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Патент USA US2116100

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May 3,1938.
RJ. CRACKNÉLL
REFRIGERATING APPARATUS
Filed March 7, 1936
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2,116,100
Patented May 3, 1938
f2,116,10()
UNITED'STATES PATENT OFFICE
2,116,100
REFRIGERATING APPARATUS
‘ Richard John Cracknell, London, England, as->
signor to U. D'. Engineering Company Limited,
London, England, a British company
.
Application March 7, 1936, Serial No. 67,672
In Great Britain A_ugustS, 1935
6 Claims. (Cl. 655-3)
This invention comprises improvements'in or
relating to refrigerating apparatus of the‘type
in which the refrigerant evaporates in pipes or
coils.It is known that the rate of heat transmission
Ul
in such evaporators is improved by increasing the
relative amount of liquid refrigerant in the pipes
or coils. This can be provided for by admitting
the refrigerant ‘liquid after passing the expan
10 sion valve into a cylindrical vessel called a sepa
rator which must be ñxed at a certain height
heat exchanger so that its temperature when it
enters the heat exchanger element will be higher
than that of the liquid surrounding it and While
still under the excess pressure it is cooled in
the heat exchanger to such a temperature that 5
when it passes through the second pressure re
ducing valve only a small amount of evaporation
due to loss of pressure at the valve will take place.
'I'his ensures that the refrigerant entering the
evaporator coils is mainly in the liquid form. 10
The heat exchanger receives from the evaporator
_above the levell of 'the evaporator coils to which a mixture of still-liquid refrigerant and of re
it is connected. In this vessel the gas formed frigerant which has been evaporated. In the
when the liquid passes the expansion valve is heat exchanger such part of the refrigerant com
15 separated from the liquid and only the liquid ing from the evaporator as is still in the liquid 15
passes into the coils. The height above the evap >form will be gasiñed by receiving heat from the
orator coils at which the separator must be fixed . refrigerant which is passing through the heat
depends on the form or length of the coils, it exchanger to the evaporator. Consequently only
being necessary to provide a sufficient head to the vapor will pass to the compressor which is
used to deliver it to the condenser and there
20 feed the liquid to the coils >by gravity. In some
cases owing to the length of theV coils in order to fore not only is the evaporator itself rendered Nl 0
provide a sufficient head to overcome the friction' more efficient by the reduction of vapor therein
or resistance in the coils it would be necessary but the risk of knocking in the compressor is
lto fix the separator at such a height above the obviated.
`
`
The heat exchanger conveniently takes the
2A on coils as to make this method impracticable. In
such cases a pump is sometimes used to force
form of a separating vessel having an inlet for
the liquid from the separator into the coils. a mixture of liquid and gases from the evapo
This arrangement has the disadvantages that it rator, an outlet in the upper part to the sepa-_
involves the cost of a pump and motor to drive rator and a heat exchange element in the lower
30 it, also the cost of running the motor and in part through which the refrigerant from the 30
addition it involves a gland on the pump spindle condenser to the evaporator passes, said heat
which must be kept gas tight.
exchange element being so located as to be in
Itis an object of the present invention to Contact with liquid refrigerant which separates
provide means whereby the quantity of refrig
3 Gl erant in the evaporator coils is increased and
at the same` time it is unnecessary to provide
either a pump or a gravity head to ensure the
< flow of the refrigerant through the evaporator.
According to the present invention in an evap
`4K0 orative refrigerator there is provided between the
condenser and the evaporator a heat exchanger
through which the refrigerant passes on its way
to the evaporator, in‘combination. with a pres
sure reducing expansion valve (for example, a
45 float-operated expansion valve) between the con
denser and the heat exchanger and a second
pressure reducing valve between the heat ex
changer and the evaporator- and means to ref
turn the refrigerantirom the evaporator to the
50 heat exchanger so as to extract heat from the
refrigerant passing through the heat exchanger
to the evaporator.
In accordance with this arrangement the re
frigerant from the condenser is not' allowed to
55 fall to the evaporator pressure while it ls in the
from gases’in the separator.
The refrigerant,
therefore, does not enter the body of the sepa- 35
rator until it has passed through the evaporator.
Around the coil forming the heat exchange ele
_ment within the separator is a free space which
is ñlled with liquid refrigerant coming from the
evaporator and the purpose of the separator is, 40
therefore, in part, to separate this liquid from
the vapor which is going to the compressor.
The pressure reducingv expansion valve for con
trolling the outflow from the condenser is con
veniently of known type comprising a iloat-op- 45
erated expansion valve capable of delivering liq
uid refrigerant to the heat exchanger coil whilst
stopping the passage of -gaseous refrigerant. At
the outlet from the heat exchanger the coil is
provided with an automatic pressure reducing 50
valve capable of maintaining a pressure of, say,
by way of example, 60 lbs. in the heat exchanger
when there is a pressure of, say, 20 lbs. in the
evaporator. As a result the float valve will re
duce from the condenser pressure to the inter- 55
2
. 2,116,100
mediate pressure of 60 lbs. or so which is main
tained in the heat exchanger. This reduction
advantage that the separator and heat exchanger
can be located at any level in relation to the
of pressure at the float valve will be accompanied
evaporator.
by a corresponding reduction of temperature and f
by some evaporation but the vapor is recondensed
in the heat exchanger and the temperature fur
I claim:
1. In an evaporative refrigerator the provision
between the condenser and the evaporator of a
ther reduced to such a level that only a small
heat exchanger comprising a conduit having a
amount of vapor is produced at the second pres
heat-exchanging wall through which conduit the
sure reducing valve.
refrigerant passes on its way to the evaporator
As the liquid passes the
10 pressure reducing valve under considerable pres- . and a refrigerant space adjacent to said conduit,
sure it is unnecessary to provide a pump or any
gravity head to force the refrigerant through
the evaporator, so that the separator and heat
exchanger can be fixed at any level in relation
15 to the evaporator.
The accompanying drawing illustrates dia
grammatically and by way of example o'ne ar
rangement of apparatus in accordance with the
invention.
In the drawing: I I is a pipe carrying a refrig
20
erant from the condenser to a float-operated ex
pansion valve I2 which may, for example, be of
the type described in my United States Patent
SpeciñcationNo. 2,024,721. From the expansion
25 valve liquid refrigerant passesby the pipe I3 to a
heat exchanger coil I4 disposed in the lower part
of a separating vessel I5 so that it is immersed
in liquid refrigerant I6 in the vessel. 'I‘he outlet
of the heat exchanger coil I4 passes to the reduc
30 ing valve I'I and thence to the evaporator coil I8.
The return pipe I9 from the evaporator coil
enters the upper part of the separating chamber
I5 and here the mixture of liquid and gaseous
refrigerant which cornes from the evaporator
separates out. Only gaseous refrigerant is re
turned by the pipe 20 to the compressor.
It will be appreciated that the liquid refriger
ant I6 in the separating vessel I5 cools the re
frigerant passing from the heat exchanger coil Il
40 and therefore is itself gradually evaporated, and
also continuously replenished by the supply from
the evaporator coil. In due course the liquid
refrigerant in the separating vessel I5 strikes a
balance of level and temperature at which it re
45 mains constant. As the evaporator coil is more
filled with liquid than when the separator I5 and
heat exchanger coil are omitted, it is necessary
_to allow suflicent extra quantity of refrigerant in
the system to keep the evaporator coil so filled
and also to allow for the extra refrigerant which
50
occupies the lower part of the separator I5.
The amount of heat removed from the liquid
coming from the condenser will depend upon the
difference of temperature between the condenser
55 and evaporator. Under average conditions with
ammonia as the refrigerant' it may be sufficient to
evaporate in the heat exchanger from 10 to 15%
of the total flow of refrigerant passing .into the
evaporator. In that case 10 to 15% of the total
60 amount of liquid entering the evaporator will
pass through the evaporator coils unevaporated
and return to the heat exchanger where it is sep
arated from the vapor and used to cool the liq
uid going into the evaporator. A continuous sup
ply of liquid is thus maintained in the heat ex
changer. There is no gain or loss in this ex
change of heat but it provides a simple means of
increasing the amount of liquid in the evapora
tor coils.
This arrangement has, furthermorefthe ad
70
vantage that it can readily be lincorporated in
existing refrigerating systems of the evapora
tor type without modification of the evaporator
or condenser units and will serve to increase the
75 capacity of the plant. It also has the important
in combination with a pressure reducing expan
sion valve between the condenser and the conduit
of the heat exchanger and a second pressure re
ducing valve between the conduit of the heat ex
changer and the evaporator and means to return
the spent refrigerant from the evaporator to the
refrigerant space of the heat exchanger so as to
extract heat from the refrigerant passing
through the heat exchanger to the evaporator.
2. In an evaporative refrigerator the provision
between the condenser and the evaporator of a
heat exchanger comprising a conduit having a
heat-exchanging wall through which conduit lthe
refrigerant passes o_n its way to the evaporator
and a refrigerant space adjacent to said conduit, 25
in combination with a pressure reducing float
operated expansion valve between the condenser '
and the conduit of the heat exchanger and a sec
ond pressure reducing valve between the conduit
of the heat exchanger and the evaporator and
means to return the spent refrigerant from the
evaporator to the refrigerant space of the heat
exchanger so as to extract heat from the refrig
erant passing through the heat exchanger to the
evaporator.
.
- 3. Apparatus as claimed in claim 1 wherein
the heat exchanger takes the form of a separat
ing vessel having an inlet for a mixture of liquid
and gases from Ithe evaporator, an outlet in the
upper part to the compressor and a heat exchange
element in the lower part through which the re-frigerant passes from the condenser to the evap
orator, said heat exchange element being so lo
cated as to be in contact with liquid refrigerant
which separates from gases in the separator.
4. Apparatus as claimed in claim 2 wherein
the heat exchanger takes the form of a separating
vessel having an inlet for a mixture of liquid and
gases from the evaporator, an outlet in the upper
part to the compressor and a heat exchange ele
ment in the lower part through which the refrig
erant passes from the condenser to the evapora
tor, said heat exchange element being so located
as to be in contact with liquid refrigerant which
separates from gases in the separator.
5. In an evaporative refrigerator, the combina
tion of a condenser, a pressure-reducing valve at
the outlet yof the condenser such as to retain un
condensed gases and pass condensed liquid there
from, a heat exchange vessel, a conduit passing 60
through the lower part of the heat exchange ves
sel ,from the pressure reducing valve, a second
pressure-reducing valve _beyond the heat ex
change vessel in the said conduit, an evaporator
beyond the second pressure-reducing Valve, a 05
connection from the return pipe of the evapora
tor to the heat exchanger so as to return unevap
orated liquid refrigerant thereto, a compressor,
a connection from the upper part of the heat ex
change vessel to the compressor, and a connec
tion from the compressor to the condenser.
6. An evaporative refrigerating system includ
ing a compressor, a condenser, a float-operated
expansion valve, a heat exchange element.- a
pressure-reducing valve, a separator vessel in the
70
\
3
2,116,100
lower part of which said element is disposed and
the passage of unevaporated liquid refrigerant
an evaporator, a conduit for the passage of liquid
and gas to the separator, the quantity of said re
frigerant in the system being in excess of the nor
mal capacity of the evaporator so that the ex
cess returns to the separator with the gas, the
excess being sufficient to submerge said heat ex
change element, a conduit from the upper part
of said separator vessel for the passage of spent
refrigerant from said condenser through said
ñoat-operated expansion'valve to said heat ex
QI change element, a conduit from said heat ex
change element for the passage of liquid refrig
erant from said element through said pressure
reducing valve to said evaporator, said- pressure
reducing valve being adapted to maintain a pres
10 sure in said element greater than the evaporator
pressure but less than the condenser pressure, a
conduit from said evaporator to aid separator for
gas to said compressor and a conduit‘from said
compressor for delivery >of compressed gaseous 1U
refrigerant to said condenser.
RICHARD JOHN CRACKNELL.
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