US2683442A - Indirect water heater - Google Patents

Description

y 1954 H. R. KARLEN 2,683,442

INDIRECT WATER HEATER Filed June 12, 1951 2 Sheets-Sheet 1 i J INVENTOR.

1 137-2192 [QT/w,

y 1954 H. R. KARLEN 2,683,442

' INDIRECT WATER HEATER Filed June 12, 1951 2 Sheets-Sheet 2 Patented July 13, 1954 INDIRECT WVATER HEATER Harvey B. Karlen, Chicago, IlL, assignor to Cory Corporation, Chicago, 111., a corporation of Delaware Application June 12, 1951, Serial No. 231,151

Claims.

This invention relates generally to a water heater, and more particularly to a water heater of the counter type employable in restaurants and the like without the provision of an externally exhausting flue.

One object of this invention is to provide a simple heater that has water of at least the desired temperature immediately on tap, and which is capable, without substantial variation, to supply water within the limit of its capacity at the temperature desired.

Another object is to provide a water heater capable of providing hot water without the gem eration of steam, should there be failure of a thermostat or other safety device.

Still another object is to provide a water heater that is compact and simple, yet efiicient and with substantial capacity for its physical size.

Other objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure l is a vertical sectional View, taken approximately on line 5-! of Fig. 2, illustrating a water heater embodying the features of this invention; and

Fig. 2 is a vertical sectional view, taken approximately along line 2-2 of Fig. 1.

In the exemplary embodiment herein illustrated, the heater comprises an upright, generally rectangular housing 5, a primary heat source 5 and heat exchange means, generally designated 7. The heater is comparatively small, so small in fact that it is readily adaptable for counter installation. While it burns so little gas as to require no outside flue for exhausting the products of combustion, it is capable of raising water from a temperature of 40 F. to 170 F. in

an amount of more than one-sixth gallon per minute. 7

The housing 5 utilizes metallic frame elements 8 to serve as supporting legs for the heater and defining the wall areas thereof. As clearly shown in the drawings, the heater has four unbroken side walls 9 formed from noncombustible insulating sheets such, for example, as the material known as Transite. A partial wall It formed from the same material covers approximately one-half of the area of the housing bottom. Similarly a partial top wall H is utilized, leaving an opening 12 extending the full width of the housing adjacent theiront wall of the heater.

Mounted in the bottom of the heater in the opening formed by its partial bottom wall [his the primary heat source =6 which herein takes the form of a gas burner of the ceramic type. Gas for the burner is delivered through a supply pipe is having interposed therein the customary safety pilot valve H2 and a modulating thermostat and manual adjusting means l5. Associated with the modulating thermostat and manual adjusting means i5 is a thermostat bulb It the location of which will be described later. Controls for the burner include a pilot I! and a thermocouple 18.

The heat exchange means 1 herein disclosed is designed to provide a source of hot water whose temperature variation during intermittent operation is far less than that of the counter heaters now available, and to avoid the generation of steam while maintaining water at not less than the desired temperature immediately available at all times. To that end the heat exchange means comprises a tank receivable within the housing 5 and adapted to contain a liquid heat transferring medium, which in this particular instance is water. The tank has a top wall 2| conforming in size to the partial top wall ll of the housing, and a bottom wall 22 resting on the bottom wall Ill but somewhat smaller than that wall. Connecting the forward edges of the top and bottom walls 2| and 22 is a wall 23 which is inclined to the vertical, herein sloping downwardly and inwardly or backwardly from the edge of the top opening [2. Extending through the top walls 2! and H is a filler port it closed by a loosely fitting cap 25.

Disposed within the tank it to be submerged by the water therein is a helical coil 26 of tubing carrying the water to be heated. This coil has its inlet at the lower end 21 and its outlet at the top 28. The lower convolution of the coil 25 is located near the bottom of the tank 26 While its upper convolution, and particularly the upper run of the tubing, is located near the top of the tank but in a position to be submerged in thewater if the tank is maintained filled to g the proper level. The tubing composing the coil 26 is of copper or some equally suitable metal having high resistance to corrosion while yet being an excellent conductor of heat.

To transfer the heat from the burner to the water in the tank 20 and thence to the water in the coil 26, a heat exchanger means is provided which herein takes the form of a plurality of heat exchanger tubes 29 arranged side by side in a row. Each of the tubes has a straight, intermediate portion a disposed parallel with the wall 23 of the tank but spaced therefrom, and curved end portions 12 and c for connecting the ends of the tube to the tank near the bottom and the top thereof. The straight portion a of each tube is provided with a great multiplicity of outwardly extending slender spine-like fins 32. These fins should be secured to the tube in good heat conducting relationship, and preferably are formed integral therewith as in the case of a product now available and known as Therrnek.

The tubes 29 are so mounted that the fins of one overlap the fins of the adjacent tube or tubes so as to be in physical contact therewith at a multitude of points, and the number of tubes is such as to cover the entire width of the heater, thereby providing, in effect, a heat exchanger wall. Because of this, as best seen in Fig. there is no unobstructed passage from the burner E upwardly to the exhaust opening [2 for the fins also extend to the front wall of the housing, as seen in Fig. 1. As further insurance that there is no unobstructed passage for the heated gases to how upwardly, through the opening l2, the tank 25 near its lower end is provided with a baffle plate 33 projecting toward the tubes and underlying the lowest course of fins 32.

It is to be noted that the tubes 29, particularly the intermediate finned portions, fall within the vertically projected margins of the burner so that this entire heat capturing portion of the tubes is exposed to the radiant heat of a ceramic type burner as well as the hot gases rising from the burner. More particularly, the tubes are here disposed to form an angle between 20 and 25 to the vertical. This angle is not so large as to interfere with good thermal flow of water upwardly through the tubes, and also is not so large as either to require a larger burner or, if no larger burner is provided, resulting in having some of the tube lie outside of the projected margins of the burner.

The thermostat bulb It which functions to regulate the burner when the controls are set for automatic operation is not positioned so to be responsive to the temperature of the water discharged from the coil 28, nor even to the temperature of the water at any point in the coil 26, but on the contrary is disposed in the tank 2% to respond to the ambient temperature of the water therein. While the bulb It could be located at various points in the tank 25, it is preferably located, as shown in Fig. 1, in the lower half of the tank and preferably also on the side of the tank which is remote from the wall 23 where the temperature might not be truly representative of the water in the tank as a whole due to the fact that the wall 23 is a heated sur-- face.

The operation of the heater is believed readily understood. Heated gases rising from the burner 5 pass upwardly, filtering through the fins on the tubes 28, with some of the gases thereby deflected striking the wall 23 of the tank. These heated gases eventually pass out through the opening l2 in the top wall of the housing. Heat is picked up by the fins and transferred to the water in the tubes 29, thereby setting up a circulation, the heater water passing from the top ends of the tubes to the top of the tank 2a, and water at lower temperatures being drawn into the tubes from the lower end of the tank. The heated surface of the wall 23 aids the tubes 29 in heating the body of water within the tank, probably setting up local currents therewithin. The amount of heat supplied by the burner will, of course, be varied by the control means in response to the temperature of the thermostat bulb It. As the temperature of the water in the tank near the thermostat bulb l6 approaches that for which the heater has been set, the operation of the burner is gradually cut down whereas, should the temperature of the water in the tank near the bulb decrease, the operation of the burner 6 will then be stepped up.

There will, of course, be a temperature gradient between the water in the bottom of the tank and that at the top. Advantage is taken of this by having the water to be heated enter the coil 2'5 at the bottom and leave at the top where the temperature of the water in the tank is the highest. With this arrangement the water within the tank 20 serves as a large reservoir of heat providing a reserve capacity that prevents the fluctuation in temperature of the discharged water that normally occurs. At the same time this arrangement prevents the generation of steam at the outlet 28 of the coil 26, even should the thermostat control fail. This is due to the fact that the cap 25 fits so loosely that pressure cannot build up within the tank 20 and hence the temperature of the water in the tank, even that at the top, cannot exceed the boiling point. Inasmuch as it is impossible to obtain a transfer of heat, the temperature of the water in the outlet of the coil 26 will have to remain at least few degrees below the boiling point.

Should the heat transferring liquid in the tank 2i] be permitted to fall to such a lever that one or more of the upper turns of the coil 26 are no longer submerged, the efficiency of the heater would, of course, be reduced, but there still would be no generation of steam in the coil 26. To guard against possible damage to the tubes 29 under such a condition of drop in the level of water in the tank 28, a fusible link, represented at 3 5 in Fig. 2, may be mounted on one of the tubes 29 near the top thereof and incorporated in the electrical control circuit for the burner in such manner as to cut off the burner, as is well known in the art.

It is manifest that the present heater of the counter type has a large capacity for producing heated water relative to its physical size, and is capable of having always and immediately available water of at least the desired temperature, without at the same time harboring the hazard of producing steam in the discharge line should the automatic thermostatic control fail. The heater also is capable of producing water at a consistently uniform temperature without the wide fluctuations and variations customary in counter heaters now available because the large body of heat transferring liquid in the tank 23 serves as a reservoir of reserve heat and as a balance wheel for removing large gyrations in temperature variation.

'1 claim:

1. A water heater comprising, in combination, a generally upright housing having side walls, a partial bottom wall and a top wall, said top wall having a narrow opening therein adjacent one side wall, a tank within said housing adapted to be filled with water, said tank having one side wall inclined downwardly and backwardly from the opening in the top wall of said housing, a coil for the water to be heated disposed in said tank with its inlet end near the bottom and its outlet end near the top of said tank, a plurality of heat exchanger tubes arranged side by side and each over the major portion of its length extending generally parallel with but spaced from the inclined wall of said tank and at its lower end connected to said tank at the lower end thereof, and at its upper end connected to said tank at its upper end, each of said tubes having a great multiplicity of outwardly projecting fins, the fins or" one tube overlapping the fins of an adjacent tube to eliminate any unobstructed passage between said tubes and extending to the wall of said housing opposite said inclined tank wall to obstruct the passage between said tubes and said housing wall, a baffle plate extending from the inclined wall of said tank near the bottom thereof toward said heat exchanger tubes to close the passage between said tubes and said inclined wall against unobstructed upward movement of gases, a source of heat disposed in the opening left by the partial bottom wall for imparting heat to the heat exchanger tubes, and means for automatically controlling said heat source including a thermostat disposed within said tank.

2. A water heater comprising, in combination, a generally upright housing, a tank within said housing adapted to be filled with a retained, liquid, heat-exchange medium, said tank having a Wall inclining outwardly from the bottom upwardly, a coil adapted for the passage therethrough of expendable water to be heated, said coil being disposed in said tank with its inlet end adjacent the bottom of said tank and with its outlet end adjacent the top of said tank, a heat source including a ceramic burner disposed at least partially beneath said inclined Wall, a plurality of heat-exchange tubes each having an intermediate, substantially straight portion provided with outstanding heat conducting fins and disposed parallel with said inclined wall and over said heat source to be in the path of the heated gases and also the radiated heat from said burner, said tubes being connected at their lower ends to said tank near the bottom thereof and at their upper ends to said tank near the top thereof to complete a closed circulatory system, and means for governing the operation of said heat source including a thermostat located within said tank.

3. A water heater according to claim 2, in which the housing has side walls, a front wall and a top wall, the latter having in it between the front wall and the juncture of the inclined wall and the top wall an opening for the escape of products of combustion and in which the fins on adjacent tubes overlap, those on the end tubes contact the side walls and those at the upper extremity of the straight portion of the tubes contact the front wall.

4. In a water heater, a generally upright housing, a tank within said housing adapted to be filled with a retained, liquid, heat-exchange medium, said tank having a wall inclining outwardly from the bottom upwardly, a coil adapted for the passage therethrough of expendable water to be heated, said coil being disposed in said tank with its inlet end adjacent the bottom of said tank and with its outlet end disposed adjacent the top of said tank, a heat source including a burner disposed at least partially beneath said inclined wall and a combined bafiie and heat-exchange tube means communicating at its lower end with said tank near the bottom there of and at its upper end with said tank near the top thereof to complete a closed circulatory system, said means having an intermediate portion provided with outstanding heat conducting fins and extending parallel with but spaced from said inclined wall and disposed over said burner and substantially entirely within the vertically projected margin of said burner.

5. A Water heater according to claim 2, in which the housing has side walls and a front Wall which with the inclined wall of the tank form an upwardly tapering chamber terminating in an opening for the escape of the products of combustion and in which said heat-exchange tube means with its fins forms a bafiie extending from side wall to side wall and from near the top of the front wall downwardly and inwardly substantially to the burner.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,851,851 Lee et al Mar. 29, 1932 1,980,424 Morgan Nov. 13, 1934 2,234,423 Wittmann Mar. 11, 1941 2,303,702 Mantz Dec. 1, 1942 FOREIGN PATENTS Number Country Date 3,905 Great Britain Apr. 14, 1904 460,710: Germany June 4, 1928 689,766 Germany Oct. 19, 1940

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