Ice-mak′ing.
Evaporation, radiation, liquefaction, and sudden reduction of pressure, are the causes by which the temperature of a body may be depressed.
Class 1.
Vaporization.
This includes those processes which depend upon the vaporization of water, ether, ammonia, benzole, etc., which, in assuming the vaporous form, change sensible heat to latent, extracting it from the objects most convenient thereto,—in this case a reservoir of water whose contents are thereby congealed.
In this class are the atomizers or spray apparatus.
One form of this machine is founded upon the old practice in Hindostan, of cooling water by the evaporation from the outer surface of porous vessels through which the contents percolate.
A part is thus sacrificed in cooling the remainder, the water in its evaporation rendering latent the heat abstracted from the contents of the jar. The extent to which this process is carried determines whether the water is cooled to the freezing-point or not.
A modification of this device is found in wrapping a non-porous jar or other vessel with a bibulous covering, which is kept wet and subjected to a draft of air. The contents of the vessel part with their sensible heat in furnishing the heat required by the evaporation of the water in the envelope.
“Protagorus, relating the voyage of King Antiochus down the river
Nile, says: ‘They expose the water in large earthen ewers on the top of the house, and two slaves are kept sprinkling the vessels with water the whole night; and at day break they bring them down and immerse the ewers in water, which is used without snow, as it is cool enough.’
” —
Deipnosophists.
The opinion prevailed among the ancients that water previously boiled or heated was more readily cooled, and in
Egypt and other warm countries earthen vessels filled with boiled or heated water were exposed to the air during the night, and in the morning placed in a pit or cellar and bound around with fresh or green plants which were moistened with water, and preserved their contents cool throughout the whole day. In the countries of
Southern Asia a similar opinion and practice still prevails.
So far, the conditions of evaporation have been the exposure of water in an atmosphere not saturated with moisture and preferably to air in motion.
It may also be added that an artificial motion by fans may be made to replace the lack of natural motion by wind or draft.
This accelerates the operation as bringing a larger amount of air in contact with the evaporative surface, and also brushing away the saturated atmosphere immediately adjacent.
Under a pressure less than that of the atmosphere, vaporization takes place at a lower temperature.
Were two thirds of the atmospheric pressure removed, water would boil at ordinary summer heat.
A vessel of water placed under the receiver of an air-pump, which is then exhausted of air, speedily enters into ebullition; but, unless the machine is kept constantly in action, the vapor which is thus formed will restore very promptly the pressure upon the surface which has been removed by the exhaustion.
If, however, the pump be powerful enough to carry off the vapor as fast as it is formed, and be steadily worked, the heat which the rising vapor withdraws from the water will presently reduce the temperature to the freezing-point, and the liquid will be converted into ice.
In 1755,
Dr. Cullen discovered that removing the pressure of air facilitated evaporation to a degree which enabled him to freeze water even in summer.
In 1777,
Mr. Nairne discovered that introducing sulphuric acid into an exhausted receiver absorbed an aqueous vapor from and thereby dried rarefied air; and by an arrangement on these principles, in 1810, by which he got rid of the vapor that rose from the water, he prevented its forming a permanent atmosphere, so as to prevent the continuance of the operation.
Professor Leslie succeeded in freezing quantities of water from 1 to 1 1/2 pounds in weight, though he could not effect the congelation of much larger quantities.
This method of promoting evaporation
John Vallance, in 1824, improved by removing the atmospheric pressure, which enabled him to carry off the vapor from large surfaces of water and consequently freeze large quantities of ice.
The Parisian restaurants have decanters (
carafes frappees) filled with water frozen by placing them in shallow tanks of sea-water, each of which is provided with a copper reservoir connected with a receiver filled with ether.
The air is exhausted from the reservoirs by an air-pump worked by steam, vaporizing the ether and reducing the temperature of the sea-water and that in the decanters below the freezing-point.
The water in the decanters usually remains liquid until stirred with a glass rod, when it immediately congeals.
Edmond Carres sulphuric-acid freezing-apparatus is upon this principle (shown at 1, Plate XXVI.), and is used to produce the
carafes frappees (frozen decanters) so frequently seen in
Paris.
It consists of a large vessel, resembling the boiler of a steam-engine, which is designed to contain the concentrated sulphuric acid; of an air-pump with tube connections to be adapted to the wide mouths of the
carafes, and of a mechanism by which the lever of the air-pump is made to keep the acid in continual agitation.
The great volume of the acid renders the loss of absorptive power by dilution very slow, and the constant agitation prevents the formation of a superficial dilute stratum, which would interfere materially with the success.
In the drawing,
a is the reservoir of sulphuric acid;
f, a
carafe of water connected by the tube
r with the apparatus, and having a stop-cock at
l. p is the barrel of the pump and
h its lever, which also agitates the oscillator, shown in dotted lines.
We have considered in regular sequence the cooling of water by the access of air under natural conditions; the acceleration of the operation by artificial draft; the facilitating of the operation by the lessening of the atmospheric pressure; the absorption of the evolved vapor by sulphuric acid.
We have now to consider the use of materials more volatile than water, notably other and ammonia, but common alcohol, ether, methylic ether or alcohol, sulphurous or carbonic acid, bisulphide of carbon, gasoline, etc., have each been used.
| Boiling-Point Fah. | Latent Heat of Vapor. | Tension of Vapor. |
| Liquids. |
| Water | 212 | 966.6 | 0.623 |
| Alcohol | 173.5 | 376 | 1.60 |
| Methylic alcohol | 119.7 | 475 | 1.11 |
| Ether | 98 | 164.4 | 2.58 |
In
Ferdinand Carreas apparatus the efficient cause producing cold is evaporation, but the liquid employed is ammonia, a substance which is not only much more volatile than water, but, under ordinary atmospheric pressure, is indeed permanently gaseous.
Gaseous ammonia is liquefied by a pressure of 8 1/2 atmospheres at a temperature of 68° Fah., or of 10 atmospheres at 77°, the pressure required rising very
[
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rapidly with the temperature.
To liquefy it by cold requires a very low temperature (-65.5 Cent.), and as its latent heat is great it would become a valuable agent for the purpose of producing cold if its vapor could be removed.
To do this with economy it must be saved and recondensed.
This may be done mechanically by a pump, but with much greater advantage by water, which has the property of absorbing ammoniacal gas in great volume and with singular rapidity.
This fact was first illustrated by
Faraday in 1823.
He used a bent glass tube, containing at one end a portion of chloride of silver saturated with ammonia at 60° Fah. or lower, and hermetically scaled after the air had been expelled by slightly warming the compound.
If the chloride be heated to 100° Fah., the ammonia expelled, and the other end of the tube plunged in a cold bath, the gas becomes liquefied.
If now the end containing the compound be plunged in a refrigeratory and the other in water, the liquid ammonia will commence boiling, the chloride will reabsorb the vapor as fast as produced, and by the rapid evaporation the water around the tube will be converted into ice.
For economic reasons (see
Professor Barnard's Report on the
French Exposition, page 369) water is to be preferred to chloride of silver.
Water absorbs at moderate temperature 700 times its own volume of ammoniacal gas, a volume capable of producing a quantity of liquid ammonia equal to two thirds the bulk and one half the weight of its own volume, and capable of converting into ice more than three times its own bulk.
On the contrary, a given quantity of chloride of silver will produce only a thirtieth part of its bulk of liquid ammonia, and a fifth part of its bulk of ice at 32° Fah.
F. Carres intermittent apparatus (2, Plate XXVI.) is similar in its operation to the
Faraday experiment, aq. amm.
being substituted for the Ag., CL. + ammonia.
In the engraving,
k is the boiler containing the liquor ammonia, and connecting by the pipe
r r with the refrigerator
t, which has a well in which is a pan containing the water
z to be frozen.
The boiler
k is placed over a portable furnace, and the apparatus purged of air, which is driven by the evolved gas out at the stop-cock
m. This being closed, and the refrigerator immersed in a tank of cool water, the temperature of the aqua ammonia is raised to 130° or 140° Cent., at which heat the ammonia is expelled and is condensed in a liquid form in the refrigerator
t. The boiler
k being now removed from the furnace and placed in the water-bath, the temperature of the water in the boiler will fall and the power of the water to dissolve ammonia will be restored.
The gas will be rapidly re-dissolved, reducing the pressure, as the liquid ammonia will evaporate with corresponding rapidity, drawing for its latent heat upon the sensible heat of the water to be frozen.
The result will be the complete evaporation of the liquefied ammonia and the restoration of an aqueous solution, in the boiler, of the original strength.
Between the ice-pan and the well is a body of alcohol which will not freeze, but will act as a conductor.
During the refrigerating, the vessel
t has a non-conducting envelope.
Ferd. Carreas continuous process (3, Plate XXVI.), like the intermittent of
Edmond Carre, depends also for its efficacy upon the evaporation of liquid ammonia.
In each process the liquefaction is effected in substantially the same way.
Aqua ammonia is introduced into a boiler, and the gas is expelled by heat into a condenser; but in order that the process may not be arrested by the exhaustion of the solution, the impoverished liquid is gradually withdrawn from the bottom of the boiler, while a corresponding volume of a fresh and strong solution is constantly flowing in at the top. The condensation is produced by the united effect of cold and pressure.
From the condenser, the ammonia in a liquid state passes on to a refrigerator, in which are placed vessels containing the water to be frozen; and as the boiler and the condenser keep up an unfailing supply of the liquid, so the refrigerator will continue to freeze successive masses, so long as the proper temperature is maintained in the boiler.
The ammoniacal vapor which leaves the refrigerator is re-dissolved to form the rich solution which is to supply the boiler; and the water of solution is the same which was previously withdrawn exhausted from the boiler itself.
Thus, as there is nothing added to the contents of the apparatus, and as there is no escape of any part of them by leakage or otherwise, the same materials go on indefinitely producing a uniform effect.
a is the boiler, exposed to the heat of the furnace
b; c is an indicator to show the level of the liquid;
i is a tube conducting gas to the liquefier
j the vertical pipe above the branch
i leads to a safety-valve, and any escaping gas passes by pipe
e to the watertank
e′ where it is absorbed.
f is a tube which brings back to the boiler saturated solution of ammonia from the absorbing apparatus
u u; this solution passes downward, trickling through the perforated trays
g, while the ascending gas rises in a sinuous course alternately around the edge of one tray and through a central hole in the next, and so on. This condenses and carries back the watery vapor which accompanies the gas.
The gas passes by tube
i to the liquefier
j, passing through a box
k and a congeries of zigzag and spiral tubes in a bath of cold water constantly renewed from reservoir
z, which also supplies other parts of the apparatus.
The congeries of tubes terminates in another box
km; and the ammonia is by this time in a liquid state under the pressure of 10 atmospheres, which is constantly maintained in the boiler.
In the liquid state the ammonia passes by the pipe
l to the efflux regulator
m, which is the dividing barrier between the part of the machine in which a regular pressure of 10 atmospheres is maintained and the following part where the pressure does not exceed 1 1/2 atmospheres.
The regulating device is a floating cup which opens or closes a hole of influx.
The liquid passes from the regulator
m by pipe
n. to the distributor
p, the pipe
n being wound spirally around the tube
t, through which the vaporized ammonia is returning from the refrigerator
q q; the vapors serving to reduce the temperature of the liquid in
n before it reaches the refrigerator.
The refrigerator itself consists of a number of zigzag or spiral tubes—in the apparatus here represented, six in all—immersed in a tank constructed of non-conducting substances.
These zigzags return upon themselves six times, forming so many partitions in the tank, between which vessels containing the substances to be subjected to cold may be placed.
Each one of the six zigzags receives an equal supply of the liquid ammonia from the distributor.
The small tubes conveying this supply are shown at
p. The vessels
r to be refrigerated are sustained on a carriage, which is slid back and forth by the same power that works the pump
g′ by which the re-saturated solution of ammonia is returned to the boiler.
The space in the tank surrounding the zigzags and the water-vessels
r is filled with an uncongealable liquid, such as alcohol or a solution of chloride of calcium.
The ammonia in the zigzags
q discharges in a vaporized form into the
collector s and passes through the tube
t to the cylinder
u, where it extends nearly to the bottom of the vessel, and there
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discharges the gas into the water which has been brought from the bottom of the boiler
a, and partially fills the cylinder
u. From this water the ammonia has been nearly exhausted, and it therefore greedily absorbs the gas ejected into it by pipe
t. On the left of vessel
u. is a water-level indicator.
Within the vessel
u is a worm which receives water by pipe
a′ from the elevated reservoir
z; after passing to the bottom of the spiral the pipe curves upward and then (marked
b) descends nearly to the bottom of the vessel
y, where it discharges.
The water from the boiler
a passes by pipes
w w to the coolers
x y before reaching the vessel
u, where it re-absorbs ammonia.
Between the boiler
a and the vessel
u the water is cooled so as to fit it for absorbing gas more freely.
The pressure in the boiler is sufficient to expel it when the stop-cock
w is opened.
The vessel
x is formed of two concentric cylinders, between which are two spiral tubes formed of the pipe
w continued, and these spirals are immersed in a liquid which fills the annular space between the cylinders and is the reconstituted ammoniacal solution on its way from the absorber
u to the boiler
a. The water from the boiler is hot and that from the absorber is cold, and the two to some extent exchange temperatures to mutual advantage, and with additional effect in that they circulate in opposite directions, the liquid from the absorber entering at the bottom and ascending, while the heated water from the boiler enters at the top and descends.
From
x the water in the spiral is conveyed in the pipe
w, still continued in a single spiral ascending in the vessel
y, and continued farther in a pipe
w alongside of the absorber
u, into which it discharges into a sieve
v and from which it descends in a shower.
The exhausted solution from the boiler
a flows freely, as has been said, from the boiler, by pipe
w, to the absorber
u, passing the coolers
x y as described, but it requires some power to force the reconstituted solution back from the absorber
u through the pipe
f to the boiler.
This power is a pump
g′ driven by a steam-engine or other motor, and taking the saturated solution from the absorber
u by pipe
h′ and discharging it by pipe
i′ into the vessel
x, from whence it passes by pipe
f to the dome above the boiler, as described some distance above.
Gas finding its way into the pump is discharged into the upper part of
u. e′ is a pipe leading to the enveloping tube
o, from whence water is conducted by
f′ for the use of the ice-vessels
r. As the water passes through
o it is cooled by the ascending vapors of ammonia.
In starting the machine, it is first blown through to expel the air. The air escaping from the vessel
u passes by pipe
c to the purger
d and passes beneath the surface of the water therein, which retains any escaping ammonia.
This apparatus requires a large amount of refrigerating water to maintain at the desired temperature the liquefier and the absorbent vessel, and it also involves a consumption of fuel, not only to heat the boiler containing the ammoniacal solution, but also to work the forcing-pump.
The pump may be worked by water-power, if such a power is obtainable, or even in small models by hand; but for an apparatus producing more than one hundred pounds of ice per hour, a motor is indispensable.
It is stated by
Mr. Carre that for every pound of coal burned there are produced from eight to twelve pounds of ice, according to the dimensions of the apparatus.
To manage the larger forms of the apparatus, the services of two men are required, and a motor also is necessary, capable of driving two hundred and twenty gallons of liquid per hour into the boiler.
The pressure in the boiler must be taken, for the purposes of computation, at not less than ten atmospheres; and as the machines are adequate to the production of five hundred pounds per hour of ice, they will, within the same time, liberate from solution, liquefy, evaporate, and re-dissolve one hundred pounds of pure ammonia.
 |
|
Hindoo Gurglet. |
On the evaporating principle are the water-jars, or
monkeys, used in tropical countries and the east of
Europe.
These are merely unglazed earthenware jugs having a small neck and a spout, and suspended in a current of air or in a doorway.
The Australian device for the same purpose is a bucket of canvas, nearly waterproof, and having a flannel cover to form a sieve, and a spout below to draw off the water.
Evaporation proceeds rapidly from the wet surface.
The East Indian
tatta (Hind.
tattah, a screen) is a curtain of bamboo placed in front of a window or doorway and kept wet by a trickling stream of water so as to cool the air passing through its meshes into the apartment.
The mode of procuring ice by exposure in shallow, porous vessels, laid on straw and exposed to the night air, is stated to be practiced in
India.
The small crust of ice is carefully removed and stored in a straw-lined pit, before sunrise.
A large plain, unobstructed as much as possible by trees or buildings, is selected for the purpose, in which pits or excavations twenty or thirty feet square and two feet deep are sunk, the floors being covered with dry stalks of corn or sugar-cane.
Upon these are placed the water-vessels, constructed of porous earthenware, and not much more than an inch deep.
In the morning, if the sky has been clear, the vessels are found to contain thin plates of ice, which are carefully gathered and stored away.
This process was successfully imitated in
England in the latter part of the last century by
Dr. Wells, author of the Essay on Dew; and soon afterward an attempt was made in
France to employ it for the systematic manufacture of ice, but the undertaking proved to be economically a failure.
Many of the modern ice-machines depend upon the conversion of sensible heat into latent by evaporation, liquids which vaporize at low temperatures being selected.
Harrison's Australian machine used ether evaporating into a partial vacuum produced by an air-pump, and instead of acting directly upon the water to be frozen it was made to reduce the temperature of a solution of salt, which does not congeal at the freezingpoint of water, and the solution, thus made extremely cold, was then made to pass between cases containing the water, and, by reducing the temperature, secured the requisite congelation of the same.
Twining's patent of 1862 is of this class.
Next in sequence may be considered a French invention, in which the freezing agent employed was amylic ether, which is capable of being dissolved by sulphuric acid.
The ether being expelled from the acid by heat, under a pressure of several atmospheres, was liquefied, and passed in this condition to a suitable reservoir, from which, by turning a valve or stop-cock, it was allowed to expand and pass through spiral ducts arranged around a cylinder containing the water to be congealed; the expansion of the fluid to a gaseous condition acting, as in the other ether machines, to abstract the heat from the water and freeze the same.
After having thus accomplished its work, the ether passed to vessels of sulphuric
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acid by which it was absorbed, to be expelled therefrom by heat on a repetition of the process.
Twining's apparatus, patented in the
United States, November 8, 1853, and subsequently extended for seven years, embraces an exhaust vessel, a pump, and a condensing vessel or “restorer.”
The water to be frozen is placed in chambers enclosed between thin metallic pipes, plates, or partitions, through which the vapor of a volatile liquid, as ether, sulphide of carbon, etc., is drawn by an air-pump.
The vapor is condensed in a coil of pipe surrounded by cold water, and is returned to the reservoir from whence the liquid originally came.
Four different modes of applying this principle, substantially the same but varying in details, are specified in the patent.
In Siebe's apparatus an air-pump is employed to vaporize the ether, the vapor of which is then conveyed into the refrigerator, which is surrounded with strong brine.
The water to be made into ice is put in metallic troughs, and the brine surrounding them is, by means of the exhaustive process above referred to, cooled down to from 10° to 18° Fah., freezing the water to a depth determined by the time it is subjected to the process.
In Van der
Weyde's machine are employed an exhaust and force pump, a cooling coil, and two refrigerators, which act as reservoirs for the condensed liquid.
Naphtha, gasoline, rhigoline, or chimogene, are preferred.
These are evaporated by an air-pump and forced through a freezer, in which are vessels containing water, surrounded by enclosing vessels filled with glycerine, the outside being surrounded by cryogene.
The evaporation of the cryogene causes the refrigeration of the water to a sufficient extent to crystallize it; that is, form it into ice.
Reece's apparatus operates substantially on the Carre principle.
The ammoniacal gas employed passes under considerable tension from the refrigerator into a cylinder having a slide valve, entry and exhaust ports, similar to those of a high-pressure engine, so that the gas is utilized to drive the pumps of the apparatus.
From the cylinder it passes to the absorber and is returned to the reservoir.
Seely employs anhydrous ammonia.
The generators are filled, or partially so, with dry, pulverized chloride of calcium.
One of the generators is heated by steam coils, the generated gas passing through the condenser, evaporating in the refrigerator, and is finally absorbed by the dry chloride in the other receiver, to which heat is then applied in its turn, the other reservoir now becoming the condenser.
In
Johnston and Whitelaw's, the liquid, bisulphide of carbon, after being vaporized is, with the air forced in by the air-pump, conducted through chambers containing oil, which absorbs the greater part of the moisture of the gas, the moisture of the air being taken up by chloride of calcium, in a pipe leading to the air-pump.
The freezing arrangements are similar to those generally employed in machines of this class.
In
Charles Tellier's machine, the liquid employed is methylic ether in a volatile state, not requiring to be subjected to heat.
It comprises a congealer, compressing-pump, condensing-coil, and reservoir.
The congealer consists of five or more receivers of a flat form connected by tubes.
The apparatus is placed in a tank containing the water to be congealed.
The fluid from the reservoir passes to the congealer, and the vapor exhausted therefrom by the air-pump is conveyed back to the reservoir through a worm.
The novelty of this apparatus consists in freezing the water by immediate contact with metallic plates forming a closed chamber.
For use on shipboard, the congealer is provided with four outlets terminating in a trap.
Late attempts at transportation, on shipboard, of fresh meat in ice, from
Australia,
Buenos Ayres, and
Texas to
European and
United States ports, have given a fillip to this class of machinery.
2.
Radiation. This does not affect the subject from a mechanical point of view, and we therefore dismiss it.
Class 3.
Liquefaction.
Machines and apparatus for icing cream, custard, lemonade, etc., may be classed under this head, and generally operate by means of a frigorific composition of pounded ice and chloride of sodium, in a vessel which surrounds the chamber in which the article to be frozen is placed.
The tub containing the ice and salt is of wood, a poor conductor of caloric; and as the ice in liquefaction converts a large quantity of sensible heat into latent, the heat of the cream is carried off to supply the demand of the melting ice, and the cream becomes frozen.
When ice or snow is not available, the combination of certain chemicals may produce the same result.
The cream is stirred to constantly expose fresh material to the sides of the vessel exposed to the cooling compound.
See tables below.
See also
ice-cream freezer.
The use of saltpeter for cooling liquids was known at a remote period in
India.
It was probably used anciently as it was, in more modern times, in
Rome.
“The wine to be cooled was put in a long-necked bottle, which was immersed in another vessel filled with cold water; saltpeter was then gradually thrown into the water, and while it was dissolving a quick rotary motion was imparted to the bottle.”
Freezing water by a mixture of snow or ice and saltpeter is first mentioned by Tancredus, a physician of
Naples, 1607, who says that, by means of it, a tumbler of water may be converted into a block of solid ice.
Santorio, in 1626, speaks of freezing wine by a mixture of snow and common salt.
Orosius (King Alfred's version), about A. D. 400, wrote: “And there is among the Esthonians a tribe that can produce cold, and therefore the dead in whom they produce that cold lie so long there and do not putrefy; and if any one sets two vessels full of ale or water, they contrive that one shall be frozen, be it summer or be it winter.”
Freezing-Mixtures.
| Thermometer sinks. | Degrees of Fall. |
| From | To |
| With Ice. | | Degs. |
| Snow or pounded ice, 2 parts; muriate of soda, 1 part | | -5 |
| Snow, 5; mur. soda, 2; mur. ammonia, 1 | | -12 |
| Snow, 24; mur. soda, 10; mur. ammonia, 5; nitrate of potash, 5 | | -18 |
| Snow, 12; mur. soda, 5; nit. amm., 5 | | -25 |
| Snow, 3; dilute sulphuric acid, 2 | +32 | -23 | 55 |
| Snow, 8; muriatic acid, 5 | +32 | -27 | 59 |
| Snow, 7; dilute nitric acid, 4 | +32 | -30 | 62 |
| Snow, 4; mur. of lime, 5 | +32 | -40 | 72 |
| Snow, 2; crystallized mur. lime, 3 | +32 | -59 | 82 |
| Snow, 3; potash, 4 | +32 | -51 | 83 |
| Without Ice. |
| Mur.
amm., 5; nit. pot., 5; water, 16 | +50 | +10 | 40 |
| Nit.
amm., 1; water, 1 | +50 | +4 | 46 |
| Mur.
amm., 5; nit. pot., 5; sulph.
soda, 8; water, 16 | +50 | +4 | 46 |
| Nit.
amm., 1: carb.
amm., 1; water, 1 | +50 | -7 | 57 |
| Sulph.
soda, 3: dilute nit. acid, 2 | +50 | -3 | 53 |
| Sulph.
soda, 6: mur. amm., 4; nit. pot., 2; dilute nit. acid, 4 | +50 | -10 | 60 |
| Sulph.
soda, 6, nit. amm., 5; dilute nit. acid, 4 | +50 | -14 | 64 |
| Phosphate of soda, 9; dilute nit. acid, 4 | +50 | -12 | 62 |
| Sulph.
soda, 8; mur. acid, 5 | +50 | 0° | 50 |
| Sulph.
soda, 5: dilute sulph.
acid, 4 | +50 | +3 | 47 |
| Phos.
soda, 9; nit. amm.
6; dil. nit. ac., 4 | +50 | -21 | 71 |
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| Thermometer sinks. | Degrees of Fall. |
| From | To |
| Sulph.
soda, 8; mur. acid, 5 | +50 | 0° | 50 |
| Sulph.
soda, 5; dilute sulph.
acid, 4 | +50 | +3 | 47 |
| With Materials previously cooled. |
| Phos.
soda, 5; nit. amm., 3; dil. nit.
ac. 4 | 0 | -34 | 34 |
| Phos. soda, 3; nit. amm., 2; dilute mixed acid, 4 | -34 | -50 | 16 |
| Snow, 3; dilute nit. acid, 2 | 0 | -46 | 46 |
| Snow, 8; dil. sulph.
ac., 3; dil. nit.
ac., 3 | -10 | -56 | 46 |
| Snow, 1; dilute sulph.
acid, 1 | -20 | -60 | 40 |
| Snow, 3; mur. lime, 4 | +20 | -48 | 68 |
| Snow, 3; mur. lime, 4 | +10 | -54 | 64 |
| Snow, 2; mur. lime, 3 | -15 | -68 | 53 |
| Snow, 1; cryst.
mur. lime, 2 | 0 | -66 | 66 |
| Snow, 1; cryst.
mur. lime, 3. | -40 | -73 | 33 |
| Snow, 8; dilute sulph.
acid, 10 | -68 | -91 | 23 |
By the evaporation of a mixture of solid carbonic acid and sulphuric ether a temperature of 166 degrees below the freezing-point has been produced.
By means of this intense cold, assisted by mechanical pressure, several of the gaseous bodies have been condensed into liquids and in some instances solidified.
Class 4.
Reduction of pressure.
Machines in which the absorption of heat from the water is accomplished by the expansion of air or gas, or of a liquid into a gaseous condition.
In this division are one class, the carbonic-acid, ether, and ammonia engines, those materials being used as a convenient fluid for the purpose.
 |
|
Windhausen's ice-machine. |
The effect of the rapid dilatation of fluids under a sudden reduction of pressure is strikingly illustrated through the apparatus as before.
The operation is thus rendered continuous.
The machine is provided with suitable valves and connections, and may be operated by hand or power.
The operation is as follows:—
During the forward stroke of the piston—that is to say, its movement toward the front cylinder head
f—the air is compressed in the compressing-chamber
a′, and by its pressure caused to open the valve and pass out through the compartment
g of the head and through the pipe
j to the cooler, in which it passes first through the pipes
c′, and afterward through the pipes
c′, and is thereby cooled.
From the cooler the compressed air passes through the pipe
m into the compartment
n of the back cylinderhead
e, whence it passes through the valve
o into the expansion-chamber
a′ of the cylinder during a porin the hydraulic machine of
Chemnitz,
Hungary (see page 28), in which air is highly compressed in a closed reservoir under a column of water.
If a stop-cock in this reservoir be suddenly opened, the expanding air rushing out produces a degree of cold sufficient to freeze the drops of water which it brings with it into pellets of ice.
Machines acting by expansion of air-envelope.
Kirk's apparatus (
English) was of this character; that is, it absorbed heat by the expansion of air when liberated after compression by suitable mechanical means, the expansion of the air rendering latent the heat in the same manner as the expansion or vaporization of the ether or equivalent fluids in the cases herein before described.
Windhausen's machine has one or two double-acting cylinders with pistons.
In case a single cylinder is employed, the air is condensed on one side of the piston and expanded on the other.
When two cylinders are used one serves as a condenser and the other serves to expand the air. From the condensing chamber the air passes into a cooler having two compartments, in one of which it is cooled by air and in the ether by a constant flow of cool water.
From the cooler it passes into the expansion chamber, whence it escapes through a temperature regulator into the refrigerator, in which the vessels containing the water are placed.
By means of this regulator a portion of the air from the expansion chamber may be admitted to one compartment of the cooler for the purpose of reducing its temperature.
When the air in the refrigerator has become too much heated to be of farther service there, though still at a low temperature, it passes through this compartment of the cooler on its way back to the compression chamber, and may be made to pass through one or more pipes surrounded by cool water, afterwards passing through the other compartment of the cooler.
It then enters the compression chamber and again circulates tion of the stroke, and until the valve
o is closed, after which the air in the latter chamber expands during the remainder of the stroke.
During the whole return or back-stroke of the piston, the expanded and cooled air from the expansion-chamber passes out through the open valve
r into compartment
b′ of the cylinder-head
c, and thence to the temperature-regulator, whence a portion of it passes through the pipe
s to the refrigerator, and a portion through the pipe
t into the space surrounding the pipes
c′ in the left compartment of the cooler.
At the same time the air displaced from the refrigerator by the incoming cold air passes out through the pipe
k into the afore said space of the cooler.
The air all passes out from this space of the cooler, through the pipe
i, into the compartment
u of the front cylinder-head, whence it is drawn by the
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piston, through the inlet-valve into the compressionchamber of the cylinder.
The refrigerator
d consists of a double-cased rectangular wooden chamber, the space between the casings being filled with loose cotton or other nonconductor of heat.
Its cover has rectangular openings for the insertion of metallic cases for containing the vessels in which the water to be frozen is placed.
To insure the air coming fully in contact with all parts of the cases, zigzag partitions are placed in the compartments between them.
The air in the refrigerator, expanded to atmospheric pressure, abstracts heat from the metallic cases, becoming gradually warmed itself, and is finally, through a pipe
k, returned to the cooler.
A uniform pressure is maintained within the refrigerator by means of an indiarubber bag, which admits or gives out air, according as the pressure is in excess of or below that of the atmosphere.
In
Gorrie's apparatus, air is compressed by a double-acting pump into which water is injected on that side of the piston on which condensation is taking place.
The condensed air passes through a worm surrounded by cold water to a reservoir, whence it is admitted to an auxiliary pump driven by the expansion of the compressed air, in which it is expanded, cooling a non-congealable fluid in a jacket surrounding the pump-cylinder.
This abstracts the heat from the water contained in a reservoir in a chamber above the pump, causing its congelation.
Lowe uses carbonic-acid gas compressed into a liquid state.
The apparatus consists of a gas-holder, a pump, a cooler, a dryer filled with chloride of calcium, a condensing coil placed in a tank and surrounded by water, and an expansion or congealing chamber in which are placed the receptacles containing the water to be frozen.
The gas is admitted to the pump, where it is liquefied.
The heat thus generated is absorbed by the cooler, and the gas is allowed to expand into the refrigerator, where it performs the office of freezing the water.
Tuttle and Lugo.
In this apparatus air is compressed and forced by a pump into a tubular chamber, the tubes of which are surrounded by cold water, and thence through a second chamber, the tubes of which are surrounded by a volatile liquid.
It next passes into the refrigerating chamber, rising through a volatile liquid as ether, bisulphide of carbon, etc., contained therein; the air and vapor from the liquid fill the interior of this chamber, surrounding the vessels in which the water is contained and congealing it. They are thence conducted through a cooling chamber back to the pump.
A pipe is provided by which the compressed air may be carried directly to the refrigerator.
Lugo and
McPherson.
The air from a blower is forced through a chamber containing porous material saturated with water, and being there cooled is conducted to a condensing-pump, the upper part of which contains water, serving to keep the pump cool and pack the piston.
The piston is driven by the epicycloidal combination of La Hire.
From the pump the air passes to a cooler, and thence to a reservoir, from which it is conducted to a large congealing chamber or ice-house, which has non-conducting walls and a track for cars carrying pans of water.
