US2819886A - Heating system - Google Patents

Description

Jan. 14, 1958' E. s. DAUGHERTY 2,819,886

' HEATING SYSTEM Filed Jan. 24, 1956 FIG. I.

FIG. 2.-

Fasfa INVENTOR.

S. DAU EHERTY HEATING SYSTEM Edgar Si Daugherty, Elkins Park, Pa., assiguor to Cochrane Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application January 24, 1956, Serial No. 561,044

4 Claims. (Cl. 261-19) This invention relates to heating systems of the direct contact heating type and has particular reference to deaerators.

Depending upon the operation pressure of the deaerator, and the quantity of water stored in its storage compartment, there is an appreciable amount of potential heat available in the storage compartment which is liberated following a reduction in imposed steam pressure through the normal supply source. The water stored in the storage compartment has been heated to, or very close to, the temperature corresponding to the saturation temperature of the steam pressure applied to the deaerator. If, for any reason, the applied steam pressure is reduced, from a shortage of steam from its input connection coincident with a continual demand for steam in the deaerating compartment due to maintenance of water flow, the entire pressure within the deaerating compartment starts to deteriorate. The available heat in the stored water in the storage compartment is then liberated in the form of flash vapor. The usual downcomer is sealed below the water line in the storage compartment, and therefore the major portion of the flash vapor which must travel from the storage compartment to the demand point in the deaerating compartment must travel through a passageway from the steam inlet region of the deaerating compartment to the storage compartment above its water line. For example, this type of phenomenon occurs quite frequently when a deaerator is operating on a turbine extraction point and the turbine load is reduced, reducing the extraction pressure.

Due to incidental resistances to flow in the system, pressure differentials are set up which, as will hereafter appear, may produce violent surges of liquid into the deaerator not only flooding the same leaving it inefiective for deaerating or heating but also causing physical damage in the deaerating compartment due to the geyser action.

It is the general object of the present invention to provide proper operation in a deaerator or other direct contact heating device with avoidance of improper situations of the type just outlined. Detailed objects of the invention relate to matters of operation and construction and will become apparent from the following description, read in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic sectional view showing the invention applied to a deaerator;

Figure 2 is a similar view showing an alternative form of the invention; and

Figure 3 is a third similar view showing still another modification of the invention.

For consistency of description, the invention will be described as applied to a deaerator, but as will become apparent the invention is equally applicable to other direct contact heating devices in which similar problems arise. The fluid involved will be referred to as water but it will he understood that the invention is applicable to the "ice handling of other fluids with or without involving the removal of dissolved gases or vapors.

There will first be briefly indicated the conventional type of device and the shortcomings thereof which are obviated by the present invention. Figure 1 shows an apparatus provided in accordance with the invention but quite similar in general form and operation to what has been heretofore used. The apparatus pictured in Figure 1 comprises a deaerating compartment 2 which may be of any conventional type, for example, tray type, spray type, atomizing type or reboiling type, and which is provided with a water inlet 4 and a steam inlet 6. The internal details of the deaerating compartment are immaterial to the matter of the present invention and it will be understood that there is provided, in the case of a deaerator, a suitable outlet for the air separated from the water. In

' the case of heaters in which separation of air or some gas or vapor is not involved, the internal construction may be simply that suitable for direct contact heating.

Associated with the deaerating compartment 2 is a storage compartment where previously deaerated water is stored or wherein there may be stored heated water or other liquid if the apparatus is not a deaerator. The vapor space of the storage compartment 8 is connected to the steam supply line 6 through the equalizing passageway 10. Water or other heated liquid is delivered through the connection 12 from the storage compartment, and in the case of a power system this passage would deliver the deaerated water to a conventional boiler feed pump.

Before proceeding further with the description, it may be pointed out that the arrangement shown in Figure 1 is purely diagrammatic and not representative of an actual physical arrangement and not intended to be limiting in its significance. While the deaerating compartment may be superimposed on a storage compartment as illustrated with an external equalizing passageway 10, it Will be understood that the particular physical arrangement may be of any conventional type: for example, both the deaerating compartment and the storage compartment may be contained in a single vertical cylindrical shell, a pair of separate vertical cylindrical shells, at single horizontal shell, a pair of separate horizontal cylindrical shells, or any other combination involving cylindrical, rectangular, spherical or otherwise shaped containers. The equalizing passageway may be located internally of the structure involved or it may be provided by external piping.

A downcomer 14 is shown as providing delivery of the deaerated water from the deaerating compartment 2 into the storage compartment 8. As commonly constructed at the present time the downcomer 14 extends closely adjacent to the mouth of the outlet 12, being spaced therefrom so that there is substantial area of communication between the end of the downcomer and the end of the water outlet to the water within the storage compartment 8 which is designed to receive excess water when the demand for water is low and to supply water at a greater rate than that at which it is supplied from the deaerating compartment when the demand is high. In the prior type of deaerator or heater one of the undesirable features of operation is that, when there is a deterioration of pressure within the deaerator as described above, as the storage compartment tends to flash, i. e., liberates steam bubbles, the water going from the deaerator through outlet 12 to the boiler feed pump is not a mass of liquid water only but a mixture of Water and steam bubbles with the result that violent cavitation occurs and loss of suction and consequent pumping ability of the pump at a time when the boiler might be requiring considerable water. To minimize this result the downcomer pipe has, as just described, been run from the deaerating compartment to the vicinity of the outlet connection 12 in the storage compartment so that the water delivered to the outlet connection is the coldest water in the unit, or the water more closely corresponding to the saturation temperature at the instantaneous pressure existing within the unit and consequently less apt to contain steam bubbles. While this tends to avoid the passage of steam bubbles to the boiler feed pump, there is an attendant disadvantage to this construction in that, during a period of rapid pressure deterioration in the deaerating compartment, the volume of water contained in the downcomer also liberates steam at the same time as that occurs in the water in the storage compartment. When a volume of water at the saturation temperature corresponding to the pressure imposed on the surface rapidly boils due to a reduction of the imposed pressure, the net result is a tremendous increase in volume and increased elevation of the water level. The extent to which boiling and level increase occurs is dependent upon the ability of the storage compartment to supply steam through passageway and connection 6, the ability of the system to supply flash vapor up the downcomer pipe, the rate of demand of steam in the deaerating compartment, and the potential heat available. In particular, the supply of steam from the vapor space of the storage compartment to the deaerating compartment is controlled by the incidental resistances involved in this connection.

The effects of What has just been described is that large quantities of water may pass upwardly through the downcomer into the deaerating compartment flooding it and rendering it ineffective for deaeration and at the same time physical damage in the deaerating compartment may result due to the flow of a large amount of water at high velocity producing impact therein. It may further be noted that in most designs of deaerators only the steam entering the deaerating compartment through its normal steam connection 6 is elfective for deaeration. Vapor which may enter the deaerating compartment by reverse flow through the downcomer may bypass the deaerating elements or may not flow through the deaerating elements in normal fashion and is consequently not fully effective for deaeration.

Referring now to the novel matters involved in the arrangement shown in Figure 1, this arrangement is such as to provide the advantages of the prior system heretofore described but with avoidance of the disadvantages thereof. As shown in Figure 1, the downcomer 14 terminates at a point a relatively short distance below the deaerating compartment, the termination being desirably within the vapor space of the storage compartment 8. As shown, the downcomer 14- opens below the upper edge of a container 16 of relatively small volume as compared with that of the storage compartment 8, and this container 16 is located so that overflow of water therefrom is received in an enlargement 18 of the upper end of a downcomer 20 which terminates at 22 adjacent to the mouth of the outlet 12 in the same fashion as in prior arrangements there terminated the lower open end of the downcomer corresponding to 14. In other words, in the prior arrangements the single downcomer running from the deaerating compartment 2 to a point adjacent to the outlet 12 consisted of a single pipe essentially combining the downcomers 14 and 20 shown in Figure l but providing a continuous closed wall.

In the operation of What is shown in Figure 1, heating of the water supplied at 4 takes place within the deaerator 2 by the action of steam entering at 6 in the usual fashion with condensation of the steam. The deaerated water flows downwardly through downcomer 14 into the container 16 from which it overflows passing downwardly through the downcomer 20 to its end 22. By reason of the fact that this end 22 is closely adjacent to the mouth of the outlet 12, during normal operation the water flowing to the boiler feed pump has its major proportion provided by the freshly deaerated water, with only a minor proportion taken from the storage compartment which serves in the usual fashion to receive extra water through the opening adjacent to the lower end 22 of the downcomer during periods of low demand by the boiler feed pump and feeds additional water during periods of high demand. In view of the fact that the freshly deaerated water is cooler than that in the storage compartment, if and when flashing occurs there is less likelihood that there will be a detrimental degree of separation of steam bubbles in the water flowing to the boiler feed pump than would be the case if the water supplying the pump was supplied from that which had remained for a considerable time in the storage compartment and had its temperature raised therein substantially to the saturation temperature corresponding to the pressure conditions normally existing. Thus the arrangement shown in Figure 1 provides the same advantages as the arrangement which has been used and has been above described. On the other hand, it will be noted that there is no direct connection between the substantial quantity of water which may exist in the downcomer 20 and the deaerating compartment, the continuity being interrupted by the free communication of the upper portion of.the downcomer 20 with the vapor space in the storage compartment 8. Accordingly, in the event that flashing conditions exist involving a degradation of pressure in the deaerating compartment 2, while there will be a pressure diflerential existing in view of resistance to flow of steam from the vapor space of the storage compartment into the deaerating compartment, the differential pressure which exists will cause to enter the deaerator only the relatively small quantity of water contained in the short downcomer 14 and the small container 16. While flashing will occur in the downcomer 20, the attendant expansion of volume will only cause the fluid to rise into the end 18 of the downcomer or thereabove without the possibility that the sudden surge which may then result will force a tremendous amount of water at high velocity into contact with the elements within the deaerating compartrnent.

Accordingly, it will be clear that the present invention guards against both flooding of the deaerating compartment and damage due to violent impact of water flowing thereinto.

While the possibility of the flashing of water in the downcomer 14 and container 16 has been referred to, it may be noted that the small volume of water thus involved is well diluted with colder water directly from the deaerator compartment so that there is a minimum of flashing of this quantity of water and little tendency of its volume to increase to such an extent as to cause even minor impact.

Furthermore, there is less flashing likely to occur in the downcomer 20 than will occur in the downcomer of the prior arrangement connected at its upper end directly to the deaerator. In the last mentioned case there would be a substantial difference of pressure between the lower and upper ends of the single downcomer. In the arrangement illustrated in Figure 1 the pressure in the downcomer 20 is that of the vapor space of the storage compartment 8 rather than that existing in the deaerator 2.

Figure 2 shows a modification of the invention which diflers from that shown in Figure 1 only in mechanical details in that the container 16 is replaced by a container 24 from which overflow takes place inwardly into the upper end 28 of the downcomer 26 which opens at its lower end 30 closely adjacent to the mouth of the outlet 12. As shown in Figure 2 the downcomer 26 is arranged so as to be out of alignment with the downcomer 14 so that water flashing therein enters the vapor space of the storage compartment 8 and cannot pass directly to the deaerating compartment 2. It will be evident that the operation is essentially the same as that which has been described in connection with Figure 1.

Figure 3 shows a further modification in which'the downcomer 14 previously described is replaced by aii enlarged tubular portion 30 of the upper end of the downcomer which terminates adjacent to the mouth of the outlet 12. Within the enlargement 36 there is located a bafile arrangement 34 in the form of a downwardly facing cylinder the upper end of which communicates through pipe 36 with the vapor space in the storage compartment 8. It will be evident that in this arrangement there is interposed between the lower end of the downcomer 32 and the deaerating compartment 2 a region within the bafiie member 34 which is at the pressure of the vapor space of the storage compartment 8. This bafile arrangement is at the upper end of the downcomer 30, 32 with the result that conditions exist substantially identical, from the standpoint of operation, with those described in connection with the modifications shown in Figures 1 and 2. Not only are the pressures of the same type, but the baflle 34 prevents violent upward movement of any liquid into the deaerating compartment. Liquid moving upwardly from the downcomer 32 will pass largely through connection 36 into the vapor space of the storage compartment.

While deaeration has been particularly referred to in the foregoing description of construction and operation, it will be evident that the removal of air from water entering at 4- has no particular part in the operation involved, and reference has been made primarily to a deaerator because there is special utility in the invention to the extent that it especially corrects operating conditions in a system designed to minimize flashing in the portion of liquid passing to a boiler feed pump, and under these conditions the device would be ordinarily a deaerator. It will be obvious that the invention is applicable to other direct contact heating devices where similar problems may occur.

What is claimed is:

l. A heating system comprising a heating compartment, means directing water and steam into said heating compartment, a storage compartment for water from said heating compartment, an outlet for water from said storage compartment, a conduit opening below the water level in said storage compartment for directing freshly heated water downwardly from said heating compartment substantially directly to said outlet so that normal flow of water from said outlet contains a major proportion of freshly heated water and a minor proportion of stored water from said storage compartment, and means preventing Water in said conduit from passing upwardly into said heating compartment upon the occurrence of substantial drop of pressure in said heating compartment relative to the pressure in said storage compartment.

2. A heating system comprising a heating compartment, means directing water and steam into said heating compartment, a storage compartment for water from said heating compartment, an outlet for water from said storage compartment, a conduit opening below the water level in said storage compartment for directing freshly heated water downwardly from said heating compartment substantially directly to said outlet so that normal flow of water from said outlet contains a major portion of freshly heated water and a minor proportion of stored water from said storage compartment, and means providing free communication between the upper end of said conduit and vapor space in said storage compartment.

3. A system according to claim 1 provided with a container receiving water from said heating compartment and providing overflow feeding said conduit.

4. A system according to claim 2 provided with a container receiving water from said heating compartment and providing overflow feeding said conduit.

References Cited in the file of this patent UNITED STATES PATENTS

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