Improvements in Processes and Apparatus for Thawing Frozen Meat and other Frozen Substances, and for Producing Warm Dry Air; and in Apparatus for Drying Air, and Desiccating and Drying other Substances.
Year: 1895

page_text: Date of Application, 4th Feb., 1895-Accepted, 29th June, 1895
COMPLETE
SPECIFICATION.
Improvements in Processes and Apparatus for Thawing Frozen
Meat and other Frozen Substances, and for Producing Warm
Dry Air; and in Apparatus for Drying Air, and Desiccating and
Drying other Substances.
I, JOHN DAVY POSTLE, of Ormby House, Esplanade, Manly, near Sydney.
New South Wales, Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and, by the following statement:-
The present invention consists in processes for thawing frozen meat and other
frozen substances generally, and for treating atmospheric air to warm and dry it;
it consists also in apparatus embodying such processes, which apparatus are usable
also for desiccating fruits, meat and other foodstuffs, and for purposes of desiccation
and drying generally.
My processes and apparatus are applicable to a variety of uses more or less
connected with the purposes aforesaid, more particularly such uses as require the
supply of dry air at a temperature which is under control. Thus, the apparatus
hereinafter described might be used for the purposes of timber or clothes drying;
and with the addition of the necessary apparatus for the purposes of evaporating
and concentrating liquids.
One of the chief objects of my invention is the thawing of frozen substances,
particularly frozen meat. For the thawing of frozen meat in a satisfactory manner,
it is desirable that the moisture should be removed as quickly as it makes its
appearance, and that when the temperature of the meat has risen to the point
determined as the maximum, the meat should be dry. In order to ensure its
keeping fresh until ready for cutting down, it is also desirable that the meat should
be kept in a lively dry atmosphere whose temperature should be under control.
Moist air is a most active agent for setting up decomposition in organic substances,
and if it be not present, and the temperature be kept down, meat or similar substance
can be stored for upwards of a week without serious loss of condition.
It has been recognised in the Specifications of existing Patents, that it is desirable
to remove the moisture which exhibits itself during the thawing of frozen meat and
it has been proposed to accomplish this purpose by the contact of dry air with
the meat.
I do not therefore claim broadly the principle of circulating dry air
with such an end in view, but confine myself more particularly to the processes
and apparatus in and by which this is done as set forth in the claiming clauses of
this Specification. If the air used for thawing is warmed only, it will, upon coming
into contact with the cold substances, precipitate its moisture upon their cold
surfaces, and to avoid this precipitation of moisture the air must be dried as well
as heated.
For the purpose of abstracting the surplus moisture from the air used, the same
is treated by contact with a deliquescent salt such as calcium chloride, or alter-
natively, its moisture is condensed and extracted by lowering its temperature and
thereby diminishing its capacity for retaining aqueous vapor. When the air,
dried, is to be warmed, a heat exchanger is employed to utilise the portion of the
sensible heat of the entering air by conveying it to the air discharged by the drying

page_text: I am
apparatus, which air, having thus regained a portion of the initial content of heat
passes to the warming apparatus, whence it passes to the thawing chamber.
not aware that a heat exchanger has been used in this connection heretofore, and I
have found considerable economy to arise from its use. When the abstraction of
moisture is effected by contact with cold surfaces, the amount of heat withdrawn
from the air may be very considerable. When the recharge of heat is given by
direct heaters, fire water or steam warmed, the total heat previously extracted
from the air must be made up again from external sources; and in like manner,
the energy required for effecting a reduction of the temperature of the air at the
first step in the treatment must be entirely supplied from external sources.
An
economy is effected by placing a heat exchanger in "circuit"; this apparatus may
be of any convenient form, the air before entering the drier being passed through
one side of it and the air leaving the drier over its other side, whereby the former
air is reduced in temperature and the energy required to be supplied to the drier
thereby diminished, whilst at the same time the temperature of the cold air
from the drier is raised and the energy required to be supplied to the heater also
itiminished.
The arrangement of the apparatus as illustrated in the accompanying drawings
is not necessarily the same as would be used in practice, and it has been shewn only
to make clear the possible modifications and combinations thereof. The first sheet
of drawings shews an arrangement with interchangeable connections, whereby
one or other method of extracting moisture from the air may be used, and the heat
exchanger or heater used or omitted as may be required to suit the circumstances
of particular cases. The arrangement shewn on the second sheet is a practical
working design for either a large or small thawing room or chamber or similar
interior. The dimensions, proportions, and form of the parts are not necessarily
exact; any case they are subject to variation and alteration to adapt the apparatus
to the circumstances of the use to which it may be applied.
Referring to Sheet 1 of the drawings annexed,
Fig. 1 is a longitudinal sectional elevation of an apparatus such as has been
herein before mentioned, the connections of whose parts may be varied for the
purposes already stated;
Figs. 2 and 3 are views enlarged of fragments of the floor and ceiling perforated
to distribute and subdivide the air currents;
Fig. 4 a view of one of the discs of the moisture extractor constructed of wire
gauze ;
Fig. 5 half views of the same constructed of metal plate perforated in two
different patterns.
The pump or blower 1-a centrifugal fan by preference is used to force the air
through the apparatus and circulate it in the thawing or drying room 2. The pump 1
draws the air into its suction 3 from the exit opening 4 of the chamber 2, or from
the external atmosphere either direct or through the heat exchanger in the
chamber 5 in the last mentioned case, the suction 3 is connected with the delivery
pipe 6 of the heat exchanger. When the atmosphere contains less moisture per
unit volume than the air discharged through the exit 4, the suction 3 is left open to
the atmosphere either direct or through the heat exchanger as already stated, but
when the reverse is the case, the same body of air is used continuously until it is
deemed advisable to renew it. The discharge 7 of the pump i is capable of being
connected by pipes either with the inlet 8 of the moisture absorbing chamber 9 or
with the inlet 10 of the moisture condensing chamber 11. 12 is a chamber
containing a number of perforated plates or equivalent contrivances 13 against
which the air discharged through the exit 14 from the absorber 9 impinges; they
arrest and filter out of the current of air particles of spray which it may have
suspended in it; the chamber 15 is in communication with the chamber 12 through
a grating or perforated partition 16, and it is packed with coarse charcoal which
will impede the air as little as possible whilst purifying it; when it is not thought
necessary to carry out this purifying process, the charcoal can be withdrawn through
1

page_text: a door or manhole. The chamber 15 is connected through a valved pipe 17 with
the chamber 5, and by another valved pipe 18 with the heating chamber 19. The
moisture condensing chamber 11 which receives its air current through the valved
pipe 10 is connected by a port 20 with the chamber 5, the chamber 5 by a port 21
with the heating chamber 19, and the heating chamber 19 by a port 22 with the
-header 23 from which the air trunks 24 branch off. 25 is a coil connected with a
source of supply of cold brine or water, and 26 a coil connected with a source of
supply of warm water or steam. The heat exchanger 28 and the chambers 12, 15, 11, 5,
and 19 are provided with drip cocks through which the moisture condensed in them
can be drawn off. 27 is the atmospheric admission pipe of the heat exchanger in
the chamber 5. The heat exchanger may be of any convenient form; the design
shewn consists of a vessel 28 cylindrical or cubical in form into which the pipes 6
and 27 lead, and through which tubes 29 pass. When the pipe 6 is connected with
the suction 3 of the pump 1, atmospheric air enters by the pipe 27 and circulates
about the tubes 29 in the vessel 28. In a modified arrangement, the pipe 27 is
provided with a connection to the exit port of the interior 2. In order to obtain
the highest possible efficiency, the surfaces of the coils 25 and 26 and the surfaces
of the heat exchanger should be of ample area, and the metal of which they are
made should be as thin as is consistent with the necessary strength. The
moisture absorber 9 consists of a cylindrical shell with end plate 30 in which
bearings are set to receive a shaft 31 placed axially in the shell. The bottom of
the shell may be dipped to form a well to carry a coil 32 which is connected with a
source of supply of cold water or brine. A stuffing box and gland 33 prevents
the escape of air into the atmosphere, and a belt pulley 34 is keyed on the overhung
end of the shaft 31. Upon the shaft 31 a number of discs 35 such as are shewn
in Figures 4 and 5 are set side by side at a little distance apart from each other.
The lower portion of the vessel 9 contains a solution of calcium chloride or other
suitable deliquescent salt, and the shaft 31 is rotated so that the surfaces of the
discs 35 are kept constantly covered with a film of the liquid.
In lieu of cold water or brine, ammonia or other compressed gas may be evaporated
into the cooling coils for the purpose of obtaining the necessary reduction of
temperature.
36 are head rails upon which the substances to be acted upon in the room 2 are
suspended. The false ceiling 37 and the floor 38 are perforated as described and
shewn in Figs. 2 and 3, in order to thoroughly distribute the current of air which
passes out through the ports 39 in the air trunks 24. In order to obtain thoroughly
satisfactory results, it is essential that this distribution of the air should be complete
so as that as far as possible the whole surfaces of the substances under treatment
should be equably acted upon.
When the solution of calcium chloride in the vessel 9 becomes too dilute as a
result of its absorbing moisture from the air under treatment, it can be drawn off
and concentrated by evaporating the surplus water. In working with the absorber,
it is necessary to keep its temperature below the point at which deleterious or
noxious gases are given off; otherwise meat or other such substances with which
the air comes in contact would be injured.
When air is forced by the pump through the absorber, has to pass successively
through and about the revolving discs 35 which are covered with a film of calcium
chloride; contact with this substance dries the air by absorbing its moisture; thence
the air passes into the chambers 12 and 15 where it is filtered and purified respec-
tively; thence it may be sent to the heating chamber 19 either direct through the
pipe 18, or via the heat exchanger through the pipe 17. It is only sent via the
beat exchanger when the suction 3 of the pump 1 is connected to the pipe 6, and
when the air has been cooled; when the pump 1 takes its feed direct from the
atmosphere or from the port 4, the heat exchanger is not placed in circuit. Having
had its temperature raised in the chamber 19 by contact with the hot coil. 26,
the air, dried and heated, passes through the port 22 into the header 23
and thence into the air trunks 24 from which it passes out through the ports 39-

page_text: If the coil 26 is not warmed, the air, as discharged from the chamber 15 passes
direct to the header 23.
In the alternative arrangement in which the absorber 9 is not used, the delivery 7
of the pump 1 is connected with the pipe 10, and the pump 1 is made to take its
feed through the heat exchanger via the pipe 6. The pump delivers the air at the
temperature at which it has received it from the heat exchanger, to the cooling
chamber 11 where it parts with a portion of its heat to the cooling coil 25; as a
result of this cooling it deposits a corresponding portion of its moisture in the
vessel 11 and then proceeds through the pipes 29 of the heat exchanger to the
heating chamber 19, where it may be warmed, and whence it proceeds as before
explained. In passing through the heat exchanger it receives an increment of beat,
the feed air, which has entered the exchanger by the pipe 27 suffering a corre-
sponding diminution of temperature; thus by the exchange effected in the heat
exchanger 28, the entering air is prepared for the action of the coil 25, whilst the
dried air is prepared for the action of the coil 26, and the energy required by both
coils reduced to a minimum.
When a cold fluid is passed through the coil 25, the absorber is caused to
operate also as a moisture condenser and to extract the moisture by reason not
only of the absorbent property of the calcium chloride solution, but also by
causing the precipitation of the moisture by reducing the temperature of the air.
Referring to Sheet 2 of the drawings, Fig. 6 is a sectional elevation through a
thawing chamber to which my invention is applied. It will be observed that the
whole of the apparatus is exterior to the chamber or interior which contains the
meat or other substances being acted upon. The chamber or interior 40 is of
appropriate dimensions, of similar construction to the chamber 2 in Fig. 1. The
air trunks 41 are built in below the floor; they receive their air supply from the
centrifugal blower 42 which is driven by a belt 43 from a pulley 44. Heating and
cooling coils are placed exterior to the chamber in air spaces which can be
economically constructed by using the walls of the chamber 40 as one of their
sides. With these spaces the chamber 40 is in communication by means of an
opening 45 in its upper portion, which opening is provided with a slide or
shutter 46 operable by means of a spindle passing through the walls. The air
pipes 47, 48, and 49 are each led to the suction of the blower 42, the pipes 48
and 49 being provided with suitable valves worked by hand-wheels 50 and 51
respectively. 52 is a heating coil and 53 a cooling coil. 54 are shutters or
dampers in the air spaces, adapted to isolate the coil 52 when they are closed;
they are mounted upon spindles also passing through the walls so as to be operable
from without. A plate 55 of copper or other metal, preferably thin and of high
heat conductivity, is placed also in the air spaces as shewn; this plate forms the
heat exchanger. 56. is an inlet opening from the external atmosphere; it is
between the opening 45. and the plate 55 and is provided with a valve or shutter.
57 is an exit opening connecting with the external atmosphere, and provided also
with a valve or a shutter; it is placed between the opening 45 and the: false
ceiling.
When it is required to use the same body of air continuously, the inlet 56. and the
valves 50 and 51 are closed, the remaining air passages being opened. When
the fan is brought into, action it draws its feed through the pipe 47 and discharges
the air so received into, the air trunks 41 whence it passes up through the
perforated floor 38, circulating through the chamber and leaving it through the
perforated false ceiling 37; thence it passes through the opening 45 and proceeds
in contact with the heat exchanger plate 55 towards the cooling coil 53 where its
temperature is finally reduced; thence it passes. upwardly on the other side of the
plate 55 until it meets the heating coil 52 where its temperature is finally raised
before it again enters the pump 42 through the pipe 47. When it is found more
economical to discharge the air after every using and operate with fresh atmo-
spheric air-that is, when it is found to be less moist than the air discharged from
the chamber 40-the slide 46 is closed and the inlet 56 is opened. The course of

page_text: the incoming air and the treatment of it is identical with the course and treatment
last described with the exception that as soon as it has passed through the false
ceiling it is discharged through the exit 57.
Again, if it be desired to merely circulate the atmospheric air, untreated, through
the chamber 40, the valves, slides, and dampers, with the exception of 51 and 57
are closed. Then the pump draws its feed through the pipe 49 and supplies the air
direct to the chamber through the air trunks 41 and perforated floor; the used-up
air is discharged through the exit 57..
The temperature of the chamber 40 may be maintained constant at any point by
the use of the same contrivances; and this is of importance, as it enables the
apparatus to be adapted as a freezing or cooling chamber for the storage. of
perishable goods. Not only is it possible to adapt the apparatus in this way, but it
is easy to effect the change almost instantaneously; to do so the valves..and
dampers 56, 57, 51, and 54 are closed, and the slide 46 and the valve 50 are opened.
The course of the air is then as follows: The pump 42 receives its feed through the
pipe 48 and valve 50, thence it discharges air into the trunks 41 whence the air
passes, as before, through the perforated floor, the chamber 40, and the perforated
ceiling, through the opening 45, in contact with the heat exchanger and the cold
pipes 53, and back to the pipe 48. The heating coil 52 will thus be seen to have
been cut out of the circuit by the shutters 54.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is,
1. In a process for producing warm dry air, drawing or forcing the air to be
acted upon through a heat exchanger, then drying it by contact with a moisture
absorbing liquid whose temperature is kept low, or, alternatively, with a cold
surface whereby its moisture is caused to be precipitated, thence leading the cooled
dried air over the heat exchanger to take up heat from the entering air before-
mentioned, and subsequently raising its temperature by bringing it into contact with
steam pipes or other heated surfaces, substantially as described.
2. A process for producing warm dry air, consisting in forcing or inducing a
current of the air to be acted upon through an apparatus adapted to subdivide said
air and bring it into intimate contact with a moisture absorbing liquid, thence
leading the dried air through an interceptor adapted to filter out of it suspended
particles of moisture, and finally warming the dried filtered air.
3. A process for producing warm dry air, consisting in forcing or inducing a
current of the air to be acted upon through a heat exchanger, thence through an
into contact with a moisture
apparatus adapted to subdivide said air and bring
absorbing liquid whose temperature has been reduced by a refrigerating coil
immersed in it, or by equivalent means or apparatus, thence leading the cooled
dried air through an interceptor adapted to filter out of it suspended particles of
moisture, thence bringing the cooled dried filtered air over the heat exchanger to
take up heat from the entering air beforementioned, and finally raising its
temperature by bringing it into contact with steam pipes or other heated surfaces,
substantially as described.
4. A process for producing warm dry air, consisting in forcing or inducing a
current of the air to be acted upon through a heat exchanger and thence through a
cooling chamber or apparatus, on whose cold surfaces the moisture of the air is
precipitated, thence leading the cooled dried air over the heat exchanger to abstract
heat from the entering current of air, and finally warming said air in a suitable
chamber or apparatus, substantially as described.
5. The construction and combination substantially as shewn in Sheet 1 of the
drawings hereto annexed, of cooling, drying, warming, and heat exchanging
apparatus and connections therefor, whereby, by manipulating the valves the
several chambers can be so connected that either of the methods prescribed in the
preceding claiming clauses can be made operable, substantially as described.

page_text: 6. Apparatus for the purposes set forth, consisting of cooling and heating coils,
air pump, air connections, inlets, and discharges, and valves, shutters, and dampers
thereon, and heat exchanger, substantially as shewn in combination in Fig. 6 of the
accompanying drawings.
1.
7. The combination with a room or interior and apparatus for the purposes
herein described, of a flat plate heat exchanger; arranged as shewn in Fig. 6 of the
accompanying drawings.
8. In a process for producing warm dry air, wherein air is cooled and dried
and finally warmed, the employment of a heat exchanger, whereby the cooled dried
air preparatory to being finally warmed is made to absorb heat from the entering
current of air.
9. In processes for producing warm dry air, the employment of the following
steps in order :-Firstly, cooling and drying the air; secondly, causing the cooled
dried air to regain heat by absorption from the entering air; thirdly, warming the
air thus treated in a chamber or apparatus containing steam pipes or equivalent
contrivances substantially as described.
10. In apparatus for drying air, a vessel in which rotates a plurality of gauze
screens or perforated plates which are mounted on a shaft and partially immersed in
a body of moisture absorbing liquid such as calcium chloride, and means or
mechanism for forcing or inducing an air current through said rotating plates or
screens so as to thoroughly subdivide it, and bring it into intimate contact with
liquid covered surfaces of the screens or plates, substantially as described.
11. In a process or method of thawing frozen substances placing the same,
distributed, in a chamber having a floor and ceiling closely perforated but otherwise
closed, and supplying warmed dried air below said floor in such a way that said
warm dried air will distribute itself equably or approximately so below the floor and
pass through the perforations therein, rising thence about and among the frozen
substances to the ceiling, and finding an exit through the perforations in the ceiling,
substantially as described.
12. In a thawing process wherein moisture held by the air is condensed and
precipitated, and the capacity of the air for absorbing moisture then increased by
reheating it, apparatus external to the thawing chamber, consisting of air circulating
mechanism and air coolers and heaters, whereby the air is successively cooled (being
thereby dried) and heated and brought into contact with the thawing substances,
substantially as described.
Dated this Thirty-first day of December 1894.