AIR - TO - AIR HEAT EXCHANGER

ECHANGEUR DE CHALEUR AIR/AIR

English Abstract

Abstract
This invention permits the transfer of heat from the exhaust air
of a building to incoming fresh air by directing counter flowing
air currents on either side of a membrane. Movement of air is
controlled by remotely mounted fans and dampers.
The basic principle of the exchange of heat from the air on one
side of a membrane to the air on the other side is common to many
air-to-air heat exchangers and it is accomplished by directing
the flow of air over a large area of membrane.

Claims

The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An air-to-air heat exchanger for fresh air and exhaust air
to reclaim heat in the exhaust air as it is being exhausted
from the space comprising: an outer tube, baffles extending
alternatingly par-t way across the interior of the outer tube
from opposite sides thereof to form a zig-zag course therethrough,
a continuous, flexible corrugated inner tube located in the
outer tube following the zig-zag course, inlets and outlets for
each of the inner and outer tubes connected to the fresh and
exhaust air flows respectively so as to effect a counter-current
flow through the heat exchanger.
2. The heat exchanger of claim 1 wherein the inner tube is formed
of metal or plastic material.
3. The heat exchanger of claim 1 wherein the outer tube is of
square cross-section and is made of plywood or other rigid
material.
4. The heat exchanger of claim 1, 2 or 3 wherein the cross-
sectional area of the inner tube in relation to the cross-
sectional area of the outer tube at a baffle is one to five.
5. The heat exchanger of claim 1, 2 or 3 wherein the length of
the inner tube is 2.5 times the length of the outer tube and
the optimum length of the outer tube is 1800mm.
6. The heat exchanger of claim 1, 2 or 3 wherein the outer
tube has a square cross-section of 300mm X 300mm and the inner
tube a diameter of 100mm.
7. The heat exchanger of claim 1, 2 or 3 whrein there are a
plurality of inner tubes.

Description

SP~CIFIC~TIONS
This invention permits -the trans~er of heat ~rom the exhaust air oE
a building to in~oming fresh air by directing colmter flowing air
curren-ts on either side o~ a membrane. ~ovement oR air ls controlled
by remotely mo~lted fans and dampers.
The basic principle o~ -the e~chan~e o~ hea-t ~rom the air on one side
o~ a membrane to -the air on the other side is common to many air--to-
air heat exchangers and it is accomplished by direc-ting -the ~low of
air over a large area of membrane..This presents -two difficulties:
1. There is a large pressure drop within the exchanger as the air
passageways are necessarily contorted and res-tricted.
2. The relatively slow Illovement o~ air at critical points within
the exchanger creates a tendency ~or freezing and ice build-up
on the exhaust side in cold weather.
This invention ~;nimi7es -these di~iculties:
1. ~ressure drop is m;n;mi7ed as the opening in the membrane is the
same shape and dimensions as the supply and delivery pipes.
Pressure drop is caused only by the turbulence and the bends in
the membrane.
2. The large passageway on the exhaus-t side o~ the exchanger
eliminates ice buildupo
The form o~ the invention is illustrated in drawings:
1. Front view, access panel in place
2. Section i'A - A", a vertical cross section showing the interior
of the invention viewed ~rom the ~rontO
3. Section "B - B", a vertical cross section showing the interior
o~ the invention viewed from the left side.
The invention is essentially a tube-within-a-tube heat exchanger.
me exterior tube is shown in square hori~ontal section and is made
of plywood. Any other shape and material which would provide a well
sealed enclosure and is capable o~ supporting ba~les can be used.
The interior tube must be corrugated or luted parallel to the
diameter o~ the tube. The tube must be continuous and ~lexible, it
can be made of either metal or plastic. Metal has better heat transfer
characteristics and is dimensionally more stable. The de~th o~ the
corrugations will have an ef~ect on total surface area available ~or
heat trans4er and on the turbulence within the exchanger; it will
thus have an e~fect on -the e~iciency o~ the exchanger.

~9~
The optimum cross section area of the inner tube in relatlon -to the
cross ~ection area o~ -the ou-ter tube is one to five ( 1:5). Note.
The cross section area of the outer tube is taken as -the ~ree flow
area past the ba~fle minus the cross sec-tion area of the inner tube.
The length o~ the inner tube should be 2.5 times the length o~ the
outer tube~ The optimum length of -the outer tube is loOOmm. The test
model use~ an outer tube with hori%on-tal dimensions of 300m~ X 300mm
and an inner tube with a diamter o~ lOOmm. With a balanced volume
o~ air flowing through both tubes and an inpu-t temperature di~ferential
of 54C., 75~ of the heat from the exhaust air is transEerred to the
incoming air. ~arger or smaller models can be made but this would
require an adjustment of the relative dimensions o~ the inner and
outer tubes to rnaintain the same e~iciency. More than one inner
tube can be used.
To -take advantage o~ the natural movement o~ warm and cold air the
exchanger is most effe~tive when installed vertically. With some
simple modifications the exchanger could be installed horizontally.
A drain is provided to remove condensed moisture.