FIELD OF INVENTION
The present invention relates to an improved plenum chamber for air cooled heat
exchangers. More particularly, the invention relates to an improved plenum chamber
for ensuring uniform air distribution over tube bundle without any air pockets for
optimum thermal performance.
BACKGROUND AND PRIOR ART OF THE INVENTION
Air Cooled Heat Exchangers are advance class High pressure, Heat Exchangers being
used in locations where water as cooling medium is not available. The Hot fluid
(Cooling water, gas, oil etc.) is normally circulated through the tubes of Air cooled
Heat Exchangers and it is cooled by air which is circulated by large fans, which are
strategically positioned along the length of the bundles. The air from the fan is
diverted towards the tube bundles through plenum chamber.
The air which is circulated over the tube bundle through the plenum chamber cools
the hot fluid. The design of plenum chamber is a vital operation which should ensure
proper distribution of air without any air pockets and also ease of manufacture,

assembly and repositioning. The prior art consists of asymmetric profile plenum
chambers with bend plates (1) suited to specific profile as shown in fig.l of Existing
plenum chamber which do not ensure uniform air distribution over tube bundle and
are also difficult to manufacture and assemble.
Disadvantages of existing plenum chamber
The following are the disadvantages:
a) Non-uniform distribution of air due to uneven profile.
b) Difficulty in manufacture, assembly and disassembly and dispatch.
c) More cycle time for manufacture
d) Additional fixtures requirement for forming the plenum chamber.
e) Possibility of stagnant air pockets
f) Construction difficulties during manufacture
Hence, there exists a need to manufacture an improved plenum chamber which is
capable of eliminating the disadvantages of prior art.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved plenum chamber for
air cooled heat exchangers which is capable of distributing cold air uniformly over the
tube bundle.

Another object of the invention is to propose an improved plenum chamber for air
cooled heat exchanger which ensures optimum thermal performance by allowing air
to reach the tubes for optimum heat transfer.
Yet another object of the invention is to propose an improved plenum chamber for air
cooled heat exchangers which is easy to manufacture and assembly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - shows a plenum chamber according to prior art
Fig.2 - shows an improved plenum chamber according to the invention
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Air being a poor conductor of heat, all efforts has been made in this improved version
of Plenum chamber to distribute cold air properly over the tubes for optimum thermal
performance. This is achieved by avoiding air pockets and focusing on proper
distribution of air across the face of tube bundle. A Symmetric geometry has been
designed to achieve ease of manufacture and repositioning resulting in considerable
reduction in manufacturing cycle time. This has resulted in significant technical

improvement over the earlier practice of manufacture of plenum chambers with
asymmetric circular profile.
The existing circular asymmetric shape plenum chambers are difficult to manufacture
and takes more time to assemble them. The new design envisages symmetric,
rectangular plenum chambers which are easy to assemble and also ensures proper air
distribution over the bundles.
Plenum chambers are critical part of air cooled heat exchangers. These plenum
chambers are mounted above the fans and below the tube bundles. The purpose of
plenum chambers is to direct the air flow properly over the tube bundle for optimum
heat transfer. They are made of sheet metal and profiled in such a way to create
optimum air flow over the bundles. A rectangular plenum chamber is a innovative
design which places the side sheets of plenum chamber in line with air flow to ensure
smooth passage. The joint between sheets is done in such a way to avoid stagnant air
pockets. These chambers are very easy to construct and dismantle whenever
necessary.
Advantages of improved plenum chamber
1) Uniform distribution of air due to symmetric profile.
2) Easy to manufacture, assembly and disassembly
3) Easy to repositioning

4) Without any air pockets
5) Less cycle time for manufacture
6) Improved thermal efficiency
Uniform distribution of air is achieved because of symmetric profile where in all four
sheets (3) of plenum chamber (I) are aligned towards tube bundle in such a way the
air slides over the sheets of plenum chamber and reaches the tubes for optimum heat
transfer.
A rectangular plenum chamber (I) (in which the asymmetric profile parts have been
eliminated) has been designed with proper flow distribution of air for optimum
thermal performance by providing segmental plates bolted with angle plates (2)
(without Profiles) as shown in Fig.2 of improved plenum chamber. The symmetry of
this plenum chamber will facilitate, ease of manufacturing, assembly and
repositioning. The prior art is an asymmetric and costly plenum chamber (P) while the
present invention discloses an improved "optimum thermal performance-oriented"
plenum chamber (I).

WE CLAIM
1. An improved plenum chamber for air cooled heat exchangers comprising:
a rectangular plenum chamber (I) provided with segmental plates bolted with
angle plates (2);
characterised in that all four sheets (3) of the plenum chambers (I) aligned
towards tube bundle for sliding of air over the sheets (3) to reach the tube for
optimum heat transfer are of symmetric profile.
2. An improved plenum chamber as claimed in claim 1, wherein the plenum
chamber is made of sheet metal.

An improved plenum chamber for air cooled heat exchangers consists of a rectangular plenum chamber (I) provided with segmental plates bolted with angle plates (2) when all the four sheets of plenum chambers (I) are aligned towards tube bundle for sliding of air over the sheets (3) to reach the tube for optimum heat transfer. Plenum chambers are made of sheet metal with symmetric profile.