Note: Descriptions are shown in the official language in which they were submitted.
I
CHEMICALLY ASSISTED MECHANICAL REFRIGERATION PROCESS
Field of the Invention
This invention relates generally to refrigeration and more
particularly -to a new and improved chemically assisted mechanical
refrigeration cycle.
Background of the Invention
The typical mechanical refrigeration system employs a
mechanical compressor to raise the pressure and to condense a
gaseous refrigerant, which thereafter absorbs its heat of
vaporization. Thus, the typical vapor compression cycle uses an
evaporator in which a liquid refrigerant, such as Freon-12, boils
at a low pressure to produce cooling; a compressor to raise the
pressure of the gaseous refrigerant after it leaves the
evaporator; a condenser, in which the refrigerant condenses and
discharges its heat to the environment; and an expansion valve
through which the liquid refrigerant leaving the condenser
expands from the high-pressure level in the condenser to the low
pressure level in the evaporator.
Much effort has been expended. over the past
few decades in developing refrigeration systems which utilize low
grade energy sources, such as solar energy, without the
need for compressors or pumps. Much of this effort
,,
I I
has been directed to the suckled absorption cycle, which
accomplishes compression by using a secondary fluid as a
solvent to absorb a refrigerant gas. typical absorption
system includes a condenser, expansion valve and evapo-
rotor, as does the vapor compression cycle. However, the compressor is replaced by an absorber-generator pair.
Lithium bromide-water or water-ammonia are typical of the
solvent-refrigerant mixtures used.
The resorption cycle has also been studied. Intro-
duped in the earlier half of this century, the resorption
cycle is similar in operation to the absorption cycle.
However, a resorter replaces the condenser and the vapor
is absorbed by a special wear solution while condensing.
This solution is then circulated to the evaporator where
the refrigerant boils and the heats of disassociation and
vaporization produce the refrigerating effect.
Although the majority of prior systems avoid the use
of compressors when using a solvent-refrigerant combine-
lion, a few processes have employed a solvent-refrigerant
pair with a compressor in the system. The system and
method described in U.S. Patent No. 4,037,426 is illustra-
live. There the gaseous refrigerant it compressed and
then mixed with liquid solvent. Thereafter, the mixture
is cooled it a heat exchanger and then passed to a
decanter, where the heavier liquid fraction is separated
from the lighter liquid refrigerant. The Lockwood refrig-
errant then passes to a zone of low pressure where it is
vaporized to absorb heat from a working fluid. Systems or
methods disclosed in U.S. Patent Nos. 3,277,659 and
4,199,961 provide other examples of compressor type
systems.
I I
These and other prior systems suffer from one or more ox
several limitations. For example, prior systems fail to take
advantage of both the heat of vaporization and the heat of
dilution to ultimately cool a working medium in a compression
type cycle. Additionally, prior systems utilizing a compressor
require a heavy duty compressor capable of sustaining relatively
high compression ratios. Other systems operate at comparatively
high pressures which require heavier duty components. Still,
other systems have relatively inefficient heat transfer
mechanics. Yet other systems fail to allow auxiliary heat
exchange between refrigerant-solvent and solvent without
decreasing the density of the flow to -the compressor while other
systems fail to provide sensible heat transfer in an auxiliary
heat exchange between refrigerant-solvent and solvent. Still
other systems fail to provide secondary evolution of gaseous
refrigerant from the solvent after the solvent leaves the
evaporator to facilitate overall efficiency. These and other
problems encountered by the prior systems are substantially
reduced, if not eliminated, by the present invention.
Summary of the Invention
There is provided a chemically assisted mechanical
refrigeration process using a refrigerant and a solvent having a
negative deviation from Roulettes Law when in combination
with each other. A stream of solution including
the solvent and a liquefied refrigerant is passed to
an evaporator. The pressure over the solution is
then reduced to allow refrigerant to vaporize and
separate from the solvent. Concurrently therewith, the evolving
refrigerant and solvent are placed in heat exchange
relation with a working medium to remove energy
from the working medium. A solvent stream and
a refrigerant system including gaseous refrigerant are formed
and leave the evaporator. Thereafter, the refrigerant stream
undergoes mechanical compression and the refrigerant stream and
Lo
,,
solvent stream are contacted at a pressure sufficient to
promote substantial dissolving of the refrigerant and the
solvent. A stream of solution is thus formed for passage
to the evaporator. As the refrigerant and solvent are
in heat exchange relation with the working medium for at
least a portion of the time they are in contact and
mixing, energy is removed therefrom.
In one embodiment, the solvent stream leaving the
evaporator is preferably passed in heat exchange relation
with the solution stream passing to the evaporator. This
occurs in an economizing zone so as to cause transfer of
heat between the solvent stream and the solution stream.
Such heat transfer may be facilitated by the mass
transfer of gaseous refrigerant in relation to one or more
of the streams passing through the economizing zone. For
example, in one embodiment the solvent stream leaving the
evaporator includes a material portion of the dissolved
refrigerant. The solvent stream is placed in fluid
communication with the refrigerant stream leaving the
evaporator to accomplish mass transfer of gaseous refrig-
errant from the solvent stream to the refrigerant stream.
This in turn facilitates heat transfer in the economizing
zone prior to passage of the solvent stream and refrig-
errant stream to the mixing zone.
In a modification of this embodiment, a mixing zone
may be provided including a mixer and a joint compression
or compressing zone. In the joint compressiorl zone, the
refrigerant and solvent stream are brought into contact
with each other and the pressure on the refrigerant-
solvent is raised sufficiently to facilitate dissolving of
the refrigerant in the solvent in the mixer.
,
., .
,_.
~3~S5
Where the refrigerant and solvent streams leaving the
evaporator are placed in fluid communication with each
other to allow evolution of gases from the solvent stream,
and the two streams thereafter pass to a joint compressing
zone including a single compressor; the compressor may be
a rotary compressor, centrifugal compressor or rotary
screw compressor.
In still a further modification, refrigerant and
solvent streams leaving the evaporator may be brought into
contact in the compressing zone to form a combined
solvent refrigerant stream. The solvent-refrigerant
stream leaving the compressing zone and passing to the
mixer may then be placed in heat exchange relation with
the stream of solution leaving the mixer prior to passage
of the stream of solution to the economizing zone. It is
believed that the temperature of the combined solvent-
refrigerant stream preferably approaches the temperature
of the mixer just prior to entering the mixer.
In another embodiment the mass transfer of gaseous
refrigerant is accomplished by passing a portion of the
refrigerant stream leaving the compression zone to the
stream of solution in the economizing zone, whereby the
percentage of refrigerant in the solution stream is
increased.
In a more detailed endowment, there may be provided
a chemically assisted mechanical refrigeration process
including several steps. A stream of solution including a
solvent and a liquefied refrigerant is passed to an
evaporator. The refrigerant and solvent have a negative
deviation from Roulettes Law when in combination. The
pressure is then reduced over the solution to allow
refrigerant to vaporize and separate from the solvent
while concurrently therewith the evolving refrigerant and
~33~SS
solvent are put in heat exchange relation with a working
medium to remove energy from the working medium and
thereby for a solvent stream and a refrigerant stream
leaving the evaporator. The refrigerant stream includes
gaseous refrigerant. The solvent stream leaving the
evaporator is then passed in heat exchange relation with
the solution stream passing to the evaporator in an
economizing zone so as to cause transfer of heat between
the solvent stream and the solution. Concurrently there-
with, the solvent and refrigerant streams are put in fluid communication with each other so as to accomplish mass
transfer of gaseous refrigerant from the solvent stream to
the refrigerant stream and so facilitate heat transfer in
the economizing zone between the solvent and solution
streams. The solvent and refrigerant streams are subset
quaintly contacted in a joint compressing zone where the
pressure over both streams is raised to form a combined
solvent-refrigerant stream. The combined solvent-refrig-
errant stream is then passed to a mixer under a pressure
sufficient to promote substantial dissolving of the
refrigerant in the solvent to form the stream of solution
for passage to the evaporator. As the mixer is in heat
exchange relation with a working medium, energy is removed
from the mixer.
In another embodiment, the vaporized refrigerant may
be compressed by passing a high velocity liquid jet of
solvent into the refrigerant. A portion of the refrig-
errant may also be passed to a generator-absorber pair
prior to entering the mixer.
There is also provided in accordance with the present
invention a chemically assisted mechanical refrigeration
apparatus including a mechanical compressor for come
pressing a refrigerant and a mixing zone including a mixer for receiving a solvent and the compressed refrigerant at
I I
a pressure sufficient to promote substantial solution of
the refrigerant in the solvent and form a solvent-refrig-
errant stream. There is also provided an evaporator zone
including or consisting of an evaporator for receiving the
refrigerant-solvent stream from the mixer and ultimately
returning the refrigerant to the mixer after allowing at
least a substantial portion of the refrigerant to separate
from the solvent and absorb heats of vaporization and
dissolution from a working medium, which medium is in heat
lo exchange relation with the evolving refrigerant-solvent.
There may also be provided an economizing zone for
placing the solvent passing from the evaporator zone to
the mixing zone in heat exchange relation with the refrig-
erant-solvent stream passing from the mixer to the evapo-
rotor zone. For example, a heat exchanger including a
conduit for passage of solvent and a surface adjacent to
the conduit for receiving a thin film of solvent-refrig-
errant may be provided. There may also be provided an
injection mechanism for passing a portion of the come
pressed refrigerant directly into solution with the
refrigerant-solvent stream after the mixture passes from
the mixer as well as a heat exchanger for placing the
refrigerant-solvent stream leaving the mixer in heat
exchange relation with the solvent or both compressed
refrigerant and solvent entering the mixer.
Coils may be substantially immersed in liquid in the
evaporator for circulating the working medium or the
evaporator may comprise a shell and tube heat exchanger
arrangement. In some embodiments, the mechanical coy
presser may be a jet compressor adapted to use solvent
from the evaporator to compress the refrigerant leaving
the evaporator.
issue
In a more detailed embodiment, there may be provided
a chemically assisted mechanical refrigeration apparatus
including an evaporator zone for receiving a refrigerant-
solvent stream at a pressure sufficient to allow the
refrigerant to separate from the solvent and absorb a
substantial portion of the heats of vaporization and
dissolution of the solvent-refrigerant stream from a
working medium which is in heft exchange relation with the
evolving refrigerant-solvent combination. A compressor is
provided and adapted to accept a gaseous stream and a
liquid stream and raise the pressure of said streams upon
combination. A solvent conduit connects the evaporator
and the compressor to allow passage of solvent from the
evaporator to the compressor. A refrigerant conduit
connects the evaporator and the compressor for passage of
a gaseous refrigerant from the evaporator to the come
presser. the refrigerant conduit is in fluid communique-
lion with the solvent conduit such that the refrigerant
conduit may receive gases evolving from the solvent
passing through the solvent conduit. A solution conduit
having one end connected to the mixer and the other end
connected to the evaporator is also provided. The soul-
lion conduit is adapted to facilitate any reduction in
pressure between the mixer and the evaporator. An equine-
mixer is also provided for placing the solvent conduit and the solution conduit in heat exchange relation with each
other.
In a still more detailed embodiment, a second heat
exchanger is provided for placing the solution conduit and
a combined solvent-refrigerant conduit running from the
compressor to the mixer in heat exchange relation with
each other. In any case where refrigerant and solvent
are contacted in the compressor, the compressor may be a
rotary compressor, centrifugal compressor or rotary screw
35 compressor.
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Various embodiments will now be described by way of example
with respect to the drawings.
Fig. 1 is a schematic view of a chemically assisted
mechanical refrigeration cycle.
Fig. 2 is a schematic view of another embodiment of the
chemically assisted mechanical refrigeration cycle.
Fig. 3 is a schematic view of an evaporator for use in the
embodiments shown in Figs. ], 2 and 4; and
Fig. 4 is a schematic view of yet another embodiment of the
present invention.
There follows a detailed description of certain embodiments
of the present invention, including those presently preferred, in
conjunction with the foregoing drawings. This description is to
be taken by way of illustration rather than limitation.
Detailed description of Preferred Embodiments
Referring now to Figure 1, there is shown a schematic
view of a chemically assisted mechanical refrigeration cycle.
An appropriate solvent-refrigerant stream preferably having
the refrigerant totally in solution is introduced into
evaporator 10 from line 21. As will hereinafter be more
fully described, refrigerant vaporizes and separates from solvent
under the operating conditions in the evaporator 10, such
that heats of dissolution and vaporization are transferred from
a working medium, such as water, circulating in conduit
22. A solvent stream leaves as a liquid and
is pumped by solvent pump 13 via line 19
to mixer-condenser 11, while a refrigerant stream of
vaporized refrigerant leaves the evaporator via line 18 and
through normally open valve 76 to be compressed in
compressor 12 before being transferred to mixer 11 via
.;
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line 14. Valves 71 and 74 are operated to prevent any
flow from occurring in lines 72 and 73, respectively.
Similarly, valve 81 prevents flow through line 82.
At the operating conditions of the mixer 11 the row
compressed refrigerant is dissolved into the solvent
entering the mixer from line 19. Heats of mixing and
condensation are withdrawn from the condenser-mixer 11 via
a working medium in line 23. There is thus formed a
solvent-refrigerant stream.
The solvent-refri~erant stream passes via line 15
through expansion valve 16 where it is reduced in pressure
before entering evaporator 10 via line 21.
The evaporator-effervescer lo is so constructed as to
allow substantial transfer of both the heat of vaporize-
lion and the heat of disassociation from the working fluid
circulating through line 22. As efficient heat transfer
is promoted through the use of a wetted heat transfer
surface, the heat transfer surface may preferably be
wetted by the solvent with or without dissolved refrig-
errant. Thus, in one embodiment the refrigerant-solvent
stream may be passed as a thin film over a heat transfer
surface with embedded coils containing the working fluid.
In another embodiment shown in Fig. 3 a working
fluid, such as chilled water, is passed via line 22
through the shell side of a shell and tube type heat
exchanger while the refrigerant-solvent stream entering
from line 21 passes through the tube side. The refrig-
errant separates from the solvent in the tubes and both
solvent and refrigerant pass to a li~uid-vapor separator
31 where the solvent and refrigerant are separated. The
liguid-vapor separator 31 may be equipped with a wire mesh
I
32 to catch entrained droplets which collect below wire
mesh 32. The solvent passes via line 33 to pump 13 while
the refrigerant passes via line 18 to compressor 12.
In another embodiment, the conduit 22 is sub Stan-
tidally immersed in liquid in the evaporator. As the
refrigerant-solvent stream enters the evaporator the
refrigerant substantially disassociates and boils off from
the solvent, thus cooling the working fluid. In such an
embodiment the evaporator may be similar in construction
to a shell and tube heat exchanger wherein the working
medium circulates through thy tubes, which are sub Stan-
tidally immersed in liquid.
Alternately, the working medium may pass through a
coil, which passes through the lower portion of the
evaporator and so is substantially immersed in liquid. By
way of example, the refrigerant solvent stream may circus
late and undergo separation in a single-tube coil of 1/2'
diameter for a one to four ton apparatus and then further
separate in a liquid-vapor separator.
As would be known to one skilled in the art having
the benefit of this disclosure, the evaporator may come
prose any one of several modified heat exchangers or evaporators.
Where it is desirable to facilitate the separation of
the vaporized refrigerant from solvent an eliminator may
be employed at the vapor outlet of the evaporator if the
vapor and liquid separate into two streams in the evapo-
rotor. This may be particularly appropriate when the
refrigerant is passed separately from the solvent to a
mechanical compressor.
r q
to
The compressor may be any one of several mechanical
types. Regardless of the type of compressor used, in
keeping with the spirit of the present invention, its
operating cost should generally be less than that of its
counterpart in a typical vapor compression refrigeration
system for a given application. This is possible due to
the increased efficiency of the present system. This
increased efficiency over prior mechanical vapor compress
soon cycles is believed to result in part from the fact
that the volubility of the refrigerant in the solvent
reduces the level of required mechanical compression. The
refrigerant need only be pressurized sufficiently to
dissolve in the solvent in the condenser at the given
operating conditions and concentrations. There is
believed to be little or no wasted compression of the
refrigerant to pressurize it sufficiently to condense at
the condenser temperature as in the usual vapor compress
soon cycle. additionally, since the refrigerant is at a
lower temperature as it leaves the mixer than in the case
of a pure refrigerant cycle, less heat transfer is
required and hence less working fluid need be circulated
to the mixer.
The compressor chosen may vary with operating condo-
lions, the refrigerant-solvent combination chosen or the
application to which the system is applied. For example,
for the embodiments shown in Figures 1 and 2, a centric-
gal, rotary or screw compressor may be preferred since
the gas refrigerant passing through line 18 may still have
some entrained liquid despite the use of an eliminator at
the outlet of the evaporator 10. Alternately, for the
embodiment shown in Figure where the refrigerant and
solvent streams leaving the evaporator are placed in fluid
communication with each other to allow evolution of gases
from the solvent stream, and the two streams thereafter
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I
pass to a single compressor, the compressor may be a
rotary compressor, centrifugal compressor or rotary screw
compressor.
Where a solvent pump is to be used, as for example in
the embodiments set out in figures l and 2, the solvent
pump 13 may be any type suitable to pump the liquid
solvent to the mixer under the operating conditions of the
system. A centrifugal pump may be preferred due to its
simplicity, low first cost, uniform non pulsating flow, low
maintenance expense, quiet operation and adaptability to
use with either a motor or a turbine drive. On the other
hand, a positive displacement pump such as a rotary, screw
or gear pump may be preferred.
Keeping in mind the difference in pressure between
the evaporator 10 and the mixer 11, the mixer may be of a
design similar to that of the evaporator, such that the
system may serve as a heater as well as a refrigerator.
The refrigerant-solvent combination comprises at
least two constituents - a refrigerant and a solvent. The
refrigerant and solvent are chosen such that the refrig-
errant will separate as a gas from the solvent under the
operating conditions in the evaporator while preferably
absorbing substantial amounts of the heats of demising,
dilution, or disassociation as well as vaporization.
Thus, a governing principle for the selection of a refrig-
erant-solvent combination is that the refrigerant be
highly soluble in the solvent, such that the pair exhibits
negative deviations from Roulettes Law.
Examples of refrigerants which are believed to be
suitable for use in the present invention with appropriate
solvents include hydrocarbons such as methane, ethanes
ethylene and propane; halogenated hydrocarbons, such as
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refrigerants R20, R21, R22, R23~ R30, R32, R40, R41, R161
and Roy; amine, including methyl amine, or gases used
in certain refrigeration processes such as methyl
chloride, sulfur dioxide, ammonia, carbon monoxide and
carbon dioxide or any appropriate combinations of these.
The solvent constituent should be a substantially
non-volatile liquid at the operating conditions of the
cycle or be at least such when in solution with a portion
of the refrigerant. Thus, the solvent, for example,
nitrous oxide, can be a gas at room temperature.
It is believed that the solvent may be an ether, an
ester, an aside, an amine or polymeric derivatives of
these, for example, dim ethyl formamide and dim ethyl ether
of tetraethylene glycol as well as halogenated hydra-
carbons, such as carbon tetrachloride and dichlorethylene;
or appropriate combinations of these. A halogenated salt
such as lithium bromide may also be a constituent of the
solvent.
Also believed to be suitable as solvents are
methanol, ethanol, acetone, chloroform and trichloro-
ethanes Organic physical solvents such as propylene
carbonate and sulfolane or other organic liquids contain-
in combined oxygen may be used.
Relatively large deviations from Roulettes Law and
hence relatively large heats of mixing are obtained when
one, or preferably both, of the refrigerant and solvent
molecules is polar. The excess volubility is believed to
be a consequence of either dipole-dipole attraction
(including hydrogen bonding) or induced dipole-dipole
attraction.
~33~ to
Alternately, limited experimental data and calculi
lions indicate that certain combinations of refrigerant
and solvent may not have a satisfactory coefficient of
performance Thus, calculations on the embodiment shown
in Figure 4 indicate that a combination of carbon dioxide
and l,l,l-trichloroethane may not be very efficient. More
particularly, calculations generally paralleling those set
out below with respect to 1,1,1-trichloroethane and R22
with respect to Figure 4 resulted in a coefficient of
performance of 1.83 for assumed evaporator and mixer
temperatures of 5F. and 86F., respectively, and 1.49 for
assumed evaporator and mixer temperatures of 40F. and
110F. This may possibly be explained by the high
critical temperatures and pressures of carbon dioxide of
87.87F. and 1069.96 Asia, respectively.
It is believed that other chemical constituents may
be added to the basic pair for other purposes, including
foaming, lubrication, inhibition of corrosion, lowering of
the freezing point, raising of the boiling point or
indication of leaks. However, such added constituents
should preferably be chosen so as not substantially to
detract from the heat of disassociation or vaporization
produced in the evaporator. Further, the constituents are
preferably such as to not detract from any negative
deviations from Raoultls Law.
The comparative efficiency of the instant invention
is illustrated by reference to available data for a
refrigerant-solvent pair comprising CHClF2 (refrigerant
22) and dim ethyl formamide (DMF). According to an
enthalpy-concentration diagram disclosed in Jelinek, M.,
et at, Enthalpy - Concentration Diagram -- ASSYRIA.
Trans., 84 ~1978), Pi II, pp. 60-67,
an R22-DMF solution is in equilibrium at
56.8 prig and 86~F. with a weight distribution of 60% R22
,~,~ I,...
. _
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arid 40% DMF. If pressure is reduced sufficiently, the R22
will boil out of the DMF, absorbing a combined heat of
vaporization and heat of mixing of slightly more than 72
Bulb Alternatively, the heat of mixing can be cowlick-
fated from Equation (14) in Tyagi, UP teat of Mixing -
-, In. Jnl. of Tech., 14 (1976), pp. 167-169,
to be 19.33 Bulb while the heat of
vaporization of the R22 is 55.92 Btutlb~ of
solution. Thus, the total heat absorbed, per pound of
solution entering the evaporator, is 75.25 Bulb in
close agreement with the enthalpy-concentration diagram
mentioned above.
Although it may be preferable that the refrigerant-
solvent mixture or combination be chosen such that a
substantial amount of refrigerant vaporizes from solution
in the evaporator, this need not always be the case. For
example, a refrigerant with a comparatively high heat of
vaporization may be circulated in small proportions
relative to the amount of solvent when the refrigerant-
solvent leaving the mixer is placed in he-at exchange
relation with the solvent leaving the evaporator, as shall
hereinafter be more fully described in conjunction with
Figure 2.
In an alternative embodiment, the solvent leaving the
evaporator can be passed through an economizer or axle-
Mary heat exchanger. Unlike many prior systems, such as
described in U.S. Patent No. 3,277,659 issued to Sylvan,
there is no need to directly heat the suction vapor
passing to the compressor, thus reducing its density and
increasing the volume of gas handled by the compressor.
One form of this embodiment is illustrated in Figure
2. 'the operation of this embodiment is similar to that of
the embodiment shown in fig. 1. However, an economizer 26,
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which may be similar to a Baudelot cooler, is employed.
Additionally, lines 43 and 44 will usually be closed
unless the compressor is to be assisted by the absorber-
generator pair as shall hereinafter be more fully
described.
The refrigerant-solvent solution flows downward in a
film over surfaces in the economizer-heat exchanger 26.
These surfaces are chilled by cold solvent returning
through conduit 24 from the e~aporator-effervescer lo
lo The cooling cascading refrigerant-solvent may also be
bathed in the atmosphere of still cool refrigerant bled
by valve 79 from the compressor outlet through conduit 27.
Consequently, the heat of condensation as well as the heat
of mixing of additional refrigerant absorbed by the cooled
refrigerant-solvent stream is transferred to the cold
solvent circulating through the economizer. Alternatively,
valve 79 may be closed and exchanger 26 operated only as a
heat exchanger without any mixing occurring therein.
In operation the compressor 12 pumps and compresses
the refrigerant gas and pumps the compressed gas through
conduit 14, while valve 79 is opened and another portion
of the compressed gas is pumped through conduit 27. The
compressed gas going to the mixer if is mixed with the
solvent and the refrigerant-solvent stream is directed
through conduit 15 to the economizer 26 and expansion
valve 16. The refrigerant-solvent is then directed to the
evaporator lo as in Fig. l. The solvent from the evapo-
rotor is conducted via conduit 24 to the economizer 26 by
the solvent pump 13 for recycling through the system. The
compressor 12 draws or sucks vaporized refrigerant through
conduit 18 to complete the cycle. The efficiency of the
process may thus be enhanced through use of an economizer
to sub cool the refrigerant-solvent and increase the net
refrigerating effect of the solution. Valve 79 may be
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operated to regulate or prevent flow through line 27 such
that a specified portion or all of the compressed refrig-
errant passes to condenser-mixer 11.
The compressed gas leaving the compressor 12, via
conduit 14, may also be put in heat exchange relation with
the refrigerant-solvent stream leaving mixer 11 to sub cool
the latter it the operating temperature of the mixer 11 is
above that of the compressed gas in conduit 14. Thus, as
shown in Figure l, valves 81 and 83, which are normally
closed, ma be opened such that compressed refrigerant
passes via line 82 to heat exchanger 85 where it exchanges
heat with the solvent-refrigerant stream passing through
line 15. The compressed refrigerant then passes via line
84 to mixer 11 as already described.
In a presently preferred embodiment, there may be
provided a chemically assisted mechanical refrigeration
process including several steps. The refrigerant and
solvent have a negative deviation from Roulettes Law when
in combination. A stream of solution including a solvent
and a liquefied refrigerant is passed to an evaporator.
The pressure is then reduced over the solution to allow
refrigerant to vaporize and separate from the solvent
while concurrently therewith the evolving refrigerant and
solvent are put in heat exchange relation with a worming
medium to remove energy from the working medium and
thereby form a solvent stream and a refrigerant stream
leaving the evaporator. The refrigerant stream includes
gaseous refrigerant. The solvent stream leaving the
evaporator is then passed in heat exchange relation with
the solution stream passing to the evaporator in an
economizing Noah so as to cause transfer of heat between
the solvent stream and the solution. Concurrently there-
with, the solvent and refrigerant streams are put in fluidco~munication with each other so as to accomplish mass
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transfer of gaseous refrigerant from the solvent stream to
the refrigerant stream and so facilitate heat transfer in
the economizing zone between the solvent and solution
streams. The solvent and refrigerant streams are subset
quaintly contacted in a joint compression zone where the pressure over both streams is raised to form a combined
solvent-refrigerant stream. The combined solvent-refrig-
errant stream is then passed to a mixer under a pressure
sufficient to promote substantial dissolving of the
refrigerant in the solvent to form the stream of solution
for passage to the evaporator. As the mixer is in heat
exchange relation with a working medium, energy is removed
from the mixer.
Turning now to Figure 4, there will be described a
more specific embodiment of the presently preferred
embodiment. A solvent-liquified refrigerant stream is
passed via line 25 to evaporator 10. The refrigerant and
solvent of the solvent-liquified refrigerant stream have a
negative deviation from Roulettes Law and may be chosen
from a number of combinations of substances already
described. By way of example, a refrigerant-solvent
combination of R22-triechloroethane might be employed.
As essentially discussed in conjunction with the
embodiments shown in Figures 1 and 2, the pressure over
the solvent-refrigerant stream is reduced in the evapo-
rotor in order to allow refrigerant to vaporize and
separate from the solvent while concurrently placing the
evolving refrigerant and solvent in heat exchange relation
with the working medium to remove energy from the working
medium. As a result, there is formed a solvent stream
which passes via line 24 and the refrigerant stream
including gaseous refrigerant which passes via line 18.
20- ~3~6~
It is believed that the solvent stream passing via
line 24 may contain a material portion of refrigerant
without hindering the efficiency of the process. More
particularly, the solvent stream leaving the evaporator
and passing via line I is placed in heat exchange rota-
lion with thy solvent-refrigerant stream passing to the
evaporator via lines 15 and 25. Further, the solvent
stream in line 24 is placed in fluid communication with
the refrigerant stream of line 18 such that gaseous
refrigerant evolving from the solvent stream 24 may pass
via conduit 92 to refrigerant stream 18. This evolution
of gas tends to cool the solvent stream, thus facilitating
heat transfer in the economizer or economizing zone, which
in turn increases the temperature drop in the solvent-
refrigerant stream as it passes through the economizing zone. Put another way, any inefficiencies in the evapo-
rotor caused by a failure of the refrigerant to separate
from the solvent are believed diminished since the refrig-
errant is allowed to further evolve from the solvent and
the resulting change in energy is transferred indirectly
to the working medium passing through the evaporator by
virtue of the lowering of temperature of the solvent-
refrigerant stream as it enters the evaporator.
Both the solvent stream and the refrigerant stream
are then brought into contact in a joint compression zone
as illustrated by compressor 88 in Figure 4. The compress
soon of the refrigerant gas along with the liquid solvent
in a joint compression zone such as compressor 88 is
believed to provide several advantages. The liquid solvent
would generally have higher heat capacity than the
refrigerant and generally act as a coolant in the come
presser, thus reducing the amount of work required to
compress the refrigerant. Additionally, a liquid solvent
may be chosen which acts both as a sealant and lubricant
as well as a coolant. Thus, when a refrigerant gas is
,,
-21-
compressed and the solvent pumped simultaneously by a single
compressor-pump, such as compressor 88 in the joint compression
zone, several advantages can accrue. For example, the solvent
provides internal cooling of the overall apparatus, thus
permitting compression which is more polytropic than isentropic
and hence generally more economical. Additionally, it is
believed that the presence of the solvent in the compressor
permits higher pressures in the case of a centrifugal compressor,
or serves as a lubricant and sealant in case of a rotary
compressor.
The resulting combined solvent-refrigerant stream flows via
line 90 through a heat exchanger such as pricklier 86 and into
mixer 11. Although optional, the heat exchanger or pricklier 86
serves to further raise the temperature of the solvent-
refrigerant combination passing to mixer 11 while concurrently beginning to cool the refrigerant-solvent stream passing via line
lo toward economizer 26. The heat exchanger, such as pricklier
86, should be operated so as to allow the temperature of the
solvent-refrigerant combination stream entering mixer 11 to
approach as closely as possible the temperature of mixer 11
without exceeding the same. Additionally, the pricklier should
be operated in such a fashion that the temperature of the
solvent-refrigerant combination passing via line 90 is such that
the refrigerant will not start to substantially dissolve and give
off heat prior to reaching the mixer 11.
As already substantially described with respect to Figures 1
and 2, in the mixer 11 the combined solvent-refrigerant
stream is maintained at a pressure sufficient for the given
temperature to promote substantial dissolving of the refrigerant
in the solvent to form the stream of solution
for passage to the evaporator 10 via lines 15
~3;~g~5~
and 25. Concurrently therewith, the mixer is in heat
exchange relation with a working medium which removes
energy or heat given off by the dissolving and condensing
refrigerant in the mixer 11.
The operation of the embodiment shown in Figure 4 is
further highlighted by the various temperatures shown in
the drawing, all of which are in degrees arrant. These
temperatures were calculated based on the following
presumptions. It is presumed that a cycle using R22 as a
refrigerant and 1,1,1-trichloroethane (TOE) as a solvent
was employed with an evaporator temperature of 40F. and a
mixer temperature of 110F. Based on the resulting
calculations from heat balances, it is believed that if
the pricklier is not present, the theoretical coefficient
of performance of the system would be 6.71, which compares
favorably with 5.75 for a pure R22 vapor compression cycle
generally used in prior art systems. However, if a heat
exchanger such as pricklier 86 is present, the refrig-
erant-solvent combination may be used to cool the refrig-
errant solvent stream exiting the mixer. Since this
combination passing via line 90 is at mixer pressure as it
enters the mixer, kit below mixer temperature as it begins
its passage through heat exchanger 86, it is assumed that
solution of refrigerant into solvent will have begun in
the pricklier 86. With R22 as a refrigerant and ill
trichloroethane as the solvent at the temperatures shown,
a theoretical maximum of only half the heat exchange
theoretically available for inert liquids is available,
and the resultant theoretical coefficient of performance
is 7.13 (The theoretical maximum coefficient of perform
mange for a perfect (Cannot) cycle is 7.14.)
The results of these calculations in comparison with
a pure ~22 vapor compression cycle, are set forth in Table
1. Various data necessary to the calculations, vapor
-23-
I
densities, discharge temperatures of isentropic compress
soon to determine polytropic discharge temperatures and so
forth were taken from American Society of Heating, Refrig-
crating and Air Conditioning Engineers, Thermophvsical
Properties of Refrigerants, 1976 and American Society of
Heating, Refrigerating and Air Conditioning Engineers,
Thermodynamic Properties of Refrigerants, 1980. Where
extrapolations had been made, it is believed that they
were generally made in the direction of conservative
estimates with respect to cycle performance.
Based on one pound of circulating mass and R22-TCE
cycle with an evaporator temperature of 40F. and a mixer
temperature of 110F., at 110F. and 94.7 Asia, 0.684 lobs.
of TOE is in equilibrium in a liquid solution with .316
lobs. of R22. At 40F. and 24.7 Asia, .262 lobs. of R22
vaporizes, leaving .054 lobs. of R22 remaining in solution.
Enthalpy measurements indicate the evolving R22 absorbs
22.65 But as a gross refrigerating effect in the
evaporator.
-24- I
TABLE: 1
Table 1: Comparison of theoretical cycles for 1 ton
capacity between 40 and 110.
R22 R22/TCE
Mass 1.18 lb 13.49 lb=4.26 lb R22 + 9.23 lb TOE
10 Gas 2.0 ft3 10.4 ft3 R22(+ .82 gal TOE)
Compression
ratio 2.88 3.83
High side
pressure 241 Asia 95 Asia
15 Low side
pressure 84 Asia 25 Asia
Pressure
differential 157 psi 70 psi
Horsepower
required .82 .66
COP 5.75 7.13
Forts
25 Gas density .41 loft
Solvent density 84.0 lb/ft3
Gas/liquid volume ratio 95/l
Gas/liquid mass ratio .47/l
-25-
Assuming perfect heat exchange and equal exit temperatures
of 69.6F., the remaining .054 lobs. of R22 should vaporize in the
economizer as the solvent entering in at 40F. flows
countercurrent -to the incoming refrigerant laden solution streams
in lines 15 and 25. The exit temperature in both cases is
approximately 70F. A temperature closer to 71F. is attained if
pricklier 86 is not employed while an exit temperature in each
case of about 69.64F. is reached where pricklier 86 is used.
The .684 lobs. of TOE, with a specific heat of .258, enters
the compressor at 70.93F., absent pricklier 84, or 69.64F. with
pricklier 86 between -the compressor 88 and mixer 11 and the
entering temperature of the .36 lobs. of R22 including warmer than
40F. gas from the economizing zone is calculated as 42.62F.,
absent the pricklier 86, or 42.5F. with the pricklier 86.
Isentropic compression of the gas alone would give a discharge
temperature of 148F., so that the discharge temperature of the
liquid and gas is 100.51F., or in case pricklier I is used,
99.25F. With respect to Figure 4 and the above temperatures,
the temperatures shown in brackets are those absent the pricklier
I
The value of n, the constant of polytropic compression is
determined from
n - 1
Tl/T2 = (Plop) - , where To = 502.62R, To = 560.51R, P
24.7 x 144 psf and Pi = I 7 x 144 psf. n = 1.09.
The work of compression in But, (P2V2-P1Vl)/J(l-n) is
2.05 But per .316 lb R22 vaporized. Al and
V2 are taken from the superheat tables of [American
Society of Heating, Refrigerating and Air Conditioning Engineers,
Thermodynamic Properties of Refrigerants, 1980]. The density of
the stripped TOE leaving the economizer 26 is 83.98
lb/ft. , the pressure head across the 70 psi differential
I
-26-
is 120.42 ft., and the Tao of pumping .684 lb of TOE is
.106. Hence the total work of comprising the gas and
pumping the liquid is 2.16 Bulb of mixture.
Since the refrigerant-solvent solution, with a
specific heat of .264 must be sub cooled 30.~3, to 40 in
the evaporator, the net available refrigerating effect,
per pound of gas-liquid circulating mass is 14.~8 But,
absent the pricklier 86.
The coefficient of performance of the cycle is thus
6.71. Since the theoretical coefficient of performance of
the pure R22 cycle at these conditions is 5.75, the
embodiment shown in Figure 4 is believed to represent a
16.7% more efficient process than a comparable vapor
compression refrigeration cycle, presuming an additional
heat exchange such as pricklier 86 is not used.
The foregoing, except for initial references above,
neglects the fact that the liquid-compressed gas mixture
exiting the compressor is still cooler than the 110 mixer
and has the capacity to sub cool the refrigerant-solvent
solution exiting the mixer. If there were no absorption
of gas by liquid, hence no generation of heat, the pro-
cooler 86 would sub cool the condenser outflow to assuming the actual temperature reduction is only half
(110-105.62), the refrigerant-solvent solution flows to
the economizer 26 at a temperature of 107.81, instead of
110.
Iterating the previous calculations back through the
economizer and the compressor, it is believed all the R22
in the solvent stream in line 24 still comes out. the
work of compression-pumping becomes 2.08 But per pound of
-27-
circulating mass. Since the condenser effluent has been
cooled a bit, the available net refrigerating effect per
pound mass is 14 83 Tao.
The coefficient of performance is now 7.13, compared
with 6.71 without the pricklier 86 as compared to 5.75 for
pure R22. Since the theoretically perfect Cannot effi-
Chinese button and 110 is 7.14, it appears that the
pricklier provides an even greater efficiency, since 7.13
is about 25% better than 5.75.
A number of variations and substitutions to the
embodiments shown in the drawing are possible. By way of
example, it is believed that the embodiment in Figure 1
may be operated such that a portion of the solvent from
line 19 may be sprayed into the refrigerant stream in line
18 and so permit a centrifugal compressor to develop
; higher pressures, since the pressure developed by a
centrifugal pump is proportional to the product of density
of the medium being handled and the square of the tip
speed. Thus, much greater pressures can be developed for
a given centrifugal pump such that a smaller pump may be
used.
In another variation on the embodiment shown in
Figure 1, the pump type compressor 12 may be replaced with
a jet compressor. Thus, a high velocity liquid jet of
solvent supplied to the jet compressor by a portion of the
solvent from line 19 may be used to compress the refrig-
errant gas coming from the evaporator-effervescer 10. The
presence of a higher specific heat solvent is believed to
result in more efficient compression, due to the greater
heat capacity of a liquid. More particularly, the come
press ion becomes more nearly isothermal, hence more
efficient.
-28~
In another embodiment, the compressor 12 and solvent
pump 13 may both be replaced by a liquid ring compressor
which compresses the refrigerant gas, circulates the
solvent and initiates mixing of gas and solvent prior to
entry into mixer 11 through a single conduit. Compression
is understood to be more nearly isothermal and hence more
efficient.
For example, as shown in Figure 1, valve 76 may be
closed off and valve 71 and liquid ring compressor 77
operated such that both solvent and refrigerant pass from
evaporator 10 via line 72 to ring compressor 77. The
compressed mixture would then pass to mixer 11. my way of
example, the ring compressor 77 might be a double lobe
compressor manufactured by Nash Engineering Co. of South
Norwalk, Connecticut and described in that company's
Bulletin No. 474-C dated 1971. .
In yet another embodiment, the refrigerant may be
foamed with the solvent and solvent pump 13 could be
eliminated from the embodiment shown in Figure 1. Both
refrigerant and solvent would be circulated from evapo
rotor 10 to the compressor 12 and hence to mixer 11.
Similarly, the embodiment shown in Figure 2 may also be
modified. For example, the solvent pump 13 may be
replaced with a device to inject the compressed refrig-
errant gas from conduit 14 into the solvent stream in
conduit 24, thus propelling both refrigerant gas and
solvent liquid to condenser-mixer 11. Also, as shown in
Figure 1, valves 71 and 74 may be operated so as to allow
at least a portion of solvent to bypass solvent pump 13
while valve 74 is operated to allow a sufficient amount of
vapor to pass from line 14 into line 72 via line 73.
~Z333~
The present invention may also be used in conjunction
with other systems. For example, a g~nerator-absorber
pair might be hooked up in tandem with the compressor to
provide a back-up for the same. The generator could
function off a secondary source of heat, such as from an
exhaust, or a form of solar energy. For example, as shown
in Figure 2, valves 41 and 42 could be placed on both
sides of compressor 12 in lines 18 and 14 to hook a
generator-absorber pair 48, 44 into the system. A portion
of the vaporized refrigerant could then pass from line 18
via line 43 to the absorber, absorbed in an appropriate
secondary solvent and then be pumped in solution by pump
46 through lines 45 and 47 to the generator 48. Upon
evaporation ox the refrigerant in the generator 48 the now
compressed vapor could be passed via line 49, valve 42 and
line 14 to the mixer 11, while secondary solvent was
returned to the absorber 44, via line 50.
The secondary solvent may be the same as used in the
I primary system.
Of course, in order to obtain all of the advantages
of the present invention, the generator-absorber pair
should not be completely substituted for the compressor
12. Rather, the generator-absorber pair and the motion-
teal compressor are complementary means of generating
pressurized refrigerant gas.
Further, with respect to the Figure 4 embodiment, as
would be known to one skilled in the art having the
benefit of this disclosure, there exist a number of
alternatives for concurrent compression-pumping of the gas
and liquid constituents. For example, large multi-stage
centrifugal compressors as manufactured by York, ire-
quaintly are designed to inject liquid refrigerant into the vapor stream as a substitute for flash inter cooling
I 336~
between stages. However, in such a case, the liquid flow
rate should be as reasonably uniform as possible. Also,
helical or rotary screw compressors, such as manufactured
by Dunham-Bush may be adapted for use with the chemically
assisted mechanical refrigeration system as disclosed
herein. However, in the chemically assisted mechanical
refrigeration system, the solvent should preferably serve
as a coolant, lubricant and sealant. Further, bulky oil
separators and oil coolers should be eliminated since the
lo solvent passes on to the mixer with the compressed gas.
For smaller capacities, the Winkle type compressor,
manufactured by Ogre Clutch of Japan, or the rolling
piston compressors of Rhetorics (Fedders) and Mitsubishi may
prove useful. Possibly useful also is the multistage
centrifugal compressor-pump of the type manufactured by
Sue. In this device, a gas-liquid mixture enters a
first, closed impeller axially and the denser liquid is
thrown to the periphery. The lighter gas is ported off to
the second and subsequent stages nearer the center of the
chamber and both gas and liquid are then carried together
through second and subsequent impeller stages.
Alternately, where an economizer is used and where
capital costs permit, a turbine may be installed in the
refrigerant-solvent stream between the economizer and
evaporator to function as a pressure reducing device,
supplementing throttling devices. Under appropriate
operating conditions, it is believed that a sub cooled
stream exiting the economizer is least likely to flash
refrigerant gas at this point and the resultant shaft work
may be used to power booster pumps, compressors for the
system, auxiliary fans or the like.
-31- ~336~
Additional items of equipment may be employed within
the framework of the present invention. For example,
control of the system as well as system versatility may be
enhanced through the use of appropriate process controls,
though the use of essentially manual control devices may
suffice for many operations. Additionally, in the embody-
mint shown in Figure 4, a low pressure drop mixing of
gaseous refrigerant and liquid could be achieved by using
an incline motionless mixer such as one offered by the
Mixing Equipment Co., Inc. of Avon, New York.
Further modifications and alternative embodiments of
the apparatus and method of this invention will be
apparent to those skilled in the art in view of this
description. Accordingly, this description is to be
construed as illustrative only and is for the purpose of
teaching those skilled in the art the manner of carrying
out the invention. It is to be understood that the forms
of the invention herewith shown and described are to be
taken as the presently preferred embodiments. Various
changes may be made in the size, shape and arrangement of
parts. For example, equivalent elements or materials may
be substituted for those illustrated and described herein,
parts may be reversed, and certain features of the invent
lion may be utilized independently of the use of other features. All this would be apparent to one skilled in
the art after having the benefit of this description of
the invention.
~L~33~5~
-32-
SUPPLEMENTARY DISCLOSURE
Various embodiments have been set forth previously herein
with respect to my invention.
In another modification of the invention, a mixing zone may
be provided, including a mixer, a liquid-pumping zone and a gas-
compressing zone. In the liquid-pumping zone, the pressure on
the liquid solvent stream is raised sufficiently to facilitate
dissolving of the refrigerant in the solvent in the mixer. In
the gas-compressing zone, the pressure on the gaseous refrigerant
is likewise raised sufficiently to facilitate dissolving of the
refrigerant in the solvent in the mixer. Furthermore, the
solvent stream, either before or after passing through the
pumping zone, is passed in heat exchange relationship, but not in
fluid communication, with the refrigerant stream in the gas-
compressing zone.
The heat exchange between the liquid solvent stream and the gaseous refrigerant stream in the gas-compressing zone may be
accomplished by a solvent stream cooling jacket around any of the
various compressors which may be used to compress the gaseous
refrigerant.
More particularly, there may be provided a chemically
assisted mechanical refrigeration process including several
steps. A stream of solution including a solvent and a liquefied
refrigerant is passed to an evaporator. The refrigerant and
solvent have a negative deviation from Roulettes Law when in
combination. The pressure is then reduced over the solution to
allow refrigerant to vaporize and separate from the solvent wile
concurrently therewith the evolving refrigerant and solvent are
put in heat exchange relation with a working medium to remove
energy from the working medium and thereby form a solvent stream
and a refrigerant stream leaving the evaporator. The refrigerant
stream includes gaseous refrigerant. The solvent stream leaving
_,,.
33~5
-33-
the evaporator is -then passed in heat exchange relation with the
solution stream passing to the evaporator in an economizing zone
so as to cause transfer of heat between the solvent stream and
the solution. Concurrently therewith, the solvent and
refrigerant streams are put in fluid communication with each
other so as to accomplish mass transfer of gaseous refrigerant
from the solvent stream to the refrigerant stream and so
facilitate heat transfer in the economizing zone between the
solvent and solution streams. The solvent and refrigerant
streams are subsequently separately pressurized in liquid-pumping
and gas-compressing zones, with the solvent stream being put into
heat exchange relation, but not in contact, with the refrigerant
in the gas-compressing zone. The solvent and refrigerant streams
are then passed to a mixer under a common pressure sufficient to
promote substantial dissolving of the refrigerant in the solvent
to form the stream of solution for passage to the evaporator. As
the mixer is in heat exchange relation with a working medium,
energy is removed from the mixer.
Furthermore, in a still more detailed embodiment of the one
described immediately above, that portion of the solvent stream
passing from the evaporator to the mixer may be put in heat
exchange relation, either before or after passage through the
liquid-pumping zone, with the solution stream passing from the
mixer to the said economizing zone.
Still further, there may be provided a chemically assisted
mechanical refrigeration apparatus including an evaporator zone
for receiving a refrigerant solvent stream at a pressure
sufficient to allow the refrigerant to separate from the solvent
and absorb a substantial portion of the heats of vaporization and
of dissolution of the solvent-refrigerant stream from a working
medium which is in heat exchange relation with the evolving
refrigerant-solvent combination. A compressor and a pump are
provided and adapted to accept a gaseous stream of refrigerant
and a liquid stream of solvent, respectively, and to raise the
;:
~23;~
I
pressures of said streams. A first solvent conduit connects the
evaporator and the pump to allow passage of solvent from the
evaporator to the pump. This first solvent conduit is adapted to
permit heat exchange between the solvent stream and the gaseous
refrigerant stream in the compressor. A first refrigerant
conduit connects the evaporator and the compressor for passage of
a gaseous refrigerant from the evaporator to the compressor.
This first refrigerant conduit is in fluid communication with
said first solvent conduit such that this first refrigerant
conduit may receive gases evolving from the solvent passing
through said first solvent conduit. Second refrigerant and
solvent conduits conduct the refrigerant and solvent streams from
compressor and pump, respectively, to the mixer. A solution
conduit having one end connected to the mixer and the other end
connected to the evaporator is also provided. The solution
conduit is adapted to facilitate any reduction in pressure
between the mixer and the evaporator. An economizer is also
provided for placing said first solvent conduit and the solution
conduit in heat exchange relation with each other.
Another more detailed embodiment differs from the one
immediately preceding only in that the first solvent conduit
between evaporator and pump is not adapted for heat exchange at
the compressor, whereas the second solvent conduit connecting the
pump and the mixer is adapted for heat exchange relationship with
the solution conduit.
In all such cases where refrigerant and solvent are
contacted in the compressor, the compressor may be a rotary
compressor, centrifugal compressor or screw compressor.
Figures pa and 5b schematically diagram other embodiments.
With reference to the embodiment schematically diagramed in
Figure pa, a solvent-liquid refrigerant stream is passed via line
25 to evaporator 10. As essentially discussed in conjunction
with embodiments of Figures 1 - 4, the refrigerant and solvent of
the solvent-li~uified refrigerant stream exhibit negative
:~33~5~
deviations prom Roulettes Law. Likewise, -the pressure over the
solvent-liquified refrigerant stream is reduced, by pressure
reducing valve 16, to allow refrigerant to vaporize and separate
from the solvent in evaporator 10. The evolving mixture is
placed, in the evaporator, in heat exchange relation with a
working medium from which it removes heat. As a result, there
are formed a solvent stream, which passes via line 24, and a
refrigerant stream including gaseous refrigerant, which passes
via line 18, exiting evaporator 10.
It is believed that the solvent stream passing via line 24
may contain a material portion of refrigerant without hindering
efficiency of the process. More particularly, the solvent stream
leaving the evaporator 10 and passing via line 24 is place in
heat exchange relation with the solvent-refrigerant stream
passing to the evaporator via lines 15 and 25. Further, the
solvent stream in line I is placed in fluid communication with
the refrigerant stream of line 18 such that gaseous refrigerant
evolving from the solvent stream 24 may pass via line 92 to
refrigerant stream 18. This evolution of gas tends to cool the
solvent stream, thus facilitating heat transfer in the economizer
or economizing zone 26. This in turn increases the temperature
drop, over what might otherwise be expected, in the solvent-
liquefied refrigerant stream as it passes through the economizing
zone, and hence increases the available refrigerating effect in
the evaporator.
The refrigerant stream is carried via line 18, as augmented
by flow from line 92, to compressor 88. In the compressor, the
gaseous refrigerant is pressurized sufficiently to dissolve into
the solvent stream in the mixing zone or mixer 11 at the
operating temperature of thy mixer, while concurrently giving up
heats of vaporization and of mixing to a working medium placed in
heat exchange relation with the combined refrigerant and solvent
streams. The pressurized gaseous refrigerant is passed from
compressor 88 via line 91 to mixer 11.
~33~
-36-
The solvent stream, stripped of a substantial portion of its
remaining dissolved refrigerant in the economizer 26, and, having
passed that portion of refrigerant mass to the refrigerant stream
via line 92, is put in heat exchange relation with the
refrigerant gas being compressed in the compressing zone 87.
Heat exchange in compressing zone 87 may be accomplished by
substantially enclosing compressor 88 in a cooling jacket through
which the solvent stream, line 24, flows. It is believed that,
by cooling the compression of the gaseous refrigerant with the
solvent stream from the economizer, polytropic rather than
isentropic compression occurs, resulting in a reduced work of
compression and improved cycle efficiency.
From compressing zone 87, the solvent stream passes via line
93 to solvent pump 13 wherein it is raised in pressure to a level
as nearly as possible equaling that of the pressurized gaseous
refrigerant in line 91.
It is believed that the temperature of the solvent stream
exiting the solvent pump in line 94 will generally be less than,
or at most equal to, that of the solvent-liquified refrigerant
solution in line 15. Hence, the solvent stream in line 94 is put
in heat exchange relation, in heat exchanger or pricklier 86,
with the solvent-liquified refrigerant solution stream of line
15. The purpose of the heat exchange is to sub cool the solution
stream leaving the mixer 11 and thus to increase the available
refrigerating effect in the evaporator.
The compressed gaseous refrigerant stream of line 91 and the
pumped solvent stream of line 94 meet and are mixed in mixing
zone or mixer 11. The mass of gaseous refrigerant and the mass
of liquid solvent combine to form a liquefied refrigerant-solvent
solution in the mixer. The heats of condensation and of mixing
released in the formation of this solution are then transferred
to a working medium with which the refrigerant and solvent masses
are in heat exchange relation.
_, . .
~L~3~5
-37-
The circulating refrigerant-solvent solution then passes in
line 15 through heat exchanges 86 and 26, being sub cooled at each
stage, to pressure-reducing valve 16 and evaporator 10. The flow
process is then repeated.
By way of example for this embodiment, a refrigerant-solvent
combination of R22-trichloroethane (TOE) might be employed. The
operation of the embodiment indicated in Figure 5 is highlighted
by the various temperatures shown in the drawing, ail of which
are in degrees Fahrenheit. I-t is presumed that a cycle using R22
as refrigerant and TOE as a solvent was employed. As in the case
of the embodiment pictured in Figure 4, cycle calculations are
based on one pound of circulating mass, with mixer temperature
and pressure of 110F. and 94.7 Asia, respectively, and
evaporator temperature and pressure of 40F. and 24.7 Asia,
respectively.
At mixer conditions, 0.684 lb of TOE is in equilibrium in a
liquid solution with 0.316 lb of R22. At evaporator conditions,
0.262 lb of R22 vaporizes from the original pound of solution.
Enthalpy measurements indicate the evolving R22 absorbs 22.65
But as gross refrigerating effect in the evaporator.
Assuming perfect heat exchange and equal exit temperatures
of 72.2F., substantially all of the remaining 0.054 lb of R22
should vaporize in the economizer 26 as the solvent entering at
40.0 flows countercurrent to the incoming refrigerant-laden
US solution stream in line 15. The exit temperature from economizer
26 is 72.2F., due in part to the evolution of refrigerant gas
from the solvent stream of line 24. The 0.684 lb of TOE, with a
specific heat of .258, enters heat exchanger-cooling jacket 87 at
70.9, and the entering temperature of the 0.262 lb of R22,
including warmer than 40 gas from the economizing zone, is
calculated as 42.7F. Isentropic compression of the gas in
compression zone 88 would give a discharge temperature of 148F.,
so that the discharge temperature of the polytropically
, .
issue
-38-
compressed gas in line 91 and heated solvent exiting the cooling jacket in line 93 is 99.8~. The value of n, the constant of
polytropic compression, is determined from:
no
To n J ,
To Pi J
Where To = 502.735 R, To = 559.813 R, Pi = 24.7 x 144 psfa and
Pi = 94-7 x 144 psfa, the number n = 1.087.
The work of compression in But, (P2V2 - PlVl), is 2.00
Jon
per 0.316 lb of R22 vaporized. (Reference values of Al, V2,
etc., are as previously cited.)
The density of the stripped TOE leaving economizer 26 is
83.98 loft , the pressure head across the 70 psi pressure
differential is 120.~2 it and the But of pumping, via solvent
pump 13, the 0.684 lb of TOE is 0.106. Hence the total work of
compressing the gas and pumping the liquid is 2.11 Bulb of
solution.
The 0.684 lb of TOE at 100.5F. next flows from solvent pump
13, via line 94 to heat exchanger-precooler 86, where it is put
in countercurrent heat exchange relation with one pound of
solution at 110F., and having a specific heat of .264. The exit
temperature of both streams is 106.8F.
Since the temperature of the refrigerant-solvent solution,
in line 15, at the entrance to the economizer has been reduced, a
new exit temperature for the solvent stream, line 24, and the
solution stream, Join 25, is calculated as 70.3F.
Sub cooling to 40F. at the pressure reducing or throttling
valve 16 by vaporizing refrigerant leaves 1.4.38 But per pound of
solution as net refrigerating effect in the evaporator 10. The
;33~
-39-
coefficient of performance, 14.38/2.11 is 6.82.
A variation on the schematically diagramed embodiment of
Figure pa would be to eliminate heat exchanger, pricklier 86 as
shown in Figure 5b~ Further in either embodiment, it will be
appreciated that solvent pump 13 could be effectively located
between the economizer 26 and the heat exchanger cooping jacket
87. (See Figure 5b.) This is particularly appropriate when
there is no heat exchanger - pricklier 86 in the system.
Other variations and modifications of the apparatus and
method will be apparent to those skilled in the art in view of
this description. Various changes may be made in the size, shape
and arrangement of parts. For example, equivalent elements or
materials may be substituted for those illustrated and described
herein, parts may be reversed, and certain features of the
invention may be utilized independently of the use of other
features. All this would be apparent to one skilled in the art
after having the benefit of this description of the invention.
