US2169683A - Generating mixed fluid heating medium - Google Patents

Description

Aug. 15, 1939. c. A. DUNHAM Er AL GENERATING IIIXED PLUID HEATING MEDIUM Filed Jan. 5, 1938 2 Sheets-Sheet 1 ll IIIII'III.

Aug. l5, 1939. c. A. DUNHAM Er Al. 2,169,683

GENERATING MIXED FLUID HEATING MEDIUM Filed Jan. 3. 1938 2 Sheets-Sheet 2 u. mr. Y

20 4 1a'. ffffyy/ 00 SMWA f Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE GENERATING MIXED FLUID HEATING ltIEDIUM Application January 3,

14 Claims.

This invention relates to certain new and useiul improvements in generating mixed fluid heating medium, and more particularly to an irnproved process and apparatus for producing a heating medium consisting of a highly saturated mixture of steam and hot products of combustion for use in a heating system.

In the type of heating system to which this invention relates, fuel is burned in proximity to an enclosed body or bodies of water and the products of combustion are passed in intimate contact with the Water so as to form steam, and the heating medium consisting of the products of combustion highly saturated with steam is delivered into radiators wherein the steam is condensed and a large portion of the heat from the products of combustion is used for heating purposes. The cooled non-condensable gases are exhausted from the radiators thus producing a partial vacuum and causing the continuous circulation of heating medium, and the condensate from the steam is returned to the generator to be reconverted into steam.

Il1here have been certain limitations and disadvantages in former means for generating this mixed iiuid heating medium, among which has been the considerable time interval which has elapsed after combustion has been started before a mixture of the desired low temperature and saturation is available at the outlet o! the generator. A prevailing diiiiculty has been that a highly super-heated mixture was first available, some time prior to the production of a mixture approaching saturation, these initial high temperatures contributing to an oxidizing or corrosive condition that, especialiy when copper is used, reduces the life of the equipment. Consequently it is desirable to obtain a mixture which is saturated almost immediately so that the production of initially excessive high temperatures is eliminated. It is desirable to arrange the equipment so that a body of water of relatively small volume is immediately available for vaporization without requiring the exchange of considerable quantities of heat. It is also desirable to provide the maximum surface contact between the liquid and gases so as to facilitate and expedite the vaporization of the liquid.

The present invention relates particularly to an improved generator and process of generating the saturated heating medium suitable for use in a heating system of the type hereinabove briefly described. This generating apparatus comprises a closed housing in which is conned a combustion chamber wherein the fuel is burned 1938. Serial N0. 183,048

or into which the products of combustion are directly introduced. This combustion chamber is surrounded at the sides and top by a body of water so that practically all of the heat not retained by the products of combustion is absorbed by the Water. The exposed upper surface of this body of Water forms a portion of the lower wall of a mixing chamber into which the products of combustion are introduced from the combustion chamber so as to directly contact with the suri'ace of the water. An auxiliary receptacle is so positioned in this mixing chamber that its lower surface is below the normal water level of the main body of water, the auxiliary body being connected through suitable tubes or conduits with the main body of Water so that a shallow pool of liquid will always remain in the auxiliary receptacle at the same level as the main liquid body when standing idle. When the body of water is highly heated a portion of the main body will be forced, as hereinafter described, into the auxiliary receptacle which will become lled and will overflow into the main body of water. The heated gases from the combustion chamber are directed beneath and around the auxiliary receptacle so as to highly heat the Water therein and to pass through the water overflowing from the auxiliary receptacle. Additional fountains of water are sprayed up into the mixing chamber so that a maximum surface contact with the combustion gases is obtained and a highly saturated mixture will be almost immediately produced and delivered through the upper outlet conduit.

The principal object of the invention is to provide an improved process and apparatus for pro ducing a highly saturated mixed uid heating medium, as briey described hereinabove and disclosed more in detail in the specifications which follow.

Another object is to provide an improved generator that furnishes an almost instantaneous heat exchange between the gases and liquid and precludes, even during initial starting, any appreciable degree of super-heat which would produce a corrosive atmosphere in the generator.

Another object is to provide an improved generator adapted to conserve a maximum proportion of heat in the gases and liquid Without the production of excessive temperatures in the heating medium.

Another object is to provide a generator so constructed as to prevent liming or the deposition oi' solids or scale deposits in those portions of the apparatus where small passages would be obstructed.

Other objects and advantages oi' this invention will be more apparent from the following detailed description of one approved form o! apparatus constructed and operating according to the principles of this invention.

In the accompanying drawings:

Fig. 1 is an assembly view partly in elevation and partly in vertical section showing the improved generator, the means for returning water thereto and maintaining the water level, the means for exhausting the cooled gases, and the improved safety means for controlling the burner in response to an abnormal lowering o1' the water level in the generator.

Fig. 2 is a central vertical section, on a larger scale, through the upper portion of the generator.

Fig. 3 is a partial horizontal section taken substantially on the line 3 3 of Fig. 2.

Fig. 4 is a central vertical section through the automatic control valve in the fuel-feed pipe.

The assembly includes in general the improved generator A including the burner B, the outlet or supply conduit C through which the heating medium is carried to the radiating system, the return pipe D through which the cooled gases and condensate return from the radiating system, the exhauster E for drawing out the cooled non-condensable gases, the mechanism F for returning the condensate to the generator and maintaining the proper water level therein. the automatic cut oif valve G in the fuel supply pipe H, and the mechanism indicated generally at K for controlling the valve G in response to abnormal variations in the water level within the generator.

The generator A is built up i'or the most part of metallic shells suitably insulated to minimize heat losses. The lower inner shell I communicates through central opening 2 with the upper inner shell 3 which encloses the combustion chamber indicated generally at 4. Shell 3 is completely closed at its sides and top except for the outlet pipe opening in the top hereinafter described. The burner B is supported in the lower portion of combustion chamber l directly above the central opening 2 leading from the lower air-feed chamber enclosed by casing I, the combustion air owing in through a suitable number of side openings 5. An intermediate metallic casing 6 encloses the greater portion of inner shell 3, and is provided with an upper domed cover I from which leads the outlet or supply conduit C. The intermediate shell 6 houses the main body of water 8 which encloses the sides and top of the combustion chamber, and has its normal water level at x. The surface of the water at :c forms the lower wall of the mixing chamber 9 in the upper portion of the intermediate housing 6. This entire assembly is enclosed in an outer metallic shell or casing l0, and the space between this outer shell and the in'ner shell is iilled with insulation II so as to minimize the heat losses.

The burner B may be of any desired form and is preferably located within the combustion chamber 4 as already described, although it might be positioned outside this chamber so as to project the names or products of combustion thereinto. A fluid fuel is used, preferably gas, which is supplied through the pipe line indicated at H. As here shown, the burner comprises an annular series of substantially radially projecting nozzles b and a second annular series of upwardly projecting nozzles b', the flames from these several DOZZleS impinging to form an annular sheet or name which is projected upwardly and outwardly toward and close to the inner walls of casing I. The flames and hot products of combustion serve not only to heat the surrounding body of water but to scour the inner walls o! the shell and keep them substantially free from soot or other deposits. The hot gases pass from combustion chamber 4 into the mixing chamber 3 through the mixlng header now to be described.

This mixing header comprises a lower header member indicated generally at I2 and including an upper cylindrical shell portion I3 which projects somewhat above the normal liquid level :c and has an open upper end surrounded by a downwardly and outwardly extending ange Il. The cylindrical outer wall I3 joins at its lower end with an intermediate annular horizontal web I5 which connects with a central cylindrical conduit portion i6 which rests on the top wall I1 of inner casing 3. The cylindrical portion Ill is internally threaded and receives the threaded lltting I8 having an outwardly extending bottom flange I8 which serves to clamp the lower header member I2 to the top wall I1 o! the inner casing 3 so as to provide a water-tight joint. A skirt portion lil extends outwardly and downwardly from the outer edge of web I5 and has a plurality of feet I9' resting on top wall I1 of casing 3, but for the most part a narrow passage 20 remains between the lower edge of skirt I3 and top wall I 1 so that water can ow in from the main body of water 8 to supply the partially confined annular body of water 2l between skirt I9 and the central cylindrical tube I6.

The mixing-header comprises also an upper pan member indicated generally at 22 and comprising a central receptacle having a bottom wall 23 positioned somewhat below the normal water level x, and a cylindrical upwardly extending wall 24 spaced inwardly from the wall I3 of the lower header member so as to provide an annular gas passage 25 leading up into the mixing chamber. The upper header member 22 is supported from the lower header member by an annular series of upwardly extending pipes or conduits 26 and 21, the lower ends of which are xed in openings in web I5. The upper open end portions of pipes 26 are also secured in the bottom wall 23 of the upper receptacle. The other pipe members 21 are intermediately secured in bottom wall 23 but extend completely upward through pan member 22 so that their upper ends terminate above this pan and serve as fountains to project highly heated water upwardly into the mixing chamber, as hereinafter described. These tubes may be bent to direct this spray as desired at the top of each. The pipes 26 serve to feed water from the conilned portion 2I of the main body of water into the central receptacle of the pan member 22, and since bottom wall 23 is positioned below the normal water level :r there will always remain a small quantity of water in this upper receptacle even when the burner is not in operation. It will be noted that in the example here shown there are six of the feed pipes 26 and three of the fountain pipes 2], although these numbers could be varied as desired.

The upper edge of cylindrical wall 24 of the central receptacle rounds outwardly at 28 to connect with a horizontal outwardly extending wall 29 provided with an outer upwardly extending rim 3|) so as to maintain a shallow outer water receptacle. A downwardly and outwardly extending overflow lip 3i extends from the upper edge of rim 3D, When the upper pan member is full It will be understood that the mixed heating of 'water this water will overflow in a thin sheet over lip 3| as indicated in lligs` 1 and 2.

An annular rib 32 projects downwardly from horizontal wall 2l near the bottom oi rim lli. The water used generally has some solid material in solution. and in addition 'the gases carry some solids. Some of the solids in solution become less soluble on heating and will oi course be precipitated out to some extent when the wateris evaporated. To prevent the growth of these crystals at points where they might interfere with the operation of the generator, the dependlng ring 32 is provided so that any residual liquid which might tend to creep around the lip 3l will not be able to travel inwardly past the rib or ring 32. As a result no crystals or scale are formed close to the outlet l! for the gases. Also these issuing gases exert a scrubbing action against the rib 32.

In operation, when burner B is started, the hot products of combustion will flow upwardly and outwardly in combustion chamber 4, as already described, preheating the surrounding body of water 8. These gases will ilow up through central conduit I8 into the chamber 34 between and around the several pipes 2B and 21 and thence out through annular passage 2l and outlet 33, beneath the upwardly extending portion of pan 22 and into the mixing chamber It will be noted that these hot gases flow around three sides of the confined body of water 2l so that this body of water will be quickly heated to a boiling temperature. The same is true of the small bodies of water in pipes 28 and in the central pan 24. It will be apparent that as the confined body of water 2| is raised substantially to a boiling temperature its density will be decreased and it will be displaced upwardly through pipes 26 so as to eventually completely lill the upper pan 22 which will overflow over the outer lip 3i and thence back into the main body of water 8. Water will also be displaced upwardly through the upper pipes 21 so as to form fountains or sprays of mixed water and steam that are dispersed into the mixing chamber 9 in intimate contact with the heated gases therein. It will be noted that the hot gases owing out beneath the pan must pass through the downwardly flowing sheet of water dropping from lip 3i where additional intimate contact is obtained between the gases and small bodies of water. The gases also contact directly with the surface oi the main body of water 8. 'This percolating action, or the upward displacement of water through pipes 28 and 21 will continue as long as the burner is in operation. water flowing in from the main body of water B through passage 2li to replenish the confined body of water in space 2|.

Due to the positioning of relatively small bodies of water in intimate contact with the hot gases, the vaporization of the water and the saturation of the gases will begin almost immediately. This acts to lower the temperature of the gases (by heat transferred therefrom to the water and absorbed in the vaporization process) and also quickly saturates the gases thus minimizing corrosion and injury of the metallic parts due to contact therewith of superheated gases. It is also desirable that the mixed heating medium conducted irom the generator through outlet C shall be saturated at all times so that an abundance of watery vapor is available to dilute any acids that might be deposited out and which might corrode the piping.

medium produced in the manner Just described will ilow or be drawn out through conduit C into a radiating system not here shown, but comprising a suitable number oi radiators usually arranged in parallel. In this radiating system the steam will be condensed giving oil' its latent heat, and the non-condensable gases will also give ofi the greater portion oi their heat. As a consequence the mixture that returns from the radiating system through return pipe D (see Fig. l) will consist oi water or condensate and cooled non-condensable gases.

The condensate will flow from return pipe D downwardly by gravity through stand pipe 35 and thence, as hereinafter described, into the generator A. The non-condensable gases are drawn from return pipe D upwardly through the looped fitting 3B and thence downwardly through pipes 31 and Il into the exhauster E from which the gases are expelled through pipe 39 and ilue 40. It will be understood that the exhauster E (which is driven by motor 4I) will create a partial vacuum in the return pipe and the radiating system. this vacuum extending to a slight degree back through supply pipe C into the generator and thus maintaining the proper iiow of heating medium through the system. The maintenance of this sub-atmospheric pressure through` out the system will also prevent any outward leakage of combustion gases into the space being heated.

The lower end of stand-pipe 35 is in communication through horizontal pipe 42 with the lower portion of easing 6 which houses the main body of water 8. Consequently, the condensate which drains back by gravity into stand-pipe 35 will flow into the generator. In order that the generator may operate at its highest eiiiciency it is preferable that the body of water therein be maintained at a substantially constant levell and in order to accomplish this automatically the apparatus indicated generally at F is provided. This comprises an upright tubular container 43, connected near its lower end into the horizontal pipe 42, and preferably provided at its upper end with a removable cover 44. Within container 43 is an overflow pipe 45 having its open upper end positioned at the desired water level .7: within the generator. The lower end of pipe 45 communicates through a water sealed drain pipe 4B with pipe 41 leading to the sewer or other point of discharge. The lower end of container 43 projects below the bottom of the water chamber in the generator so as to form a sediment collecting pocket 48 from which a pipe connection 49 provided with a normally closed valve ill leads to drain pipe 41. By opening the valve 50 the sediment pocket can be ilushed out, or ii desired the entire water system can be drained. It will also be noted that a water sealed drain connection 5i leads from the lower portion of exhauster E to the sewer connection 41 so that any water that mav collect in the exhauster from the gases drawn therethrough may be discharged. The discharge connection 5I will also serve to dispose of anv water that may flow into the exhauster from the safety connection K hereinafter described.

After the heating system is once started there will normally be a surplus of water in the system since the supply is augmented by the watery vapors formed in the process of combustion. This will normally offset the losses through leakage and the vapors which pass out through flue 40. Any such excess liquid returned along with the condensate will be discharged through overflow pipe Iii while still relatively cool, thus avoiding the waste o! heat through the drain.

However, it is desirable to add some additional fresh water to the system from time to time tc insure a desired dilution of any acids that may accumulate in the system.

To accomplish this, a pipe 52 is provided, leading from the city water supply into the upper portion of container l and provided with a normally closed, electrically-operated valve 53. By opening this valve, or the hand-valve l in bypass 56. the apparatus may be filled with water. and additional water may be added whenever needed to re-establish the desired water-level in the generator. In the example here shown, valve 53 is controlled electrically by means of the thermostatically operated switch Sii comprising a thermostat 51 projecting into the body of water B directly below the normal water-level x. This thermostat will not be subjected to a temperature of over 212 Fahrenheit as long as the water is maintained at the desired level. When the water level falls, thermostat B1 will be exposed to the more highly heated gases in mixing chamber 9, thereupon functioning in well-known manner to operate switch 66 and close the circuit indicated by wires 5B, I9 and 60 so as to open valve 53 and admit more water to the system. As soon as the desired water-level has been restored the temperature to which thermostat l1 is subjected will be lowered again to abut 212 F. whereupon the circuit will be broken and valve 53 closed.

Now each time the generating process is restarted a quantity of Water (mostly in the vapor state) will be retained in the piping and radiating system before the water commences to come back through the return main D. As a consequence the water-level in the generator will be lowered somewhat and fresh water will be added automatically by the opening of valve 53. This will provide a desired dilution of the water in the system, which of course will be augmented by the water formed in the combustion process, as already described.

The automatic control valve G positioned in the fuel supply pipe H comprises (see Fig. 4) a main valve casing 6I connected between adjacent sections of the fuel pipe H. Valve casing 6i is provided with an internal web 62 having a vertical port E3 with a seat at its top that may be closed by movable valve member 64. Movable valve member B4 is connected through stern 65 with a weight B6 carried by the central portion of a diaphragm 61 which divides valve casing 68 into a lower chamber 69 maintained at atmospheric pressure through vent 10, and an upper suction or low pressure chamber 1i. The weight 66 (together with spring 12 compressed between this weight and an adjusting screw 13 if this spring is used) serves to normally force valve member 64 to its seat and thus close the valve and cut oir the ow of fuel to burner B. When the pressure is reduced sufficiently in the upper chamber 1I, atmospheric pressure acting on the lower face of diaphragm B1 will open the valve in opposition to the forces exerted by weight 66 and spring 12.

A pipe 1l leads from suction chamber 1I into exhaust pipe 38 at the low pressure side of exhauster E, and when the exhauster is in operation the suction through pipe 14 will sudiciently reduce the pressure in chamber 1I to hold the valve in open position and permit the free ow of fuel to burner B. An adjustable' air leak 15 communicating with suction chamber II permits a sumcient leakage of air into this chamber and out through pipe 14 to keep the diaphragm chamber and piping dry.

This safety mechanism K also comprises a branch pipe 18 leading from pipe 1l into the lower portion oi' a vertical receptacle 11 into which extends the upright arm 1I of a pipe 19 leading from the water chamber l a predetermined short distance below the normal water level .'r. Since the pressure in the exhaust connections and the low pressure side of the system is considerably lower than that existing in the mixing chamber 9 of the generator, the water will normally extend up a considerable distance in vertical pipe 18, but will not normally overflow the upper end of this pipe. In case the pressure difference should become suillcient to cause this pipe to overilow, the water will flow down through pipe 16 into the exhauster E and will thence be discharged through drain connection 5i. The water standing in pipes 1B and 19 normally serves as a water seal at the upper end oi' branch pipe 1B so that the desired low pressure can be maintained in diaphragm chamber 1i. However, in the event that the body of water B in the generator should fall materially below its normal level x, the water will drain out of pipes 18 and 18 thus breaking the water seal and placing pipe 16 in connection with the higher pressure mixing chamber 9. As a consequence the vacuum in diaphragm chamber 1| will be broken and the valve 64 will automatically close under the pressure exerted by weight 8G and spring 12. Consequently the burner B will not be permitted to operate when the water level has fallen suillciently so that injury to the metallic parts might be caused by the superheating thereof. As soon as the proper water levelhas been reestablished in the generator. the water seal in pipe 18 will be reestablished and the exhauster E will again function to cause valve G to open. It will also be apparent that the flow of fuel to the burner B will be cut o whenever the exhauster E ceases to operate, since the vacuum in the upper diaphragm chamber will soon be broken.

It will be understood that a heating system of this type will usually be provided with automatically operating thermostatic burner controls so that the generator will be turned on and off at intervals to maintain a desired temperature in the space being heated. It will be understood that a pilot burner or ignition means for the main burner will be provided, as usual, to reignite the burner B as soon as the fuel supply is turned on. It will be noted that after each period of non-use a reserve supply oi water will remain in the lower portion of the inner pan 24 and the pipes 26, so that these small supplies of water together with that confined in annular space 2| will be very quickly heated and the saturation process will begin almost immediately after the combustion gases commence to iiow through into the upper mixing space 9 and before the construction can be overheated. Convection currents will be set up tending to quickly raise the temperature of all of the water in the receptacle, and substantially all of the water that is brought into intimate and dispersed contact with the gases will be turbulent and at a boiling temperature so that rapid vaporization will take place, and the gases will be completely saturated. 'I'he supply of water in the generator is normally maintained at a substantially constant and most eillcient level by the return of condensate from the system. and wheneyerthis water level is lowered materially below its proper levellextra wa- `iierwillbefedinftorestorethewat'erleweland .apparatus and the formation of an improperly saturated heating medium. This apparatus `wi1l little attention over a lo'ng period of time.

Those portions oi' theapparatus where liming" or the deposition 'of 4solids may occur vare isolated from the gas and liquid, passages so that the free ilow oi.' iluidwill not be disturbed and cleaning will be lrequired only after long periods bluse.

While the component parts of the generator have for the most part been described as cylindrical Aor' of horizontally circular cross section (and are preferably so formed), it will be apparent that these elements could be given other crosssectional congurations without departing from the general principles o! this invention.

We claim:

l. A generator for a mixed iluid heating medinm consisting o! hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, means for replenishing the body of water, an outlet for the mixed heating medium leading from themixing chamber, a passage for conducting hot combustion gases in heat exchange relation tothe body of water and into the mixing chamber, means for partially confining a portion of the body of water closel'y adjacent the hot gases so that this water will be partially boiled, said conned portion being in communication with the main body of water and supplied with water therefrom, and a conduit projecting from this coniined space through which a fountain of water is forced upwardly into the mixing chamber.

2. A generator for a mixed iiuld heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, means ior replenishing the body oi water, anjoutlet for the mixed heating medium leading from the mixing chamber, a passage for conducting hot 'combustion gases in heat exchange relation to the body of water and into the mixing chamber, means for partially conilning a portion of the body of water closely adjacent the hot gases so that this water will be' partially boiled, an open receptacle positioned within the mixing chamber for holding an auxiliary body of water, the passage opening'intb the mixing chamber beneath the receptacle so that the gases will pass through the water overflowing from the receptacle, and a conduit leading upwardly from the conilned space to the receptacle through which water is forced upwardly from the conned space.

3. A generator for a mixed uid heating medium consisting of hot products ci combustion and steam, comprising a. housing enclosing a body oi' water and a mixing chamber thereabove, means for replenishing the body o! water, an outlet for r the mixed heating medium leading from the mixing chamber, a passage for conducting hot combustion gases in heat exchange relation to the body of water and into the mixing chamber, means for partially conning a portion of the body of water closely adjacent the hot gases so that this water will bev partially boiled, an open receptacle positioned within the mixing chamber for holding an auxiliary body of water, the passa'ge opening into themixing chamber beneath the receptacle so that the gases will pass through the water overiiowing from the receptacle. a conduit leading upwardly from the confined space to the receptacle through which water is forced `upwardly from the confined-space, and other conduits leading trom the confined space into the mixing 'chamber through which fountains of v waterv are forced upwardly.

4. A generator for a mixed um consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, means for replenishing the body oi water, an outlet for the mixed heating medium leading from the mixing chamber, a passage for conducting hot combustion gases in heat exchange relation to the body of water and into the mixing chamber. means for partially confining a portion o! the body ci' water closely adjacent the hot gases so that this water will be partially boiled. an open receptacle positioned within the mixing chamber for holding an auxiliary body oi' water, the passage opening into the mixing chamber beneath the renum nesting medi# ceptacle so that the gases will pass through the water overflowing from the receptacle, and a conduit leading upwardly from the confined space to the receptacle through which water is forced upwardly from the conned space. the bottom of said receptacle being below the normal level of the body of water so that some water will remain in the receptacle.

5. A generator for a mixed iiuid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, means for replenishing the body cf water, an outlet i'or the mixed heating medium leading from the mixing chamber, a passage leading substantially centrally through the body of water for conducting hot combustion gases into the mixing chamber. means for partially conining an annular portion ci the body of water closely adjacent the hot gases so that this water will be partially boiled, and a conduit projecting from the confined space through which a fountain of water is forced upwardly into the mixing chamber.

6. A. generator for a mixed iluid heating medium consisting of products oi combustion and steam, comprising a housing enclosing a `combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the rst housing so as to hold a body oi water around the first chamber and also enclose a mixing chamber above the 'combustion chamber, the upper surface ofthe body ci water forming part of the lower wall o! the mixing chamber, means for repienishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, a conduit for conducting the hot gases from the combustion chamber into the mixing chamber, 'means for partially confining a portion of the body oi' water closely adjacent the hot gases so that this water will be partially boiled, and a conduit projecting upwardly from this conned space through which a fountain oi' water is forced upwardly into the mixing chamber.

7. A generator for a mixed iluid heating medium consisting oi products of combustion and steam, comprising a housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the first housing so as to hold a body of water around the rst chamber and also enclose a mixing chamber above the combustion chamber, the upper surface ol the body of water forming part of the lower wallV of the mixing chamber, means for replenishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, a. conduit for conducting the hot gases from the combustion chamber into the mixing chamber, means for partially confining a portion of the body of water closely adjacent the hot gases so that thiswater will be partially boiled, an open receptacle positioned within the mixing chamber for supporting an auxiliary body of` water adapted to overflow through the hot gases into'the main body of water, and a conduit leading upwardly from the confined space into the receptacle through which water is forced upwardly.

8. A generator for a mixed uid heating medium consisting of products of' combustion and steam, comprising a housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the rst housing so as to hold a body of water around the first chamber and also enclose a mixing chamber above the combustion chamber, the upper surface of the body of water forming part of the lower wall ofthe mixing chamber, means for replenishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, a conduit for conducting the hot gases from the combustion chamber into the mixing chamber, means for partially confining a portion of the body of water closely adjacent the hot gases so that this water will be partially boiled, an open receptacle positioned within the mixing chamber for supporting an auxiliary body of Water adapted to overflow through the hot gases into the main body of Water, and conduits leading upwardly from the conned space into the receptacle and into the mixing chamber, water from the confined space being forced upwardly to replenish the auxiliary body of water and to spray into the mixing chamber above the receptacle.

9. A generator for a mixed fluid heating medium consisting of products of combustion and steam, comprising a housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the first housing so as to hold a. body of water around the first chamber and also enclose a mixing chamber aboye the combustion chamber, the upper surface of the body of water forming part of the lower wall of the mixing chamber, means for replenishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, a conduit for conducting the hot gases from the combustion chamber into the mixing chamber, means for partially confining a. portion of the body of water closely adjacent the hot gases so that this water will be partially boiled, an open receptacle positloned within the mixing chamber for supporting an auxiliary body of water adapted to overflow through the hot gases into the main body of water, and a conduit leading upwardly from the confined space into the receptacle through which water is forced upwardly, the bottom of said receptacle being below the normal level of the main body of water so that a reserve body of water will remain in the receptacle.

10. A generator for a mixed fluid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the rst chamber so as to hold a body of 'water around the first chamber and enclose a mixing chamber above the combustion chamben'the upper surface of the body of water forming the lower wall of the mixing chamber, means for replenishing the body of water, an outlet `for the mixed heating medium leading from the mixing chamber, an open receptacle supported within the mixing chamber above the body of water for supporting an auxiliary body of water, a conduit leading centrally from the combustion chamber into the mixing chamber through which the hot gases flow upwardly beneath the receptacle and thence outwardly around the receptacle through the water overflowing therefrom, `means for partially confining an annular portion of the main body of water around the central conduit adjacent the hot gases so that this water will be partially boiled, and a conduit leading from this confined space to the receptacle through which water is forced up into the receptacle.

1l. A generator for a mixed fluid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the ilrst chamber so as to hold a body of water around the first chamber and enclose a mixing chamber above the combustion chamber, the upper surface of the body of water forming the lower wall of the mixing chamber, means for replenishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, an open receptacle supported within the mixing chamber above the body of Water for supporting an auxiliary body of water, a conduit leading centrally from the combustion chamber into the mixing chamber through which the hot gases flow upwardly beneath the receptacle and thence outwardly around the receptacle through the water overflowing therefrom, means for partially confining an annular portion of the main body of water around the central conduit adjacent the hot gases so that this water will be partially boiled, a conduit leading from this conlined space to the receptacle through which water is forced up into the receptacle, and a conduit leading upwardly from the confined space into the mixing chamber through which a fountain of water is sprayed upwardly.

l2. A generator for a mixed fluid heating medium consisting of hot products of combustion and steam, comprislnga housing enclosing a combustion chamber, means for introducing hot combustion gases into this chamber, a second housing enclosing the first chamber so as to hold a body of water around the ilrst chamber and enclose a mixing chamber above the combustion chamber, the upper surface of the body of water forming the lower wall of the mixing chamber, means for replenishing the body of water, an outlet for the mixed heating medium leading from the mixing chamber, an open receptacle supported within the mixing chamber above the body of water for supporting an auxiliary body of water. a conduit leading centrally from the combustion chamber into the mixing chamber through which the hot gases flow upwardly beneath the receptacle and thence outwardly around the receptacle through the water overflowing therefrom, means for partially confining an annular portion of the main body of water around the central conduit adjacent the hot gases so that this water will be partially boiled. and a conduit leading from this conned space to the receptacle through which water is forced up into the receptacle, the bottom of said receptacle being below the normal level oi' the body of water so that some Water will remain in the receptacle.

13. A generator for a mixed uid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, an open receptacle positioned within the mixing chamber i'or holding an auxiliary body of water which overflows into the main body, means comprising a passage opening into the mixing chamber beneath the receptacle for conducting hot combustion gases in heat exchange relation to the bodies of water and through the water over- Iiowing from the .auxiliary body. the receptacle having a shallow annular edge portion with a. downturned rim, there being a second downwardly extending drip flange on the lower wall of the annular edge portion and spaced inwardly from the rim.

14. A generator for a mixed-duid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove. an open receptacle positioned within the mixing chamber for holding an auxiliary body of water which overiiows into the main body, means comprising a. passage opening into the mixing chamber beneath the receptacle for conducting hot combustion gases in heat exchange relation to the bodies of water and through the water overiiowing from the auxiliary body, means actuated by heat from the combustion gases for feeding water upwardly from the main body of water into the auxiliary body, the receptacle having a shallow annular edge portion with a downturned rim, there being a second downwardly extending drip flange on the lower wall oi the annular edge portion and spaced inwardly from the rim.

CLAYTON A. DUNHAM.

AUBRA R.. DUNHAM.

, DAVID N. CROSTHWAIT, Jn.

PAUL D. MILLER.

CERTIFICATE 0F CORREO TION.

Patent No. 2,169,685.

August 15, 1959.

CLAYTON A. DUNHAH; ET AL'.- It is hereby certified-that error appears in the printed specification of the above numbered patent requiring correction as follows: column, line 52, for "abut" read about; claim 5, for the article "thle'l readthie;

Page Il, first page 5,` second colmnn, line h5, and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 10th day of October,V A. D. 1959.V

(Seal.)4

Henry Yen Arsdale, Acting Commissioner of Patents.

water is forced up into the receptacle, the bottom of said receptacle being below the normal level oi' the body of water so that some Water will remain in the receptacle.

13. A generator for a mixed uid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove, an open receptacle positioned within the mixing chamber i'or holding an auxiliary body of water which overflows into the main body, means comprising a passage opening into the mixing chamber beneath the receptacle for conducting hot combustion gases in heat exchange relation to the bodies of water and through the water over- Iiowing from the .auxiliary body. the receptacle having a shallow annular edge portion with a. downturned rim, there being a second downwardly extending drip flange on the lower wall of the annular edge portion and spaced inwardly from the rim.

14. A generator for a mixed-duid heating medium consisting of hot products of combustion and steam, comprising a housing enclosing a body of water and a mixing chamber thereabove. an open receptacle positioned within the mixing chamber for holding an auxiliary body of water which overiiows into the main body, means comprising a. passage opening into the mixing chamber beneath the receptacle for conducting hot combustion gases in heat exchange relation to the bodies of water and through the water overiiowing from the auxiliary body, means actuated by heat from the combustion gases for feeding water upwardly from the main body of water into the auxiliary body, the receptacle having a shallow annular edge portion with a downturned rim, there being a second downwardly extending drip flange on the lower wall oi the annular edge portion and spaced inwardly from the rim.

CLAYTON A. DUNHAM.

AUBRA R.. DUNHAM.

, DAVID N. CROSTHWAIT, Jn.

PAUL D. MILLER.

CERTIFICATE 0F CORREO TION.

Patent No. 2,169,685.

August 15, 1959.

CLAYTON A. DUNHAH; ET AL'.- It is hereby certified-that error appears in the printed specification of the above numbered patent requiring correction as follows: column, line 52, for "abut" read about; claim 5, for the article "thle'l readthie;

Page Il, first page 5,` second colmnn, line h5, and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 10th day of October,V A. D. 1959.V

(Seal.)4

Henry Yen Arsdale, Acting Commissioner of Patents.

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