FIELD OF THE INVENTION
The present invention relates to a rotary regenerative air preheater. More
particularly, the invention relates to propose a dimensionally - optimized
regenerative air preheater with improved heat transfer element to reduce the
pressure drop.
BACKGROUND OF THE INVENTION
Rotary regenerative air preheaters are used in Thermal power stations/Industrial
applications to transfer the heat from the flue gas leaving boiler / furnace to the
entering combustion air through air and gas streams.
A rotary regenerated air preheater transfers sensible heat from the flue gas
leaving a boiler to the entering combustion air through regenerative heat transfer
surface in a rotor which turns continuously through air and gas streams. A
cylindrical rotor is disposed on a horizontal or vertical central rotor post divided
into a plurality of sector shaped compartments by a plurality of radial partitions,
referred to as diaphragms, extending from the rotor post to the outer peripheral
shell of the rotor. These sector shaped compartments are loaded with heat
exchange baskets which contain the mass of heat absorbent material commonly
formed of stacked plate-like heat transfer elements.
In a typical rotary regenerative heat exchanger, the hot flue gas and the
combustion air enter the rotary shell from opposite ends and pass in opposite
directions over the heat exchange material housed with the rotor. Consequently,
the cold air inlet and the cooled gas outlet are at one end of the heat exchanger,
referred to as the cold end, and the hot gas inlet and the heated air outlet are at
the opposite end of the heat exchanger, referred to as the hot end.
The air preheater is divided in to a flue gas side or sector and one or more
combustion air sides or sectors by sector plates. Flexible radial seals on the rotor,
usually mounted on the top and bottom edges of the diaphragms, are in close
proximity to these sector plates and minimize leakage of gas and air between
sectors to separate the air and the flue gas streams from each other. Likewise, a
rotor shell is mounted to the outboard ends of the diaphragms, forming the
periphery of the rotor, to prevent the air and gas streams from flowing through
the peripheral ends of the sectors and bypassing the heat transfer surface.
Circumferential seals seal the gap between the rotor and the rotor housing to
prevent bypass flow through the annulus formed between the rotor and the rotor
housing.
Prior art teaches different profiled heat transfer elements as shown in Fig.l,
Fig.2 and Fig.3 were used. These heat transfer elements are packed in spaced
relationship to provide a plurality of passageways between adjacent elements for
flowing the heat exchange fluid between them. Generally, the heat transfer
elements induce a highly turbulent flow through the passages between them in
order to increase the heat transfer from the heat exchange fluid to the elements
at the same time providing low resistance to flow between the passages and also
presenting a surface configuration which is readily cleanable. To clean the heat
transfer elements, soot blowers are provided to deliver a high pressure steam or
air between the heat transfer elements to remove the dust particles from the
surface and leave away the clean surface. Due to blowing of high pressure
steam or air on thin heat transfer elements, cracking / erosion of the heat
transfer elements takes place and there by heat transfer effectiveness
decreased. To increase the effectiveness of the elements, and to avoid erosion
of the heat transfer elements, suitable measures need to be developed.
A heat transfer element assembly of this type is disclosed in International Patent
Application No. IN/PCT/2001/00701. In the above mentioned application, the
heat transfer element have less number of notches because of wider pitch
between the notches.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a dimensionally -
optimized regenerative airpreheater with improved heat transfer elements to
reduce the pressure drop.
Another object of the invention is to propose a dimensionally - optimized
regenerative air preheater with improved heat transfer element to reduce the
pressure drop, in which the heat transfer elements have longitudinal notches in
the direction of fluid flow.
A still another object of the invention is to propose a dimensionally - optimized
regenerative air preheater with improved heat transfer element to reduce the
pressure drop in which the heat transfer elements are corrugated to provide a
series of undulations between the notches to an angle of the fluid direction.
A further object of the invention is to propose a dimensionally - optimized
regenerative air preheater with improved heat transfer element to reduce the
pressure drop, in which corrugation in one heat transfer element is in one
direction and corrugation in an adjacent heat transfer element is in the opposite
direction.
A still further object of the invention is to propose a dimensionally - optimized
regenerative air preheater with improved heat transfer element to reduce the
pressure drop, in which a plurality of notches in the elements are provided to
obtain closer pitch (P) between the notches, leading to high heat transfer area
and improved effectiveness of the air preheater.
SUMMARY OF THE INVENTION
Accordingly, there is provided a rotary regenerative air preheater comprising a
plurality of heat transfer elements (01), a first element (01) having a first
plurality of longitudinal notches (03), and a first series of corrugations (02)
inclined to the first plurality of notches (03) in one direction, the adjacent
profiled element (04) having a second series of corrugations (05) inclined to a
second plurality of notches (06) in opposite direction, the notches (03, 06) in the
profiled elements (01, 04) being parallel to fluid direction and the corrugations
(02, 05) are inclined to the fluid direction.
Thus the heat transfer elements of the air preheater of the invention provide
high heat transfer and reduced pressure drop because of the pair of elements
are having longitudinal notches and corrugations. The corrugation of the
adjacent elements are in opposite directions to have a optimum design of air
preheaters.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
FIGURE 1, FIGURE 2, FIGURE 3 - shows different profiles of heat transfer
elements of prior art
FIGURE 4 - shows a profile of heat transfer element of a rotary regenerator
preheater according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The details of the improved heat transfer elements of the rotary regenerative air
preheater of the invention is shown in 4.
As shown in Figure 4, the heat transfer element provide high heat transfer and
reduced pressure drop because of the pair of elements are having longitudinal
notches and corrugations. The profiled element (01) having series of
corrugations (02) inclined to notches (03) in one direction. The adjacent profiled
element (04) having series of corrugations (05) inclined to notches (06) in
opposite direction. The notches (05) in the profiled elements (01) are parallel to
fluid direction and the corrugations (02) are inclined to fluid direction. And also,
the heat transfer element (01) have more number of notches (03) because of a
closer pitch (P) between the notches. This will lead to high heat transfer area
and improved effectiveness of the air preheater. Due to improved effectiveness,
air preheater size is reduced.
In the present invention, the heat transfer element as shown in Figure 4 have
more number of will notches because of closer pitch (P) between notches. This
lead to high heat transfer area and improved effectiveness of the air preheater.
Because of this improved effectiveness, air preheater size can be reduced.
WE CLAIM:
1. A rotary regenerative air preheater comprising a plurality of heat
transfer elements (01) a first element (01) having a first plurality of
longitudinal notches (03), and a first series of corrugations (02)
inclined to the first plurality of notches (03) in one direction, the
adjacent profiled element (04) having a second series of corrugations
(05) inclined to a second plurality of notches (06) in opposite direction,
the notches (03, 06) in the profiled elements (01, 04) being parallel to
fluid direction and the corrugations (02, 05) are inclined to the fluid
direction.
2. The air preheater as claimed in claim 1, wherein the plurality of the
first heat Transfer element (01) and the plurality of the second heat
transfer element (04) are packed alternatively in a defined space to
provide a series of passage ways between the elements (01, 04).
3. The air preheater as claimed in claim 1, wherein the pitch (P) between
the notches is up to 50 mm.
4. The air preheater as claimed in claim 1 wherein the size of the air
preheater is optimized.
5. A rotary regenerative air preheater substantially as herein described
and illustrative with reference to the accompanying drawings.

This invention relates a rotary regenerative air preheater comprising a plurality of
heat transfer elements (01) a first element (01) having a first plurality of
longitudinal notches (03), and a first series of corrugations (02) inclined to the
first plurality of notches (03) in one direction, the adjacent profiled element (04)
having a second series of corrugations (05) inclined to a second plurality of
notches (06) in opposite direction, the notches (03,06) in the profiled elements
(01,04) being parallel to fluid direction and the corrugations (02,05) are inclined
to the fluid direction.