US2522373A - Storage type liquid-heating system - Google Patents

Description

sept l2, 1950 G. E. Jour-:LL 2,522,373

s'roRAGE TYPE LIQUID-mums SYSTEM Filed April 25, 1945 s sheets-sheet 1 A l ll /M ade/WR- WW! M Sept. 12, 1950 G. E. Joni-:LL

STORAGE TYPE LIQUID-HEATING SYSTEM I5 Sheets-Sheet 2 Filed April 25, 1945 a INVEN TOR mf/,ffy

3 Sheets-Sheet 3 STORAGE TYPE LIQUID-HEATING SYSTEM Sept. l2, 1950 Filed April 25, 1945 INVEN TOR.

Patented Sept. 12, 1950 STORAGE TYPE LIQUID-HEATING SYSTEM Georg Elis J odell, Prahran, Victoria, Australia, assignor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation of Sweden Application April 25, 1945, Serial No. 590,206 In Australia October 26, 1944 16 Claims.

My invention relates to improvements in liquidheating systems and especially relates to improvements in water-heating systems; and the objects of my improvements are, first, to ensure that the liquid when it reaches a predetermined temperature is not thereafter heated substantially above that temperature; second, to ensure that the hot liquid in the upper portion of the tank is separated from any cold liquid in the lower portion of the tank by a substantially sharper stratification than with previous systems; third, to ensure that the temperature of the hot liquid will not continually drop during the drawing off period; fourth, to prevent or minimise the deposit of limestone from water used in or heated by the system; fifth, to prevent substantial heat losses due to reverse circulation when the heat supply is switched off; sixth, to prevent condensation from the flue gases; seventh, to prevent over-heating of the liquid if the thermostat fails to cut out; and, eighth, in general to provide a more eflicient liquid-heating system of the storage type than those previously 1n use.

I attain these objects by the means illustrated in the accompanying drawings, in which- Figure l is a schematic view of a suitable arrangement of the apparatus, lled with an inert gas, and operated by a gas burner;

Figure 1A is a view generally similar to Figure l illustrating another embodiment of the invention; and

Figure 2 is a similar view showing a modied construction adapted to operate with water pressure instead of gas pressure.

The system, according to this invention, could be applied, not only to the heating of liquid in a main storage tank but equally to the heating of liquid in any container where a quantity of liquid is stored for heating. Consequently, the term tank is used herein to include any such container. The system could, of course, be applied not merely to the heating up or the maintaining of the temperature of water but also to the heating or temperature-maintaining of other liquids; but, as its normal'application will be to the heating of water in a storage system, it is primarily so described hereinafter.

In the arrangement shown in Figure 1, a small boiler 2 is located beneath the main hot water tank I. It could be heated by gas, kerosene,oil or the like, or electrically, but for convenience it is shown heated by a gas burner 3 from which the hot combustion gases pass downwards and. then upwards, around the lower edge 2 of the boiler, to the flue pipe 3A. The heat supply can be shut off by thermostatic means 4, 5, either completely in the case of electric heating or so that only a pilot flame is burning in cases Where fuels are used. This thermostatic means is actuated by an impulse from the tank when the temperature in the tank reaches a predetermined level. The tank is provided with an outlet pipe IA, an inlet pipe IB and insulation IC. When in operation the boiler is partly filled with a vapourising liquid 6, for instance water. The vapour passes through a vapour pipe 1 leading to the top of the tank and thereafter connecting with a condenser 8 located inside the tank and extending downwards through the whole height of the tank.

At the commencement of the operation the condenser contains at a predetermined pressure a gas which is uncondensible under the conditions of operation, which is not reactive on the water or other liquid medium or on the vapour thereof, and which does not seriously corrode the material of which the apparatus is built. For convenience, hereinafter in the description and claims such gas is termed an inert gas. There should be a space available above the liquid in the boiler to prevent liquid from boiling up with the vapour and passing into the condenser. As this liquidcooled condenser will normally be constructed in the form of a coil, it is referred to hereinafter in the description as a coil The tail end of this coil at the bottom of the tank is connected by means of a pipe 9 to a container I0 forming a gas reservoir and air-cooled condenser which is located outside the insulation of the tank in such a position that it is above the boiler and also above the lowest point of the aforementioned coil. The air-cooled condenser and the gas reservoir are normally the same vessel but, if desired, they could be separate structures with the former leading into the latter. Cooling fins IOA are provided. The lower end of the condenser is also connected with the side of the boiler by means of a comparatively narrow pipe II forming a water lock IIA. This pipe serves as a return pipe to bring the condensed vapour back to the boiler for further evaporation. The boiler, vapour pipe 1, coil, pipe 9, gas reservoir and air-cooled condenser I0, and return pipe II taken together form an hermetically sealed evaporating-condensing system having a charging or filling valve I2.

This closed system operates as follows:

The liquid vaporiZing medium boils in the boiler and the vapour presses back the inert gas 3 so that the vapour extends into the first portion ofthe coil. The liquid used in the closed system will normally but not necessarily be water. The vapour in this rst portion of the coil gives up heat to the surrounding water and condenses. The liquid in the system boils readily at a prede-- termined temperature depending on the pressure of the inert gas. When heating water in an ordinary household hot-water system, the pressure in the coil is substantially below atmospheric pressure, and the liquid then boils substantially below its boiling point at atmospheric pressure. Naturally th water surrounding the first portion of the coil is not raised above that predetermined temperature. The temperature in question is regulated by the pressure of the inert gas. The condensate flows down the coil and returns to the boiler. When the temperature of the water surrounding this rst portion of the coil reaches or approaches the predetermined temperature the vapour tends to remain uncondensed at that point and to pass on, compressing inert gas in front of it. The vapour on reaching the next portion of the coil condenses there while the water surrounding this next portion of the coil becomes heated. Consequently, the zone of application of the heat becomes progressively lower and lower in the tank. During this heatin T of the successive portions of the water, the Water already heated up to the desired temperature remains virtually stationary in temperature except that it may rise in temperature through one or two degrees, for example, due to the fact that the slight rise in pressure results in a slight rise of the boiling point of the liquid and thus also results in a slight increase of the temperature of the vapour. As the heat transferred from the vapour to the water in the tank is mainly the latent heat given up in condensation, the slightly higher temperature of the vapour at the later` stages of the heating has very little effect in raising the temperature of the top portions of the water in the tank, as condensation of vapour has ceased or virtually ceased in the top portions of the coil. It is desirable, however, that the vapour should not be superheated when it leaves the boiler as otherwise a portion of the superheat will pass into the already heated top portions of the water in the tank. The heating progresses through the water in the tank in this way until all the water has reached a temperature which, preferably, is only a few degrees above the ternperature at which the liquid boiled at the commencement of the operation. A thermostat then operates to out off the supply of heat. As this system preferably operates with water as a vapourising liquid, this liquid is referred to as water hereinafter in this description. The inert gas may be, lfor example, nitrogen. The system is first fully evacuated, then distilled water is filled into the system, the quantity being sufiicient to partly ill the boiler only, and then inert gas is filled into the system through a valve l2 up to a predetermined pressure.

By heating a water tank in accord with the invention, certain advantages are realized over water-heating systems of the type in which a body of water is heated by natural circulation resulting from the difference in density of hot and cold water. In such cases cold water flows from the bottom of the tank to a source of heat supply and then flows by natural circulation through piping to the top of the tank. Also, heat is often supplied to tubes or ues which downwardly i pass directly through the tank, such heating iiues giving up heat directly to water in the tank, thereby inducing natural circulation which causes the hottest water to be at the top of the tank.

When water is heated by natural circulation as just described, it is not possible to concentrate all of the heat supplied by the heat source at the top layer of water only, so that it becomes necessary, when starting from cold, for a considerable length of time to pass before water at a suiciently high temperature can be withdrawn from the top of the tank. This situation also arises when the entire supply of heated Water has been withdrawn from a tank.

Since hot water is usually withdrawn from the top of the tank and cold Water is introduced at the bottom of the tank which forces the hot water through the outlet under line pressure, it is highly important for the stratification of temperature in the tank to be as marked as possible. The more effective the stratification, the sooner hot water can be made available in the top section of the tank. When temperature stratication is created by natural circulation of the water itself, theftemperature in the tank usually falls practically uniformly from the higher tern` perature at the top to the lower temperature at the bottom. In such case, only a comparatively small quantity of useful water often is available at the top of the tank even though a considerable quantity of heat has been supplied to the lower layers which nevertheless have not been heated to a useful temperature level.

Although stratification is desirable from they point of view of enabling hot water to be drawn olf quickly, such stratification, if maintained during storage, is undesirable; for example, if stratification takes place in the tank so that the top temperature is 70 C. when the bottom teniperature is 20 C., then the average temperature in the tank is normally only about 35 C. and consequently the storage capacity of heat in the tank is much less than would be the caseif a uniform temperature could bev maintained in the tank, after heating is completed, or, in other words, if stratification during storage could be avoided.

By correctly selecting the volumes of the different parts that constitute the evaporatingcondensing system as well as by selecting a correct filling pressure of the inert gas this system in its operation will obviate the weaknesses above-enumerated in connection with known hotwater systems.

If the evaporating-condensing system is filled at a pressure of one-tenth (.1) of an atmosphere and heat is applied to the boiler, the water. will start to boil and to give off steam at a temperature of approximately forty six degrees centigrade. The steam passes up the vapour pipe, pushing away the inert gas. When the inert gas has been pushed away to the extent that the top portion of the coil in the tank is free from inert gas, the pressure of the inert gas and consequently the pressure of the Whole system has increased. This increase is due to the fact that the inert gas now occupies a smaller volume than the volume which it originally occupied. This increased pressure means, in turn, that the water in the boiler is now boiling at a slightly higher temperature than was the case at the start. By selecting the dimensions of the parts embodied'inv the system, this increase in pressure and consequently also increase in temprature of the vapour, can be predetermined at will. If we assume that the dimensions are such that when the top portion of the coil in the tank is free from inert gas the pressure is .l1 atmospheres, then this corresponds to a temperature of approximately 47.5 centigrade. The water will now be condensing in the top portion of the coil and thereby heating the tank water that surrounds this portion of the coil, that is, the upper layer of the water in the tank. When the temperature of this water has reached a level of 47.5 C. or close to this temperature, the water vapour is no longer condensible but passes on compressing the inert gas in front of it and largely ejecting the inert gas from the next portion of the coil. Condensation thus takes place in this next portion of the coil and the water surrounding this next portion of the coil becomes heated. And so the heating progresses in the manner before-described. The heating progresses downwardly through the water in the storage tank in this way until the whole coil is freed from inert gas, which inert gas has now collected in the gas reservoir. It will be realised that by selecting the volume of the coil so that, for instance, it has a quarter of the volume of the gas reservoir, the final pressure of the system when the whole coil is freed from inert gas will be .11 plus 25% (i. e. .1375) atmospheres which pressure corresponds approximately to a boiling point and a vapour temperature of 51 C. Although the process is described above as if it took place in stages, in actual fact it will be a continuous operation. The water resulting from the condensation of the vapour passes on in each case and returns to the boiler through the return pipe previously described. At the end of the heating period the water in the tank is not stratied as far as heat is concerned. The difference in temperature between the top layer `and the bottom layer should amount to two or three degrees only.

The tank, in conformity with the commonly used hot water systems, has an outlet pipe for hot water at the top and an inlet pipe for cold water at the bottom. If a comparatively small quantity of hot water, say a quarter of the whole volume of the tank, is Withdrawn after the heating period is completed, this means that the bottom quarter of the tank is lled up with cold water, whereas the other three quarters of the tank still retains its hot water. The entry of the cold water into the bottom of the tank results in a slight lowering of the pressure in the system which brings the inert gas back into the lower portion of the coil to approximately the same position as it occupied when only three quarters of the tank, measured from the top, was heated, and the heating up of the lower quarter of the storage tank now takes place in the same way as the normal heating up above-described. It will conseequently be seen that after tapping any desired quantity of hot water from the tank, the heat supply from the boiler will automatically be directed into the cold water that has entered the bottom of the tank and that no portion of the heat will be supplied to the top layers of the tank.

It has already been shown how by lling the system with inert gas of one-tenth of an atmos phere pressure a practically uniform temperature of about 50 C. is obtained in the tank. It is quite obvious that if the original filling pressure were selected higher than .l atmosphere the temperature obtained in the storage tank would be higher.. kThe; system can therefore, by selecting the iilling pressure, be made to raise the temperature in the storage tank to any desired level. The pressure may even be more than an atmosphere; thus, for example, to heat a liquid above C., water and inert gas above normal atmosphere pressure could be used in the closed system.` When the desired level of temperature in the storage tank is reached, the thermostat should cut off the heat supply. The impulse part 4 of the thermostat should naturally be located at the bottom of the tank so that the heat supply is immediately switched on as soon as withdrawal of water takes place. Should, however, the thermostat fail to cut out, heat continues to be supplied to the tank but this immediately means an increase in pressure and consequently the inert gas will be further compressed. As the inert gas is just clear of the heating coil in the storage tank, the increased pressure means that the inert gas will now compress in the gas reservoir l0, leaving the bottom portion of this gas reservoir free from inert gas. The result of this is that the vapour will pass into the gas reservoir and condense at the bottom of this chamber. Such condensation will, readily take place because the gas reservoir is located outside the insulation of the hot water system and functions as an air-cooled condenser- As the pressure increases in the system the inertgas in the gas reservoir will compress more and more, and consequently a larger and larger condensing surface for the vapour will be freed in the gas reservoir and eventually a stage will be reached where all vapour supplied from the boiler will enter the gas reservoir, condense there and return through the return pipe to the boiler. A pressure in the system of, say, one half (.5) of an atmosphere corresponds to a temperature of approximately 81y C., and there is no difliculty in dimensioning the gas reservoir with a large enough surface area, for instance by firming it as shown at IDA, so that all the vapour can condense in the gas reservoir and all the heat from the condensation can be removed at this point without any further increase in pressure. It is therefore obvious that by a suitable dimensioning of the gas reservoir this part of the unit can be made to safeguard the hot water system so that the temperature can never increase above, for example, 81 C. As soon as the heat supply is shut off, no more vapour is created in the boiler and consequently the circulation in the vapourising-condensing system has ceased. As the hot water in the tank is not in contact with the heating surfaces located outside the tank there is no possibility of a cooling down of the water in the tank taking place by circulation of this water.

In the present invention the heating surfaces, i.k e., the surfaces of the boiler, are in contact with the'vapourising liquid only, which preferably is, distilled water,. and this water continues to circulate in the form of outgoing saturated steam and incoming condensed water all the time the system is in operation and consequently there can be no limestone deposit on the heating surfaces in the boiler. The risk of limestone depositing on the coil in the tank is not nearly as great as on the direct heating surfaces, particu-v larly as with a system built for household use according to this invention the temperature in the tank need not be brought up to a level where the risk of deposit is great. As the boiler has a very small volume of vapourising medium it very quickly reaches a temperature above' thev condensing point of the flue gases. For this reason condensation of the ue gasesvs almost entirely eliminated.

If desired,.the gas reservoir could be positioned within the tank as illustrated in the embodi-Y ment shown in Fig. 1A. In Fig. 1A the gas reservoir IDB is disposed within the tank and the lower end of coil 8Y isconnected thereto at 9B. Condensate formed in the evaporatingcondensing system flows through return pipe IIB and liquid trap IIA to the boiler 2. It will be understood that in the embodiment of Fig. 1A the gas reservoir IOB would then no longer function as a condenser and it would' be necessary to rely entirely upon the thermostat to switch off the heat at the correct temperature but there would be certain advantages-from thel point of view of cost andsimplicity of construction.

'Ihe level of the water in the water lock IIA willbe higher in the outer arm than inthe arm nearer to the boiler because the pressure at the outlet end of the coil is slightly less than at the inlet end due to frictional, resistance to the flow of vapour.

Other means could be used for carryingv out the method of heating the water in the tank according to this invention; for example, instead of utilizing the compression of an inert gas to control the downwardly progressive application of the heat as hereinbefore described, the' head of a, column of liquid could be usedfor that purpose. Such an arrangement is shownin Figure 2. In this arrangement, the lower end of `the coil 8 is connected as beforeby a pipe IIv to the boiler 2 but, instead of. being connected to a gas reservoir such as I0 (Figure l), it is-connected to an upwardly extending pipeY |31 or other suitable container, accommodating a column of liquid. Preferably, the pipe I3 terminates in an upper water reservoir I3A provided with a filling valve I2A. At the commencement of the operation the water would be at the same level throughout the closed system and it would gradually be pressed out of the coil, thus creating a steadily increasing. head of liquid in the vertical pipe I3, or other suitable container, and consequently placing the vapour under steadily increasing pressure. The resistance to expansion of the container I3A itself might be used to exert the final pressure when the last portion of the coil has been freed of water. If desired, the use of a head of liquid could be combined with the use of an inert gas in the container ISA. This arrangement using ak headv of liquid is believed to be less eilicient than that using inert gas alone.

I claim:

l. In a method of heating a body of liquid from which heated liquid is withdrawn at a flrst level at the upper part of a liquid body and such withdrawn liquid is replenished by liquid introduced at a second lower level, the improvement which comprises the steps of passing. condensible vaporous fluid in a downward path of flow in thermal exchange relation and out of physical Contact with the liquid body through a vertical height extending downwardly from a vicinity adjacent said rst level, the heat of condensation produced upon condensation of the vaporous fluid in said-path of flow being given up to the liquid body, and maintaining a supply of blanketing fluid which can enterl said path of flow at the lower end thereof and be 8 displaced therefrom by the vaporous fluid to blanket olf a varying length of said path of flow from the vaporous fluid so as to progressively heat to an elevated temperature in a denite'temperature range successive portions of the liquid body in a downward direction from the vicinity adjacent said first level.

2. In a method of heating a body of liquid from which heated liquid is withdrawn at a first level at the upper part of a liquid body and such withdrawn liquid is replenished by liquid introduced at a second lower level, the improvement which comprises the steps of passing condensible vaporous fluid in a downward path of flow in thermal exchange relation and out of physical contact with the liquid body through a vertical height extending downwardly from a vicinity adjacent said first level, the heat of condensation produced upon condensation of the vaporous fluid in said path of ow being given up to the liquid body, and maintaining a supply of inert gas which can enter said path of flow at the lower end thereof and be displaced therefrom by the vaporous fluid to blanket off a varying length of said path of flow from the vaporous fluid so as to progressively heat to an elevated temperature in a definite temperature range successive portions of the liquid body in a downward direction from the vicinity adjacent said first level.

3. In a method of heating a body of liquid from which heated liquid is withdrawn at a first level at the upper part of the liquid body and such withdrawn liquid is replenished by liquid introduced at a second lower level, the improvement which comprises the steps of passing condensible vaporous fluid in a downward path of flow in thermal exchange relation and out of physical contact with the liquid body through a vertical height extending downwardly from a region adjacent said first level toward said second lower level, the heat of condensation produced upon condensation of the vaporous fluid in said path of flow being given up to said liquid body, maintaining a body of blanketing fluid at a place from which such fluid can enter said path of flow at the lower end thereof and be displaced therefrom by the vaporous fluid to blanket off a varying length of said path of flow from the vaporous fluid so as to progressively heat to an elevated temperature in a definite temperature range successive portions of the liquid body in a downward direction from the vicinity adjacent said one level, and. when all of the blanketing fluid is displaced from said path of flow, flowing the vaporous fluid therefrom to said place at which the blanketing fluid is maintained, and giving up heat of condensation produced upon condensation of vaporous fluid at such place to a medium in thermal relation therewith and at a lower temperature than that to which said liquid body is heated.

4. In a method of heating a body of liquid from which heated liquid is withdrawn at a first level at the upper part of the liquid body and such withdrawn liquid is replenishedr by liquid introduced at a second lower level, the improvement which comprises the steps of passing condensible vaporous fluid in a downward path of flow in thermal exchange relation and out of physical contact with the liquid body through a Vertical height extending downwardly from a region adjacent said first level toward said second lower level, the heat of condensation produced upon condensation of the vaporous fluid in4 said path of flow being given up to said liquid` body;

maintaining a body of inert gas at a place from which such gas can enter said path of flow at the lower end thereof and be displaced therefrom by the vaporous fluid to blanket off a varying length of said path of flow from the vaporous fluid so as to progressively heat to an elevated temperature in a definite temperature range successive portions of the liquid body in a downward direction from the vicinity adjacent said one level, and, when all of the inert gas is displaced from said path of flow, flowing the vaporous fluid therefrom to said place at which the inert gas is maintained, and giving up heat of condensation produced upon condensation of vaporous fluid at such place to a medium in thermal relation therewith and at a lower temperature than that to which said liquid body is heated.

5. In a system for transferring heat from a primary heat source to a body of liquid adapted to be held in a vessel having an inlet through which liquid is introduced at a first level and an outlet from which liquid is withdrawn at a second higher level, such system comprising a circuit containing a vaporizable fluid and naving a first part associated with the source of heat and a second vertically extending part connected to receive vaporous fluid at the upper end thereof from said rst part, said second part being arranged in thermal exchange relation with the body of liquid through a vertical height extending downwardly from ya region at the vicinity of the outlet, and said circuit including a vessel for inert gas which is connected to said second part at the lower end thereof and into which inert gas can pass and be displaced therefrom to blanket off said second part to an extent dependent upon the vapor pressure in said circuit.

6. In a system for transferring heat from a primary heat source to a body of liquid adapted to be held in a vessel having an inlet at one level through which liquid is introduced and an outlet at a higher level from which liquid is withdrawn, such system comprising a circuit containing a vaporizable fluid and an inert gas and including a vaporizing element associated with the source of heat, a vertically extending condensing element connected to receive vaporized fluid at the upper end thereof from said vaporizing element, conduit means including a liquid trap for returning condensate by gravity from the lower end of said condensing element to said vaporizing element and a vessel for collecting inert gas which is connected to the lower end of said condensing element, said condensing element being arranged in thermal exchange relation with the body of liquid through a vertical height extending downwardly from a region at the vicinity of the outlet, and said collecting vessel serving to hold inert gas during operation of the system and from which inert gas can pass into said condensing element at the lower end thereof and be displaced therefrom to blanket off said condensing element from vaporized fluid to an extent dependent upon the vapor pressure in said circuit.

'7. In a system as set forth in claim 6 in which said vertically extending condensing element is in the form of a coil and said collecting vessel is disposed within such coil.

8. In a system as set forth in claim 6 in which said collecting vessel is outside the vessel for holding the body of liquid and serves as an extension of said condensing element, said collecting vessel being connected in said circuit for 10 condensate to flow therefrom by gravity to said vaporizing element.

9. The method of transferring heat which cornprises evaporating liquid at a place of evaporationassociated with a source of heat, flowing vapor from the place of evaporation to a first place of heat rejection in thermal exchange relation with a place of heating and from which first place such vapor displaces inert gas to a second place of heat rejection, condensing the vapor at the first place of heat rejection to transfer heat to the place of heating, flowing vapor from the first place of heat rejection to the second place of heat rejection to displace inert gas therein when the place of heating reaches a definite average maximum temperature, condensing such last-mentioned vapor at the second place of heat rejection to transfer heat to a medium which is in thermal exchange relation therewith and at a lower temperature than the place of heating, and, regardless of the pressure of the vapor flowing to the first and second places of heat rejection when condensation of vapor is effected in such heat rejection places, always flowing by gravity any condensate present in said rst and second places of heat rejection in paths of flow leading therefrom to the place of evaporation, so as to make available to the place of evaporation at all times during transfer of heat therefrom substantially the same amount of condensate irrespective of which place of heat rejection it is formed.

10. A method of heating a body of liquid at a. place of heating which comprises evaporating volatile fluid at a place of vaporization associated with a source of heat, 'owing vapor from the place of vaporization in a path of flow including a downwardly directed portion which is in thermal exchange relation and out of physical contact with the liquid body and from which downwardly directed portion such vapor displaces inert gas to a place in which the inert gas collects, condensing the vapor in the downwardly directed portion to transfer heat to the liquid body and flowing condensate therefrom to the place of vaporization, flowing Vapor from the downwardly directed portion to the place where inert gas collects to displace inert gas therein when the liquid body reaches substantially a deilnite average maximum temperature, condensing such last-mentioned vapor at the place where inert gas collects to transfer heatto a medium which is in thermal exchange relation therewith and at a lower temperature than the liquid body, and ilowing such last-mentioned condensate to the place of vaporization substantiallyk immediately upon its formation so as to make available to the place of vaporization at all times during transfer of heat therefrom substantially the same amount of condensate irrespective of where it is formed.

l1. Apparatus for transferring heat from a source -of heat to a heat consuming device removed therefrom comprising a circuit containing a vaporizable fluid and an inert gas and including a vaporizing element associated with the source of heat, a condensing element connected to receive vaporized fluid at one end thereof from said vaporizing element and in which such fluid condenses to transfer heat to the heat consuming device in thermal exchange relation therewith, a member for collecting inert gas connected to the opposite end of said condensing element and into which vaporized fluid passes upon a definite increase in vapor pressure in said circuit, the vaporized fluid passing into said member condensing therein to transfer heat to a medium in thermal relation therewith, and conduit means for `conducting condensate from said condensing element and said member to said vaporizing element, said conduit means being so formed andarranged that condensate can always freely flow from said member irrespective of the vapor pressure in said circuit.

12. Apparatus for transferring heat from a source of heat to a heat consuming device removed therefrom comprising a circuit containing a vaporizable fluid and aninert gas and including a vaporizing element associated with the source of heat, a vertically extending condensing `element connected to receive vaporized fluid at the upper end thereof from said vaporizing element and in which such fluid condenses Ato transfer -heat to the heat consuming device in thermal exchange relation therewith, a member ,for collecting inert gas connected to the lower end of said condensing element and into which vaporized .fluid passes upon a definite increase in vapor pressure in said circuit, the vaporized fluid passing into said member condensing therein to transfer heat to a medium in thermal relation therewith,

and conduit means for conducting condensate from said condensing element and said member tosaid vaporizing element, said conduit means being so formed and arranged that condensate can always freely flow from said member irrespective of the vapor pressure in said circuit.

13. Apparatus comprising rneans providing a source of heat, a vessel removed from such heat source for holding a Abody of liquid, a heat translfercircuit containing a vaporizable fluid and an inert gasand including a vaporizing element associated with the source of heat, a vertically extending condensing element disposed in said vessel which is connected to receive vaporized fluid at the upper end thereof from said vaporvizing element and in which such fluid condenses to transfer heat to liquid held in said vessel, a member for collecting inert gas connected to .the lower end of said condensing element and into which vaporized fluid passes upon a definite increase in vapor pressure in said circuit, said member `being out of thermal contact with said vessel and liquid therein and the vaporizedvuid passing into said member condensing therein to transfer heat to a medum in thermal relation therewith, and conduit means for conducting condensate by gravity from said condensing element and said member to said vaporizing element, said conduit means being so formed and arranged that condensate can always freely flow from said member irrespective of the vapor pressure in said circuit.

14. In a system for transferring heat from a primary heat source to a body of liquid adapted to be held in a vessel having an inlet through which liquid is introduced at a first level and an outlet from which liquid is withdrawn at a second higher level, such system comprising a circuit containing a vaporizable fluid and having a rst part associated with the source of heat and a second vertically extending part connected to receive vaporous fluid at the upper end thereof from said first part, said second part being arranged in thermal exchange relation with the body of liquid through a vertical height extending downwardly from a region at the vicinity of the outlet and providing a path of flow for vaporous fluid therein in which only movement of such vaporous iiuid in a generally downward direction is effected while in thermal exchange relation with the body of liquid, yand means forming an extension of said circuit for maintaining a supply of blanketing fluid which can freely pass into said second part at the lower end thereof and be displaced therefrom to blanket off said second part from vaporous fluid to an extent dependent upon the vapor pressure in said circuit for progressively heating to an elevated temperature in a denite temperature range successive portions of the liquid body in a downward direction from the vicinity of the outlet at said second higher level, said extension for blanketing fluid always being in unobstructed fluid communication with the lower end of said second part.

15. In a system for transferring heat from a primary heat source to a body of liquid adapted to be held in a vessel having an inlet at one level through which liquid is introduced and an outlet at a higher level from which liquid is withdrawn, such system comprising a circuit containing a vaporzable fluid and including a vaporizing element associated with the source of heat, a vertically extending condensing element connected to receive vaporized fluid at the upper end thereof from said vaporizing element, conduit means for returning condensate from the lower end of said condensing element to said vaporizing element, and a riser pipe for holding liquid which is connected at its lower end to said conduit means and in unobstructed fluid communication therewith, said condensing element being arranged in thermal exchange relation with the body of liquid through a vertical height extending downwardly from a region at the vicinity of the outlet to a region at the vicinity of the inlet and providing a path of flow for vaporized fluid therein in which only movement of such fluid in a generally downward direction is effected while in thermal exchange relation with the body of liquid, and said riser pipe serving to hold liquid during operation of the system and from which liquid can pass into said condensing element at the lower end thereof and be displaced therefrom to blanket off a varying length of lsaid condensing element from the Vaporized fluid so as to progressively heat to an elevated temperature in a definite temperature range successive portions of the liquid body in a downward direction from the region at the vicinity of the outlet.

16. In a system as set forth in claim 15 in which a vessel having a cross-sectional area greater than said riser pipe is connected to the upper end of such pipe and contains inert gas.

GEORG ELIS JODELL.

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

UNITED STATES PATENTS Number Name Date 44,153 Bayley Sept. 13, 1864 1,101,243 Bell June 23, 1914 1,987,182 Dalen et al Jan. 8, 1935 2,142,828 Smith Jan. 3, 1939

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