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Патент USA US2405895

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Aug. 13,1946.
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E, Lonwle
_
2,405,895
LOW TEMPERATURE CHAMBER REFRIGERATION _
Filed May 281 1.942
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INVENTOR
BY
///; ATTORNEYS
2,405,895
Patented Aug. 13, 1946
,UNITED STATES PATENT OFFICE
2,405,895
LOWrTEMPERATUREVCHAMBER
,
REFRIGERATION
Erwin Lodwig, Franklin Square, N. Y., assignor to
, Mobile Refrigeration, Inc., New York, N. Y., a
corporation of New York
Application May 28, 1942, Serial No. 444,800
6 Claims.
This invention relates to refrigeration and more
particularly concerns improved apparatus for
rapidly cooling the atmosphere in a chamber to
very low temperatures.
In the development and testing of aircraft,
parts thereof, and instruments and other appa
ratus for use thereon, it is necessary to subject
various parts and devices to the extreme condi
(01. 62-402)
chamber air. I have found it desirable in cham
bers of the type described to provide separate
refrigerant evaporating means for respectively
cooling the walls of the chamber and the ‘air in
the chamber. I have further discovered that by
circulating the air in the chamber successively
over the separate evaporating means but at a
higher velocity over the air cooling evaporator
than over the wall cooling evaporator means, ac
tions of atmospheric'temperature and pressure
cumulations of frost or ice may be removed from
encountered in ?ight. These conditions include 10 the air cooling evaporator, and the accumulation
temperature changes from the highest ground
of frost on that evaporator when the chamber is
temperature to temperatures well below 100 de
closed may be avoided. I have also discovered
grees below zero Fahrenheit, and pressure changes
from normal atmospheric pressure at sea level
to less than four inches of mercury absolute.
that accumulations of frost may be quickly re
moved from the inner surface of‘ a sight opening
Since the conditions to be reproduced include sub
atmospheric pressures, a closed chamber must be
used, and in order that the operation of the in
tion of air in the chamber over the window and
or window in the chamber by successive circula
the cooled chamber walls.
Other objects, advantages, and features of the
struments or devices may be observed, a window
invention will be apparent from the following de
20
or sight opening is preferably provided in the
scription of a typical embodiment thereof which
is illustrated in the accompanying drawing.
In the operation of a chamber under the condi
In the drawing
tions described, the formation of frost is a serious
Fig. l is a sectional elevation illustrating a re-,
problem. Moisture is condensed from the air
frigerating. chamber provided with cooling means
25
within the chamber as its temperature is lowered
and. embodying my invention;
below the dew‘ point of the air, and freezes on
Fig. 2 is a sectional view of the air cooling evap
the evaporators or other surfaces employed to
orator taken along the line 2-2 of Fig. l and
cool the chamber. Further, it is frequently nec
viewed in. the direction of the arrows; and
essary to open the chamber while the atmosphere 30 Fig. 3 is a sectional view on a reduced scale of
therein and the interior surfaces thereof are at
one of the wall evaporators of the chamber illus
very low temperatures, and under such conditions,
trated in Fig. l.
frost quickly accumulates on the cold interior
Refrigerated chambers embodying the inven
surfaces of the chamber, including the inner sur
tion may be of any desired form and are usually
faces of any windows or sight openings therein.
rectangular or cylindrical. The chamber illus
This frosting is ‘caused by the entry of air at room 03 01 trated in the drawing is rectangular and its six
temperature and relative humidity and the sud
surfaces comprise a door D and five wall sections,
den condensation and freezing of moisture from
of which four are illustrated in Fig. l at W, W1,
such air when its temperature is lowered, by mix
W2, and W3. Since the chamber is ‘substantially
ture with the cold air and contact with the cold
completely evacuated in use, itswalls must be
surfaces within the chamber. The frost both
strong enough to withstand substantially full at
obscuresthe sight opening and reduces the effi
mospheric pressure. This could be accomplished
ciency of the cooling surfaces by partially insulat
by constructing the walls of heavy gauge metal,
ing them from the air within the chamber so that
but I prefer instead to employ wall sections
the rate of cooling of the chamber air is retarded
formed of two spaced metal plates or sheets hav
45
and it is impossible to accurately observe the
ing passages therebetween. This arrangement
operation of devices in the chamber through the
provides walls having the requisite strength and
window.
‘
relatively little mass, whereby the heat load im
With the above and other. considerations in
posed by the walls is reduced. The arrangement
mind, it is proposed in accordance withv the pres
also provides passages between the wall plates so
ent invention to devise an improved chamber hav
that the wall sections comprise evaporators in
ing cooling means capable of rapidly lowering
which refrigerant may be evaporated to cool the 1
the temperature of the air in the chamber to very
Walls, and, to some extent, the air in the chamber.
low values without producing frost accumulations
In the illustratedv embodiment, each wall sec
thateither obscure a window in the chamber or
tion comprises two spaced metal plates 4 and 5.
chamber.
'
.
substantially retard the rate of cooling of the 55
3
2,405,895
connected along their edges by edge spacers 6
and at intermediate points by reinforcing ba?le
spacers 7. The baffle spacers ‘l are preferably
staggered as shown in Fig. 3 to provide a cir
cuitous passage between the wall plates for the
?ow of refrigerant.
The edge spacers S are
welded "or otherwise tightly sealed to the wall
plates 14 and 5 so that each Wall section forms
a sealed refrigerant evaporator. The several wall
sections W, W1, W2, etc., may be of identical con
struction and are welded together .alcngtheir
meeting edges to form an air-tight chamber.
Instead of using the spacers E and 7, the plates
4 and 5 may be offset or embossed to provide
4
through a suction line 27. Condensed refrigerant
may be similarly supplied to the several Wall
section evaporators through the ducts 28, 29, 30,
and 3|, and evaporated refrigerant is returned
therefrom to the unit 25 through suction lines
32, 33, 34, and 35. It should be understood that
the unit 25 will include suitable known expan
sion valves and thermostatic controls to regu
late the supply of refrigerant to the several
to, '
evaporators in accordance with conventional
practice,
' In the operation of the illustrated embodiment
of’ my invention, considering ?rst the cooling of
meeting areas that de?ne circuitous'refrigerant 16 the chamber and the air and equipment therein
from room temperature to a low temperature re
passages between the plates. The outer surfaces“
quired for test or development operations, the
door D is closed and the refrigeration unit 25
and fan 22 are started. Due to the arrangement
of the flue 11, the air propelled by the fan 22 is
The chamber door D may be of any suitable
construction, and as shown covers substantially 20 con?ned to a path closely adjacent the coil 15
and ?ns l6 of the evaporator E and flows at a
allot one'surface of ‘the chamber. The door
relatively high velocity over these parts, where
D may be hingedly secured to a frame or ?ange
as the air is circulated at lower velocities over
8. around the door opening, and may be held
the inner surfaces of the chamber walls and the
closed by suitable clamps or latches,not shown.
pane 9 of the window 0. Refrigerant evaporates
A sight opening’ or window .0 is preferably pro
in the chamberwall sections W, W1, W2, etc., and
vided in the chamber door D, and as shown may
rapidly withdraws heat therefrom, thereby re
‘comprise a plurality of spaced glass panes 9 and
ducing the chamber wall temperature. At the
10; sealed in the‘frame ll of the door. Spaced
same time, the evaporator E rapidly cools the air
gaskets l2 and 13 may .be provided between the
of the chamber walls may be heat insulatedby
any suitable material, and such insulation has
been diagrammatically represented at M.
dolor frame H and the chamber opening ?ange 8 30 in'the chamber, and the instruments and devices
therein. As the cooling progresses, the tempera
.
'
' I .
ture of the chamber walls falls below the dew
A-n evaporator E is provided within the charm
point of the air in the chamber and belowthe
ber‘for cooling the air therein and the instru
freezing point, with the result that moisture is
ments or other apparatus under test or observa
to insure a tight closure.
tion; ‘ In accordance with the present invention,
means are provided for. circulating air in the
chamber successively .over this evaporator and
the‘inner surfaces of the chamber wall section
evaporators W, W1, W2, etc. The arrangement
is such that the velocity of the circulated air
passing over the evaporator E .is considerably
higher than that of the air passing over the
‘chamber wall surfaces. In the disclosed. embodi
-ment,.the evaporator E comprises a coil I 5 having a
vertically disposed heat conductingfms I76 there
on, and the?nnedcbil-unitiis enclosed in a?ue
or dust H. The ?ue H has a fan compartment
l8 below the evaporator coil .|5.and in communi
cation therewith through an opening [9. Anair '
inlet opening 20 is provided in the front wall
of the ?ue l1, and an outlet opening 2| is pro
vided in the front wall of the fan compartment
l8. l, A fan or blower_.22 of any suitable construc
condensed from the air and frozen on the inner
surfaces of the walls. The temperature of the
evaporator E also falls below the dew point of
the air and the freezing point of water, and the
accumulation of frost on the evaporator coil l5
and ?ns I 8 would also be expected. However,
with the air ?owing over the evaporator E at a
considerably higher velocity than over the charm
ber walls, frost does not form on the evaporator
E. The temperature of the instruments or other
apparatus under test or observation in the cham
ber also falls below the dew point and the freez
ing point as these objects are cooled by the cir~
culated air, but frost does not accumulate
thereon.
'
.
~
The selective formation of frost on the cham
ber walls rather than on the evaporator E is ap
parently caused by the more rapid circulation
of air over the evaporator which transfers heat
thereto more rapidly than to the walls and ac
tionfis disposed. to propel air at relatively high
velocity through the ?ue l1, and. as shownthis 55 cordingly maintains the evaporator at a some
what higher temperature than the walls. Simi
fan-is disposedajdjacent the outlet opening 2|
larly the absence of frost on the apparatus under
of the fan compartment [3. The fan22 may be
test in the chamber is believed due to the fact
'
that such apparatus, being cooled by the circu
The assembly comprising theevaporator E and
flue I‘! is preferably spaced from the window 0 60 lated air, is at a higher temperature than the
drivenby an electric motor. 23.. '
chamber walls. Regardless of the reason for
this selective frost formation, the observed fact
wall section W1 of the chamber with the air
is that even after frost has accumulated on the
inlet and outlet openings 20 and 2| directed to
ward the "opposite wall of the chamber, in the 65 surfaces of the evaporator E and; on apparatus
in the chamber, due to the opening of the cham
illustrated embodiment toward the chamber
ber door D when the surfaces andapparatus ‘are
door D;
‘
.
below freezing temperature, operation of the fan
The evaporator coil 15 and thewall section
22 with theidoor D closed rapidly removes not
evaporators are supplied with refrigerant from
only the frost accumulated on the evaporator and
any suitable source such as a; refrigerant com
pressing and condensing unit, conventionally 70 the apparatus, but that formed on the inner sur
face ‘of the glass pane 9 of the window 0 as well.
represented ‘at 25. The coil 15 of the evaporator
It is frequently necessary to :open ‘the cham
E may be supplied with condensed refrigerant
her door D to give access to instruments or de~
through‘a pipe 26-, and evaporated ‘refrigerant
vices in the chamber while the air in the cham
may be returned from the coil to the unit 25
and may be disposed as shown adjacent the back
ber, ‘the. apparatus therein, the evaporator E,
2,405,895
v5
the inner surfaces of the chamber “61 evaporator
sections,'and the inner pane 9_ of the window 0
are at temperatures well below the freezing
point. Before opening the door D, the fan 22
is stopped to avoid unnecessary heating by blow
ing chilled air out of the chamber. When the
.door D is opened, relatively warm moist room
air enters the chamber and mingles with the
relatively warmer surfaces and its relative hu
midity, is thereby decreased, The air then ap
parently picksup moisture from these surfaces by
sublimation of the frost. thereon._ Although this
explanation is believed correct, it should be un
derstood that the invention is in _ no way de
pendent upon the accuracy thereof.
I
claim:,
.
1
.,
1. In ‘apparatus of the type described, in ‘com
the room air increases the relative humidity of 10 bination, a vclosed chamber having a: window
therein, at least two evaporators disposed at
the mixed air in the chamber to a point above
spaced points, in said chamber and having sur
saturation at the prevailing mixed air tempera
faces exposedto the atmosphere therein, means
ture with the result that immediate condensa
for supplying refrigerant, to said evaporators
tion takes place, forming a fog or mist in the
whereby
their exposed surfaces ‘are cooled, and
15
chamber. The temperature of the chamber
means including an air propelling device for cir
walls, the evaporator E,.the inner surface of the
culating some of the air within said chamber suc
glass pane 9 of the window 01, and any appa
cessively over said evaporators and said window
ratus under test in the chamber, are not only
and
at a higher velocity over one of said evapora
well below the dew point of themixed air, but
than over, the window and the other evape
below the freezing point as well. Therefore, 20 tors
orator, whereby frost accumulations are removed
frost quickly forms on these surfaces within the
from the window and from the evaporator over
chamber. The formation of frost on the pane 9
which the air is circulated at the higher velocity.
is particularly rapid, since with the door open,
2. In apparatus of the type described, in com
the cold pane is in direct contact with warm
cold air therein. The moisture introduced by
moist room air.
The formation of frost on ap
paratus in the chamber prevents accurate ob
servation thereof, particularly in the case of the
dials or glass cover plates of indicating instru
ments, and if permitted to remain,‘ such frost
might impair the operation or accuracy of cer
tain devices.
When the chamber door D is
again closed and the fan 22 started, the frost
quickly disappears from the evaporator E and
also from the inner surface of the window pane
bination, a closed chamber having at least a por
tion of its wall structure formed of metallic plates
spaced to provide passages for the evaporation
of refrigerant therebetween, an evaporator in said
chamber spaced from the chamber wall structure,
means for supplying refrigerant to said wall struc
ture refrigerant passages and to said evaporator
whereby said evaporatorand the inner surfaces
of said portion of said wall structure are cooled,
and means including an air propelling device
for circulating air in said chambersuccessively at
9. At the same time, frost is quickly removed 35 high velocity over said evaporator and at a rela
from the devices in the chamber. Removal of
tively lower velocity over the cooled inner surfaces
frost from the pane 9 and from the devices per
of said portion of said wall structure, whereby ac
mits clear observation of the devices in the
cumulation
of frost on said evaporator is avoided.
chamber. Defrosting of the evaporator coil E
3. In apparatus of the type described, in com
increases the rate at which heat is absorbed
bination, a closed chamber including a wall struc
thereby from the chamber air. As a conse
ture formed of metallic plates secured together
quence, the chamber air temperature is quickly
and having passages for the evaporation of refrig
lowered to the desired value, the cooling of the
erant therebetween, an evaporator in said cham
instruments or devices in the chamber is not
delayed, and the testing or development work 45 ber, means for supplying refrigerant to said evap
orator and to said wall passages whereby said
proceeds rapidly.
evaporator and the chamber wall structure are
It is my belief that the above described de
cooled, air propelling means in said chamber ad
frosting of the evaporator E, the Window pane 9,
jacent said evaporator and a flue closely enclos
and apparatus in the chamber involves a trans
ing said air propelling means and said evaporator
fer of frost from these parts to the inner sur
and having openings therein spaced from said
faces of the chamber wall evaporator sections
cooled wall structure for directing air propelled
W, W1, W2, etc., and results from the difference
by said means successively at a high velocity over
in temperature of the several parts and the suc
said evaporator and at a lower velocity over said
cessive circulation of air thereover. Since the
air in the chamber is circulated at a higher 55 cooled wall structure, whereby frost accumula
velocity over the evaporator E than over the
chamber wall evaporator surfaces, the evaporator
E is maintained at a somewhat higher tempera
ture than the chamber walls. The apparatus in
tions on said evaporator are removed.
4. In apparatus of the type described, in com
bination, a closed chamber including a wall struc
ture formed of metallic plates secured together
and having passages for the evaporation of re-_
the chamber which is cooled by the circulated air, 60 frigerant therebetween, an evaporator in said
is at a higher temperature than the chamber
chamber, a window in said chamber spaced from
walls. Also, heat loss through the window struc
said evaporator, means for supplying refrigerant
ture O keeps the inner window pane 9 at a higher
to said evaporator and to said wall passages
temperature than, the chamber wall evaporator
surfaces. It is therefore probable that the air 65 whereby said evaporator and the chamber wall
structure are cooled, and means including an air
circulating at relatively low velocity along the
propelling device for circulating air in said cham
surfaces of the chamber wall evaporators is
ber successively at a high velocity over said evap
chilled to a temperature where moisture is con
orator and at a lower velocity over said cooled
densed therefrom and deposited on these walls
in the form of frost, reducing the moisture con 70 wall structure and said window, whereby frost
accumulations are removed from said evaporator
tent of the air at this point. The air thus dried
and said window.
or dehydrated then passes over the surfaces of
5. In apparatus of the type described, in com
the evaporator E and the window pane 9, and
bination, a closed chamber including a wall struc
over the apparatus under test in the chamber,
its temperature is raised by contact with these 76 ture formed of metallic plates secured together
7
2,405,895
and having passages for the evaporation of re
frigerant therebetween,- an evaporator in said
chamber, a window in said chamber spaced from
said evaporator, means for supplying refrigerant
to said evaporator and to said wall passages
whereby said evaporator and the chamber wall
structure are cooled, air propelling means in said
chamber adjacent said evaporator, and a ?ue
closely enclosing said air propelling means and
said‘ evaporator and having openings therein
spaced from said cooled wall structure for direct
ing air propelled by said means successively at a
high velocity over said evaporator and at a lower
velocity over said cooled wall structure and said
window, whereby frost accumulations on said
8
metallic plates secured together and providing
passages therebetween for the evaporation of re
frigerant, an evaporator in said chamber spaced
from said door, means for supplying refriger
ant to said evaporator and to said wall structure
refrigerant passages whereby said evaporator and
the chamber wall structure are cooled, air propel
l-iing means adjacent said evaporator, and means
for con?ning air propelled by said propelling
means to a path closely adjacent said evapora
tor and for directing some of the air so propelled
in an uncon?ned circulatory path successively
over said cooled wall structure and said window,
whereby air is circulated in said chamber at a
higher velocity over said evaporator and at a
lower velocity over said cooled wall structure and
6. In apparatus of the type described, in com
said window and frost accumulations are removed
bination, a closed chamber having an openable
from said evaporator and said window.
door therein, a window in said door, said cham
ber having a wall structure formed of spaced 20
ERWIN LODWIG.
evaporator and on said window are removed.
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