US3514034A - Gas-fired and powered heating system - Google Patents

Description

May 26, 1970 w. w. CUSHMAN 3,514,034

GAS-FIRED AND POWERED HEATING SYSTEM Filed March 20, 1968 5 Sheets-Sheet. l

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GAS-FIRED AND POWERED HEATING SYSTEM Filed March 20, 1968 3 Sheets-Sheet 2 ZEMW Q y 1970 w. w. CUSHMAN 3,514,034

GAS-FIRED AND POWERED HEATING SYSTEM Filed March 20, 1968 3 Sheets-Sheet 3 \D q) I V N N M "a N Q Q N INVENTOR.

United States Patent O 3,514,034 GAS-FIRED AND POWERED HEATING SYSTEM Walton W. Cushman, 401 N. Penn St., Webb City, Mo. 64870 Filed Mar. 20, 1968, Ser. No. 714,649 Int. Cl. F24d 3/02 US. Cl. 237-8 19 Claims ABSTRACT OF THE DISCLOSURE An automatic, self-modulating, gas-fired, gas-powered, forced-circulation residential or other hot water heating system, which is fully and efliciently operable without electricity or any other form of externally supplied power, other than the natural or other gas used for combustion, and includes a zone temperature-responsive control system which likewise requires no electricity or other external source of power.

BRIEF SUMMARY OF THE INVENTION This invention relates generally to hot water heating systems, and more particularly to such systems wherein any suitable gaseous fuel is fired in a combustion chamber associated with a hot water boiler construction wherein the temperature of the water is substantially elevated prior to its being force-circulated within a substantially closed system to thermal radiation devices Where most of the heat is released prior to its return to the boiler assembly for reheating and recirculation.

In most such installations, current practice requires the use of one or more electrically or otherwise mechanically driven pumps to provide the necessary hot water circulation, along with some form of electro-mechanical or electro-thermal valving or zone circuitry and gas-burner control, including certain safety controls. This invention contemplates the complete elimination of the need for electricity as a source of power, either for hot water circulation or to activate the control system.

Further, most systems currently used are designed to operate on a characteristic ON-OFF cycle. That is, when the thermostat or other thermally-sensitive element cools, it closes an electrical circuit which, in most cases, simultaneously or sequentially actuates the gas burner, the circulating pump, and a valve for the zone or zones to be heated. Since the water in the radiation system served by this particular thermostat has very likely already lost all or most of its heat, the sudden inrush of hot water from the boiler often results in considerable undesirable noise caused by the expansion of the pipes, and other elements of the radiation system.

This invention reduces or eliminates the noise problem in that it contemplates that both the circulatory system and its corresponding gas-burner system are modulated so as to eliminate this characteristic ON-OFF cycle. That is, instead of cycling between ON and OFF, the proposed system automatically and simultaneously modulates both the gas flame and the rate of water circulation to substantially match the heat loss requirements of the zone affected. If, for example, the outside ambient is such that a conventional system would be ON for a period and then OFF for a period, the system of thisinvention would automatically select an intermediate flame or gas consumption rate, along with a corresponding intermediate hot water circulatory rate, and operate so as to make only "ice infinitely small corrections of increase or decrease in each rate as required. Such operation not only virtually eliminates all thermally induced noise, but it also substantially increases the overall thermal efficiency. I

From the standpoint of operating economies, there is probably nothing quite so wasteful as a system requiring repetitious OFF and ON cycles, with its corresponding relatively cold fire box, followed by a highly contrasting very hot fire box and its inescapable over-drafting. The latter condition continues for a considerable period of time after the start of an OFF cycle because the stack temperature is so high that it causes the interior air to be drawn up and out for several minutes after combustion has completely stopped. Not only does this remove a substantial portion of the already heated room-temperature air from within the structure, but it also excessively cools the boiler and stack at a very rapid rate, ejecting the now overheated air to the outside atmosphere through the chimney. At the same time, a condition is created such that reasonably proper combustion cannot again get underway until the next ON cycle has been in operation long enough for the fire box temperature to come up to efficient operating temperatures, which is the reason that most heating engineers recommend against an installation with a total heat capacity that is even slightly over and above that which is absolutely required on the coldest day that can be anticipated.

It is known that continuous, uninterrupted operation of conventional heating systems will provide maximum fuel economies, particularly on those relatively infrequent very cold and windy days when the system must operate continuously to just barely replace the heat lost. Such an engineering compromise is of very little value, however, during those milder portions of the heating season when the heating system, because it is essentially too large for such moderate weather, must necessarily cycle between ON and OFF, and it is of small comfort to those individuals who would prefer to have at least some margin of safety for the unpredictable, record-breaking, ultra-cold and windy day.

Equally important, it is not at all unusual for a conventional heating system to break down or fail for any number of reasons, including an electrical power or component failure. At such times, the building or other structure rapidly loses much of its heat, and, only when the system has been repaired and restarted, is it often discovered that the system may be unable, even when operating at continuous full output capacity for a reasonable period of time, to replace all the heat lost during the earlier shut-down period. By completely eliminating the electrical system, the invention eliminates virtually all of the major and most frequent causes of failure in heating systems, including failures in both the source of the electricity and in the many electrically driven or electrically activated components of existing conventional systems.

Another important problem associated with conventional heating systems is the matter of personal comfort due to the excessive (some average about 3 /2 degrees F.) temperature differential required to cycle the thermostat. When the temperature in a zone must be raised 3 /z F. above the temperature where it last came ON before recycling the heating system to OFF, the result is not only exceedingly uncomfortable, but it is also wasteful. It will be seen that the control apparatus of this invention is capable of holding the temperature variation of a given closed area to less than plus or minus 0.1 F.

3 There are, of course, other problems and disadvantages with conventional gas-fired, hot water heating systems, and a main object of the invention is to provide such a system that is capable of operation by the combustion gas alone, totally independent of electricity or other mechanical sources of power, either for circulation or automatic control.

Another object of the invention is to provide such a system having two principal circuits, a gas circuit and a water circuit, the gas circuit providing the power for automatic control of water circulation.

Another object of the invention is to provide such a system wherein the water is force-circulated by the compression energy contained in the combustion gas.

Still another object of the invention is to provide such a system wherein the heating capability of the water heating element is automatically modulated to substantially match the heat loss of the area or zone being heated.

Another object of the invention is to provide such a system wherein the Water circulation rate is automatically modulated to substantially match the heat balance between the water heating element and the heat radiating elements.

Another object of the invention is to provide such a system wherein heated water circulation is accomplished by a gas-lift water pump provided by cooperative action between the gas and water circuits.

Another object of the invention is to provide a novel gas-lift water pump construction.

Still another object of the invention is to provide such a system having means for automatically modulating the combustion gas pressure to the burner.

Another object of the invention is to provide a novel closed pressure modulation means for accurately sensing and controlling the heated zone temperature.

Another object of the invention is to provide such a system wherein the gas pressure modulating means operates on a balance between a primary zone temperature responsive pressure and a secondary, adjustable, gravityinduced, heavy-liquid pressure to control a gas pressure control valve.

A further object of the invention is to provide a novel gas pressure and/ or flow control valve.

A still further object of the invention is to provide such a system wherein the modulated gas pressure and/ or flow is effective to modulate the water circulation rate.

A further object of the invention is to provide such a system having a novel self-modulating gas burner construction.

A still further object of the invention is to provide such a system wherein modulation of the gas pressure and/ or flow afiects automatic modulation of the burner.

Another object of the invention is to provide such a system that is automatically self-modulating so as to provide substantially infinitely variable or stepless heat gradients, eliminating thermally induced noise, shock and vibration, as well as inefliciencies due to widely varying stack and combustion chamber temperature and/or inadequate or excessive drafting.

Still another object of the invention is to provide such a. system capable of highly consistent and stable temperature and comfort control.

Another equally important object of the invention is to provide such a system that is dependable, eflicient and less expensive to manufacture, install, and operate.

Another object of the invention is to provide such a system that requires essentially zero maintenance of any kind, except as might be required to repair physical damage resulting from abnormal causes not related to operation of the system.

These and other objects and advantages of the invention will become readily apparent upon references to the following detailed description and the attached drawings.

BRIEF DESCRIPTION OF THE VARIOUS VIEWS OF THE DRAWINGS FIG. 1 is a diagrammatic illustration of a heating system embodying the invention.

FIG. 2 is an enlarged schematic elevational view illustrating the heated zone temperature control and modulated gas supply portion of the system shown by FIG. 1.

FIG. 3 is an enlarged top plan view of a portion of FIG. 2.

FIG. 4 is an enlarged cross-sectional view of a portion of FIG. 2.

FIG. 5 is an enlarged cross-sectional view of a portion of FIG. 3.. p 7

FIG. 6 is an enlarged schematic elevational view of the water heating burner and gas-lift, forced-circulation pump portion of the systemshown by FIG. 1.

FIG. 7 is an enlarged cross-sectional view taken on the plane of line 77 of FIG. 6, looking in the direction of the arrows.

FIG. 8 is an enlarged side elevational view, with portions thereof broken away and in cross section, of the automatically self-modulating water heating burner of the system shown by FIG. 1.

DETAILED DESCRIPTION (A) General structure Under this heading, the general structure of the heating system will first be briefly described. The operation of the system and the structural details necessary or relating to such operation will be discussed under the heading (B) Operation.

Referring now to the drawings in greater detail, and to FIG. 1 in particular, a heating system 10 according to the invention includes a gas circuit 12, indicated by tailed arrows, and a water circuit 14, indicated by the nontailed arrows, such designation of the gas and water circuits being employed throughout the drawings. In the former circuit, gas flows from a regulated pressure source 16, through a gas flow control valve 18, (shown in greater detail in FIG. 4), through the gas-lift pump (shown in greater detail in FIG. 6) and then to the modulated burner 22 (shown in greater detail in FIG. 8), the combustion products being discharged to atmosphere through the usual stack 24. In the water circuit 14, the pump 20- circulates water heated in the burner-boiler 22 to the radiators 26 in the heated zone 28 and back to the burner-boiler 22.

Referring now to FIG. 2, the gas from the main (not shown) enters conduit 30, which may have manual valves 32 positioned on both sides of any suitable gas pressure regulating valve 34. The conduit also includes a gas flow control valve 18, which, as shown in FIG. 4, may comprise a conduit section 36 having an elastomeric sleeve 38 suitably mounted therein. The ends 40 of sleeve 38 may be rolled over the ends of the section 36, for example, and retained by means of rings 42 threaded on the ends 44 of the conduit 30. Any suitable means may be provided to compress the elastomeric sleeve 38 to provide a gas-tight seal, and, in the FIG. 4 structure, this is accomplished by the rings 42 drawing the conduit ends 44 axially toward the section 36 to compress the rolled sleeve ends therebetween. The rings 42 may be restrained axially by the annular beveled flange 46 on the section 36, and sealing compound, soldering or other known specific means may be employed to enhance the sealing.

The variable volume 48 between the elastic sleeve 38 and the rigid section 36 communicates through a standpipe 50 with a reservoir.52 containing a float valve 54 for at times closing the port 56 at the top of the reservoir so that the heavy liquid 58 contained therein and in the standpipe 50 and the variable volume 48, for a purpose to be described under Operation, cannot rise beyond the port 56. A hollow bellows assembly 35 having an opening 37 at its upper end may be threaded or otherwise sealably secured into the section 36, the bellows being adjustable axially by a screw 39 carried by a bracket 41 secured to the section 36, whereby liquid 58 within the bellows 35 may be, for example, forced out to increase the height of the column 58 for control purposes.

Referring now to FIGS. 1-3 and 5, the zone or space to be heated 28, such as a room of a residence, may include a window 60 or other surface, and the room temperature rapidly decreases, during the heating season, as the window 60 is approached. A hollow pressure bulb 62 is mounted on the wall 64 adjacent the window 60 n a pivot mechanism 66 and connected by any suitable gastight means to a small conduit 68, which may be disposed in the wall 64 and is connected by gas-tight means to the reservoir 52 at port 56. The bulb 62 and the conduit 68 contain a gas and/or liquid 70 that is not miscible with the heavy liquid 58 contained in the reservoir 52, and whose vapor pressure varies substantially with tem perature variations at the bulb which may be pivoted closer to the window when additional heat or a higher temperature is desired, and vice versa, as shown by the arrow 72.

While the operation of the system is described below, it will be apparent at this point that increased temperature at and pressure in the bulb 62 forces the heavy liquid level downwardly in the reservoir 52 and causes the liquid 58 to constrict the elastic sleeve 38 and thus reduce the gas flow area therethrough. The converse is also true because the elastomeric sleeve 38 opposes such constriction and tends to retain a maximum flow area.

Referring now to FIG. 6, any gas passing through the sleeve 38 flows from conduit 30 into the innermost vertical tube 74 of the gas-lift pump 20, which further comprises an outer pipe or tube 76, which is closed at the bottom and the open upper end 78 of which extends into the water reservoir 80 and has formed on or attached thereto a conical .ring 82 for a purpose to be described. Water 84 in the reservoir is replenished from the usual supply conduit 86, and a float valve 88, which is shown only schematically and may include any well-known levered structure adequate to close conduit against the water pressure therein, maintains the water at any desired level, as at the level 90. The water leaves the reservoir by way of conduit 92, and it enters the pump 20 at the bottom through conduit 94.

An intermediate constant submergence tube 96, opcrl at its bottom and closed at its top, is fitted with clear ance over the inner tube 74 so as to receive gas therefrom, and it preferably may have secured at its bottom end a plate 98 having small openings 100 therein for a purpose to be described. The inverted intermediate tube 96, which is filled with gas, thus floats in the water contained in the outer tube 76, and it may rise into the tube 102 extending from the top of the water reservoir 30. Gas thus flows from the inner tube 74 into the inverted tube 96, downwardly through the clearance 104 between the inner and the inverted tube, through the perforated plate 98, up through the water in the clearance 106 between the inverted tube and the outer tube, into the volume 108 in the water reservoir 80 above the water level, up the tube 102 and out the conduit 110 leading to the burner-boiler 22. Pumping of the water is, of course, accomplished by the gas rising and expanding in the outer tube.

As shown in FIG. 6, heated water pumped into the reservoir 80 is circulated by gravity through conduit 92 to the radiators or other heat radiating devices 26, which may be in series or parallel connection, and then to the burner-boiler 22 through conduit 112 for heating and return through conduit 94 to the bottom of the pump 20.

Reference is now made to FIG. 8, which is a substantially enlarged side elevation, with portions thereof cut away and in cross section, of the burner-boiler 22 shown in FIGS. 1 and 6. It will be understood that except for the specific structural features to be described, the burner-boiler 22 may be of any desired construction.

The burner-boiler is formed to include a fire box 114 having a stack 24 and surrounded to any desired extent by a water chamber or boiler 118 having a cold water inlet, conduit 112, and a hot water outlet, conduit 94. The burner 120 is formed with an inclined passage 122 connected to the gas supply conduit 110 and having a series of burner nozzle risers 124 of progressively increasing height extending upwardly therefrom. The lower end of the inclined passage 122 is connected by the conduit 126 to the bottom of the control tank 128, the upper end of which is conected by conduit 129 to a venturi restriction 130 in the gas supply conduit 110 and which contains a float valve 132 for sealing the conduit, and by a branch conduit 134 to a fluid reserve tank 136 that may be refilled through non-vented plug 138.

The reserve tank 136 operates on the inverted container principle to maintain the inclined passage 122 and nozzles 124 filled with a liquid 140 to the level 142 only when gas flow is stopped; that is, the liquid 140 will be replenished to the intersection of conduit 134 with conduit 126 whenever it drops below that level and when no gas is flowing. While the nature and function of the liquid 140 will be described below, it should be n ted that increasing gas flow through the venturi restriction 130 will cause a decreasing pressure in the control tank 128, this increasing pressure differential across the liquid 140 causing the level 142 thereof to drop in the burner 120 and rise into the control tank 128, thereby successively permitting additional nozzles 124 to flow gas into the fire box.

(B) Operation Temperature control of heated space.The temperature control mechanism employed in the proposed heating system uses a highly temperature-sensitive gas/liquid 70 in combination with a static head of heavy liquid 48 to modulate the flow of combustion gas through the gaslift, forced-circulation water pump 20, and thence to the modulated gas burner-boiler 22. The number of variations which may be employed with this type of control mechanism is virtually unlimited, but only one specific example will be described in detail, for purposes of illustration.

It is first necessary to consider some of the more pertinent and critical objectives of such a system. Since the combustion process is itself modulated without frequent recourse to the extremes of either ON or OFF, it is necessary that some specific temperature control range be selected as representative of these two extremes. In this specific example, 72 F. has been selected to be normal, with provision that a temperature rise of 05 F. will completely stop the water pumping and gas combustion process, whereas a drop of 0.5 F. will cause combustion gas flow and pumping to be at design maximum, which in this case has been arbitrarily selected to be 60,000 B.t.us/ hr. input or one cubic foot of gas/ min. for a typical single heated zone installation. This input capacity can, of course, be modified as necessary by the design engineer.

In other words, a control temperature range of 1.0 F. should govern the entire gas-flow range from zero to the design maximum. In practice it will be found that this is capable of holding the temperature of a given heated space to within plus or minus 005 F., provided, of course, that the total output capacity of the burner 120 is equal to or in excess of the maximum heat loss that can be expected on the coldest and/or windiest day anticipated.

Beginning in the heated zone 28, the control system consists of a small pressurized bulb 62 containing a suitable gas and/ or fluid 70 and mounted on a pivot 66 that is attached to the wall or ceiling 64 so that it can be moved into and out of slightly higher or lower temperatures, as, for example, close to the window 60 or other similarly cooler area, or away from such an area and into inherently warmer areas, including positions immediately.

above or close to the zone heat radiation devices. This is the only normal manual adjustment of temperature control available in the system for actuation within the heated space involved, but the liquid column in standpipe 50 (secondary heavy-liquid control column to be discussed later) may be constructed so that it can also be adjusted (screw 39 in FIG. 4), thereby olfering two independent forms of manual control.

Using the single control, if an increase in temperature moved closer to a window 60 or other similarly cooler were desired, for example, the pressure bulb 62 would be area; if a temperature decrease were desired, the bulb would be moved away from the cooler area into a normally warmer location. Since the temperature variation within only a few inches of a window may be quite pronounced, it will be found that the required bulb movement will usually be quite small. The bulb motion could, if desired, be calibrated to reflect simulated or actual temperature settings.

In order that the bulb 62 may be moved or swiveled in and out on its pivot 66, it is necessary that a highly durable flexible tubing 69 or an absolutely gas-tight swivel fitting 66 be provided for the connection of the bulb to the tubing 68 permanently installed and concealed within the walls 64. The tubing may be quite small, and ordinary A commercial copper tubing is adequate. The other end of the tubing 68 connects with the top of a relatively small diameter vertical standpipe or column 50 containing a predetermined static head of some suitable heavy liquid 58 with low vapor pressure characteristics and completely non-miscible with the gas/liquid 70 used in the pressure bulb. The internal volume of the connecting tubing 68 should be small in relation to the volume of the pressure bulb 62. Wherever it is practicable to do so, the tubing 68 should be routed so as to not pass through or near any hot areas as this can adversely affect uniformity of control, particularly if such areas are subject to considerable temperature variations that do not necessarily parallel temperature variations within the heated zone. The column of heavy liquid 58 communicates with and operates the flow valve 18 controlling gas flow, as

shown in FIGS. 2 and 4. The height of the column of liquid 58 is inversely proportional to its specific gravity,

i.e., a fluid with only half as much specific gravity would require a column height or head twice as high,

If Freon 11 (OCI F) is used as the primary control gas/liquid 70, then the height of the secondary heavy liquid column 50 should be such that when a vacuum of exactly 0.575 p.s.i.g. (when atmospheric pressure is standard or 14.7 p.s.i.a.). or an absolute pressure of 14.125 p.s.i.a. (when atmospheric pressure is standard) exists in conduit 68 connected to the top of the column, the weight of the liquid 58 is just sufiicient to completely construct the sleeve 38 and stop all gas flow-against; the regulated input gas pressure in conduit} 30. Further, the

cross-sectional area "and the volume above the liquid pressure of 13.835 whenatmospheric pressure is 14.7 a:

p.s.i.a.

Since these pressure values maybe too critical for equipment and instrumentation available to most installation personnel, this problem can be greatly simplified by me A.

merely using a transparent tubing 50 for the" vertical J'i has been checked to insure complete constriction of sleeve 38 and' gas-"flow stoppage when the upper'en'd' the column 58 is open to the atmosphere prior to its being connected to the control gas/liquid in bulb 62 and conduit 68.

Additional desirable fine adjustment is made possible by the screw 39 to vary, within design limits, the height of the heavy liquid column." It should be noted here that a normal heated zone temperature of 72 F. will give Freon 11 a'pressure of approximately 13:98 p.s.i.a., or about 0.72. p.s.i.g. below atmospheric pressure, and that this reduced pressure will tend to reduce the sleeve constricting pressure in the gas-flow control valve 18 by an equal'amount.

g The elastomeric sleeve 38 in the gas-flow control valve 18 should be one that is completely impermeable and totally unaffected by the gasused for combustion or by the control liquid 58 used in the vertical column. It should also possess good elastic recovery properties, along with very little tendency to acquire a permanent set. Such requirements narrow the field somewhat so as to eliminate almost all known elastomers with the exception of certain of the silicones and polyurethanes. The elas tomeric sleeve 38 should be assembled or installed with suflicient initial stretch so as to be capable of expulging all of the control liquid 58 from the valved chamber 48 without any assistance from gas pressure within the sleeve, and with the heavy liquid control column 50 disconnected.

Itwillthus be apparent that a combination of three forces tends to maximize combustion gas flow. These forces are (a) the elastic recovery capabilities of the elastomeric sleeve 38 in the gas flow control valve 18, (b) the combustion gas pressure itself and (c) the absence of pressure or partial vacuum in the primary gas/liquid (bulb 62) control system. The latter force amounts to 0.29 pound per square inch (0.29 p.s.i.) for the entire 1 F. operating range, plus an additional 0.575 p.s.i. to account for the reduction below atmospheric pressure when Freon 11 is at 725 R, which is the upper limit of the control range. I

It is further apparent that the incoming combustion gas pressure is, by far, the largest of the forces involved. In designing the heating system 10, certain realistic values should first be assumed for the purpose of making a trial computation. Thus, let it be assumed that the input combustion gas pressure is 5 p.s.i.g., that the primary gas/ liquid control' pressure variation (over 71.5-72.5) is 0.29'p.s.i.g. and that'the elastic recovery forces in the gas-flow control sleeve 38, when translated into the hydraulicpress'ures generated by the secondary heavy liquid column 58, are 0.39 p.s.i.g. when the sleeve is fully extended inwardly to the position wherein gas flow is completely stopped and 0.1 p.s.i.g. when it is fully contracted so assto permit maximum combustion-gas flow. This establishes the two extreme critical pressures on the hydraulic side of the elasto'meric'sleeve 38, i.e., 5.39 p.s.i.g. when combustion gas flow is stopped, and 5.1 p.s.i.g. when gas flow is at a'maximurn.

The above 0.29 p.s.i.g. differential (5.395.1) corresponds to th'e'working pressure variation in the primary gas/liquid pressure control system. It means that the height of the heavy liquid 58 in-the secondary pressure controlsystein acting to constrict the combustion gas'control valve'sle'eve should" be such as to produce a pressure of 5.39 p.s.i.g. plus 0.575 p.s.i.g. additional to compensate for the pressure reduction in Freon 11 when it is at 725 'F.,*or-a total' of 5.965 p.s.i.g. acting on the sleeve when the topiof' the secondary :pressure control column is open to atmospheric'pressure. If this liquid were water (not recommended),:-the 'height of'the filled portion of the column 50- should -ibe=- 5.965 x 2.31:11779151 or approx. 13.78 feet. 1 'The volume of the reservoir 52 should be suflicient to accommodate all of the liquid58 within the control sleeve -38 when 'th'erconduitdis' is= connectedto the reservoir and the -primary gas/liquid control pressure therein is a vacuum of 0.865 p.s.i.g. or more. A float-type check valve 54 should be provided in the reservoir 52, or at the top of the secondary pressure control system, so as to prevent any of the heavy secondary control liquid from overflowing back into the primary system when the primary control pressure is more than 0.865 p.s.i.g. below atmospheric pressure. If no such check valve were provided, such overflow back into the primary system could happen, for example, if the heating plant were to be shut down so that there is no combustion gas pressure acting on the sleeve 38 and the normally heated zone where the primary pressure control bulb 62 is located might become quite cold.

Should a given sleeve construction and elastomeric composition be found to require too much pressure for actuation under optimum conditions, it may be stretched more tightly by lengthening the tube 36 on which it is mounted, and the liquid withdrawal volume above the hydraulic fill line in the secondary pressure control system should be increased accordingly. It is preferable that this withdrawal volume be a substantially enlarged section of the secondary pressure control tubing, like the reservoir 52, so as to provide room for the check valve float, and to reduce the overall height requirements for withdrawal.

The overall height requirements may be further reduced by using a liquid heavier than water, or water containing some soluble material such as calcium chloride, whereby the specific gravity may be increased to about 1.54 in a saturated solution. In the earlier example where water required an initial fill height of some 13.78 ft., this can be reduced to or approx. 8.95 ft. However, the use of CaCl solution will require that the tube 36 in which the elastomeric sleeve 38 is mounted be adequately protected on its inner surface with some material not adversely atfected by a calcium chloride solution. CaCl has the advantage of being readily available at low cost, and it provides adequate protection against freezing. There are numerous other heavy (heavier than 7 water) non-freezing liquids which may also be adapted to use in this system, however.

Gas-lift forced-circulation water pump.-As previously stated, the forced-circulation water pump 20 operates on the gas-lift principle, using the pressure already available in the combustion gas. Combustion gas passing through the flow-control valve 18 is made to enter the base of a vertical water pumping tube-like apparatus 20, the diameter of the outer tube 76 being greatly exaggerated in size in the drawings for clarity. The gas then passes upwardly through the smaller tube 74 which terminates at some intermediate height which will be more accurately defined. The inverted tube 96 encloses the first tube 74, and it serves the function of causing combustion gas to be discharged into the circulating water at some predetermined constant submergence depth. This is necessary in order to maximize water volumetric flow, since the gaspressure required to start the pumping operation from some given submergence depth is greater than the pressure required to keep the pumping action going once it is started. Stated in another way, the water level between the main pump casing 76 and the gas-filled constant submergence tube 96 will, when no gas is flowing, normally be very near the top of the main casing 76, about midway in the overflow tank or water reservoir 80, as at 90. The

cone at the top of outer tube 76 is provided to prevent the noise of falling water.

When pumping action begins, the small gas bubbles, formed in part by the apertured plate 98 attached to the 'open bottom end of tube 96, intermingle with the water so that the combined weight of the water and gas mixture above the bottom of the constant submergence tube will be considerably less than it would if the gas bubbles were not present. Since the constant submergence tube floats in this water, it cannot float as high when the weight of the flotation water is reduced by intermixed gas bubbles, and consequently it sinks to a lower level. The net effect is to insure that the gas will always exit from the base of the constant submergence tube at or very near the design operating gas pressure as controlled by the automatic pressure-reduction valve 34. As a specific example, if the operating combustion gas pressure is 5 p.s.i.g., then the distance from the normal static water level 90, when no gas is flowing, to the bottom of the constant submergence tube a plate 98 should be just under 5 2.3l=1l.55 ft. In other words, the constant submergence tube 96 should be ballasted to float submerged to this depth.

To maximize efficiency, the constant submergence tube 96 should be tapered so that its diameter is slightly smaller at the top, or the outer casing 7 6 should be similarly but oppositely tapered so that its diameter is slightly larger at the top. The amount of this taper is much too small to be shown in the drawings; however, it can be calculated on the basis that the cross-sectional area at any elevation of the gas-water flow should be equal to the combined volumes of gas and water at that elevation, it being clear that the rising gas is constantly expanding because its submergence depth is steadily decreasing. The smallest cross sectional area for the gas-water mixture should be, in square inches, equal to the gallons of water flow/min. divided by 12.

Pumping will be more eflicient if the water is raised at a steady uniform flow rate rather than at a continuously accelerated rate, and a uniform flow rate can be attained by incorporating a suitable expansion taper into the design. The efliciency is further enhanced by attaching the finely perforated plate 98 to the bottom of the constant submergence tube 96 to divide the gas into smaller bubbles because larger bubbles offer a somewhat lesser amount of total surface area for contact or cohesion with the water.

The amount of water than can be pumped by this gaslift method is dependent upon many variables, not the least of which is the total resistance to flow offered by the radiation system and its connecting piping to and from the boiler room. It is essential that the hydrostatic head or pressure of the water pumped be such as to overcome this flow resistance to the extent that the return water flow to and through the boiler 22 and then to the base of the gas-lift pumping assembly 20 will be at a rate sufficient to replace the water in the gas-lift column within outer pipe 76 without an excessive amount of pull-down on the constant submergence tube. Should tube 96 bottom, it is clear thatthe combustion gas could exhaust from its base at a much higher rate because of the reduced resistance resulting from a decrease in the effective weight of the overlying water, and as a consequence the amount of water actually circulated would be reduced.

The total volumetric water flow required is primarily related to the heat input to the boiler 22, and secondly to the heat output through the radiation system. On the input side, one cu. ft./ min. or 1000 B.t.u.s/ min. was previously hypothetically assumed as an operating maximum for a typical single heating zone installation. If the boiler 22 is efiicient, then some 800 B.t.u.s/ min. will enter the water. If the boiler contained only 8 lbs. or just slightly under one gal. of water, the temperature of this 8 lbs. of water would be raised 100 F., say from 100 F. to 200 F., and it would be necessary that this water be replaced once/minute, i.e., the required minimum water circulation would be approx. one gal/min. This situation would, of course, also require that the radiation system be capable of losing 800 B.t.u.s/min, but it might be extremely difficult or impracticable to distribute or spread out only 8 lbs. of water over a large enough area as to be able to lose 800 B.t.u.s/hr. It is therefore preferable that the volume of water pumped be greater than 8 lbs./

Fortunately, the gas-lift system is capable of pumping considerably more water, just how much more depending 1 1 upon several factors, including the total lift height. The maximum lift height is limited by the effective gas pressure. In the construction of the proposed system 10, it can be seen that there is an over-pressure imposed upon the water pumping system which is greater than atmospheric pressure, but less than the sum of atmospheric pres sure plus the incoming gas pressure, the amount of this over-pressure depending upon the rate of gas flow through the burner 120. That is, if the gas flow is restricted only a small amount, then the over-pressure will be relatively low. If the burner orifices 124 are substantially the same as those presently used in the so-called low-pressure systems, i.e., for operation at about 0.25 p.s.i.g., and if the .pressure drop due to friction in the pipes leading from the top of the water pump 20 to the burner 120 is another 0.25 p.s.i.g., then the over-pressure could be approximately 0.5 p.s.i.g. If the incoming gas is at p.s.i.g., and if the pumping system were 100% efficient, then one cu. ft. of gas/min. at 5 p.s.i.g. could lift one cu. ft. of water a distance of 2.31 (5-0.5) =10.395 or approx. /3 ft. Since such systems are only about 50% efficient, the amount of water would be halved so that one cu. ft. gas/min. at 5 p.s.i.g. would lift gals/min. to a height of 10 /3 ft. With an overapressure of 0.5 p.s.i.g., the constant submergence tube 96 should be ballasted to float at a depth of approx. 10 /3 ft. instead of the 11.55 feet previously indicated.

This 10% ft. submergence depth also represents the effective pressure head for the circulation of water except that there is a small loss because of the need to insure that the water level in the overflow tank is always a few inches lower than the top of the pump outlet. Four inches or /3 ft. should be adequate for this purpose, and this leaves an effective pumping head of 10 ft. or

or about 4.33 p.s.i.g. for water circulation, which should be adequate for most 60,000 B.t.u./hr. single heated zone installations.

It should be noted here that it is not essential that the incoming gas pressure be limited to only the 5 p.s.ig. used in the preceding hypothetical installation, and many modern gas companies are already equipped to supply gas at pressures up to 50 p.s.i.g. or more. It can be seen that if the incoming gas pressure were to be increased to 10 p.s.i.g., for example, and if the burner construction and the pipe friction loss were the same, then the pressure available for water circulation could be increased to ft. or a pressure of p.s.ig. (approx) for-circulation. Such a pressure increase would,v of course, require that the' secondary heav'y liquid) pressure control system be, appropriately redesigned, together with the substitution of an appropriate pressure-reduction valve 34.

It should be noted here that as the water temperature increasesyit decreases in weight (to 8.039 lbs./ gal. at 200 F.) and therefore lifts easier; at the same time, the pumping gas is expanded due to increased temperature so that its volume is increased substantially to; further increase the amount of water pumped. v

, Some water vapor is lost in this system because it mixes with the combustion gas and enters the'combustion chamher. This is more of an asset than a liability, however,

the water chamber of the burner-boiler 22, according to numerous researchers, including several US. Governbecause this substantially improves thermal conductivity 1 and Jheattransfer between the hot combustion gases and ment laboratories.

The heat gained by the combustion gas when passing through the pump 20 is not lost since it is returned to the combustion chamber 114 if the connecting lines are suitably insulated. In fact, the entire pumping, overflow tank, boiler, and all associated lines should be properly insulated to minimize losses.

Automatically self-modulating gas burner.Referring to FIG. 8, burner 120 employs a high-temperature, exceptionally low-vapor pressure liquid 140' having high cohesion and low adhesion properties as the modulation control media. For example, some of the high temperature silicone lubricants are well-suited to this application. When the burner is inoperative, i.e., when no 'gas is flowing in conduit 110, the control liquid 140 seeks the horiontally level position 142. The reserve tank 136 provides replenishment fluid as required, even though the amount of fluid expected to be consumed has been calculated to be extremely low, probably less than 0.01 gal/year for an average 60,000 B.t.u./hour installation. It will be noted that the temperature of liquid 140 is never very high, in spite of its close proximity to the fire box 114, since the burner 120 is cooled by both the incoming gas and the air used for combustion. As stated previously, certain details of the burner-boiler 22 are of no significance to the invention, among these being the combustion air supply, which is not shown except for the air jets represented at '125. Further, FIG. 8 illustrates a sectional view of a single row of burner nozzles 124, and it will be understood that the burner 120 could have any desired number of rows of nozzles 124, in a variety of configurations.

The reserve tank is of the inverted container type so that the fluid level 142 in the burner control system will be held constant, and it will be noted that filling can only occur when the burner 120 is inoperative and when the fluid level 142 is below the level of the connection (conduit 134) to the reserve tank 136.

As shown in FIG. 8, when combustion gas is flowing at a very slow rate, only the three burner nozzles 124 at the extreme left (FIG. 8) will ignite (the pilot light for ignition is not shown) and be operative. Three nozzles are a purely arbitrary consideration, and only one or any number of nozzles may be used for the lowest operating condition just above completely OFF. It will be recognized that the orifice size of these individual burner nozzles 124 will largely dictate the number to be activated in the lowest heating condition.

Even when cobustion gas flow is at a predetermined minimum, there will generally be enough pressure in the burner assembly 120 to cause the fluid 140 at the extreme left in passage 122 to depress slightly, while concurrently causing the fluid inall nozzles 124 except the first three on the left to' raise even less slightly since the fluid volume decrease on the left will be distributed equally among all the other inactive fluid columns or nozzles 124 plus the control column in conduit 126 on the extreme right.

As combu stion'gas flow is increased, its passage through the venturi 130 in conduit will tend to generate a gradually increasing vacuum transmitted to the top of the control tank 128, which normally would be insulated from the burner-boiler 22. As the vacuum increases, fluid 140 is withdrawn from the burner control assembly, until none remains when gas flow is at a design maximum. Thus, the venturi should be selected on the basis of its ability to lift all of the fluid into the control tank 128 until the last burner orifice 124 at the extreme right is uncovered and operating.

j Thefloatvalve 132 in the control tank is for the purpose of providing safety against the possibility that gas flow might in some manner inadvertently exceed the design maximum, and thus tend to pull the control liquid 140 and over into the venturi. This could do no real damage, of course, since the fluid 140 would merely fall back down through the gas inlet conduit 110. However, there is some possibility that a condition could exist wherein the reserve tank 136 might be caused to overfill the system, and this could either cause the entire burner assembly 120 to shut down or cause some of the liquid 140 to pass upwardly through the nozzles and spill over into the combustion air inlet openings 125. The float valve is therefore considered to be reasonably essential. It should be noted here that the volume of the control tank 12-8 with the float 132 against its seat 127 should be equal to the volume of fluid required to fill the burner control assembly from the bottom of the standpipe conduit 126 to the design fluid level 142 when no or minimum gas is flowing. To allow for normal manufacturing variations, this volumetric relationship may be finely adjusted at the time of installation by moving the float valve seat 127 up or down, or by the addition or removal of spacer washers (not shown) as necessary.

It will be apparent from the above description, wherein the invention has been disclosed in such clear and concise terms as to allow those skilled in the art to practice the same, that the invention provides an automatic, selfmodulating, gas-fired, gas-powered, forced-circulation hot water heating system that requires no electrical power and is characterized by the numerous initially-stated objectives, as well as providing other advantageous results.

While the invention has been shown and described as embodied in a hot water heating system, certain portions thereof are applicable to any system, such as a forced air system, as well as for other uses.

To those skilled in the art to which this invention relates, many variations in construction and widely differing embodiments of the invention will suggest themselves without departing from the spirit and scope of the invention. Thus, the disclosures and description herein are purely illustrative and are not intended to be in any sense limiting.

What I claim as my invention is:

1. A gas-fired, forced-circulation, heating system for an enclosed heated zone, comprising combustion gas circuit means adapted for connection to an associated source of combustion gas under pressure, a heatconveying fluid circuit means, burner means fired by said combustion gas for heating said heat-conveying fluid within said heat-conveying fluid circuit means, pump means for pumping said heated heat-conveying fluid through said heat-conveying fluid circuit means to said zone, said pump means including a portion of said combustion gas circuit means for enabling the controlled rate of escape of said combustion gas into a portion of said heat-conveying fluid circuit means in order to permit said escaped combustion gas to bubble through said heatconveying fluid and thereby cause a pumping action of said heat-conveying fluid, combustion gas throttling means in circuit with said combustion gas circuit means effective for variably throttling the rate of flow of said combustion gas therethrough, and thermally expansible means responsive to the temperature within said heated zone and operatively connected to said combustion gas throttling means, said thermally expansible means being effective to vary the opening of said throttling means to regulate the rate of flow of said combustible gas therethrough in order to thereby regulate the rate of heat supplied to said heated zone.

2. A gas-fired, forced-circulation, heating system for an enclosed heated zone, comprising a combustion gas circuit means and a heat-conveying fluid circuit means, said system being powered entirely by the flow of said combustion gas; said gas circuit including in sequence a pressure-regulated source for said combustion gas, a gas flow control valve, a pump for said heat-conveying fluid powered by the percolation of said combustion gas therethrough, a burner, and first conduit means connecting said source, said valve, said pump and said burner; and said heat-conveying fluid circuit means comprising a boiler associated with said burner, a portion of said pump, heat radiating means and second conduit means connecting said boiler, pump and radiating means.

3. A gas-fired, forced-circulation, heating system for an enclosed heating zone, comprising a combustion gas circuit means and a heat-conveying fluid circuit means, said system being powered entirely by the flow of said combustion gas, said gas circuit means including in sequence a pressure-regulated gas source, a gas flow control valve, a pump for said heat-conveying fluid and a burnerboiler, conduit means connecting said gas source, gas control valve, pump and burner-boiler, said gas flow control valve comprising a rigid conduit having a highrecovery elastomeric sleeve therein, said sleeve having the ends thereof connected to said conduit and the intermediate portion thereof free therefrom thereby defining a generally annular chamber between said conduit and sleeve, and means for communicating a variable pressure developed externally of said annular chamber and dependent upon heated-zone temperature to said annular chamber to variably constrict said sleeve, thereby determining a variable flow area controlling gas flow in accordance with heated-zone temperature.

4. A system such as that recited in claim 2, wherein said burner comprises a plurality of burner nozzles, and means responsive to the volume rate of flow of said combustion gas to said burner for both completing and terminating the flow of said combustion gas to one or more of said plurality of burner nozzles.

5. A system as that recited in claim 4, wherein said burner comprises an inclined passage connected at the upper end to said combustion gas circuit means, a venturi carried within a portion of said combustion gas circuit means, the lower end of said passage being connected to a control chamber and to a liquid supply tank, conduit means communicating between said venturi and said control chamber effective to communicate to said control chamber a variable venturi pressure corresponding to the rate of flow of said combustion gas through said venturi and to said inclined passage, said inclined passage having individual upwardly extending branch passages of progressively increasing length respectively feeding said nozzles, said branch passage being filled with said liquid to a predetermined level whereby at least one of said branch passages is uncovered thereby at a minimum rate of flow of said combustion gas, the pressure of said combustion gas at the upper end of said inclined passage applied to the surface of said liquid and the variable venturi pressure being applied to said control chamber and liquid supply tan-k being effective to cause said liquid to flow into said control tank and progressively uncover additional branch passages in accordance with the rate of flow of said combustion gas.

6. A gas fired, forced-circulation, heating system for an enclosed heated zone, comprising a combustion gas circuit means and a heat-conveying fluid circuit means, said system being powered entirely by the flow of said combustion gas, said gas and heat-conveying fluid circuits cooperating to provide a pump for circulating said heat-conveying fluid, said pump comprising means containing a column of said heat-conveying fluid to be pumped and means for causing said combustion gas at a predetermined design pressure to be discharged into said column of said heat-conveying fluid in the form of bubbles, whereby the compression energy of said bubbles of combustion gas as said bubbles rise in said column lifts said heat-conveying fluid at a substantially uniform rate dependent upon the rate of flow of said combustion gas.

7. A gas-fired, forced-circulation, heating system for an enclosed heated zone, comprising a combustion gas circuit means and a heat-conveying fluid circuit means, said system being powered entirely by the flow of said combustion gas, said gas and heat-conveying fluid circuits cooperating to provide a pump for circulating said heat-conveying fluid, said pump comprising an outer cas- 15 ing closed at the bottom end and having an open upper end disposed in a heat-conveying fluid reservoir, conduit means supplying heat-conveying fluid at the bottom of said casing and conduit means discharging said heat-conveying fluid from said reservoir, a gas supply standpipe extending substantially axially a predetermined distance from the bottom of said casing with clearance therebetween, a closed-top, open-bottom intermediate tube having its lower end disposed in the clearance between said standpipe and said casing and having a perforated member secured at the bottom and externally thereof, means for maintaining a predetermined minimum level of said heat-conveying fluid in said reservoir and a gas outlet from said reservoir disposed above said level, whereby gas under pressure flows up said standpipe and into said intermediate tube, out the bottom of said intermediate tube and then through said perforated member and upwardly in the form of gas bubbles through said heat-conveying fluid in the clearance between said intermediate tube and said casing and finally out said gas outlet, said rising gas bubbles causing said heat-conveying fluid to be lifted upwardly through said casing and discharged into said reservoir for subsequent discharge by gravity through said heat-conveying fluid discharge conduit.

-8. A system such as that recited in claim 2, wherein said burner comprises a combustion gas manifold having an inlet, a plurality of burner nozzles fed from said manifold, and automatic means responsive to the velocity rate of flow of said combustion gas to said manifold for varying the number of said nozzles fed with said combustion gas.

9. A system such as that recited in claim 2, wherein said burner comprises an inclined passage, the upper end of said passage having connected thereto a combustion gas supply conduit with a venturi therein for sensing the rate of flow of said combustion gas to said inclined passage, the lower end of said inclined passage being connected by third conduit means to a control chamber, fourth conduit means connecting said venturi with said control chamber, said nozzles being disposed substantially at a common level and respectively connected to said inclined passage by branch passages of progressively increasing length, a liquid filling said inclined passage and said branch passages to a common variable level so as to block the flow of said combustion gas to said nozzles, said level being determined at least in part upon the rate of flow of said combustion gas through said venturi as indicated by the pressure of said combustion gas at said venturi and communicated to said control chamber via said fourth conduit means.

10. A gas-fired, forced-circulation, heating system for an enclosed heated zone, comprising a combustion gas circuit means and a heat-conveying fluid circuit means, said system being powered entirely by the flow of said combustion gas, said gas circuit means including heatedzone temperature responsive closed pressure means for modulating combustion gas flow, said closed pressure means comprising a container filled with a second fluid whose vapor pressure'varies substantially with heatedzone temperature and.means connecting said container with means responding to said vapor pressure, and said responding means comprising a pressure-operated gas flow valve.

11. A heating system according to claim '1, wherein said pump means comprises upwardly extending first conduit means for receiving at a lower portion thereof said heat-conveying fluid heated by said burner, said first conduit means including a first discharge orifice at a height substantially above said lower portion for discharging said heated heat-conveying fluid therethrough, second conduit means operatively connected to and forming a part of said combustion gas circuit means, a second discharge orifice formed in said second conduit means for discharging said combustion gas into said heated heat-conveying fluid within said first conduit means at a height above said lower portion but substantially below the height of said first discharge orifice, and means responsive at least in part to the pressure of said combustion gas for automatically determining the relative height within said first conduit means at which said combustion gas is discharged into said heated heat-conveying fluid within said first conduit means, said combustion gas being elfective when discharged into said heated heatconveying fluid to form bubbles which steadily increase in volume as said bubbles rise toward said first discharge orifice, thereby causing an attendant upward pumping action on said heated heat-conveying fluid to thereby cause said heat-conveying fluid to be pumped through said first discharge orifice at a rate of flow dependent on the rate of flow of said combustion gas.

12. A heating system according-to claim 33, wherein said means responsive to the pressure of said combustion gas comprises a chamber-like structure floatingly received within said first conduit means and having a closed upper end and an open lower end, said chamber-like structure being adapted to at least loosely telescopingly receive through said open end a portion of said second conduit means so as to thereby regulate the rate of discharge of said combustion gas into said heated water.

13. A heating system according to claim 1, wherein said throttling means comprises a variable flow area conduit section within said combustion gas circuit means, said conduit section comprising a generally annular wall radially deflectable to define internally thereof said variable flow area, a generally annular pressure chamber formed about and radially outwardly of said annular wall, a first fluid pressure medium contained within said pressure chamber for applying a variable pressure against said wall in order to effect deflection thereof, and a second fluid pressure transmitting medium communicating with said first fluid pressure medium in order to at times apply an increasing pressure to said first medium and thereby causeincreased deflection of said wall and a reduction in the effective area of said variable flow area.

14. A heating system according to claim 13 wherein said second fluid pressure medium creates said increasing pressure in said first fluid medium by undergoing volumetric displacement in accordance with the temperature sensed within said heated zone.

15. A heating system according to claim 14, wherein said thermally expansible means is operatively placed in communication with said second fluid mediumand upon sensing an increase of said temperature within said heated zone causes said volumetric displacement of said second medium.

16. A heating system according to claim 14; including adjustment means associated with said pressure chamber for adjustably varying the volume of said pressure chamber, said adjustment means comprising a second chamber communicating with said pressure chamber and being volumetrically collapsible.

17. A heating system according to claim 14, wherein said thermally expansible means comprises a pressure bulb, a thermally responsive fluid contained in said bulb and in communication with said second fluid pressure medium, said thermally responsive fluid being effective to expand upon an increase of temperature'and to cause 17 responsive fiuid effective to expand upon an increase in temperature, said thermally responsive fluid being effective upon expansion to cause a control pressure which in turn causes said throttling means to further restrict the flow of said combustion gas therethrough.

References Cited UNITED STATES PATENTS 1,576,086 3/ 1926 Browne. 2,241,086 5/1941 Gould 236-99 X 2,707,593 5/1955 Woodcock 237-60 1 8 3,078,044 2/1963 Brandl 237-19 X 3,307,785 3/1967 Currie. 3,372,871 3/1968 Pfluger 237-64 FOREIGN PATENTS 237,032 7/1911 Germany.

EDWARD J. MICHAEL, Primary Examiner US. Cl. X.R.

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