U.S. patent number 3,728,869 [Application Number 05/211,933] was granted by the patent office on 1973-04-24 for coolant system for heat removal apparatus.
Invention is credited to Harry Schmidt.
United States Patent |
3,728,869 |
Schmidt |
April 24, 1973 |
COOLANT SYSTEM FOR HEAT REMOVAL APPARATUS
Abstract
A system and apparatus is provided for continuous coolant of
products such as food products with liquid refrigerants which
apparatus minimizes atmospheric contamination with gaseous
refrigerant and is useful in the recovery of the condensable,
normally gaseous refrigerant. The apparatus comprises a cooling
chamber having inlet and outlet vestibules, conveying means for
transporting products such as food products through the cooling
chamber via the vestibules, means for applying and distributing
refrigerant in liquid form to the food product while in said
chamber, recovery traps associated with the vestibules for
gravitational recovery of gaseous refrigerant, conduits leading
from the traps to recirculate the gaseous refrigerant to a
compressor, means for compression and liquification of the gaseous
refrigerant and conduit means for conducting liquified refrigerant
to the distributing means. A process for the cooling of food or
other products is also provided which comprises passing units of
product to be cooled in a continuous stream through a cooling zone
chamber, provided with inlet and outlet vestibules, applying liquid
refrigerant to products in the chamber, which refrigerant is
normally gaseous and heavier than air at ambient operating
temperatures, to thereby reduce the temperature of the produce,
regulating the rate of introduction of refrigerant into said
chamber to provide a slight positive refrigerant gas pressure in
said chamber, recovering the gaseous refrigerant at inlet and
outlet vestibules by gravitational separation from atmospheric air,
liquifying the gaseous refrigerant and recycling the liquified
refrigerant in the process.
Inventors: |
Schmidt; Harry (Chicago,
IL) |
Family
ID: |
22788858 |
Appl.
No.: |
05/211,933 |
Filed: |
December 27, 1971 |
Current U.S.
Class: |
62/266;
62/380 |
Current CPC
Class: |
F25D
3/11 (20130101); F25D 29/001 (20130101) |
Current International
Class: |
F25D
3/11 (20060101); F25D 29/00 (20060101); F25D
3/10 (20060101); F25d 023/02 () |
Field of
Search: |
;62/63,374,375,376,380,54,265,266 ;99/192,198 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Dea; William F.
Assistant Examiner: Capossela; Ronald C.
Claims
What is claimed is:
1. An apparatus for cooling of product units by contact with liquid
refrigerant materials which are normally gaseous and
heavier-than-air at ambient room temperature conditions in a
cooling chamber which, under normal operation conditions, contains
said refrigerant in gaseous form at a positive pressure with
respect to the atmosphere which apparatus comprises:
a. a cooling chamber essentially closed to the atmosphere having at
least one portal means for introduction and removal of product
units, said chamber having direct communication to the surrounding
atmosphere only at said portal means;
b. a cooling zone and refrigerant contact means within said chamber
for contacting said products with liquid refrigerant;
c. means for introducing liquid refrigerant into said cooling zone
and to said contact means;
d. conveyor means for conveying products into and out of said
chamber and cooling zone;
e. trough-like trap means located outside the cooling chamber
adjacent to, below and cooperating with said portal means for
gravitationally recovering a heavier-than-air gaseous refrigerant
emanating from said portal and maintaining the refrigerant
separated from the atmospheric gases;
f. means for conducting gaseous refrigerant from the trap means to
a gaseous refrigerant liquifying means;
g. means for liquifying a gaseous refrigerant recovered in said
traps; and
h. means for conducting and recirculating liquified refrigerant
from said refrigerant liquifying means to the liquid refrigerant
contact means in said cooling zone.
2. An apparatus according to claim 1 wherein the liquid refrigerant
contact means are a spray distribution means.
3. An apparatus according to claim 1 wherein means are provided to
produce supplemental gaseous refrigerant and introduce the same
into said chamber.
4. An apparatus for continuous spray cooling of product units with
liquid refrigerants in a cooling chamber which, under normal
operation conditions, contains said liquid refrigerant in gaseous
form at a positive pressure with respect to the atmosphere which
apparatus comprises:
a. a cooling chamber essentially closed to the atmosphere and
having inlet and outlet portal means for passage of product units
into and out of the chamber, said chamber having direct
communication to the surrounding atmosphere only at said portal
means;
b. conveyor means for conducting product units through said chamber
via the inlet and outlet means;
c. spray means for contacting product units with liquid refrigerant
while said product units are in transit through said chamber;
d. trough-like recovery trap means adjacent to, below and
cooperatively associated with said inlet and outlet means for
gravitational recovery of a heavier-than-air gaseous refrigerant
emanating through said portal from said chamber and maintaining
said gaseous refrigerant separated from the atmosphere;
e. conduit means for conducting gaseous refrigerant from the trap
means to a gaseous refrigerant liquifying means;
f. means cooperating with said conduit means for liquifying a
gaseous refrigerant recovered in said traps; and
g. conduit means for conducting and recycling a liquified
refrigerant from the gas liquifying means to the spray contacting
means.
5. An apparatus according to claim 4 wherein temperature sensor
means are provided in said chamber and interconnected with a liquid
refrigerant supply control means to control the quantity of liquid
refrigerant conducted to said liquid refrigerant contact means.
6. An apparatus according to claim 4 which includes means for
vaporizing liquid refrigerant and conduit means for conducting a
stream of said vaporized gaseous refrigerant from the vaporizing
means into the chamber.
7. An apparatus according to claim 6 wherein the outlet of the
conduit means are positioned to discharge a gaseous refrigerant
stream at a point adjacent a food conveyor inlet and outlet means
of the chamber.
8. An apparatus according to claim 6 wherein control means are
provided to regulate and coordinate the supply of liquid
refrigerant to the liquid refrigerant contact means and the
vaporizer means.
9. An apparatus according to claim 8 wherein the control means are
responsive to a temperature sensor means in said chamber.
10. An apparatus according to claim 4 wherein shielded vestibule
means associated with said trap means are provided at the conveyor
inlet and outlet means.
11. An apparatus according to claim 10 wherein said vestibule
comprises a baffel element disposed above said conveyor portal and
a trough shaped trap means disposed below the portal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to refrigeration system apparatus and
processes for cooling products with a cold liquid form of normally
gaseous refrigerant material.
2. Description of the Prior Art
The prior art processes for direct contact refrigeration have not
acquired broad use. The procedures normally employed in the past
were processes which involved the cooling or food or other products
wherein a liquified refrigerant material contacts a product in a
closed chamber or a vat, vaporizes and concomitantly reduces the
product in temperature by removal of the quantity of heat
associated with the latent heat of vaporization for the particular
refrigerant employed. The refrigerant gases normally are vented to
the atmosphere without attempt to recover and recycle. The
refrigerant gas in some cases was obnoxious and represented a
pollutant in the atmosphere. Furthermore, the operation resulted in
cold draft problems from spillover of gases as well as a
respiratory hazard to workers. Obviously, the loss of refrigerant
adds to the cost of the operation and prevents this type of system
from enjoying any widespread use.
In those cases where a continuous process or system is employed,
attempts to recover gases for recycle and reliquification were not
commercially successful.
Of course, the conventional continuous cooling and refrigeration
techniques of products such as foods which involve blast cooling
(cold air) or radiation cooling are still practiced and in some
cases on a production line basis. These systems, however, are not
as effective or rapid as liquid refrigerant, direct contact
cooling, and require a longer process time and much larger
equipment space for a given production volume.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to an apparatus for cooling product
by contact with a liquified, normally gaseous refrigerant, which
apparatus in one broad form comprises, a cooling chamber having a
portal for introduction and removal of products; a cooling zone
within said chamber for contacting said products with liquid
refrigerant; means for introducing liquified refrigerant into said
cooling zone; conveyor means for conveying products into and out of
said chamber and said cooling zone; trap means adjacent to and
cooperating with said portal for recovering heavier-than-air
gaseous refrigerant and maintaining the same separated from
atmospheric gases; compressor means for liquifying the gaseous
refrigerant recovered in said trap and means for recirculating the
liquified refrigerant to said means for introducing the same into
the cooling zone.
More particularly, this invention relates to an apparatus for the
continuous cooling of products, such as food products, with liquid
refrigerant which is normally gaseous and heavier-than-air at
normal room temperatures and recovery of the refrigerant with
minimal contamination of the atmosphere or the refrigerant which
comprises:
a. a cooling chamber having inlet and outlet vestibule means for
passage of food product into and out of the chamber;
b. conveyor means for passing food products through the cooling
chamber via said vestibules;
c. application means for applying liquid refrigerant on conveyed
food products in the chamber;
d. recovery traps associated with said vestibules for recovery of
heavier-than-air gaseous refrigerant;
e. conduit leading from said traps to a gas liquifying apparatus;
and
f. conduit means for conducting liquified refrigerant to the
application means.
A liquid refrigerant contact cooling process is also provided which
comprises:
a. passing units of product in a continuous stream through a
confined cooling zone chamber;
b. contacting the product units while in the confined zone with a
chilled liquid refrigerant which is normally gaseous at room
temperature to reduce the temperature of the food product by
evaporative cooling;
c. regulating the rate of introduction of refrigerant into said
cooling zone chamber to provide the requisite cooling of product
and maintain a slight positive pressure of gaseous refrigerant in
said chamber;
d. recovering the gaseous refrigerant by gravitational separation
from atmospheric gases at the points of inlet and outlet of the
product unit stream to the confined cooling zone;
e. conducting the recovered gaseous refrigerant to a liquification
zone and liquifying the same; and
f. recycling the liquified refrigerant to the cooling zone.
In the process of the present invention, the refrigerant may be any
typical refrigerant which is normally gaseous at ambient room
temperatures but which may be readily liquified by compression and
cooling. In the case of cooling and freezing of food products,
refrigerants which are non-toxic and unreactive to the food, such a
liquid nitrogen, carbon dioxide or freons are preferred. Exemplary
of refrigerants which may be employed in cooling of non-food
products are ammonia, carbon dioxide, sulfur dioxide, freon, or the
like. Liquid nitrogen or carbon dioxide, because of their inert,
non-toxic, non-explosive, non-polluting characteristic, is a
preferred refrigerant, especially for food products.
While the present invention is especially adapted to cooling and
freezing of food products, it should be understood that it also may
be used to freeze or cool non-food products such as
pharmaceuticals, vitamins, blood, biologicals, metal parts such as
shafts or axles on which heated gears or wheels are shrunk in a
friction fit, rubber or plastic parts which must be rigidified at
low temperatures for machinery and the like.
The process and apparatus is adapted to recover refrigerants of the
type described which are heavier-than-air. The recovery is by means
of gas traps placed at the vestibules at the points of entry and
exit of the product units which pass on a conveyor through the
chamber in a continuous stream.
The recovery of essentially uncontaminated gaseous refrigerant is
accomplished by a gravitational separation in the gas trap and
maintaining the refrigerant gas in the chamber at a slight positive
pressure with respect to the atmosphere which is usually 14.7
psia.
The recovery of uncontaminated refrigerant is assisted by the
gaseous refrigerant which sweeps the inlet and outlet vestibules in
such a manner as to prevent ingress of the atmospheric gases which
are considered as contaminants.
Means are also associated with the traps for collection of
condensed moisture and melting of snow or the like and collecting
the resulting moisture. The removal of moisture, of course,
prevents that material from contaminating the gaseous refrigerant
stream and requiring removal prior to recycle in the process.
The apparatus also permits the rapid evacuation of gases from the
chamber to permit workmen to enter for repairs, maintenance or the
like.
BRIEF DESCRIPTION OF THE DRAWING
For a more complete understanding of the invention reference is
made to the Drawing which is a diagramatic side elevational view of
the apparatus and process flow sequence.
DETAILED DESCRIPTION OF THE INVENTION
In the attached drawing, there is illustrated a side elevation,
cut-away, diagramatic and schematic view of one form of the novel
apparatus 10 employed in practicing the process of the present
invention, including a cooling chamber 12 provided with conveyor
inlet and outlet ports 14 and 16 respectively and associated
vestibules 18 and 20. A product conveying means 22 is also shown
having a path of travel indicated by the arrows. The conveyor 22
may be a link belt or the like and the travel may be disposed as a
single pass or to follow a circuitous route as shown in the
drawing. The chamber 12 is box-like or tunnel-like in form and is
illustrated in the drawing in the vertical position with 12a
forming the base, walls 12b and 12c forming the sides, wall 12d the
top, and wall 12e the rear. The front wall of the chamber is not
shown in the cut-away side elevational view.
Associated with each vestibule is a trap 18a and 20a which is in
the form of a trough or cup-like receptacle. Conduits or ducts 24
and 26 lead from the traps 18a and 20a respectively and conduct
gases recovered from the traps to conduit 25, fan 27 and exhaust
vent 28 or recycle conduit 30. Condensate drains 32 and 34 are
provided in each trap to drain moisture, with associated drain
lines 32a and 34a, with drain line heaters and check valves 32b,
32c, and 34b and 34c respectively. Heating means 32b and 34b
maintain the liquidity of condensate (water) to assure free flowing
and eliminate freezing of the valve and line. Other heating means
such as heating cables or the like 32d and 34d serve to melt frost
or snow on the inner walls of traps 18a and 20a. The vestibules 18
and 20 are formed by the baffle elements 101 and 102 in the form of
removal panels which provide easy access to the vestibules and
chamber, extending from the outer side walls 12b and 12c of the
chamber 12 and above the trough-like trap elements 18a and 20a.
Front and rear walls are also provided for each vestibule of which
the rear walls 18b and 20b only are shown. Doors 108 and 109 are
provided to close off vestibules 18 and 20 during shut down.
Conduits or ducts 36 and 38 for carrying gaseous refrigerant are
provided which terminate at 36a and 38a adjacent the ports 14 and
16 and are positioned to discharge refrigerant gas at termination
points 36a and 38a into the vestibules 18 and 20. The conduits 36
and 38 join in common conduit 40 which leads to vaporizer chamber
60a. By-pass conduit 42 leads from conduit 40 to conduit 25 to
either fan 27 and exhaust 28 or to gas recycle line 30.
A spray nozzle or other liquid refrigerant distribution means 44
provides for distributing liquid refrigerant onto the food or
similar products indicated as 22a on conveyor 22 in chamber 12
causing them to be cooled or frozen as desired. The liquid
refrigerant is conducted via line 46 to spray head 44 with
intervening automatic flow regulating valves 48, strainer 50 (for
ice or dirt particles), and manual shut-off valve 51. Line 46 is
connected to source 52 through 4-way junction 52c and line 52a.
Line 52b carries liquid refrigerant from junction 52c and source 52
via valves 54 (manual), strainer 56, automatic flow control valve
58 to distribution means 60 which dispenses liquid refrigerant to
heating coils 62 in vaporizer chamber 60a. The coils 62 vaporize
liquid refrigerant from 60 and the resulting vapor or gaseous
refrigerant passes through conduit 40, conduits 36 and 38 to points
36a and 38a adjacent ports 14 and 16 of chamber 12. The heater
element or coil 62 is heated by fluid supplied via inlet line 64
and return line 66. It should be understood that other heater means
and heat sources may be employed in lieu of coil 60 described
above. Valves (manual shut-off) 64a, and automatic flow control
valve 66a, temperature controller 66b, flow rate transmitter 66c,
manual shut-off valve 66d, and manual flow control flow valve 66e
control flow of fluid heating medium in this system.
A recycle system is provided which includes conduit 30 (fed by
conduits 25, 24, 26 and 42) which conducts gaseous refrigerant to a
compression and liquifying station 84. The cooling of the
compressed refrigerant gas at 84 may be partially accomplished
under certain thermal conditions by the use of effluent coolant in
line 66 from vaporizer coil 62 which may be returned from station
84 as heated fluid in line 64 for recycle to coil 62. The liquified
refrigerant from station 84 is recycled in the process via line 86
to junction 52c and lines 46 and 52b for recycle in the process.
The entire refrigerant recycle system may employ recycle through
compressor 84 and source 52 would merely be for start-up or to
supplement small losses of gaseous refrigerant to the atmosphere
which, of course, would occur in normal operation.
Motor controlled dampers 68, 69, 70, 72 and 74 are provided to
control flow of refrigerant gas in the conduits 24, 25, 26, 36, 38,
40, 42 and 80. The motors are designated as 68a, 70a, 72a and
74a.
An exhaust fan 78 is connected to chamber 12 via conduit or duct 80
and passes gases to exit or atmosphere via conduit 80a.
Temperature control 90 measures temperature in chamber 12, gas
concentration meter 92 is provided to determine gas concentration
in chamber 12. A draft gauge 94 measures pressure in the chamber.
These units may be interconnected to the various flow control
valves for automatic operation as will be more fully explained
hereinafter.
In operation, food or other product 22a on conveyor 22 passes into
chamber 12. Cold, liquid refrigerant is distributed onto the food
by nozzle 44 and the food is chilled or frozen by evaporation of
the liquid refrigerant to the gaseous or vapor state. The food
product enters at port 14 and is discharged in chilled or frozen
state at port 16. During operation, additional liquid refrigerant
from source 52 or compressor 84 may be vaporized by spraying from
spray 60 onto coils 62 in chamber 60a. The gaseous or vaporized
refrigerant passes via conduits 40, 38, and 36 to chamber 12 and
discharges adjacent ports 14 and 16. The gas volume generated in
the chamber by vaporization of the liquid refrigerant sprayed on
the food and that from lines 38 and 36 provides a positive pressure
in chamber 12 only slightly above normal atmospheric pressure of
14.7 psia. Ordinarily, a pressure of up to about 0.2 inch above
normal atmospheric pressure is adequate.
The refrigerant gas in chamber 12, being at a positive pressure
slightly above atmospheric pressure, of course, tends to pass out
ports 14 and 16. Being heavier-than-air, the refrigerant gas drops
into and collects in traps 18a and 20a of the vestibules 18 and 20,
and thence via collector or recovery conduits 24 and 26 to exhaust
via conduit 25 and fan 27 or recycle (condensation or liquification
at 84) via conduit 30. In recycle, reliquified refrigerant gas from
84 is returned to the system via line 86 for reuse as described
above. When gas is exhausted via fan 27, liquified refrigerant is
obtained exclusively from source 52.
The positive pressurization of chamber 12 results in the outward
flow of gaseous refrigerant through ports 14 and 16, preventing
atmospheric gases from flowing into chamber 12 through ports 14 and
16; and the distinct separation caused by the heavier-than-air
character of the gaseous refrigerant minimizes any substantial
contamination by atmospheric gases or air in vestibules 18 and 20.
As noted above, the heavy gaseous underlying refrigerant forms an
interface with the overlying atmospheric air or gases which is
indicated by the dotted lines 100 and 100a in vestibules 18 and 20.
Of course, there will be some minor contamination so that after a
period of time, the system will require purging and charging with
fresh refrigerant gas. It is also possible that a certain amount of
refrigerant will be lost from the process due to the absorbtion of
other types of retention by the cooled product as it leaves chamber
12. However, the addition of a constant amount of fresh refrigerant
from source 52 tends to reduce this problem since any losses of gas
to the atmosphere are always of gas that contains contaminants and
replacement is with pure refrigerant.
The control of the freezing operation is monitored by the
temperature control 90, which measures conditions within the
chamber 12. Temperature control 90 is preset to predetermined
temperature and is connected to automatic flow control valve 48
which controls the flow of liquid refrigerant spray into chamber
12. The evaporation of the liquid refrigerant produces a volume of
gaseous refrigerant in chamber 12. To maintain the necessary sweep
of gas through the chamber and out of the ports 14 and 16 to the
collection traps 18a and 20a and prevent ingress of atmospheric air
into chamber 12, additional gaseous refrigerant may have to be
supplied by vaporizer chamber 60a whenever the amount of gaseous
refrigerant evaporated by the product heat is insufficient to
create an adequate positive pressure in chamber 12. The total
volume of gas passing out of chamber 12 to recovery should be such
as very little or none is lost by spillover through doorways 108
and 109 from the traps 18a and 20a in vestibules 18 and 20.
The temperature control 90 controls valves 48 and 58 in either a
two-position or proportioning-modulation manner so that when valve
48 opens, valve 58 closes and the sum total of fluid passing
through valves 48 and 58 remains constant and the gas in the
system, of course, remains at the proper pressure levels and volume
flows. Temperature control 90 also effects a reset of temperature
control 110 to the temperature set at 90 so that vapor leaving
chamber 60a will be at the temperature of chamber 12. Controller
110 is coordinated with automatic flow control valve 66a which
controls flow of heating fluid or heat energy through coil 62.
Temperature controller 66b senses temperature of heating fluid
return and if the fluid is water, brine or the like, and becomes
too cold with the hazard of freeze-up, 66b closes valve 58 to
reduce through-put to coil 62. If the flow rate of heating fluid in
line 66 becomes too low as determined by flow measuring device 66c,
a flow rate transmitter will also cut off valve 58 to prevent
excessive drop of temperature of heating fluid in line 66.
In start-up, shut-down, or during operation gas concentration meter
92 determines the purity of the gaseous vapor in chamber 12. In the
normal operation damper 68 is opened, and interconnected damper 69
is closed. At the same time dampers 70 and 74 for recycle are open;
damper 72 is closed and fan 78 is inoperative.
In the event of a temporary shut-down, valve 48 is closed, dampers
68, 70 and 74 are closed, and dampers 69 and 72 are opened and fan
78 is activated by interconnection with 72. This exhausts all
vapors in chamber 12 by pulling fresh air through ports 14 and
16.
In this shut-down procedure, gaseous refrigerant is continually
generated at 60a but the gas passes through conduits 42, 25 and 30
to station 84 for reliquification and recycle to 60. This
procedure, in effect, by-passes chamber 12 during the temporary
shut-down of the freezing operation. After the refrigerant gas has
been removed from chamber 12, access may be had thereto when gas
concentration meter 92 indicates a safe atmosphere in chamber 12
for human occupancy.
If a shut-down is for a more extended period, valves 51, 54, 58 and
64a are also closed, recycling system 84 or fan 27 are shut down,
and no gas is generated in chamber 60a.
After correction of the problem, the chamber is reactivated by
closing port doors 108 and 109, opening dampers 68, 70, 74, valve
48 and valves 51, 54, 58 and 64a, if necessary. Damper 72 is open
and fan 78 continues to run drawing out air until temperature
control 90, and gas concentration meter 92, indicate recharge of
the system and deactivate fan 78. At that time port doors 108 and
109 are opened and the freezing of items on conveyor 22
recommences. At the time when fan 78 is deactivated, damper 72 is
closed, fan 27 and/or recycling system is reactivated, if
necessary, and the circulation of gaseous refrigerant is restarted
from chamber 12 through the recycle operation or exhaust fan
27.
In operation condensate, in the form of water or snow, is formed
during the freezing operation. This tends to collect in traps 18a
and 20a and is melted by heaters 32d and 34d and the water passes
to drain via conduits 32a and 34a. The drain lines 32a and 34a have
check valves 32c and 34c to prevent loss of gas or contamination by
air and line heaters 32b and 34b to prevent freeze-up of
condensate.
The apparatus and process described in the foregoing are eminently
suitable for freezing or cooling of various products such as food
products by direct contact freezing or cooling with liquid,
normally gaseous refrigerants or cryogenic materials. Of course,
modifications of the apparatus are possible which will permit
carrying out of the cooling or freezing process and recovery and
recycle of refrigerant without substantial contamination of the
atmosphere through leakage.
For example, the conveyor 22 may ingress and exit through a single
portal equipped with a vestibule and traps such as 18 and 18a which
would also eliminate vestibule and trap 20 and 20a and conduit 38.
Likewise, instead of distributor or spray head 44, the food or
other products may be passed through a liquid bath of cryogenic
material or refrigerant placed in chamber 12 and supplied via line
46 with appropriate level control systems for the vat containing
the refrigerant bath. The other systems for recycle (84) and flow
of gaseous refrigerant 60, 60a and 62 would remain in effect. Of
course, this alternative embodiment would utilize a liquid
refrigerant bath which may not be desired and in some cases would
be more difficult to control.
It should also be understood that while reference is made herein to
compressor means used to liquify recycle refrigerant gases, that
equivalent alternatives of gas liquifying systems which do not
employ a compression step per se may also be employed in lieu
thereof.
* * * * *