GB2031563A

GB2031563A - Indirect fired water heater

Info

Publication number: GB2031563A
Application number: GB7840177A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-10-11
Filing date: 1978-10-11
Publication date: 1980-04-23

Abstract

An indirect fired water heater has a lined metallic vessel 12 of a multi- piece construction, having upper and lower portions welded together. The vessel contains potable water which is heated by contact with a finned tube heat exchanger 14 through which passes hot boiler water. The vessel is lined with a plastic material or the like 13 to prevent corrosion of the vessel. Insulation is provided around the exterior of the lined vessel to prevent undue heat loss by radiation and takes the form of insulating material applied to the exterior vessel surface, or a vacuum space between the vessel and an outer vessel surrounding the lined metallic vessel. <IMAGE>

Description

SPECIFICATION Indirect fired water heater Technical field of the invention The present invention relates to indirect fired water heaters, more particularly to such heaters having a lined metallic vessel.

Background art Typical prior art hot water heaters comprise a generally cylindrical storage tank, and heating means to heat the water stored in the tank. In direct fired water heaters the heating means may take the form of a gas burner located at the base of the cylindrical tank (as shown in U.S. Patents 817,589 and 2,187,917) or electrical heating elements extending into the tank (shown in U.S. Patent 2,303,126).

The cold water usually enters through the top of the tank passing downwardly in a tube and exiting near the bottom of the tank. When heated, the water rises and is drawn off by a hot water exit tube.

Indirect fired water heaters are also known. They differ from the aforementioned direct fired type insofar as the heated water within the storage tank is not withdrawn and used, but acts as a heat exchange medium. Cold water is circulated through a pipe or tube passing through the heated, stored water and is warmed by heat exchange with the heated water. No direct contact is made between the heating means, the heated stored water, or the cold water.

Most of the prior art water heaters, whether the direct or the indirect type, use some form of unsulation around the tank to prevent undue loss of heat by radiation. Solid, flexible insulation is placed around the tank and retained in position by an outer wall, as shown in U.S. Patents 2,303,126 and 2,187,917.

It is also known to make a water storage tank having concentrically arranged inner and outer tanks with a vacuum insulating space therebetween (U.S.

Patent 1,327,963). However, such tanks are normally used only for the storage and not the heating of water, since the insulating space on the bottom would prevent heat transfer between a burner and the inner tank.

Containers having inner and outer spaced apart walls with an insulating vacuum therebetween are shown in U.S. Patents 1,511,852 and 1,673,653.

These containers are used to store a liquid and to prevent transfer of heat to or from the liquid. Other related U.S. patents are as follows: 999,672; 1,691,912; 2,666,979; and 3,123,054.

Disclosure of the invention The instant invention is directed toward a novel construction of an indirect fired water heater. The water heater comprises a corrosion resistant lined metallic vessel having a finned tube heat exchanger disposed therein. Cold water contained within the vessel is heated by hot water circulating through the heat exchanger. The vessel is of multi-piece construction having upper and lower sections welded together about their circumferences.

The cold water to be heated enters the interior of the vessel via one or more through fittings extending through the wall of the vessel. Alternately, the fittings may extend through the top plate. After or during heating, the water may be withdrawn through one or more similar through fittings. The water is heated via hot water passing through a finned tube heat exchanger located within the inner vessel. The inlet and outlet for the finned tube heat exchanger extend through the top plate covering an opening in the vessel and are connected to a heating device to heat the water circulating through the heat exchanger.

The vessel is fully lined with a plastic or other inert material so as to avoid corrosion of the vessel by the water contained therein.

The exterior surface of the vessel is provided with insulation means to prevent undue heat loss by radiation and to prevent injury caused by an individual coming into contact with the heated vessel.

The insulation means may take the form of a flexible, solid material fastened to the exterior of the vessel.

Alternatively, the insulation means may be a vacuum space between the exterior surface of the vessel and another, outer vessel disposed concentrically about the lined vessel.

Brief description of the drawings Figure lisa cross-sectional view of an indirect fired water heater according to the invention.

Figure 2 is a cross-sectional view of an alternative embodiment of an indirect fired water heater according to the invention.

Best modes for carrying out the invention The indirect fired hot water heater according to the invention is shown in cross-section in Figure 1 and is indicated generally by number 10. It comprises vessel 12 having upper portion 12a and lower portion 1 2b fastened together, such as by welding, along line 15. Finned tube heat exchanger 14 extends into the interior of vessel 12 with inlet 16 and outlet 18 extending through top plate 20 covering the opening of upper vessel portion 12a.

Vessel 12 has a separate plastic liner 13 covering its interior surface, as described in copending U.S.

Patent Application Serial Number 789,235 entitled "Lined Metallic Pressure Vessel" to Joseph A. Lane filed on April 20, 1977. This lining prevents corrosion of vessel 12.

The lining may be vinyl, having a thickness of approximately 20 mils, or urethane. Obviously, any other plastic material may be used as long as it does not contaminate the water in vessel 12 and prevents corrosion of the vessel itself.

Top plate 20 is fastened across the opening vessel 12 such as by welding or the like. Attached to top plate 20 is finned tube heat exchanger 14 having inlet and outlet tubes 16 and 18 extending externally of water heater 10. Inlet and outlet tubes 16 and 18 are connected to heater 22 via conduits 24 and 26 shown diagrammatically in Figure 1. Heater 22 may be any known apparatus for heating water, such as an electric or gas burner. A pump (not shown) may also be used to transfer the hot water from heater 22 and cause it to circulate through finned heat exchan ger 14 and back to the heater. No detailed description of the pump or its connection to the circuit is believed to be necessary since such are well within the ordinary level of skill in the art.

Through fittings 28 and 30 connect the interior of vessel 12 with external conduits (not shown) to supply cold water to water heater 10, and to draw off the water after it has been heated. The fittings may have standard pipe connections on their external end to facilitate connection with the aforementioned conduits. Although only two fittings are shown, it is understood that any number of such fittings may be used. These fittings may alternately be located in top plate 20.

Insulation 32 is provided over the exterior surface of vessel 12 to minimize heat loss by radiation and to prevent injury by contacting the metallic surface of vessel 12 which is quite warm after the cold water has been brought up to its desired temperature.

Insulation 32 may be flexible, solid material, such as fiberglass or the like, retained in position by an outer shell 34. Outer shell 34 may be sheet metal or similar material which will prevent damage to insulation 32 during the normal course of usage. Means for and methods of attachment of insulation 32 and outer shell 34 are well known to those skilled in the art and need not be described in detail.

In operation, the cold water to be heated is pumped into vessel 12 by standard, known pumping means. Hot water is caused to circulate through finned, tube heat exchanger 14 thereby transferring its heat to the colder water within the vessel. The water within the heat exchanger then returns to heater 22 via conduit 26 to be reheated. The water within vessel 12, which is now heated, may be withdrawn through the fittings attached to the vessel.

Lining 13 is a protective lining applied to the interior surface of vessel 12 to prevent corrosion of the vessel 12 and to prevent contamination of the water in vessel 12 which would render same unfit for human consumption.

An alternative embodiment of the invention is shown in Figure 2. The construction and operation of vessel 12, heat exchanger 14 and heater 22 are the same as the aforedescribed embodiment. Other similar elements bear the same numerals as Figure 1. However, in the embodiment shown in Figure 2, insulation of lined vessel 12 is provided by vacuum space 36 between vessel 12 and outer vessel 38.

Outer vessel 38 is similar in configuration to vessel 12, but having larger dimensions so as to fully encompass vessel 12. Vessel 38 comprises upper portion 38a and lower portion 38b fastened together, such as by welding, along line 40. Spacers 42 position vessel 12 with respect to outer vessel 38 and are preferably made of an insulating material to prevent heat transfer from vessel 12 to outer vessel 38. It is understood that spacers 42 are discontinuous about the circumference of vessel 12, or have openings therethrough to aliow a vacuum to be drawn around substantially the entire outer surface of vessel 12.

Through fittings 28 and 30 extend through outer vessel 38 and are sealed around their point of passing through outer vessel 38 to prevent destruction of the vacuum. Top plate 20 extends radially beyond the opening of vessel 12 and is attached about the upper opening of outer vessel 38. The vacuum may be drawn in space 36 by any known means.

To minimize production costs, vessels 12 and 38 may be standard, metallic pressure vessels of multipiece construction sized such that one will fit inside the other.

Claims

1. An indirect fired water heater comprising: a) a lined multi-piece vessel; b) means to place water to be heated within said vessel and to withdraw same therefrom; c) heat exchange means located within said vessel to transfer heat from a fluid passing therethrough to said water within said vessel; and d) heat insulation means disposed about said vessel.

2. The indirect fired water heater of Claim 1 wherein said multi-piece vessel comprises upper and lower portions affixed together.

3. The indirect fired water heater of Claim 2 wherein said multi-piece vessel is metal.

4. The indirect fired water heater of Claim 3 wherein said multi-piece vessel portions are affixed together by welding.

5. The indirect fired water heater of Claim 1 wherein said heat exchange means is of the finned tubing type.

6. The indirect fired water heater of Claim 5 further comprising means to circulate a heated liquid through said finned tubing heat exchanger.

7. The indirect fired water heater of Claim 6 wherein said heated liquid is water.

8. The indirect fired water heater of Claim 1 wherein said heat insulation means comprises an outer vessel disposed about said lined vessel so as to define an insulating space therebetween.

9. The indirect fired water heater of Claim 8 wherein said outer vessel is a multi-piece vessel.

10. The indirect fired water heater of Claim 9 wherein said outer vessel is metal.

11. The indirect fired water heater of Claim 10 wherein said outer vessel portions are welded together.

12. The indirect fired water heater of Claim 8 wherein said insulating space is a vacuum space.

13. The indirect fired water heater of Claim 11 wherein said insulating material attached to said lined vessel so as to cover substantially the entire exterior surface thereof.

14. The indirect fired water heater of Claim 1 wherein said lining on said lined vessel is vinyl.

15. The indirect fired water heater of Claim 14 wherein said vinyl liner has a thickness of approximately 20 mils.

16. The indirect fired water heater of Claim 1 wherein said lining on said lined vessel is urethane.

17. An indirect fired water heater substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

18. An indirect fired water heater substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.