US3216485A

US3216485A - Self cleaning heat transfer surface

Info

Publication number: US3216485A
Application number: US232531A
Authority: US
Inventors: Elio J Speca
Original assignee: Air Preheater Co Inc
Current assignee: Alstom Power Inc
Priority date: 1962-10-23
Filing date: 1962-10-23
Publication date: 1965-11-09
Anticipated expiration: 1982-11-09
Also published as: GB992099A

Description

Nov. 9, 1965 E. J. SPECA 3,

SELF CLEANING HEAT TRANSFER SURFACE Filed Oct. 23, 1962 2 Sheets-Sheet 1 5 "I PH- u! llfk INVENTOR.

Y [//0 J fpeca Nov. 9, 1965 E. J. SPECA 3,216,435

SELF CLEANING HEAT TRANSFER SURFACE Filed Oct. 25, 1962 2 Sheets-Sheet 2 IN V EN TOR.

4 7/0 J, fpeca Y M A I United States Patent 3,216,485 SELF CLEANING HEAT TRANSFER SURFACE Elio J. Speca, Wellsville, N.Y., assignor, by mesne assignments, to The Air Preheater Company, Inc., a corporation of Delaware Filed Oct. 23, 1962, Ser. No. 232,531 8 Claims. (Cl. 1655) The present invention relates to heat exchangers of the rotary regenerative type, and particularly to a heat absorbent surface for such a heat exchanger that is by itself maintained substantially free from all deposits.

In rotary regenerative heat exchange apparatus of the type herein referred to, a cylindrical rotor carrying compartments of regenerative heat transfer material is first exposed to a flow of hot gases directed through the rotor and is then subsequently positioned in the path of the stream of air or other fluid to be heated to impart heat from the gas thereto. The rotor is surrounded by a housing having end or sector plates formed with openings that permit the gas and air to flow through the rotor compartments.

The heat transfer material used most commonly in such apparatus is in the form of metallic plates spaced apart to provide flow passageways therethrough. When subjected to sufficient amounts of dirty gases or air, the heat transfer material frequently becomes fouled with deposits of soot and fly ash to the extent that the flow passageways become severely restricted and the resistance to fluid flow through the spaces between the heat transfer plates is increased until operation is necessarily curtailed.

I-Ieretofore is has been customary to provide soot blowers and cleaners which deliver air or steam under pressure to the surface of the elements to dislodge the deposits and carry them away leaving behind a relatively clean surface. However, such cleaning operations are frequently unsatisfactory in that they are expensive and in many cases, ineflicient. In certain applications involving gases having an unusually heavy dust loading, or where the nature of the impurities being deposited on the heat transfer surfaces causes them to cling tenaciously thereto, it becomes impossible to clean them satisfactorily, and installations of heat exchange apparatus cannot then be considered practical. In other cases somewhat less severe, the energy expended to clean the heat transfer surfaces is so great that thermal gain from the heat exchanger is substantially negated.

The principal object of this invention therefore is to provide a self-cleaning heat absorbing surface fora rotary regenerative heat exchanger that is adapted for installa- Lions where conditions of element fouling preclude the eflicient use of rotary regenerative heat exchange apparatus of the usual type.

A further object of this invention is to provide a highly efiicient self-cleaning heat transfer surface that will preclude the necessity of requiring additional cleaning apparatus of the usual type.

The manner in which these objects are carried out will be best understood upon reference to the following detailed description when read in conjunction with the accompanying drawing in which:

FIGURE 1 is a side elevation of a heat exchanger embodying the present invention.

FIGURE 2 is a sectional view as seen from line 2-2 of FIGURE 1.

FIGURE 3 is an enlarged view of a sectorial rotor compartment shown in FIGURE 2.

FIGURE 4 is a sectional view of a rotor compartment as seen from line 44 of FIGURE 3.

FIGURES 5, 6 and 7 show various modified forms of the invention and,

ice

FIGURE 8 shows a still further modified form of the invention.

As illustrated in the drawing the regenerative air preheater which contains the invention includes a rotor having a rotor shell 10 joined to a rotor post 12 by radial partitions 14 to form a series of sectorial compartments therebetween. The rotor compartments 16 are each adapted to carry a mass of heat exchange material that is alternately disposed in spaced passages to permit the hot gas and cooler air to flow therethrough. The rotor must be inclined from its vertical axis to properly actuate the device and an arrangement wherein the rotor is inclined to a fully horizontal position is ordinarily preferred.

The rotor is surrounded with a pair of axially spaced

ducts

22 and 24 that direct hot gas through the intervening compartments of the rotor While an adjacent pair of similarly spaced

ducts

26 and 28 simultaneously directs cool air or other fluid to be heated through spaced compartments of the rot-or.

The driving means 32 is connected to the rotor whereby it may be intermittently or continuously rotated about its axis to permit the mass of heat absorbent elements carried in the sectorial compartments of the rotor to be alternately passed through the heating fluid and the fluid to be heated. In this manner the elements alternately absorb heat from the hot gas and give it up to the cooler air.

The particular improvement of the invention comprises essentially a myriad of closely spaced rods or tubular members disposed in the compartments in a plane or planes other than parallel to the axis of the rotor. These rods may be attached to the side walls of the compartments or they may be attached to the side walls of the frame-like sub-divisions of the rotor commonly termed baskets that are adapted to fit into the compartments of the rotor, and they may be adapted to occupy the entire rotor or only that portion which is most subject to severe fouling conditions.

The rods 34 are each provided with a loosely fitting collar-like member 36 that is adapted to slide longitudinally over the rod when its ends are alternately raised and lowered during rotation of the rotor about its axis. The collar-like members 36 are shaped generally to agree with the cross-sectional configuration of the rods in order that movement of the collars longitudinally over the surface of the rods will effectively remove foreign materials that have been deposited thereon. Inasmuch as one rotation of the rotor will alternately raise and lower each end of each rod 34, a single rotation of the rotor will cause each collar to make two longitudinal passes over the surface of the rod. Since a rotor normally makes from two to three revolutions per minute, each collar will make from four to six longitudinal passes over the surface of the rod each minute of operation and thus preclude any build-up of deposits that would restrict fluid flow through the rotor.

The rods 34 may be shaped according to the dictates of design to provide optimum performance under a variety of conditions. Thus circular rods 34, rectangular rods 38, streamline rods 42 or other suitably shaped rods having loosely fitted collar members may be used in the manner illustrated by FIGURES 5, 6 and 7.

An especially effective variation of the invention is shown in FIGURE 8 where the cleaning collar carried by the rod 34 comprises a spring-like member 44 having an inside diameter slightly greater than the outside diameter of the rod, and an overall length somewhat less than that of the rod.

In this arrangement the spring-like cleaning collar 44 itself provides a significant heat absorbing surface that substantially increases the heat capacity of the apparatus. Furthermore, the successive convolutions of the collar 42 provide multiple cleaning edges that remove deposits from the rods by means of abrasion, while the rapping action produced When the collar strikes the side walls of the compartment effectively removesresidual deposits from the collar itself as well as from the fixed parts of the rotor.

Thus, while the invention has been described with reference to the various embodiments illustrated in the drawing, it is evident that various'changes may be made in the physical characteristics of the heating element or the cleaning collar without departing from the spirit of the invention, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. Rotary regenerative heat exchange apparatus having a cylindrical rotor shell displaced from its vertical axis, a central rotor post, imperforate partitions extending radially between the rotor post and the rotor shell to provide spaced walls that enclose a series of open-ended compartments, means for rotating the rotor about its axis, a quantity of heat absorbent material carried by each compartment of the rotor comprising a multiplicity of elongate rods secured to spaced walls of the compartments, and collar-like means surrounding each rod having an inside aperture larger than the outside dimensions of each rod to permit said collar to slide longitudinally between ends of the rod in response to the force of gravity thereon as the rotor is turned about its axis.

2. Rotary regenerative heat exchange apparatus having a rotor including a rotor shell and a central rotor post displaced from their vertical axis, imperforate partitions extending radially between the rotor post and rotor shell to provide walls enclosing a series of open-ended compartments, means for rotating the rotor about its axis, a quantity of heat absorbing element carried by each compartment of the rotor arranged in a plurality of axially spaced element layers, said element layers each comprising a multiplicity of elongate rods extending similarly between compartment walls with adjacent layers of said element arranged to extend between difierent pairs of compartment walls, and collar means carried by each of said elongate rods adapted to slide longitudinally thereover and abrade deposits therefrom as the rotor is rotated about its axis.

3. Rotary regenerative heat exchange apparatus as defined in claim 1 wherein the elongate rods are shaped as cylindrical tubes and provided with similarly shaped collar means.

4. Rotary regenerative heat exchange apparatus as defined in claim 1 wherein the elongate rods are shaped rectangularly and provided with collar means having a similarly shaped aperture.

5. Rotary regenerative heat exchange apparatus as defined in claim 1 wherein the elongate rods are streamlined in cross section to provide a low resistance to fluid flowing thereover.

6. Rotary regenerative heat exchange apparatus as defined in claim 1 wherein axially spaced layers of element comprise rods whose shape varies from layer to layer.

7. Rotary regenerative heat exchange apparatus as defined in claim 1 wherein the collar means carried by each rod comprises a resilient helically formed member.

8. Rotary regenerative heat exchange apparatus having a rotor displaced from its vertical axis, a.cylindrical rotor shell and a central rotor post, imperforate partitions extending radially between the rotor post and rotor shell to provide walls enclosing a series of open ended compartments, means for rotating the rotor about its axis, a quantity of heat absorbing material carried by each compartment of the rotor, said heat absorbing material comprising a multiplicity of fixed rods extending between walls of said compartments, and collar means loosely encircling each of said rods adapted to move relative to said rods as the rotor is turned about its axis, said collar means each comprising a helically formed member having a normal length less than that of the rod it surrounds.

References Cited by the Examiner UNITED STATES PATENTS 84,079 11/68 Baker 15-10404 X 617,397 1/99 Hoyt 15l60 1,037,672 9/12 Selick 15l04.04 X 2,740,615 4/56 Scholl l-6 2,746,725 5/56 Reed -6 2,757,907 8/56 Williams l65-9 2,890,862 6/59 Heller 15104.04 2,925,144 2/60 Kroll 55296 3,061,721 10/62 Brenner l5104.04 X

FOREIGN PATENTS 144,899 4/54 Sweden.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.