Note: Descriptions are shown in the official language in which they were submitted.
~his inven~ion rclates to an air conclitioning installation
in combination with a processing plant producing ho~ waste gases.
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According to the present invention we provide an air conditioning
installation in combination with a processing plant producing
hot waste gases, the installation comprising an air handling unit
through which fresh air at ambient temperature is drawn for ducting
to a desired location, and a heat exchanger through which the hot
waste gases pass in spatial flow to fresh air which is thereby
heated and can be selectively admixed w-ith said arnbient temperature
fresh air to raise the temperature of the latter, waste gas
collection ducti~g extendin~ between the processing plant ~d an
inlet of the heat exchangër and damper controlled diverting duct
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means upstream of said inlet for egressing the hot waste gases
to a location other than the heat exchanger when a predetermined
situation prevails.
~he application of this invention to a processing plant
'i~ provides substantial energy conservation with consequent
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considerable economic advantages.
~ he processing plant is preferably a food p~ocessing
plan~ and in particular comprises a food baking oven which may be
fired by any convenient means. ~or example, the oven may be
fired by gas, oil and/or electricity.
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An example of the present inv~ntlon will now be described
~ as applied to a food processing plant and with reference to
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~ the accompanying drawings in which -
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`~ ~ Fig. 1 is a plan view of the food processing area of the
i food processing plant;
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~ ig. 2 is a plan view of aheat recovery and air conditioning
installation for use with the food processing plant;
~ ig~ 3 is an elevation on the line '1'1'1 - IIl in Fig. 2;
~ ig. 4 is a cross-sectional elevation, to an enlarged scale,
on the line ~-~V in Fig. ?;
~ ig. 5 is a cross-sectional elevation, to an enlar~ed scale,
on the line ~-~ in Fig. 2;
;~'ig. 6 is a fragmentary perspective view, to an enlarged scale, of the
portion indicated'by arrow~Il in Fig. 2;
Fig. 7 is a view to an enlarged scale of part of Fig. 3, portions
of which have been broken away, and showing greater detail therein;
and Fig. 8 is a plan view of part of Fig. 7.
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¦~he food processing plant comprises a food processing area 20
,with an adjacent heat recovery and air conditioning installation for
the plant ho'used within a nearby separate building. '~he plant is'
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arranged so that food to be processed is admitted to the area 20,
processed-therein, and thence passes on one of a plurality of conveyors
tbrough one of a plurality of ovens disposed along the length of the
area 20. In Flg. 1, only two ovens 21 and 22 are shown. After cooling,
j;'the baked processed food i5 packaged and transported by conveyor to
an adjacent warehouse (not shown).
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~ he oven 21 is an direct fired oven, such as is sold under
the Registered '~rade Mark '~URBORADIAN~ of Baker Perkins Holdings
imited, with five gas-fired buxner points 23. '~o'prevent con-
tamination of the food within the oven 21 by fuTnes frolll-the oil b~l~ne~s
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within the burner points 23 heated air is passed around the
outside of a jacket (not shown) withint;he oven 21.
~ ying parallel with the oven 21 and disposed above it are
two subsidiary waste gas collector ducts 24 and 25 which mexge
with a main collector duct 26 disposed perpendicular thereto.
~ach of the subsidary collector ducts 24 and 25 is made up of
pipe sections with expansion joints 27 between adjacent pipe
sections. At each of the burner points 23, exhaust ducts 28
and 29 merge with the subsidiary collector ducts 24 and 25 res-
pectively. ~he ducts 28 collect the flue products and hot air
from the oil burners and from around the Jacket within the oven
21, whereas the exhaust ~-ucts 29 collect hot air and moisture ~rom
within the jacket in the oven 21. ~he waste hot gases from the
oven and the oven burners are collected in the separate subsidiary
ducts 24 and 25, again to prevent any possible contamination of ~he
baking food by the flue products. To prevent backflow of the
waste gases along the subsidiary collector ducts 24 and 25 up-
stream of each of the exhaust ducts 28 and 29 where these merge
with respective collector ducts 24 and 25 is a suction fan 30
and a butterfly damper (not shown).
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~ he oven 22 is a semi direct fired oven, such as is sold
under the Registered ~rade Mark CO~VEC~ORADIAN~ of Baker PerXins
Holdings Limited, and has~three ~as-fired burner points 31. As
the oven burners are gas burners, there are no flue products
which can contaminate the food within oven 22 so that within
the oven the hot air from the burners comes into direct contact
with the food.
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Above the oven 22 and parallel therewith is a sin~le sub-
sidiary collector duct 32 which again merges with the main
ollector duct 26. At each of4the burn~r points 31, an CY~}1aU~t
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duct 33 merges l~ith the collector duct 32 a~d carries flue
gases, hot air and moisture from withi~ the ov~n 22 to the
collector duct 3~. As with subsidiary collector ducts 24
and 25, a suction fan and butter~ly damper are positio~ed do,~-
stream o~ each point of entry of the exhaust ducts 33 i~to
the collector duc-t 32, which is again made up of pipe sectio~s
with an expansio~ joint between adjacent sections.
Arxanged ad,jacent the outlets from ~he ovens 21 and 22
are coolers (not sho~m) throu~h w'nich the baked food is passed
for cooling before packa~ing. Also, in the case of the ove~
21, a microwave o~en (not sho~m) is interposed between the
coolers and the microwa~e oven is also ducted to the subsidia~
collector ducts 24 a~d 32 by exhaust ducts 340
Before e~teri~g the main collector duct 26, each of the
subsidiary collector ducts 24, 25 and 32 has an outlet to
a vertical chimney 35. Each o~ the chimneys 35 for the ducts
24, 25 and 32 terminates in a discharge cowl 36 a~d within
the cowl 36 is a butterfly damper (not shown) which is
normall~ closed. Dowstream of each of the chim~e~s 35 in each
of the subsidiary collector ducts 24, 25 a~d 32 are further
buttexfly dampers (not shown) driven by motors 37 which are
normall~ open and co-operate with the dampers in each of the
discharg'e cowls 36 as will be described later. These dampers
within the subsidiary collector ducts a~d the cowls are operated
by motors a~d controls are provided for the manager of the food
processing area to open or close these as desire.
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~ The main col~ector duct 26 is highly insultated to prevent
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heat loss and passes over the roof of the food processin;r,
area into the building 39 housing the heat recovery md air
conditioning installation, as aforesaid. ~ownstream ol each
of the points of entry of the subsidiary collector ducts
26
24, 25 and 32 into the main collector duct/is a fan (no-t shoT~n)
which sucks the waste hot gases from the subsidiary collector
ducts into the main collector duc-t 26 and ma~n-tains a constant
negative pressure on the ovens to prevent pressure bu d-up
therein. A pressure sensor 40 is loca-ted in the main collector
duct and is linked to the butterfly dampers 37 in the ducts
24, 25 and ~2 respectively and the dampers in the cowls 36.
If the sensor 40 detects an increase in pressure in the main
collector duct above a-predetermined value, which pressure
increase may, for example, be caused by a blockage in the main
collector duct, then the appropriate damper 37 is closed and the
corresponding damper in the cowl 36 i5 opened by an override
mechanism so that one or more of the subsidiary collector
ducts 24, 25 or 32 is vented to atmosphere and the duct inlet
into the main collector duct 26 closed. ~hus, the baking
process in all ovens can carry on uninterrupted if for any
reason the heat recovery installation is closed dow~
or is working at reduced capacity. It is envisaged that the vent
ing may be other than to atmosphere, for example a secondary heat
exchanger.
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After receiving the hot waste gases from each of the subsid-
iary collector ducts, the main collector duct 26 passes into the
; building 39,~Iowever, before passing into the building
39, the main collector duct 26 is fitted with an inlet 41 for
¦ fresh air. ~he inlet ~1-can be opened or closed by a val~e con-
trolled by a motor 42 and the inlet of fresh air into the duct
26 is thermostatically controlled to maintain a substantially
¦ constant input temperature of gas into the heat recovery
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installation and thereby maintain an Optimum cf~icienc~ of a
heat excha~ge carried ou~ during the heat recover~ ~rocess i~ the
i~stallation as ~ill be described~
~ he heat recovery and air conditioning ins-tallation comprises
a heat exchanger 43 whereby heat is transferred from the hot waste
gases produced in the food proce$sing plant to fresh air, and at
least onc air handling u~it ~ which also utilizes fresh air and
the heated fresh air from the heat exchanger to air condition
all parts of the ~ood processing plant. ~
~ he heat exchanger 43 comprises a u~it contai~ing, in a cen-tral
portion 45 thereoft aluminium sheets spaced approximately o~e inch
apart. '~he sheets separate the hot ex~aust gase~ from the fresh
air which circulate i~ conuQter-flow around the sheets. The heat
exchanger 43 has diametricall~ opposed inlets ~ and 47 for the hot
waste gases and the fresh air respectively, In a similar fashion,
there are diametrically opposed outlets 48 and ~r9 for the waste
exhaust gases and the now heated fresh air respe~tivelyr Across
the inlet 46 is a filter 50 to prevent an~ food particles carried
in the exhaust gases from entering the heàt exchanger 43. The
temperature o~ gases through the heat exchanger 43 is automaticall~
co~trolled through a co~trol stat 5~ and a limit stat 52 so that
optimum efficiency of the heat exchanger 43 is maintained. ~he
auto~atic controls are also li~ked to the pressure sen~or 40
in the main collector duct 26 so that a constant pressure can be
maintained at the baking ove~s 20 and 21 thus ensuring there is
nO influx in the air extracted from the oven compartmentsO Also
at the inlets 46 and 47 and at the outlet ~8 there are manuall~
controllable dampers 53 for maintenance purposes to by-pass
the heat exchanger 43 in the event of a fault developi~g.
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~ he c~iciency o~ the heat exchanger 4~ is improved by t~e r~l_o~-a
o~ late~t heat from ~he moisture of the ga~es passing through the
heat exchanger and for this pul~ose a conden$ate trap 54 i.s
provid~d beneath the central portio~ 45.
For maintenance purposes, the heat exchanger 43 is provided with
an acces$ door (not shown) and the top of the exchan~er 4~ can be
removed ~or internal cleaningO A by-pass duct 55 is also provided
whereby the hot e~haust gases ca~ be ducted away from the heat
exchanger 43 a~d discharged directly to.atmosphere via a vertical
chimney 56.
~ fter passing through the heat exchanger 50, the waste
exhaust gases, now in a cooled co~dition, are also discharged i~to
the atmosphere via the vertical chimney 56. ~he chimney 55 has
. a cowl 57 and i.s con~ected by a transition duct 58 to a
collection chamber 59 which is connected b~ ducti~g to the outlet
48. At the inlet to the collection chamber 59 is an extraction
fan (not sho~m) drive~ by a motor 60 to Suck the waste gases .
from the heat exchanger ~3 and prevent prassure build-up
therei~ by helping to maintain a constant pressure on the ~.Thole
system. Also~ at the inlet to the collection chamber 59 there
is an automatically-controlled iris damper 61, which da~per
61 co~trols the rate of waSte ga~ outflow from the chimney 56.
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~he ~resh air is întroduced into th`e heat exchanger 43 b~ means
~i of an inlet 62 i~ the side of the building 39. ~he inlet 62
is covered by a bird guard to prevent blockage occuring, and
~he fresh air is sucked i~to the inlet 47 by a ~an 6~ driven by a
3 motor 64.
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After passing through the heat ex ~ an~er 43, the now heated
fresh air is ducted along a duct 65 to the air handling unit 44.
Other ducts, such as duct 66 can be led~ off to further air handling
units (not shown) as required. The duct 65 splits into t~Jo branches
67 and 68, branch 67 leading into the air handling unit and br~xh 68
being a bleed to atmosphere to control pressure wi-thin the duct s~ste
as will be described below.
'~he air handling unit 44 is designed to supply fresh air for
plant
air conditioning to an~ part of the food processing/or elsewhere
as desired. The temperature of the air so supplied is predetermined
and is thermostatically controlled, a thermostat in the air
conditioned area being linked to the air handling unit 44. ~1hen the
air handling unit is in operation, fresh air is continuously
drawn into a plenum chamber 69 of the unit 44 through an inlet
louvre 70 which i5 covered by a bird guard. The inlet louvre 70
is located in a wall of the building 39 in an area 71 of the buildin~
39 which is open to the atmosphere. Cnce inside the air handling
unit, the fresh air is filtered and can be heated, cooled or left
at ambient temperature before being ducted to the area to be air
conditioned according to the thermostat setting.
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.'rhe fresh air within the air handiing unit 44 is heated
by admixture with the heated fresh air from the heat exchanger 43
and can be additionally hbated, if a hlgher temperature than can
be achieved by this admixture is required, by a Gas-fired heatin~
unit 72 which is controlled from the thermostat but also
has a manual override control panel 73.
The heated fresh air from the duct 67 is admitted to the air
handling unit 44 through a plurality of hollow air distribution
fingers 74 forming a unit 75 as shown in F1~. 6~ Th~ air distributi~
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finger unit 75 is located at the entrc~nce of the plenum chamber 69 in
the air ha~dling unit ~ and the cooler fresh ajr ente~s the plenu~
chamber 69 by flowing around and betwecn the fingers 74~ To
reduce the pressure drop of the cooler air as it flows around the
fingers 74, the back of each finger 74 is fit-ted with a
cover 76 of semi-circular cross-section.
Each of the distribution fingers 74- comprises an elongated
box construction with an air inlet aperture 77 at the upper end
thereof. '~he air outlet from each finger 74 comprises two vertical
sli~s 78 at either side of the front of the elongate box. ~Jithin each
finger 74 is an inclined partition 79 ~lhich causes the finger to taper
towards its lower end~ '~his tapering shape together with the shape
of the outlet slits 78 causes the heated fresh air to be distributed
evenly into the cool air stream in the plenum chamber 69 without
stratification by ensuring an equal air velocity along the vertical
length of the finger 74.
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When the heated air is not required to be admixed with the cooler
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fresh air in the air handling unit 44, each of the air distribution
' fingers 74 is closed by at its inlet aperture 77/damper (not sho~n).
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' ~hese dampers are linked together so that the whole of thë unit 75
can be closed. The operation of the dampers is controlled by a
motor 80 which is itself controlled according to the signal
from the thermostat in the area to be air conditioned. The dampers
can shut off tightly the inflow of air to the fingers 74 and are able
to withstand a build-up of pressure when closed and high temperatures.
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The control of the air pressure within the duct 65 and generally
throughout the duct system through which the heated fresh air ~rom the
heat exchanger flows, especially when the damper is preventing egress of
air from the distribution unit 751 is achieved by selectively operatir~
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a motorised damper 81 in a duct 82 to perrnit the heated air to
discharge to the atmosphere. As previously stated, the duct 68
branches off from the main duct 65 from the heat exchanger and a
bleed of the heated fresh air passes along this duct 68 past a
pressure sensor 83. ~he pressure sensor 83 selectively controls
a motor 84 which drives the damper 81 permitting air to egress
to the atmosphere via the duct 82 when a pressure build-up occurs.
are
~he controls/pre-set so that a substantially constant pressure is
maintained throughout the heated fresh air duct system and the settin
is sufficient to ovexcome the pressure drop through the open
damper 81, the outlet slits 78 of the fingers 74, and the
connecting branch duct 6~ ~rom the main duct 65.
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Thus, it can be seen that the heat recovered from the hot waste
gases can be utilized selectively to heat fresh air for air
conditioning the food processing plant or discharged to atmosphere.
Further heating of the air can be accomplished by use of the
heating unit 72 as required. ~fter heating, the air passes through
a filter unit 85 adjacent the heating unit 72 in the air handling
unit before being ducted to the required area.
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, When cooled fxesh air is requiredj then the hot-waste gases are
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discharged to atmosphere through the chi~neys 35, no heat exchange
takes place and the distribution fingers are closed. ~he air
flowing through the air handling unit 44 is cooled by passing
over coils containing chilled water. These coils are contained
j within a xegion 86 of the air handling unit, downstream of the
¦ filter unit 85.
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3 Chilled water is supplied to the coils in the region 86
¦ from one or more packaged air cooled chillers 87, two of which
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are depicted in the drawings. ~he chillers 87 are located in the
area 71 of the buildin~r 39 which is open to the atmosphexe,
adjacent the inlet louvre 70 to the air handling unit 44. The
chillers 87 Pperate in a kno~n manner similar to a refrigerator
to produce the chilled water which travels around a closed
path between each chiller 87 and the coils~ithinthe air
handling unit 44. When more than one chiller 87 is installed, they
are operated in sequence according to the load and are controlled
by a thermostat 88. The thermostat 88 prevents the chillers
87 from operating below a predetermined temperature, which will vary
according to the climate, when atmosphe~c air can be used for cooling
by admixture in a greater proportion with the already heated air
supplied by the distributio1l-~fingers 74.
Each chiller 87 has inlet and ou-tlet pipes, 89 and 90 respectivel~.
~he outlet pipe 90 is connected to a pipe 91 through a valve 92
which pipe 91 then rises vertically upwards and enters a horizontal
header pipe 93 for pumps 94 . Two pumps 94 and 94A are provided,
one 94A being a stand-by fcr use in the event of the other breaking do~
or as an additional back-up. A further pump 94B can also be supplied
for future ~se if the number of chillers 87 is to be lncreased. ~he
pumps 94 and 9L~ are supplied with water from the header pipe 93
down vertical pipes 95. A further valve 96 iS also provided
in each of the pipes 95 so that the pumps can be isolated from the
header pipe 93. 'rhe pumps 94~-are connected at their outlet to further
pipes 97, in each of which there is a valve 98 so that the pumps
94 can be completely isolated, and the pipes 97 all enter a common
pipe 99 which conducts the chilled water to the coils in the air
handling unit 44.
At the location of the air handling unit 44, the pipe 99 is fitted
with a valve 100 and a strainer 101 before ]eading into a vertical
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header pipe 102 which is fitted with four connecting points
for pipes from the coils within the air handling unit. Between
the strainer 101 and the header pipe 102, the pipe 99 is also
co~lected to one port of a three-way valve 103 which regulates
the flow of chilled water as will be described. The vertical
header pipe 102 is fitted with an air cock 104 at its upper
end, so that any air within the pipework can be bled off, and
a drain valve 105 at its lower end.
After passing around the coils, the water leaves the air
handling unit 44 and enters a second vertical header pipe 106,
which is again fitted with an air cock 107 and a drain valve
~08. From the header pipe 106, one pipe 109 leads into a
second port of the three-way valve 103 and a second pipe 110
leads via a valve 111 directly into a common return pipe 112 for
the water back to the chillers 87. m e third port of the three-
way valve 103 is also connected to the return pipe 112. The
return pipe 112 terminates in a horizontal header pipe 113 at
the location of the chillers 87 and from this header pipe 113
vertical pipes 114 lead off which are connected via valves
115 to each of the inlet pipes 89 of the chillers 87.
Thus, it can be seen that by opening and~closing of the
appropriate ports of the three-way valve 103 and the valves
100 and 111 the flow of chilled water around the coils can
be controlled. This control is automatic and the three-wa~
valve 103 regulates the flow of chilled water at the dictate
of the thermostat in the air conditioned area. Also provided is
a frost thermostat 116 which starts the pumps 94 during cold
weather to circulate water through the pipework and coils to
prevent freezing of the pipework.
The air handling unit 44 can thus supply air conditioning
over a wide temperature range according to demand by selective
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operation of hot air from the distribution finger unit 75,
the gas-fired heating unit 72, and the chillers 87. As
previosuly ~tated, fresh air is sucked into the air handling
unit 44 ~rom the exterior and this is accompllshed by a motor-
driven, non over~oading fan 117 with backward curved blades
located at the outlet o~ the air-handling unit 44. The fan
117 blows the air conditioning air from the air handling
unit 44 into a duct 118 for transport to the appropriate
area in the food processing plant. A damper 119 is provided
adjacent the ~an 117 so that the volume of air pas~ing
through the duct 118 can be set manually.
In the present example, duct 118 leads to the ~ood
processing area 20 where it runs along and to one side of
the ceiling. Approximately half-way along the length of
the duct 118 in the area 20, the duct 118 branches into
two further ducts 120 and 121. Duct 120 leads into a further
T-shaped duct system which is used for distributing air
throu~hout the area 20 whereas duct 121 leads off to another
area of the plant. Motorised butterfly dampers 122 and 123
are positioned in the duct 118 before division into ducts 120
and 121, and at the inlet to duct 121 respectively.
The T-shaped duct system comprises a stem 124 which runs
centrally and longitudinally through the area 20. Grilles
125 with ad~ustable louvred blades and volume control dampers
are positioned in the stem duct 124 at spaced intervals.
The cross bar 126 o~ the T-shaped duct system runs transversely
across the area 20 and æpaced grilled outle~s 127 are provided
therealong, which outlets can be swivelled in a vertical
plane.
In use, the hot waste gases ~om ~he ovens 21 and 22
are ducted to the heat recovery and air conditioning system
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wherein a heat exchange takes place with transfer of the heat
from the waste gases to fresh air. The air handling unit 44
draws in fresh air from the atmosphere and according to a
pre-set thermostatic control in the area to be air conditioned
selectively operates heating or cooling systems to bring the
fresh air to the desired temperature. Use is made of the
heated fresh air from the heat exchange to admix with air
in the air handling unit 44 as necessary and further heating
by use of the heating units 72 is only carried out when the
desired temperature canrlot otherwise be attained. The
conditioned air is then ducted to the appropriate area of the
plant or elsewhere for both spatial heating or cooling and
air conditioning purposes. The use of more than one air hand-
ling unit 44 would enable both heated and cooled conditioned
air to be ducted to different areas simultaneously as
required. ~hus the whole heat recovery and air conditioning
system forms a pre-set automatically controlled unit for
the supply of conditioned air to any region as desired.
While the installation has been described solely for
air conditioning purposes, it is envisaged that the hot waste
gases may also be employed in part for, inter alia, water
heating purposes.
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