US1906422A - Apparatus for heating - Google Patents

Description

May 2, 1933. J. A. RCULTON APPARATUS FOR HEATING Filed Nov. 14, 1931 Patented May 2, 1933 UNITED STATES,

PATENT OFFICE JOHN A. ROULT ON, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO 'THE ATLANTIC REFINING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA arraaa'rus FOR HEATING Application filed November 14, 1931. Serial No. 575,045.

The present'invention relates to process for heating or heat exchange and apparatus in which such process may be carried out.

In accordance with my invention, vapor under substantial pressure, as for example, under pressures of the order of lbs. per

, square inch and higher, is employed as the I C, D, E, and F are alike,

heating medium; heat exchange is efiected by bringing materialto'be heated into indirect contact and heat exchange relation with the heating medium; and in performing its function, the heating medium gives up its latent heat and condenses, without the pressure thereupon being decreased to substantial extent.

As the heating medium, I employ steam or other Vaporous material, such as, vaporized mercury, diphenyl Vapors, or vapors of other liquids, similar to these in their: vaporizing andcondensing properties. I prefer to use dry saturated vapors, such as dry saturated steam or equivalent. 7

My invention may be applied to any of a number of various types of apparatus. For a better understanding of my invention, and in order to -illustrate one type of apparatus in which my heating process may be carried out, but without intending to limit my invention to the specific structure disclosed, reference is'had' to the accompanying drawing in which: v Fig. 1 is a diagrammatic elevational view of a heating system; I

Fig. 2 is'an elevational View in section of one of the heating units employed in the system disclosed in Fig. 1.

Referring to the drawing, 1 indicates a supply line through which vaporized.heat ing medium is fed from boiler B into one or more of the heating units, C, D, E, and F. 2 designates a return line through which condensate passes from the respective heating uniltgs and eventually is returned to the boiler As shown in the drawing, the heating units so that a detailed description of one will sufiice for all. Beferring to a heating unit, 3 designates a line,

' equipped with valve 3a, through which material to be heated may be introduced into the unit, while 4 designates a line through which the heated material may be passed therefrom. Line 5 connects supply line 1 with the heating 'unit, whilelinefi joins the unit to the return line'2.

Line 5 is equipped with valve 7 which is thermostatically controlledby means of element 8 extending into line 4, so that valve 7 may be controlled by the temperature of the heated material passing from the unit. Line 6 is equipped with valve9 controlled by liquid level device 10 associated with such line.

Each of the heating units C, D, E, and F comprises an outer casing 11, having arranged internally thereof, and between header plates 12 and 13 a series of tubes 14. The material to be heated is introduced into'the unit through line 3 at its bottom, whereupon it passes through the tubes 14, thence out of the unit through line 4. The heating medium is passed into the unit through line 5 and circulates around'the tubes 14 in indirect contact and in heat exchange relation with the material to'be heated, thence, after being condensed, out of the unit through line 6.

Beyondthe portionof line 2 with which lines 6 from the respective heating units connect, line 2 is equipped with a check; valve G to prevent pulsations in the forward portion thereof; and next beyond said check valve at point H, line 2 communicates with line 15 which-leads from make-up supply tank Line 15 is equipped with pump P by means of .which additional or make-up liquid toserve as heating medium is passed from tank K and impelled into line 2. Operation of pump P is controlled by valve 17 in the line through which driving medium is supplied to the pump, the valve 17 being actuated by pressure controlled device 18 located in line 2, just beyond the point, at which line 15 communicates therewith.

, Tank K communicates with feed line 19, controlled by valve 190 which latter is controlled by liquid level device 19?) actuated by the level of liquid in tank K. The tank is also provided adjacent its top with sealed overflow 20, and with vent the point at which pump P is located and the a point. at which this line taps into line 2, a

, it is desired to return line 16, equipped with relief valve 16a, which line leads into tank K. When pressure in excess of a predetermined maximum occurs in line 15 between pump P and point H and/or in line 2 beyond check valve G, relief valve 16a opens, thus permitting flow of liquid into tank K.

Next beyond pressure control device 18, line 2 is equipped with a pump P, preferably of the centrifugal type, by means of which liquid is forced into the boiler B; and between pump P and the end of line 2 which communicates with boiler 18, line 2 is provided with valve 23, controlled by the level of liquid in boiler B, and in addition, with check valve L.

In beginning to operate a system as above described, the vaporized heating medium under pressure, as for example, under a pressure of 400 pounds per square inch, supplied from boiler B, ispassed-through feed line 1',

thence through one or more of the lines 5 into one or more of the heating units Under starting conditions the valves 7 in line 5 leading to the respective heating units are wide open, the thermostatic actuating mechanism 8 of each valve having been set so that it will begin closing its valve upon becoming heated to a temperature above that to which heat the material passing through the particular heating unit. aterial to be heated is introduced into the heating unit through line 3, whereupon such material comes into indirect contact and heat exclian e relation with the heating medium, which later condenses. If there is no head of liquid in the lower part of the heater nor in line 6 leading from the heater, valve 9 in line 6, which is controlled by liquid level device 10, is completely closed. Under these conditions condensate builds up in line 6 above the point at which valve 9 is located, to the level of the point at which line (3 connects with the heater, and preferably also to some extent in the lower part of the heater, but in either event to an extent so that vapors can not pass from the heater through line 6. When condensate has built up in line 6 above a predetermined level, devicelO acts to completely open valve 9 in line 6, whereupon condensate passes from the heater through such line into return line 2. In designing the heating system, it will be understood that .as a practicalmatter,the cross-scction al area of l i no 5, will, in generalfbe greater than the crossseetional area of line 6; however,theoretically, there is no objection to having line 6 of substantially the same or greater cross-sew tional area than line 5. The pressure in line 2 is maintained constant and substantially equal to the pressure on the outlet sides of valves 9 by means of the portion of the system comprising tank K, line 15, and pump P, the relief valve Gin line 2 closing only when pressure in the portion of line 2 to the right ofyalve G, as shown in the drawing, is less than pressure in line 2 at point H.

After operation of the system 'is under way, with a given heat requirement, less, for

example, than the maximum heating capacity for which one of the heating units has been designed, when the heated material passing from the heater reaches a predetermined temperature, thermostatic device 8 in line 4: acts to gradually partially close valve 7 in line 5 to slightly reduce the pressure at which heating medium is being supplied; This is accompanied by a reduction in the pressure acting to force condensate from the heater, and a consequent accumulation of condensate and rise ofcondensate level in the heater will result, thus reducing the effective area of heat transfer between vapors and the materlal bemg heated to that necessary to just maintain the material leaving the heater at the predetermined and desired tempera- -ture.

\Vhen, for example, the heating requirement for a unit is increased, as when there is an increase inthe rateat which material to be heated is passed through the heater, the temperature of the heated material passing out through line 4 will be slightly lowered, thus causing device 8 to open wider the slightly closed valve 7, whereupon additional pressure in the heater caused by opening of such valve, will force liquid from the heater at a greater rate, thus lowering the level of liquid within the heater and exposing greater amounts of heating surface within the heater,

through which heat from the vaporized heating medium may pass into indirect contact and heat exchange relation with the material to be heated. v

WVhen, for example, decrease in the rate of passage of material to be heated into the heater occurs, the incident slight rise of temperature above the predetermined desired temperature of the material passing out of the heater through line 4 will cause device 8 to slightly close valve 7' in line 5, and thus s ightly decrease the pressure in the heater, whereupon condensate will gradually build up in the heater to a level or headsuificient to compensate for the difference in pressure caused by the slight closing of valve 7. Thls gradual accumulation of condensate will cut down more and more the area through which transfer of heat from the vaporized heating medium to the material being heated may to allow heat transfer-at the rate necessary.

to maintain the outgoing heated material at. the desired temperature. The principle upon which the operation above described is based, is that heat transfer from a vaporous heating medium at a given temperature to material to be heated, when brought into indirectheat exchange relation therewith, will take place at a considerably greater rate than if the heating medium were in the liquid state at the same temperature; and this principle is well understood by heat engineers. To illustrate, in the case of steam at its condensation point, the coefficient of heat transfer is about 5 times that of liquid water at the same temperature. See standard tables of heat transfer coefficients. In other words, on the basis of equal areas and equal temperature differential, the rate of heat transfer in the area in which steam is condensing would be several times that in the condensate area. The difference in heat transfer between the liquid and condensable vapor areas is further accentuated by the fact that the liquid is present as a more or less quiescent body while the vapor is in circulation.

Summarily, the vaporized heating medium undersubstantial pressure passes intoa heating unit of my system, and upon giving up its latent heat condenses and accumulates in line 6 and in the lower part of the heating unit to a height sufiicient to cover up with liquid that portion of the tubes of the 'unit which is not required to provide the desired heat exchange between the vaporized heating medium and the material being heated. Therefore, each of the units automatically maintains at a predetermined temperature the heated material passing therefrom, and this substantially by the extraction of latent heat from the heating medium. Since each heating unit operates substantially independently in the manner aforesaid, my invention provides for maximum flexibility in meeting varying heating demands. Materials to be heated may be brought to varying temperatures in the several heating units and at.varying rates. In

the units themselves the area of heat exchange is automatically controlled by the building up of condensate to cover that area not needed to effect a particular heating result. The pressure upon the heating medium is maintained as nearly constant as possible throughout the entire system, there being no substantial pressure loss in the system due to throttling of the heating medium.

In accordance with my'process and in 'a system suchl as disclosed, the pressure differential between the line through which heating medium is supplied in the form of vapors to the one or more heating units and the pressure in the line through which condensate is returned from the heating units to the boiler, is of a much lower order than in systems heretofore employed, since in my system, there is no substantial drop in ressure due to throttling. 1 The distinct a vantage thus gained is that less work will be required to bring the condensed heating mediumback to the pressure required to feed it into the boiler against the pressure in the boiler itself.

ne or more units, in accordance with my invention, may be fed with heating medium through a common supply line, and the condensed heating medium may be passed from i the one or more units through a common return line. If a plurality of units are employed, a rate of heating may be maintained in each unit independently of and, if desired,.

different from the rate of heating in each of the other units.

It will be understood that when more than one heating unit is employed, theunits may be of different sizes and of varying structural details. For example, the tubes of the heater may be arranged horizontally instead of vertically, the heating medium may be passed through the tubes and the fluid to be heated passed around the-tubes, instead of as described above. Or, in fact, the heating unit I may be in the form of a jacketed chamber or the like, in which the heating medium is passed into and condensed in the jacket.

" Since in the ordinary course of operation,

ing medium entering a heating unit, is necessary regardless of the heating requirement in 105 the particular unit, since variations in such requirement are taken care of" by drowning greater or less amounts of the area of heat exchange exposed to the vaporous heating medium. I 1 What I claim is: 1. In heat exchange apparatus, a compartment wherein indirect contact and heat ex- 7 change between vaporous heating fluid and material to be heated may be effected, where- .by heat. maybe imparted to the material to cause condensation of the fluid, means associated with said compartment, whereby the rate of passage of vaporous fluid thereinto may be controlledby the temperature of material therein beingheated, and means associated with said compartment whereby flow of condensate of the heating fluid from the compartmentis prevented when condensate therein falls below a predetermined level, but

which otherwise permits flow of condensate from the compartment.

2. In heat exchange apparatus, a plurality of compartments in each of which heating fluid may be passed into indirect contact and heat exchange relation with material to be heated, whereby heat is imparted to the material and condensation of the fluid is eflected, a common supply line, a branch pipe leading therefromto each of said compartments,means associated with said branch lines whereby the rate of flow of fluid into the compartments may be controlled by the temperatures of the materials being heated, a return line, a pipe leading from each of the compartments t0 the return line, means interposed within each of the return lines whereby flow of condensate from the compartment is prevented when condensate falls below a predetermined level, but

which otherwise permits flow of condensate throu h the pipe and into the return line.-

3. I n heat exchange apparatus, a plurality of compartments in each of which heating fluid may be passed into indirect'contact and heat exchange relation with material to be heated whereby heat is imparted to the material, and condensation ofthe fluid is ef- V fected, a common supply line, a branch pipe leading therefrom to each of said compartments, means associated with said branch line whereby the rate of flow of fluid into the compartment may be controlled by thestema perature of the material being heated, a return line, a pipe leading from each of the compartments to the return line, means interposed within each of the return lines whereby flow of condensate from the compa rtmexgt s prevented when condensate falls below a redetermined level, but which otherwise permits flow of condensate through the pipe and into the return line, and means associated with said returnline whereby the pressure therein is maintained at substantially that of the pressure at the junction of each of the pipes leading'from the compartments with the return line.

In testimony whereof I aflix my signature.

J OHN A. BOUT-TON,

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