to the geyser. As far as the inventor is aware, no heat exchangers, which circulates compressed gas through the geyser have been successfully brought to market despite the need to efficiently provide heated household water.

Such heat exchangers have long tubing and are difficult to retrofit into existing electrical geysers. In addition, metal tubing required to conduct heat to the water in the geyser suffers from rapid galvanic corrosion, expansion and contraction cycles which can cause loss of integrity and sufficient surface area for heat exchange. In addition, should the heat pump or heat exchange fail, the geyser will be out of commission until the heat pump or Heat exchanger is repaired or replaced.

It is an object of the invention to provide a heat exchanger assembly, which can be retrofitted to existing electrical geysers and which do not suffer from any of the abovementioned disadvantages.

General description of the invention

According to the invention there is provided a heat exchanger assembly for transferring heat from compressed gas to heat water in a household type geyser, which heat exchanger includes: a frame for supporting and holding tubing, which tubing is shaped to occupy an elongate cylindrical space of which the diameter is less than the electrical element access opening provided on flanged electrical water geysers; a flanged hub configured to be attached to a geyser in the place of an electrical heating element normally provided with the household type geyser; and corrugated metal tubing shaped and supported on the frame with an inlet and outlet extending through the hub, which tubing is wrapped in a water resistant sheath.

The heat exchanger assembly may preferably include a thermostat pocket which extends through the hub and/ or through which electrical wiring extends through the flanged hub. It is to be appreciated that the thermostat can be used to control a heat pump connected to the heat exchanger. The inside of the hub may be hollow and after all tubing and connections are connected to the hub, the hollow may be filled with resin and allowed to harden.

It is to be appreciated that the corrugation of the corrugated metal tubing increases the heat exchange surface area however, the corrugation makes it difficult to apply a water resistant sheath thereon. According to a method in accordance with the invention, the water resistant sheath may be heat shrink tubing which is fitted over the metal tubing while the heat shrink tubing is inflated followed by applying a vacuum followed by heat shrinking from a furthest point from the vacuum applied end of the heat shrink tubing towards the vacuum applied end of the heat shrink tubing. It is to be appreciated that this method allows the heat shrink tubing to be fitted over the normally friction resistant corrugated metal tubing and to ensure that all air is removed between the sheath and the corrugated tubing when shrunk to snugly fit over and conform to the shape of the corrugated tubing to ensure maximum heat transfer efficiency as well as preventing ingress of water.

In a preferred embodiment of the invention the frame includes end caps provided with outer parallel grooves to allow the tubing to follow along the length of the frame and be wrapped around the outside of the end caps two or more times. In addition, an end cap may be provided with an inner groove to allow more tubing to follow the frame and be wrapped on the inside of the end caps, preferably transverse to the outside wrapped tubing.

The frame may be configured to include two or more elongate support members which extends between the end caps and the joints between the ends of the elongate members and the end caps may preferably be expandable to allow for expansion and contraction of the tubing.

The frame may preferably be configured to provide an elongate space within the frame. The frame may include one or more brackets provided with C- shaped snap lock members for receiving elongate members and tubing and which is configured to fit transversely to the elongate members in a snap-lock manner. The bracket may preferably be provided with an opening through its middle to provide the elongate space within the frame.

The heat exchanger assembly may include an electrical heating element and associated thermostat which is fitted inside the elongate space defined within the frame. It is to be appreciated that the electrical heating element may serve as a backup or complementary heating element should the heat pump fail. The heat exchanger assembly may include a hub for connecting the electrical heating element and the electrical cables in a watertight manner and shaped and configured to fit on the inside of the elongate space within the frame. The hub may be provided with grooves on its outside, the grooves being c-shaped in cross section to receive the elongate members snugly therein to locate and position the electrical element within the elongate space within the frame.

The invention also extends to a method in accordance with the invention, the water resistant sheath may be heat shrink tubing which is fitted over the metal tubing while the heat shrink tubing is inflated followed by applying a vacuum followed by heat shrinking from a furthest point from the vacuum applied end of the heat shrink tubing towards the vacuum applied end of the heat shrink tubing. It is to be appreciated that this method allows the heat shrink tubing to be fitted over the normally friction resistant corrugated metal tubing and to ensure that all air is removed between the sheath and the corrugated tubing when shrunk to snugly fit over and conform to the shape of the corrugated tubing to ensure maximum heat transfer efficiency as well as preventing ingress of water. In addition, the sheathing guards against galvanic corrosion of the water tank and protects the piping.

Detailed description of the invention

The invention is now described by way of example with reference to the accompanying drawings.

In the drawings:

Figure 1 shows a perspective and expanded view of a heat exchanger assembly, in accordance with the invention;

Figure 2 shows further details of the heat exchanger assembly, with the tubing removed;

Figure 3 shows details of the hub;

Figure 4 shows further details of the hub;

Figure 5 shows details of frame; and

Figure 6 shows cross sectional details of the electrical hub.

Referring now to the drawings, the heat exchanger, in accordance with the invention, is generally indicated by reference numeral 10. The heat exchanger assembly 10 for transferring heat from compressed gas to heat water in a household type geyser (not shown), includes a frame 12 for supporting and holding tubing 14, which tubing is shaped to occupy an elongate cylindrical space of which the diameter is less than the electrical element access opening provided on electrical water geysers (not shown). The assembly 10 further includes a brass flanged hub 16 configured to be attached to a geyser (not shown) in the place of an electrical heating element (not shown) normally provided with the household type geyser. The tubing 14 is in the form of stainless steel corrugated metal tubing shaped and supported on the frame 12 with an inlet 18 and outlet 20 extending through the hub 16, which tubing is brazed onto tubular fittings 23 provided on the hub 16, and is wrapped in a water resistant sheath 22. The hub 16 is provided with tubular fittings 23 which is The water resistant sheath 22 is only partially shown to show other features of the invention more clearly.

The heat exchanger assembly 10 includes a thermostat pocket 24 which extends through the hub 16 to control a heat pump (not shown) connected to the heat exchanger assembly 10. The inside of the hub 16 is hollow and after all tubing and connections are connected to the hub, the hollow is filled with a resin and allowed to harden.

The water resistant sheath 22 comprises heat shrink tubing which is fitted over the metal tubing 14 while the heat shrink tubing is inflated followed by applying a vacuum followed by heat shrinking from a furthest point from the vacuum applied end of the heat shrink tubing towards the vacuum applied end of the heat shrink tubing to allow the heat shrink tubing to be fitted over the normally friction resistant corrugated metal tubing and to ensure that all air is removed between the sheath and the corrugated tubing when shrunk to snugly fit over and conform to the shape of the corrugated tubing to ensure maximum heat transfer efficiency as well as preventing ingress of water and protects against galvanic corrosion of the water tank.

The frame 12 includes a pair of end caps 26 and 28 provided with outer parallel grooves 30 to allow the tubing 14 to follow along the length of the frame 12 and be wrapped around the outside of the end caps 26 and 28 for three times. In addition, the end cap 26 may be provided with an inner groove 32 to allow more tubing to follow the frame 12 and be wrapped on the inside of the end caps 26 and 28, transverse to the outside wrapped tubing.

The frame 12 includes four elongate support members 34 which extends between the end caps 26 and 28 and the joints between the ends of the elongate members and the end caps includes sleeves 36 which fit slideably over the ends of the support members 34 and are expandable to allow for expansion and contraction of the tubing 14. The frame 12 is configured to provide an elongate space 38 within the frame. The frame further includes five brackets 40, each provided with eight C- shaped tubing snap lock members 42 for receiving the tubing 14 therein. The brackets 40 also include four C-shaped snap support member lock members 44 for receiving the elongate support members 34 therein transversely to the elongate support members. The bracket 40 is provided with an opening 41 through its middle to provide the elongate space 38 within the frame 12.

The heat exchanger assembly 10 further includes an electrical heating element 46 and associated thermostat 48 which is fitted inside the elongate space defined within the frame. The electrical wiring 47 is waterproof and extends through the flanged hub 16. The heat exchanger assembly 10 also includes a hollow hub 50 for connecting the electrical heating element 52 and the electrical cables 54 in a watertight manner and shaped and configured to fit on the inside of the elongate space 38 within the frame 12. The inside of the hub 50 is filled with resin and allowed to set after all the connections have been made. The hub 50 is provided with grooves 56 on its outside, the grooves being c- shaped in cross section to receive the elongate members 34 snugly therein to locate and position the electrical element 52 within the elongate space 38 within the frame 12. The inside of the hub is filled with resin and allowed to set and a sleeve covering the electrical cables is filled with silicone and allowed to set through the straw 58.

It shall be understood that the example is provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and is not meant to be construed as unduly limiting the reasonable scope of the invention.