CA1038368A

CA1038368A - Rotor for heat exchanger

Info

Publication number: CA1038368A
Application number: CA222,565A
Authority: CA
Inventors: Robert E. Mahoney
Original assignee: Air Preheater Co Inc
Current assignee: Alstom Power Inc
Priority date: 1974-03-25
Filing date: 1975-03-19
Publication date: 1978-09-12
Also published as: BR7410886A; DE2512817A1; JPS50133542A; FR2266135B1; DE2512817B2; AU7885575A; FR2266135A1; OA04972A; DE2512817C3

Abstract

Abstract of the Disclosure A rotor for a rotary regenerative heat exchanger comprising a series of sector-shaped compartments that surround a rotatable rotor post. The compartments are formed between diaphragms that extend radially outward from the rotor post and are connected at their outward ends by an arrangement of double arcuate walls. The double walls are spaced apart to provide an expansion space sufficient to permit relative distortion of the arcuate walls without inducing interference therebetween.

Description

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1. Field of the Invention This application relates to a rotor for a regenerative heat exchanger that is arranged about a rotatable rotor post. The rotor is comprised of independent sector-shaped rotor compartments that carry a mass of heat absorbent material alternately between a heating fluid and a fluid to be heated.

2. Description of Prior Art In a rotary regenerative heat exchanger of conventional design radially disposed diaphragms extend outward from a central rotor post to form sectorial compartments or baskets that carry a mass of heat absorbent material. The heat absorbent material is subjected to extremes of temperature that induce the transfer heat from the hot fluid to the cooler fluid. Such extremes of tempera-ture also effect thermal deformation of the rotor, fluid leakage and a drop in efficiency of the heat exchanger.
Various heat exchangers having either a horizontally or vertically disposed rotor post have been developed to utilize or avoid the adverse affects of thermal distortion. In U.S. Patent No. 3,182,715, a sealing means has been disclosed that neutralizes the fluid leakage that results from rotor distortion, while U.S.
Patent No. 3,088,518 actually utilizes the temperature differential encountered by a rotor of a rotary regenerative heat exchanger to actuate a sealing means that precludes fluid leakage. Although attempts have been thus m~e to preclude, neutralize or to utilize the effects of leakage in the rotor of a rotary regenerative air pre-heater, such attempts have been uniformly unsuccessful in their results and fluid leakage continues to be a problem of major im-portance.
Accordingly the present invention provides rotary regen-erative heat exchange apparatus having a central rotor post and aninner rotor shell concentric therewith, a plurality of radially disposed diaphragms connecting the rotor post to the rotor sh~ell - 2 - ~ ~

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to produce a series of sectorial compartments therebetween, a mass of heat absorbent material carried in the several compart-ments of the rotor, a housing enclosing the rotor having end plates at opposite ends of the rotor including spaced openings that direct a heating fluid and a fluid to be heated to and through the heat absorbent material in the rotor, means for ro-tating the rotor about its axis within the housing, and an outer rotor shell concentric with and spaced from the inner rotor shell adapted to provide a void therebetween that permits fluid flowing through said rotor shell to subject said shell to a uniform tem-perature change that imparts the same rate of expansion to the inner shell that it imparts to the radially disposed diaphragms.
The rotor is designed to permit thermal expansion of the several component parts thereof without negatively affecting physical form or the heat absorbent characteristics of the heat exchanger. Moreover, the inner arcuate wall is subjected to fluid flow on opposite sides thereof of the same temperature flowing over the element within the compartment whereby the diaphragms, the ; arcuate walls, and the element will be subjected to substantially the same rate of thermal expansion.
Brief Description of the Drawing For a better understanding of the true nature and objectives of my invention, reference may be made to the following detailed description taken in conjunction with the accompanying drawings in which:

Figure 1 is a sectional view of a hori7ontal shaft rotary regenerative heat exchanger constructed in accordance with the present invention, Figure 2 is a plan view of a segment of a rotor as seen from ; 5 line 2 - 2, and Figure 3 is a perspective view of a sector-shaped rotor segment constructed in accordance with the invention.
Description of the Preferred Embodiment The arrangement of the drawing shows a rotary regenerative heat exchanger having a horizontal rotor post 12 supported on bearings 14 and rotated about its axis by means of a drive motor 16 that is connected through suitable reduction gearing to the rotor post. A mass of heat exchange material 18 is adapted to absorb heat from hot fluid flowing therethrough and then give up to a cooler fluid as the rotor is slowly rotated so that the heated element is aligned with the stream of cooler fluid.
The sector-shaped compartments 22 are open at opposite end~
thereof to permit the flow of fluid therethrough, while the individual compartments of the rotor are pivotally secured to the rotor post 12 by a pivotal coupling 24 that permits a degree of relative movement between the rotor post and the surrounding compartments.
A rotor of adjacent sector-shaped compartments 22 is surrounded by a rotor housing 28 having end plates positioned opposite ends of the rotor with openings 32, 34, 35 and 37 that comprise the inlet and outlet openings for a heating fluid and a fluid to be heated. To preclude leakage of fluid through the space between the rotor and the rotor housing, sealing leaves are positioned on the end edges of the rotor to bridge the space between the rotor and the rotor housing. Accordingly, the arcuate ends 46 of the rotor are provided with sealing means 50 that are bolted thereto and adapted to rub against the ad~acent face of the rotor housing while ~038368 radial seals 48 are positioned between open ends of adJacent baskets to bridge the space between the rotor and the adjacent end plate.
The baskets or compartments are connected together at their outer edges at connecting flanges 60 with bolts 62 to form a composite rotor shell that extends continuously around the rotor post.
When the radial walls 42 are sub~ected to an increase in temperature they accordingly expand and sub~ect the outer shell 46 to an elongate or stretching that produces a phenomenon called "chording"
whereby segments of the arcuate shell between diaphragms actually are stretched until they approach a planar configuration.
If the rotor compartments are packed with heat absorbent element that itself is heated and accordingly subjected to thermal expansion, a "chording" of the rotor segment constructed with a single rotor shell in accordance with the customary design will produce an even tighter packing 15 of the rotor and a stretching of the welded ~oints by which the arcuate segments 46 are ~oined to the radial walls 42. Repeated stretching of the welded ~oints produces a strain that eventually results in cracking and breaking the ~oints and failure of the entire structure.
In accordance with this invention I provide an arrangement of 20 double chamber walls whereby a second arcuate wall 44 is concentrically spaced inward from the outer arcuate wall 46 to provide an expansion space 55 therebetween. The expansion space 55 is sufficient to permit thermal expansion of the element 18 within each compartment to force the wall 44 outwardly. Simultaneously, expansion of radial walls 42 will produce a 25 "chording" of the rotor which will draw the segments 46 radially inward into space 55 without inducing interference between the arcuate walls.
The inner arcuate shell 44 is preferably comprised of material which is of somewhat lighter thickness gauge than that of the outer shell 46 in order that there is an inherent resiliency to the inner compartment into which the element 18 is packed.

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Other modifications may become apparent in view of the above teachings, and it is understood that equivalent means may be used without resorting to invention. It is also intended that all material shown in the accompanying drawings or described in the accompanying specification shall be interpreted as illustrative and not in a limiting sense.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Rotary regenerative heat exchange apparatus having a central rotor post and an inner rotor shell concentric therewith, a plurality of radially disposed diaphragms connecting the rotor post to the rotor shell to produce a series of rectorial compartments therebetween, a mass of heat absorbent material carried in the several compartments of the rotor, a housing enclosing the rotor having end plates at opposite ends of the rotor including spaced openings that direct a heating fluid and a fluid to be heated to and through the heat absorbent material in the rotor, means for rotating the rotor about its axis within the housing, and an outer rotor shell concentric with and spaced from the inner rotor shell adapted to provide a void therebetween that permits fluid flowing through said rotor shell to subject said shell to a uniform temperature change that imparts the same rate of expansion to the inner shell that it imparts to the radially disposed diaphragms.

2. Rotary regenerative heat exchange apparatus as defined in claim 1, wherein the outer rotor shell is stronger than the inner rotor shell to support a majority of the load transmitted to the inner and outer shells.