US2565796A - Central heating system - Google Patents

Description

B. B. s. BARFEACLOUGH 2,565,796

CENTRAL HEATING SYSTEM Aug. 28, 1951 Filed March 23 1949 5 Sheets-Sheet 1 I Attorney 5 I Inventor:

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Aug. 28, 1951 CENTRAL HEATING SYSTEM 5 Sheets-Sheet 2 Filed March 23 1949 Attorneys B. B. s. BARRACLOUGH 2,565,796

Aug. 28, 1951 CENTRAL HEATING SYSTEM z Sheets-Sheet- 5 Filed March 23, I949 G MK r n andmwv,

Attorneys Patented Aug. 28, 1951 CENTRAL HEATING SYSTEM Benjamin Brian S. Barraclcugh, Greenfield, England Application March 23, 1949, Serial No. 83,041 In Great Britain March 24, 1948 1 Claim.

This invention relates to central heating sys" tems, and has particular reference to the provision of a system capable of efliciently heating a large area, or supplying heat to preselected radiating points remotely located from one another and from the central sourceof heat. The use of the present invention is contemplated for large scale heating, such as distribution of heat to the separate houses of a housing estate, or the separate shops of a large shopping area, football grounds, grounds or areas for all other outdoor or indoor sports, orchards, hot-houses, large blocks of warehouses, hospitals, flats, and the like.

It would appear that central heating systems have not heretofore been employed on such a large and widespread scale or, alternatively, not so efficiently as herein contemplated. The widest extent of known systems generaly employed is for the heating of large buildings,e. g. hospitals, blocks of flats, offices, etc., and for that purpose it has been common practice to heat water in a central boiler, to circulate it through suitable pipe assemblies to remotely located radiators, and from there back to the boiler. Although it has been suggested that oil might be used in place of water as the heat absorbing and radiating medium in domestic units or small circulating systems, it has apparently not been appreciated that on account of its physical and chemical properties, oil, in someof its forms, is more efficient than water, and thus enables circulatory central heating systems to be extended to ranges of distance and of temperature for which water is completely unsuitable.

The present invention contemplates a central heating system for application to ranges of op eration where water could not be satisfactorily employed as circulatory heat-carrying medium, and has as an object the provision of a system of great flexibility and adaptability employing oil as the circulatory medium for conveying heat to, and radiating it from, desired radiation points. The system is preferably entirely automatic in operation may be remotely controllede. g., electrically, in which case standard electrical technique, employing known and conventional forms of control, wiring, etc., are preferably employed.

Certain technical considerations arise when oil is to be employed as the heat-conveyin meand the following details may be regarded as some of the matters which need tobe borne in mind in carrying th present invention into effect, as will hereinafter appear.

invention.

1. The circulatory oil should be hermetically sealed within the apparatus through which it circulates, but provision should be made to accommodate variation of volume arising from changes of temperature to which the oil is subjected, and no air should be allowed to remain in the circulatory system becaus of its deleterious effect upon the oil.

2. Provision should preferably be madefor initially filling the circulatory system with oil without leaving air trapped in pockets therein, and for allowing replenishment of oil, preferably automatically and through a hermetic seal, -to replace that which, in course of time-may leak out through junctions, bushings, etc., in the system. Further, it is desirable to provide means for automatically trapping any air bubbles which might find their way into the circulatory system, and

means, preferably manually operated, at infrequent intervals, for releasing air thus trapped.

3. The whole circulatory system except the radiation units, should preferably be insulated by suitable covering material, with or without the provision of vacuum ackets, to minimize heat losses. This provision of means to mini- ,mize heat losses is especially important, bearing in mind the substantialdistances, e. g. two miles or more, over which it is intended, in some cases, to convey heat in accordance with the present It can be shown theoretically that by appropriate'choice of values for relevant factors, in accordance with known principles, the circu" latory mediumneed be subject to only about 40% temperature drop between the central heating unit and the remote radiation point to which it is transmitted. These relevant factors include:

(a) the internal diameter, and length of the conveying pipe line;

(b) the specific heat, specific gravity, and rate of flow of the circulatory medium;

(0) the form ofpiping employed, e. g. screwed or flanged sections, constant diameter, smooth internal bore, need for bends, etc., and installation requirements, e. g. above or'below ground level or under water.

4. The heat-conveying medium is preferably impelled alongits course, e. g., by one .or more electric pumps, which closely approximate to 10.0% positive thrust in operation, but allow a slight slip to accommodate shock which might be transmitted through the circulatory systemin any given circumstances.

5. Having regard to the possibility that one flow circuit may incorporate several spaced radiating units through which the circulatory medium flows successively, and that the heat-conveying medium will be successively cooler as it flows into these units, the invention contemplates the provision of means for reversing the flow of the heat-conveying medium, as and when desired, so that those radiation units near the outlet end of the circuit when the medium is flowing in one sense, will become the first to receive the heated medium when the fiOW is reversed. Mechanical means, e. g., slide valve devices, may be provided to control this flow reversal, and such means may be arranged to function automatically. Smooth change of flow is desirable, and shock-absorbing devices may, if desired, be provided to assist to that end.

6. In consideration of thermal efiiciency, and of substantially uniform heating at the various radiation points served, the system may be arranged so that the flow of the heat-conveying medium may be directed, preferably automatically, to any selected radiation unit or units, or a sub-circuit or circuits embodying a number of radiation units, in preference to, or to the exclusion of, other units or sub-circuits. Thus several, e. g., six, units or sub-circuits may be provided, e. g. in parallel, and means may be incorporated for separate flow control through those units or sub-circuits. Thermostat means of known and conventional form may control the flow in each sub-circuit independently of the other sub-circuits according to heat-requirements therein; and/or means may also be provided for sequential control of flow in the different sub-circuits whereby they receive the heatconveying medium, one sub-circuit at a time, in any prearranged order. Each sub-circuit, and/or the complete circulatory system, may be provided with the flow-reversing means mentioned above. It will be seen that combination of these features allows each sub-circuit to receive its appropriate proportion of the heat-conveying medium, if and when heat is required therein, while remaining inoperative as long as further heat is not required at its radiation point or points. When inoperative, each sub-circuit and/or the complete circulatory system preferably remains locked against the flow of medium therethrough, and the stationary medium therein continues to radiate its heat without appreciable flow due to convection or gravitational forces, of which forces flow is preferably completely independent, thus allowing the central heating unit and the various radiation points to be widely separated and/ or at different levels. If desired, booster pumps for assisting 5,,

flow, and/or supplementary heating units for boosting up the temperatLue of the circulatory medium, may be installed in the circulatory system at selected positions. This arrangement allows of even wider extension of the area capable of being served by a single circulatory system according to the present invention.

Y With these various technical considerations in mind, and to achieve the objects mentioned above, the present invention consists of a heat-exchange or transfer system wherein a pipe circuit, completely filled with a mixture comprising, in suitable proportions, an oil selected to have such characteristics that, throughout the range of temperatures to which it will be subjected, it will remain chemically stable, and of low viscosity to allow comparatively easy flow, and a liquid inhibitor against oxidation of the oil and rusting or like chemical reaction with the pipe, is connected by its intake and discharge ends to a main heat- 4 exchange unit, and incorporates power-driven pump or like means for effecting circulation of the mixture through the circuit.

The present invention also consists of a heatexch-ange or transfer system comprising a pipe circuit through which is circulated a heat-carrying medium to successive heat-transfer points incorporated in the pipe circuit, and means for reversing, at will, the direction of fiowof the heatcarrying medium through the pipe-circuit.

The present invention further consists of a heat-exchange or transfer system comprising a heat-exchange unit, a plurality of pipe circuits connected to the heat-exchange unit, through which circuits can be circulated a suitable heatcarrying medium, and valve means for selectively controlling and/or stopping and starting the flow of the heat-carrying medium through th vari ous pipe circuits.

The present invention will be clearly understood from the following description of one form thereof, given, however, merely by way of exam= ple, and this description may be more readily followed by reference to the accompanying drawings wherein:

Figure 1 represents, diagrammatically, the main parts of a central heating system according to the present invention,

Figure 2 is an enlarged, vertical, sectional view of a single valve assembly incorporating a director valve and two independently operable flowreversing valves,

Figure 3 is a vertical, sectional view of a form of air trip suitable for insertion at any convenient point in the circulatory system,

Figure 4 is a diagrammatic, horizontal, sectional view of a system embodying a plurality of furnaced boilers arranged as a battery and operating in series,

Figure 5 is a vertical, sectional view of an oilflow reversing valve, showing the movable control element in one extreme position,

Figure 6 is a fragmentary view similar to Figure 5 showing the movable control element in the other extreme position,

Figure '7 is a transverse, sectional view on the line A-A of Figure 5,

Figures 8 and 9 are transverse, sectional views on the lines B--B and CC, respectively, of Figure 6, and

Figure 10 is a fragmentary, horizontal, sectional view on the line D-D of Figure 6.

In carryin the present invention into effect in one convenient manner, as shown diagrammatically in Figure 1 of the accompanying drawings, a central heating system may comprise a furnace heated boiler I, a storage tank or container 2 for the heated circulatory medium, valve means 3a, 312 for controlling flow of the fluid circulatory medium, and radiator units 4, all interconnected by piping to form an enclosed circuit.

The furnace-heated boiler I comprises an electrically operated oil-burning furnace embodying a combustion chamber 5, through the top of which projects a downwardly-directed burner nozzle 6, from which is directed downwardly a jet of atomized fuel oil and air. This jet of fuel oil and air may be electrically ignited to produce a flame, which also burns secondary air introduced from vents which may be provided at the bottom of the combustion chamber 5. This flame is approximately the shape of an inverted mushroom, and its edges rise vertically, and in so doing heats a cylindrical container 1 made of ceramic, e, g, of a fireclay. The flame then passes over the topof 'this cylindr-ical container 1 which is open at the top, andthen passes down-the outer sides of 'said cerazmiccontainer and inso' doing heatsan outer jacket 8 -containing part of the circulatory :rnedium-in' the boiler '9. The flame "finally reaches the "bottom of thefurnace where there is a flue or vent/I 0;

This type of furnace with'a base "flue" 1.0 has the advantage of negativing any tendency, after flame has ceased, to cool by convection; because the flue '10 is at the base and not at the top. Thus 'the internalheat losses, after the flame has been=extinguished-, are minimized, and theheated ceramics can continue to give off heat to the surrounding boiler-contents by radiation.

The fueland/Orair supplies, and thus-the temperature of the-furnace, should be controlled by well known and conventional means in such a manner that "furnace working-'-temperatures can be adjusted swiftly at will betweenprearranged max-imum'and minimum-values. Fleeheating-0f the boiler may thus be controlled, e. g., thermostatically, and as-near instantaneously as possible. It is advantageous that the furnace be extremely responsive to these control requirements, as otherwise the contents of theboiler will not be heated quickly enough, or may be heated to too-high *a temperature, with either disastrous results or lack of economy-of fuel, or

both;

It is a feature of the invention that the boiler and circulatory system shall be filled with oil, to act as the heat-conveying medium, as will hereinafter be more fully'described, and-the boiler should be so-constructed that, in conjunction with the furnace controls referred to above, the local or skin temperature of the circulatory 'oil shall not reach a value in excess of a predetermined maximumtemperature of 680*: F., as otherwise the-circulatory-oil will be damaged by excessive heat-whereby the effic'iency ofthe-system will be impaired. If desired, the invention may be modified-in orderto guard against-this danger', by having the furnace heat 'a water-filled boiler, to produce superheated steam, which steam is then used' in a calorifier or' *heat exchanger to heat the circulatory -oil. Thusa cushion of steam is interposed betweenthe relatively high-maximum furnacetemper-ature and the relatively low maximumpermissible' temperature or the circulatory oil. By controlling and regulating the supply: and application of the source of heat by means of well known'and conventiona'l mechanisms; the :steam temperature,

and'thus thecirculatoryxoil temperaturemaybe 1 regulated and. stabilized. In Ilieuv of steam, :any other suitable lheatingmediums liquid or gaseous, may be employed,.iorxexample; aknown heating fluid composed of 73.5% di-phenyl oxide and 25.5% 'di-pheny'l.

As the steam. thus. preheated, or the intermediate'heating fluid; as the case maybe, is never physically expended, it need not be constantly replenished. and, except for a necessary-safety valve,.'m'ay be "contained .in a sealed boiler'and calorifiercoi1;. The typerand design of the boiler will depend on, and :be. appropriate to, the. type of intermediate thermal cushion selected. in any particular case: according-to the special requirements particular to preheated steam .or special heatingfluid, as the; case .may be-. Thetselected intermediate thermal cushion may itself be heated ina furnace burning. solidliquidotgase'ous fuel, or maybe 11831336151337 electric; energy,

and the boiler andszilurnace. shown: in- Eigure. :1

are purely diagrammatic to representzany selected source of heat and appropriate applicae tion thereof, upon the conditions already mentioned, to the circulatory oil medium.

The boiler preferably contains its owrrsset. of maximum and minimum thermostats to. control the application of heat to the boiler,.such.means being conventional'and being, of well known construction to those skilled in the art relating to furnaceandboileroperation and control.

The boiler 9 is connected by pipes Ha, lib to the hot oil storage tank or container .2, of suitable size, having regard to the purposes of the heating system, to hold sufficient oil 'to convey the required amount of heat. This amount of oil will normally be much greater than can .be conveniently and efilciently contained inv the boiler 9. For heating efficiency, the oil is pref-- erably maintained in circulation between the boiler'll-and storage tank 2 independently of flow throng-nether parts of the circuit, and for this purpose. an electric pump l2 maybe incorporated in the'pipe line Ha. The tankz and boiler :9 are preferably insulated against heat loss, and the tank 2 is represented diagrammatically in Figure 1 as provided with an outer casing l3, theintervening space being evacuated and/or-packed with suitable insulating material. A suitable form of tank which may be employed will be described more-indetailhereinafter.

The heated oil is taken from storage tank 2 through pipe i land introduced into the circulatory pipe system. Flow of oil is effected and maintained by a pump 15 which may be electr-icall-y driven and controlled in stopping and starting and rate of pumping by thermostatic means of well known and conventional construction located atla point or points of radiation. Thus, when 'a point of radiation.requiresheat, the thermostat functions and the pump 15 impels oil from the :container 2 through the pipe l l toward the pointof radiation.

The pump l5 should not be as positive as, for example, the pump l-2-, which latter should be verypositive. Whereas the pump IZbetween-the boiler B and storage tank '2' should have no mar- .gin-ofslip, the pump .lli whic'h impels the circullator zOll-fiOW- from the storage tank 2- towards the radiation point should-be such as to absorb or: acoommodate sudden shocks 7 or arrest-ive n10- tions'which may occur in the circulatory flow for reasons which will hereinafter appear. These shocks arelentirely instantaneous and of nomore duration than a fraction of a second, but they areconstantl-y recurring and in the course'of time would have a ,clele't'erious effect on the apparatuszincluded inthe-system if such shocks were notabsorbedtor..accommodatedi Oneimanner of. absorbing or accommodating such shocks is illustrated in Figure 1'. A ba-Il I-S has .a good, but easy, :fit Within a constant- -bore 1-pipe lil; Thi ballzllfiitendstto remain. at restznear thepump lv5i either bybeing gently spring loaded, it-having afbias bygravity, but wh'enla sudden l-BSlSta-DCEEDJ. stoppage. takes place in the :circulatory'rlow against: the-thrust of the-pump f5, this ball it is driven,:-*by reason of such pressure, towards-the -lower end-.of pipe H where thereis provided a spring 18 sufiiciently flexible to .be compressed by theballxuntil pressure :isrele'ased 'at the m'outh'ofalpipe ll Swhich pipe is connected to -the 'main return pipe Zilfrom: the radiation point into 'the'hotioil reservoir :2.

By virtue'of; :the yielding of :the ball it. as :describedabove; to the collision or impact :hetween pump thrust and arrested flow, any shock which would otherwise ensue, is efiectively absorbed. The ball 16 is ableto yield because the oil displacement caused by the yield is a return displacement into the reservoir 2 and, therefore, back into the pump so that, in effect, the shock is by-passed.

The ball i6 should normally remain resilient to the normal thrust of the impeller or pump l5, so that it is easier for the circulatory oil to flow into the main circulatory system than it is to bypass it. For this reason, the ball l6 should be loaded by a spring l8 of adequate resiliency to resist the normal thrust of the circulatory flow.

The heated circulatory oil in the heating system may flow direct from the impeller E to a desired radiation point or points and back to the oil reservoir 2 in a simple circuit or in a number of such circuits, arranged in parallel.

Accordingto a further feature of the invention however, means may be provided whereby the flow may be selectively directed to one point of radiation exclusively or to another exclusively. It will be appreciated that once a radiation point has received its full heat requirements for a given period, the heat resources of the system are available for another task, and the further feature of the invention present now referred to allows the fulfillment of such other tasks. For this purpose, the pipe circuits may be provided with one or more two-way taps hereafter referred to as directors or director valves, whereby the circuits can be switched to supply hot oil to one or another of the radiation points when they require heat as indicated by their respective thermostats.

By means of a plurality of such director valves, electrically operated and placed in appropriate and correct relationship to one another, and appropriately wired for the correct and necessary electric remote control by means of orthodox time switches, motor-driven cam switches and similar conventional and well known electrical devices, any number of alternative radiation points may be served from a single main circulatory flow.

A simple form of such a, director valve is represented diagrammatically at 3a in Figure 1. The oil flow from the pump l5 towards difierent radiation points is bifurcated into the twin delivery pipes 2| and 22. By a slide valve '23 having two bores 24, 25, the flow may be connected by bore 25 from pipe 22 to pipe 21, during which period the flow from pipe 2| is blocked by valve 23.

Conversely, when the slide valve 23 is raised, oil flow is established from pipe 2| to pipe 26 and the flow from pipe 22 is blocked by valve 23. Valve 23 may be moved manually, or by electromagnetic means described more fully hereinafter, or by any other suitable means.

The director valve 3a may be arranged to serve more than two alternative flow circuits or groups of alternative flow circuits by the provision therein of more than two ports 24, 25. Thus the delivery pipes 2!, 22 may be duplicated, within limits, and each of the alternative pipe lines can lead to another director valve, thus multiplying the number of alternative circuits which can be supplied from one initial main flow.

In Figure 1, the return pipe from one independent but alternative circulatory flow served by pipe 26 is shown at 28, while another return pipe 29 runs from another independent and alternative circulatory flow served by pipe 21. The said return pipes 28 and 29 make a common junction with pipe 26 which returns thecirculating fluid to the heat reservoir 2 for reheating in the boiler-systems. Where a director valve is operated by electromagnetic means of conventional and well known construction, such valve may be controlled by a conventional thermostat at a radiation point, or by-a conventional time switch, operated electrically, or by a biased combination of both.

According to a further feature of the present invention, means may be provided whereby, in any given independent flow circuit, the direction of flow of the heated circulatory oil may be reversed as and when desired, and preferably automatically, at prearranged periods, or under predetermined conditions. A simple form of such an arrangement is illustrated diagrammatically at 312 in Figure 1, and may comprise a slide valve 30, hereinafter referred to as an alternator valve, having two direct bores 3|, 32 and, therebetween, two independent crossed bores 33, 34.

With the alternator valve 30 in the position shown in Figure 1, oil flows from pipe 27 through duct 33 and pipe 35 towards the radiation point and returns by pipe 36, duct 34 and pipes 29, 20, to the tank 2.

If the valve 30 is shifted downwards, the direct duct 3| connectspipes 21 and 36, which latter pipe now becomes the inflow pipe to the radiator'unit, while direct duct 32- connects pipes 29 and 35 by way of the by-pass passages 31 and 38, and pipes 29 and 35 thus become the return flow pipes. With the valve 30 in this lower position, the independent crossed ducts 33 and 34 are sealed against oil flow therethrough.

This alternator valve 30 thus provides reversible flow serving a common radiation point or points, and it is a very desirable feature in all cases where there are a plurality'of radiation points or sub-circuits served by a given main circuit.

In Figure 2 of the accompanying drawings there is shown a single valve assembly incorporating a director valve 25a serving two independently operable flow-reversing valves 30a, 301). From the above description with reference to Figure 1, the operation of the valve assembly shown in Figure 2 will be readily understood, and it will also be appreciated how such a device enables full controlto be exercised over the operation of parallel flow-circuits, in a simple and flexible manner.

Referring again to Figure 1 of the accompanying drawings, it will be seen that after the circulatory oil has left the valve 38, it proceeds to the point 4, or series of points, where radiation is required. At any convenient point in this stage there can be placed one or more pumps 3.9.to help or boost the flow, for it will be appreciated that in a system containing a large amount of oil, the inertia to be overcome by reason of the weight of the oil and the frictional resistance offered by the internal bore of the pipes and appliances and the bendsthereinwill, in the aggregate,'amount to a considerable resistance, and so, at convenient places, additional pumps may be convenient or necessary.

These pumps 39 may be centrifugal pumps and similar to pump l5, and not positive, but allowing a certain amount of slip, and they may be so controlled by standard electrical means of conventional and well known construction, that they, or if less than two, the single pump, will stop and start simultaneously with all other pumps having a similar and common purpose in the same independent circuit. Thus between pumps l and 39 there are the director valve tionpoint t causes the pump 39 .to operate, it will also cause the pump IE to operate simultaneously. But there is this. dlfferencein operation between all pumps such as 39 whichare .locatedon the radiation side of the alternator valve 30,

namely, that the: pumps such as 39 on the radiation side of said valve .3dmustJbe reversible pumps, and, moreover,-must be so electrically linked to the control of valve that they pump the circulatory oil in the direction of flow 'determined by the operating position of said valve.

"Further, pumpssuch as as on the radiation side of valve 33, should-be so controlled electrically that they stop a momentsbefore the valve 38 is about to change the direction of the flow. Such a pause is desirable inorder to allow the momentum of the moving columnof circulatory oil to be absorbed'and the column to become static, whereby to minimize the shock to the containing pipes and appliances, which shock would otherwise occur were a reversed how to be arbitrarily imposed against a pre-established oil flow. Such momentary delay may be efiected, for example, by a cam switch of conventional and well known construction controlled from the valve-operating thermostat.

To assist this cushioning effect, a-shock absorbing device maybe provided as shown in Fig ure 1, which device comprises a ball 46) capable of moving in its containing pipe ii of constant bore but not able to escape from either end of said pipe. This ball at has a good but easy fit within its containing pipe ll which interconnects the two pipes and it. It will be apparent that when the valve 30 causes an, interruption of oil flow and the immediate reversal of said flow, there will be, by the act of reversal and arrest .and opposition of moving forces, a resultant difference .in pressure momentarilyin the pipe system between pipes 35 and (35 and the one, say, i

in the positive sense,.will be the. complement of the other in, say, the negative sense. A displace- .mentof oil, restoring immediate equilibrium, is

permitted by the ballad which acts. as a movable and yielding partition between the opposed forces, until they become balanced. The communication pipe 4i may be lengthened to give any desired tolerance or displacement accommodation, and may, for example, be in the form of a coil, in which case it should be in a horizontal plane and not a vertical plane, since in the latter case gravity would bias the ball.

With reference to the provision of pumps within a group of separate alternating flow circuits,

it is preferable to arrange that whenever any one'" of such alternating flow circuits is in operation by reason of the operationofits own pump then, at the same time, the main positive pump, such as pump l5, and its ancillary pumps, if any,

should also be in operation and the electric cir-' cuit wiring should provide for thisrequirement. It follows, therefore, that in practice, the main constant directional pump 15 will seldom be at rest because whenever any circulatory flow requirements.

through any radiation point is in process, the main pump also will be in operation,

In addition to the units above described, there may also be placed in the circulatory system at any convenient point or points, a heat booster in the form of an ancillarybut appropriate type of furnace and boiler, with or without a calorifier, to reheat the circulatory oil. This feature is desirablein the case of extreme long range service There may likewise be provided, if required, booster pumps to assist the circulatory How. The heat boosters may be thermostatically controlled by thermostats of any conventional well known construction responsive to the temperature of the-oil entering the booster, and

should havev a cut out device to insure that the furnace does not function when the circulatory flow. ceases.

.As stated above, it is important to arrange for air. bubbles to be elimin...red, and to remain eliminated, in the sealed system containing the oil,

since the presence of these bubbles would have a harmful effect upon the chemical constituent of the oil and would aifect its stability over a period of time. I

To this end, whcn the circulatory system is initially filled with oil, it should be filled from the lowest point or the system so that air therein may-be the more easily displaced and will escape at the highest point of the system. In addition, some or all of the. components or unit parts of the system may be provided with means for drawing off air bubbles at the highest point of that piping ofthe circulatory system. Air bubbles travelling in the direction of the-arrow through the pipe-fii-enter the chamber M which is enlarged so as to dissipate the main current of oil, and thus to permit the air bubbles to rise into the .collecting pipe i'5, at which point they can be manually drawn off by releasing the stop cock 42.

It will-be obvious that over a period of time there will be oil leakage from the system which contains many junctions although the circuit is designed to embody a minimum of points where mechanical internal movement occurs, or where rotating parts or levers extend or communicates through the fabric walls of the apparatus.

- It is desirablefor such lost oil to be immediately replaced, preferably automatically, in order to obviate the entry of air .into .the system.

One formof oil recuperation device is shown in Figure 1 and comprises a header tank orIcontainer M5, whichmay be cylindrical, connected to the pipe system-by pipes 41, 48, through which replacement oil is fed by gravity. A plurality of such header tanks may be installed at convenient places in the system, according to the requirements of any particular lay-out. The header tank .45 should ,be sealed at the top from the outer atmosphere by a piston type follower 49 having a close airtight fit within the cylinder-.45, and in order to exert some general and internal pressure upon the oil content of the circulatory system and to provide against the riskof jam- .ming, this follower may-be spring loadedas at 50 so as to exert a pressure upon the contents of the tank. In order, further, to insure a secure oil seal between the follower and the cylinder 46, a layer of oil may cover the top of the follower 49. To guard this layer of oil from oxidation by long exposure to the atmosphere, and to prevent entry of dust particles and foreign matter it may be shielded by a piston type follower similar to 49, riding or floating independently upon the shaft of follower 49 and itself spring loaded as at 50.

Normal inspection and maintenance service will provide a record of the positions of these piston type followers, showing Whether or not there has, since the date of a previous inspection, been any oil leakage, so that such leakage can then be traced and effectively prevented.

It will further be noted that the internal expansion and contraction of the circulatory oil, due' to continual changes in temperature, is accommodated by the rise and fall of the piston type follower or followers 49 in the header tank or header tanks 46 against light resistance from load springs 50.

In accordance with the present invention, a circulatory system such as described above, is filled with oil, acting as the circulatory heatconveying medium, specially selected having regard to its chemical and physical properties, for the desired purpose.

The oil used should exhibit the following values, or approximately the following values, of characteristics Specific gravity at 60 F.0.870.

Flash point (closed)390 F.

Viscosity (R/l) at 70 F.310 seconds. Viscosity (R/l) at 100 F.-140 seconds. Viscosity (R/ 1) at 140 F.68 seconds. Pour test-minus 20 F.

Maximum temperature tolerance: 680 F.

In addition, the oil should contain, in appropriate proportion, an inhibitor against rust and oxidation, and this may be any known suitable inhibiting agent.

In addition to the abovementioned values for the characteristics of the oil, due consideration should also be given, in accordance with known principles, to the following features relating to the selected oil:

1. Its characteristics should not be affected by repeated heating and cooling over a wide temperature range of approximately 700 F., and it should deposit no sediment.

2. It should be of low infiammability, and have no explosive characteristics.

3. It should be chemically inert, within its working temperature range, in respect of the metal or alloy pipes and chambers through which it passes, and in respect of fibrous or resilient packing materials in contact with which it may flow.

As previously stated, the selected oil is hermetically sealed in the pipe system, and care should be taken in filling the system to exclude air and chemical impurities liable to affect the characteristics and performance of the oil.

By various modifications of the form of the invention above described, detailed improvements and refinements, and improved performance may be achieved.

The circulating'pipes of the system are connected with suitable gaskets or packing of material resistant to the heated oil. In general, rubber gaskets are unsuitable, and the preferred gaskets may be formed, for example, of artificial or vegetable fibre or the like. Except at the heat supply points, the circulating pipes, over the major portion of their length, are preferably provided with insulating coverings to prevent heat losses.

For heating efiiciently, the system may employ a plurality of furnaced boilers arranged as a battery and operating in series. An example of such an arrangement is shown diagrammatically in Figure 4 of the accompanying drawings, and embodies four furnaced boilers 5|, 52, 53, 54 connected in series, and having also in series an oil-circulating pump 55. This series battery of boilers is connected by its end pipes to the reservoir 56, from which the heated oil is drawn off, and to which it is returned after circulation through the heating circuits, as above described.

The reservoir 56 may contain a set of maximum and minimum thermostats of conventional or well known construction which invoke flame in all the boilers simultaneously, at the same time that they cause the pump 55 to be driven. The maximum thermostat causes flame to cease simultaneously when maximum temperature is reached in the reservoir 55.

Details of a convenient form of oil-flow reversing valve which may be employed in the present invention, are illustrated in Figures 5-10 inclusive, of the accompanying drawings, wherein Figure 5 is a vertical, sectional view of the valve with the movable control element thereof in one extreme position; Figure 6 is a like view of part of the valve with the movable control element thereof in the other extreme position; Figure 7 is a transverse, sectional View taken on the line A-A of Figure 5; Figures 8 and 9 are transverse, sectional views taken, respectively, on the lines BB and 0-0 of Figures 6; and Figure 10 is a fragmentary, horizontal View on the line D-D of Figure 6.

This form of oil-flow reversing valve is electromagnetically operated, and, as shown, comprises a hollow, rectangular block 51 of metal, preferably of substantially square cross section. The hollow space within said block 51 may also be of substantially square cross section, and is closed at each end by a wall having a screw-tapped bore normally sealed by a screw plug 58 held in set position by a lock nut 59. Within this hollow block 51, and having a tight sliding fit therein, is a block of metal 60 which is somewhat shorter than the space in which it is housed, so that it can be reciprocated, longitudinally within said space, and light compression springs 6! are provided between the ends of this block 60 and the sealing screw-plugs 58, to act as buffers when the block 60 is moved from one extreme position to the other. If desired, the block 60 may have a longitudinally-bored oil or air vent 62.

Through one side wall of the hollow metal block 51, are two pipe bores 63, 64 adapted to be coupled, respectively, to the outlet and return pipes from the hot fluid reservoir 2, while in alignment with said pipe bores and extending through the opposite side wall of the hollow block 51, are two like pipe bores 65, 66 adapted to be connected, respectively, to the pipes of the heatdistributing circuit. Around the sides of the metal block 60 are provided grooves or channels 61 which, when said block 60 is in one extreme position of its reciprocatory movement as shown in Figure 5, come into alignment with these opposite pairs of bores 63, 65, and 64, 66 through the Walls of hollow block 51. It will be appreciated that when the block 60 is in that position, fluid from the outlet pipe of the reservoir can flow along one of these grooves or channels, out of the walls of hollow block at 65, to the heat distributing circuit, while return fluid can flow through the other of these grooves or channels in the valve back to the reservoir.

One of the bores 64 through a wall of the block 51 on one side thereof, and the corresponding bore 66 through the opposite wall of said block 51, are each in communication with a passage 98, 69 as shown in Figure 6, running for a short distance longitudinally of the wall of said block 51, towards the adjacent bore on the same side of said block, and thereafter opening into the interior of said block. The metal block 60 is provided between the above mentioned grooves, and on the faces running against the pipe bores of the said hollow block, with pairs of recesses '16, II and 12, i3 spaced so as to come into alignment, when the block is in its other extreme position of movement, with the openings of the aforesaid sidepassages 68, 69 from one pair of pipe bores, and the openings of the other pair of pipe bores 63, 65. These recesses 10, H, l2, 13 in the block are connected together, in pairs, by grooves or channels l4, 15 each of which extends along one side only of the block 60, from a recess, e. g. the recess 19 on one face, to the obliquely opposite recess, e. g., the recess 13 on the other face. These two oblique grooves 74, 15 are located on opposite sides of the block 69, and are not in communication with one another.

From the above description, it will be appreciated that when the block 60 occupies one extreme position as shown in Figure 5 it allows flow of fluid from one pipe bore, e. g., the pipe bore 64, of the hollow block 51, through one of the grooves or channels 61, to a pipe bore, e. g., the pipe bore 56, directly opposite to the pipe bore 64, but when the block 60 is moved to the other extreme position as shown in Figure 6, the grooves or channels 67 move away from alignment with the pipe bores 64, 69, and the oblique grooves 14, 15 and associated recesses 10, TI, l2, l3 align with the pipe bores, with the result that the fluid flows between opposite pipe bores in a reversed sense. In either extreme position, the pipe bores or associate passages not in use are sealed off by contact between the body of the block 60 and the wall defining the hollow space within block 51, which contact closes their openings.

Preferably, the block 69 is moved between its extreme positions by electro-magnetic means. For this purpose, the block 69 is formed of, or embodies an inset portion of, soft iron to form a magnetic core sensitive to the magnetic fields set up by solenoid windings 16 positioned externally of, and at each end of, the hollow block 51. These solenoids 16 may alternately be supplied with current from a rotary time switch 11 in an electric power circuit which includes said solenoids. If desired, the circuit of each solenoid may include an interrupter switch l8, 19 so that when the block 60 is in each extreme position, the circuit of the solenoid which has caused it to move thereto is broken, while the circuit of the other solenoid is closed in readiness to return the block 60 to its opposite extreme position.

The interrupter switches 18, I9 may each be in the form of a spring-loaded plunger 80 extending through the wall of the hollow block 51, and carrying at its inner end a roller 8| running in a longitudinal groove or slot in the block 59, which groove or slot has a sloping base 82, so that movement of the block 50 causes the plungers to reciprocate and thereby actuate, at their outer ends, switches 83 in the solenoid circuits. The bases 82 of the slots with which the plunger rollers 91 engage, may be provided with depressions engaged by the said rollers when the block 69 is in its extreme positions, to serve as locating detents for the said block.

From the above description it will be clear that the invention provides a central heating system capable of serving a wide area with great efiiciency and flexibility of operation, but it should be understood that the invention is not restricted solely to the details of the form of the invention described, which may be modified in order to meet various conditions and requirements encountered, without departing in any way from the scope of the invention.

What I claim is:

A heat-transfer system comprising a container; a heat-generating unit adapted to convey heat to the contents of said container; an outlet pipe constituting a supply pipe, and an inlet pipe constituting a return pipe, bothof said pipes communicating with said container; two independent pipe circuits adapted for connection with said supply pipe and said return pipe, and

each including heat-radiating means and inlet and outlet pipes communicating with the heatradiating means in its circuit; selective valve means between the said supply pipe from said container and said independent pipe circuits for connecting said supply pipe to either one of said pipe circuits to the exclusion of the other; reversible valve means between said selective valve means and the inlet and outlet pipes of one of said independent pipe circuits operative at will to reverse the connection of the supply and return pipes to the inlet and outlet pipes, respee tively, of said one pipe circuit to thereby reverse the direction of flow through the heat-radiating means in said one circuit; a heat-transfer medium substantially filling said container and its associated pipes and pipe circuits and comprising a mixture of oil having characteristics selected in accordance with the conditions under which the system is to work, and a liquid inhibitor against chemical reactions within the system; and means for circulating said medium from said container, through said supply pipe, selective valve means, selected independent pipe circuit, and return pipe back to said container.

B. BRIAN S. BARRACLOUGH.

EEFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 639,541 Dyer et al Dec. 19, 1899 717,308 Weichmann Dec. 30, 1902 1,440,926 MacDonald Jan. 2, 1923 1,985,215 Shivers Dec. 18, 1934 2,030,544 Ross Feb. 11, 1936 2,152,699 Kuester et al Apr. 4, 1939 2,159,284 Miller May 23, 1939 2,166,509 Smith July 18, 1939 2,204,708 Smith June 18, 1940' 2,240,731 Van Vulpin May 6, 1941

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