US2924203A - Heating unit for heat transfer liquid - Google Patents

Description

Feb. 9, 1960 F. A. Lol-:BEL

HEATING UNIT FOR HEAT TRANSFER LIQUID Filed Nov. 17, 1954 Nm, EQ.

United States Patent 2,924,203 HEATING UNIT FOR HEAT TRANSFER LIQUID Frederick A. Loebel, Milwaukee, Wis., assignor to Cleaver-Brooks Company, a corporation of Wisconsm Application November 17, 1954, Serial No. 469,341 3 Claims. (Cl. 122-149) is ordinarily desirable to employ as little heat input as y possible to the transfer liquid to effect a desired heating of the product. Time is also usually a governing factor as ordinarily the heating should be accomplished quickly in order to avoid unnecessary delays.

2,924,203 Fatented Feb. 9, 1960 ice? 2 to the embodiment illustrated. The scope of the inventionvwill be pointed out in the appended claims.

The present invention, in general, provides a heating unit to which a coil and suitable lines will be attached to form, with the liquid space in the heater, a closed circuit for circulation of heat transfer liquid. The pres- The present invention is concerned with an improved heating unit for raising the temperature of a heat transfer liquid and circulating it into and out of the heater in a closed circuit. The present unit has several advantages which have not been present in existing units for the same purposes. t The structure is so arranged that all of the heating surfaces of the furnace have the transmaintaining a minimum differential between the temperatures of the heated surfaces and the transfer liquid. Diflculties of expansion and contraction of the furnace parts are avoided since, in effect, the furnace structure is full floating and at the sarne time permitting ready removal of the furnace for cleaning.

A further advantage of the new structure is that it permits a minimum quantity of liquid in the heater thus reducing the cost.

It is, therefore, the principal object of this invention to provide a new and improved heating unit of the character described.

Another object is to provide a heating unit for heat transfer liquid in which the liquid may be passed at high uniform velocity in contact with substantially all of the heated surfaces of the unit.

A further object is to provide a heating unit of particularly high eiciency coupled with a low operating cost.

Other features, advantages and objects of the present invention will be apparent from the following description of a preferred embodiment illustrated in the accompanying drawings in which:

Figure 1 is a side elevational view, partly in section, of the improved heating unit of this invention;

Figure 2 is a vertical sectional view taken through the heating unit substantially along line 2 2 in Figure l; and

Figure 3 is a vertical sectional view taken through the heating unit substantially along line 3 3 in Figure l.

fer liquid pumped thereover at a uniform high velocity ent invention is concerned with the heating unit, its structure and mode of operation. In the past, boiler type constructions, in Iwhich a number of fire tubes secured at Iopposite ends in tube sheets, have been used within a shell for the passage of combustion products which heat the transfer liquid in an out-of-contact heat exchange relation. Diiculties have been encountered since the transferliquid did not come in contact with all of the heated surfaces in a uniform manner, thus permitting parts of the furnace to be at much higher temperatures than other parts. Some parts of the furnace were stressed to such a degree that an actual pulling loose of the parts sometimes occurred.

In the present structure, the furnace extends into the shell of the heater in a manner allowing expansion and contraction of the furnace Without danger of the breakage of any of the parts. At the same time, the structure is so arranged that the heating liquid is pumped over the furnace structure at a very high velocity compared with what has been possible in the past. This results in a very small differential in temperature between'the heated surfaces and the liquid. Uniformity in the expansion and contraction of the furnace parts is also achieved by this structure.

The unit is intended for use in the field so that it is ordinarily mounted on skids 4 forming the base for sup-l porting the shell 5 about which an insulating layer of material 6 is placed and covered by a retaining sheet metal cover 7. The heater ordinarily operates at atmospheric pressure and an expansion tank or space is provided to maintain the pressure at atmospheric pressure. The shell is provided with a flange 8 at one end and a dome-shaped or spherical end 9 opposite the flange. The front of the unit mounts a burner structure generally indicated l0 which includes the burner 11, anda motor 12 for operating a blower inside an air plenum cham.- ber 13 having an air intake at 14. The burner structure 10 is generally the same as disclosed in the application of Cleaver et al., Serial No. 403,286 tiled January l1, 1954, now Patent No. 2,835,230.

This burner structure is mounted on a door which is hinged to a combustion products gas chamber 15 directly The products of combustion formed in the burner 11 are discharged into a burner section 16 so that the flame may travel down the main re tube 17 of the furnace toward the spherical end 18 thereof. At the end of the main re tube 17, the combustion products enter one or an other of a plurality of return ues 19, each of which has an end portion 20 communicating through an opening with the interior of the main fire tube. The return fiues are each helically wound about the tire tube and communicate at the burner end with the chamber 15 and stack 21. For instance, the particular return ilue connecting with the fire tube on the near side of the same, as illustrated in Figure 1, has its exit into the combustion products chamber at 22. The return flues are generally wound in parallel lines so that in a sense the live ilues are in the form of a compound thread. For the particular size of fire tube and flues illustrated, each flue makes about While this invention is susceptible of embodiments in many different forms, there is shown n the drawings and is herein described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplcation of the principles 0f the invention and is not intended to limit the invention two and three-quarters turns about the tire tube.

The particular form of the furnace or heating element is advantageous in that it permits expansion and contraction of the tire tubes and ues without the danger of breaking any of the connections. The products chamber 15, tire tubes and ilues are all supported by a heavy ange i 2,924,203 p q i y f- 23 secured to the flange 8 of the shell and are extended thereby in a cantilever fashion into the shell. This Apermits ready removal for cleaning which must be done from time to time as the formation of coke is dependent upon a time-temperature relationship.

The heattransfer liquid `is conducted :into and Yout `o'f the :shell .through an inlet 25 and anioutlet 26. V.I'he space within the shell about the furnace forms a part :of .aclosed circuit with a coil of pipelines which may be `connected with the inlet and outlet. "Ordinarily, a circulating pump is connected `to .the outlet 26 for forcing the heated Voil or other liquid through heat transfer equipmentsuch asstorage tanks, heating :coils or other heat exchangers.

,Theiform of the present heater employs a shroud '.27 `of generally cylindrical form `placed in 1the shell and :about the-.tire tube Yand 'flues concentrically. Spacers '28 vserve to "hold .the shroudtin position. The end of the ,shroud adjacent .the `stack 21 is open while `the other end has a partially spherical end `29 with a neck portion 30 forming a `central opening. The shroud thus divides the interior of `the shell into a return passage between itself and the shell and a heating passage between the shroud and the fire tube. The transfer liquid is heated passing over `the furnace surface after which `is passes around thegend vof thelshroud to the-outlet 26. Cold Lliquid vis draw-n back into the shell through the inlet 2S while at thefs'ame time some oil may be by-'passed around the outsideV of the shroud to-again pass to the heatingzone. Spacer Iinembers 31 are also employed to `space the Vshroud `around the tire tube. i

'One of-Ytheimportant features of thel present invention is'the Astructure by which the transfer'liquid Yis forced foyer the heated surfaces -at a uniform `high velocit-y.A

maintains the heated surfaces at a lower temperature-than otherwise would be possible. ln the 4present invention, a propeller 40 "is mounted on Ya shaft in the end foftheshell so that iit rests withinithereduced portiox1i30=of`th`e shroud and-is positionedfbetweenfthe passages mentioned. A suitablernotor 441 is providedgwith a belt 42 for drivingthe propeller. Cold oilmay pass from lthe linletthrough louvers i143 :to the blades of the propeller '40 and 'is -then forced longitudinally over the re tube aad return flues. The propeller `turns in the direction of the-'windingiof -theV ilues so that the oil may follow a path slightly helical in nature `rather than strictly longitudinally of the 's'hell. This structure .contributes to a very'low yhead 'loss which has `vbeen experiencedywith theunit.

The primary benet of the pumping arrangement just described is the maintenance of a relatively highyelocity of ow of the transfer 'liquid over-the-heated surfaces. it has been found that velocities 4of the order 'of seven to eight feet per-second may 1be=maintained without requiring especially large driving motors foithe propeller. At such f-velocities, a temperature differential Vbetween the heated 'surfaces vand the liquid of not substantiallymore than 570 :F.have beenrachieved. The-shroudis placed quite close to the return ues -so that a generally uniform, relatively thin passage is providedforthe liquid over the heated'surfaces. There is practically no obstruction in the pathof the liquid throughthisuniformsize channel. The fact thatltheremay be more space betweenthe `shroud and the flire tube in between the flues 'does'not interferelwith heated surfaces of the furnace to the transfer liquid. Gas .temperaturesfin .the -inlets to the -return `ilues have been found in the range of l500 to 1850 F. whereas the metal temperatures close to the same locations would be under 500 and in some cases below 400 1F. The gas in the stack would generally run no more than 200 F. higher than the metal temperatures. lt was found that when the propeller pump 40 was stopped the heated surfaces would ,rise -in :temperature quite Lrapidly and would accordingly .as rapidly be brought ,down in temperature once l:the -pump `.wasreturned toguse The structure of the present invention is intended for longservice `of a very eicient nature. It may be easily serviced since the furnace 'may Aibe removed from the shell quite readily.

Safety features `are employed by the use of a pop-olf pressure valve44 and a blow-out plug 45. To accommodate any expansion in the heated transfer fluid, a line 46 communicating with the space within the shell may be connected tosan expansion tank.`

' 4iiIlt-:laim: i

1. A- heating unit'for heat transfer liquid subject tofde'- composition by .applicationfof heat, comprising: an elongatedxshelli; Y`a 'heatinguelement secured only to one end t ofth'eish'ellwand'Y having 'a generally cylindrical nfire tube and'iretiiiinfliuescantilevered intoi'the she1l,"isaid return nues l:beinggenerally lhelicali and Wound about the lire tubeglanope'n-ended.shroud closely spaced about the re tubeianti lluesforming `a narrow liquid passage over fthe i tire tube randiue surfaces; .a circulating pump impeller i mounted in #thexotheriend ofthe shell and arranged to` force `iliquid V.through said liquid lpassage at generally 'unif for'm velocity over allthe heated surfacesof there tube andireturn ues, said pump impeller forcing the `transfer t liquid, in vthe direction of the helical path 'of the zretum ues Zso as to minimize `head lloss in the liquid passage;

and aftransferliquid inlet in the ishell adjacent l'thepumpu and anoutlet in the'shell `spaced from saidinlet.

2. -A heating unit for `heat transfer liquid subject lto decomposition by application of heat,` comprising:` an

elongated shell; a heating element Isecured only lto one endlof lthe shell and `having a re tubey and return ilues cantilevered into `the shell; an open-ended `shroud suff ciently closely spaced about the tire tubeand flues to Iform a narrow liquid passage bounded 'bythe-shroud ireftube andiiue surfaces; a circulating pump-impeller mounted in the other end of the shell and arranged *to -force liquid through said liquid passage at generally uniform Avelocity overall the 'heated surfaces of the re tube and `return nues; and a transfer liquid imei inthe sheuaaiceniihe thei-uniformow. Thus,-"theshroud is placed quite close pump and an outletin thezshellzspaced from said inlet.

'-3. A vheating `unit for heat transfer `o'il `toibe kcirculated through coils, lines and the like, comprising: a base; a heating shell mounted upon `the base y,andkhaving a transfer oil inlet `and an outlet therein; a heating, element L secured-to one end of the'shell and having :ah'portion extending into said heating `shell in cantiIeVeraSh'iQn, said heating unit including an inwardly extendingire tubeand a plurality ofreturn ilues Iarranged about'the Afire tube in helical pattern for conducting flue gases out of the shell; an `open-,ended "shroud, surrounding the 'helical ues in suilcien'tly closely spaced relation thereto .as to `form helioal passages'therewith, said shroudfbeing spaced from theA shell andhaving a portion of diminished :size about thefree end of the furnace, saidtransferoil inlet and outlet communicating. with a space within the shell about the shroud; and a.,c`i rculating pump impellenmounted in saiddiminished sizeportion of the shroud for forcing t transferroil from the; spaceoutside `-the shroud `over the lengthof the Ifurnace ,-in `the direction of ,the -helical passag=S.,` Said shroudv having a portion aboutthe flues; forming an' annularelongated passage-for the liquid-substantally Vufnizihstructed permitting @relatively t uniform high v'elocityidw over the tube and'llue surfaces.

(Re'ferences on rfllowingtpage) i UNITED STATES PATENTS Maxim Nov. 1, 1910 Prache Feb. 17, 1920 Schwarz June 24, 1930 Howard Feb. 10, 1931 Morgan Nov. 13, 1934 Gallagher July 2, 1935 Derby Oct. 8, 1940 Aldridge Nov. 18, 1941 6 Brantly Aug. 4, 1942 Nelson Dec. 11, 1951 Glasgow et al. Jan. 20, 1953 Ray Oct. 27, 1953 Lustig Mar. 8, 1955 Putney July 23, 1957 FOREIGN PATENTS Germany uly 26, 1904 Great Britain Nov. 10, 1932

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