Abstrict A liquid glycol enhanced with a polymer-salt solution such as a
desiccant in an air pre-conditioner system with a heat-pipe having
its heat absorber section in an outside air inlet duct following
water vapor adsorption into the desiccant by a contacter section
of a dehumidifier, the heat-pipe having its heat rejecter section
in an exhaust air duct and preferably preceeding water vapor discharge
from the desiccant by a regenerater section of the dehumidifier,
a desuperheater for efficient refrigerant compression, a reflux
boiler for desiccant regeneration, and a glycol interchanger recovery
system for desiccant recovery.
Claims I claim:
1. An air dehumidifying desiccant recovery system having an outside
air inlet duct, a conditioned air supply duct into a conditioned
space, a return air duct from said conditioned space and a relief
exhaust air duct exhausting return air displaced by outside air
and with blower means to transport said outside, supply, return
and relief air, and including;
a heat-pipe means having a heat absorber section in the inlet duct
and forming a contacter to remove the heat of adsorption by dehumidifying
the inlet air, and a heat rejecter section in the relief exhaust
air duct for discharging heat into exhaust relief air flow therethrough,
a water adsorptive liquid glycol base desiccant and spray bar means
applying the same to the heat absorber section-contacter of the
heat-pipe means for interface contact with incoming outside air
to absorb water vapor therefrom,
and desiccant regenerater means external of said air ducts and
receiving weakened liquid glycol desiccant from said heat absorber
section-contacter of the heat-pipe means, and comprised of a heat
source means applying heat to the weakened liquid glycol base desiccant
to remove water therefrom and discharge said water.
2. The air dehumidifying desiccant recovery system as set forth
in claim 1 wherein the water adsorptive liquid glycol base desiccant
is predominantly polyethylene glycol.
3. The air dehumidifying desiccant recovery system as set forth
in claim 2 wherein a moisture adsorptive additive is admixed to
the liquid glycol base desiccant.
4. The air dehumidifying desiccant recovery system as set forth
in claim 2 wherein a moisture adsorptive polymer additive is admixed
to the liquid glycol base desiccant.
5. The air dehumidifying desiccant recovery system as set forth
in claim 4 wherein a moisture adsorptive polymer is admixed by
at least 10% by weight of said adsorptive mixture.
6. The air dehumidifying desiccant recovery system as set forth
in claim 4 wherein the moisture adsorptive polymer is polystyrene
sulfonic acid sodium salt.
7. The air dehumudifying desiccant recovery system as set forth
in claim 4 wherein the moisture adsorptive polymer is polystyrene
sulfonic acid lithium salt.
8. The air dehumidifying desiccant recovery system as set forth
in claim 5 wherein the moisture adsorptive polymer additive is
polystyrene sulfonic acid sodium salt.
9. The air dehumidifying desiccant recovery system as set forth
in claim 5 wherein the moisture adsorptive polymer additive is
polystyrene sulfonic acid lithium salt.
10. The air dehumidifying desiccant recovery system as set forth
in claim 1 wherein the heat absorber section of the heat-pipe means
is comprised of heat-absorption ends of tubes wetted with said desiccant
and having interface contact with incoming outside air.
11. The air dehumidifying desiccant recovery system as set forth
in claim 1 wherein the heatabsorber section of the heat-pipe means
is comprised of finned heat-absorption ends of tubes wetted with
said desiccant and having interface contact with incoming outside
air.
12. The air dehumidifying desiccant recovery system as set forth
in claim 1 wherein the desiccant regenerater means is a reflux
boiler means for separating the water from weakened desiccant collected
from the heat absorber section-contacter, there being pump means
for recirculating strengthened desiccant to said spray bar means.
13. The air dehumidifying desiccant recovery system as set forth
in claim 12 wherein the reflux boiler means is comprised of a vapor
separator column through which liquid desiccant drops, with heat
subjecting means for vaporizing water therefrom, and a water vapor
condensing means for separately collecting said water.
14. The air dehumidifying desiccant recovery system as set forth
in claim 12 wherein the reflux boiler means is comprised of a vapor
separator column through which liquid desiccant drops, with heat
subjecting means operating within a range of temperature for vaporizing
water therefrom, and a water vapor condensing means operating at
the dew point of water for separately condensing said water vapor.
15. The air dehumidifying desiccant recovery system as set forth
in claim 12 wherein the reflux boiler means is comprised of a vapor
separator column through which liquid desiccant drops, with heat
subjecting means operating within a temperature range of 212.degree.
F. to 345.degree. F. for vaporizing water therefrom, and a water
vapor condensing means operating at the 212.degree. F. dew point
of water for separately condensing said water vapor.
16. The air dehumidifying desiccant recovery system as set forth
in claim 1 wherein a water spray bar means applies evaporative
water to the heat rejecter section of the heat-pipe means for interface
contact with the exhaust flow of relief air to increase the cooling
effect of the heat absorber section of the heat-pipe by means of
both sensible and evaporative cooling.
17. The air dehumidifying desiccant recovery system as set forth
in claim 16 wherein the heat rejecter section of the heat-pipe
means is comprised of heat-rejection ends of tubes wetted with said
evaportive water and having interface contact with outgoing relief
air.
18. The air dehumidifying desiccant recovery system as set forth
in claim 16 wherein the heat rejecter section of the heat-pipe
means is comprised of heat-rejection ends of finned tubes wetted
with said evaporative water and having interface contact with outgoing
relief air.
19. An air dehumidifying desiccant recovery system having an outside
air inlet duct, a conditioned air supply duct into a conditioned
space, a return air duct from said conditioned space and a relief
exhaust air duct exhausting return air displaced by outside air
and with blower means to transport said outside, supply, return
and relief air, and including;
a heat-pipe means having a heat absorber section in the inlet duct
and forming a contacter to remove the heat of adsorption by dehumidifying
the inlet air, and a heat rejecter section in the relief exhaust
air duct for discharging heat into exhaust relief air flow therethrough,
a water adsorptive liquid glycol base desiccant and spray bar means
applying the same to the heat absorber section-contacter of the
heat-pipe means for interface contact with incoming outside air
to absorb water vapor therefrom,
and desiccant regenerater and glycol recovery means in the relief
exhaust air duct, receiving weakened liquid glycol base desiccant
from said heat absorber section-contacter of the heat-pipe means,
and comprised of a heat source means having means heating the relief
air with a water spray bar means applying evaporative water to the
heat rejecter section of the heat-pipe means for interface contact
with the exhaust flow of relief air to increase the cooling effect
of the heat absorber section of the heat-pipe by means of both sensible
and evaporative cooling.
20. The air dehumidifying desiccant recovery system as set forth
in claim 19 wherein the desiccant regenerater heat source means
includes heating the relief air with heat of compression from a
condenser of an associated air conditioning refrigeration unit,
said condenser being disposed in the relief exhaust air duct.
21. The air dehumidifying desiccant recovery system as set forth
in claim 19 wherein the desiccant regenerater heat source means
includes heating the relief air with a furnace operating up to the
relief air temperature required to vaporize water from the weakened
desiccant, said furnace being disposed in the relief exhaust air
duct.
22. The air dehumidifying desiccant recovery system as set forth
in claim 19 wherein the desiccant regenerater heat source means
includes first stage heating of the relief air with said water spray
bar means, a second stage heating of the relief air with heat of
compression from a condenser of an associated air conditioning refrigeration
unit, said condenser being disposed in the relief exhaust air duct,
and a third stage heating of the relief air with a furnace operating
up to the relief air temperature required to vaporize water from
the weakened desiccant, said furnace being disposed in the relief
exhaust air duct.
23. The air dehumidifying desiccant recovery system as set forth
in claim 19 wherein the desiccant regenerater and glycol recovery
means includes an air to desiccant contacter mesh downstream from
the heat source means, and spray bar means applying weakened glycol
base desiccant thereto for interface contact with the outgoing relief
exhaust air, said weakened desiccant being transported to said spray
bar means by pump means from a sump underlying the heat absorber
section of the heat-pipe means.
24. The air dehumidifying desiccant recovery system as set forth
in claim 23 there being a heat exchanger means transferring heat
out of the strengthened desiccant heated by regeneration and pre-heating
the weakened desiccant for regeneration by the heated exhaust relief
air.
25. The air dehumidifying desiccant recovery system as set forth
in claim 23 wherein the means to recover glycol includes a dual
purpose glycol recovery coil downstream from said air to desiccant
contacter mesh and spray bar means, and through which coil the weakened
glycol base desiccant passes at a temperature below the dew point
of the glycol therein and above the dew point of the water vapor
entrained in the exhaust relief air, whereby entrained glycol vapors
are condensed for recirculation with the strengthened glycol base
desiccant.
26. The air dehumidifying desiccant recovery system as set forth
in claim 23 wherein the means to recover glycol includes an eliminator
pack downstream from the air to desiccant contacter mesh and through
which the relief air exhausts, for collection of glycol droplets
condensed thereby for recirculation with the strengthened glycol
base desiccant.
27. The air dehumidifying desiccant recovery system as set forth
in claim 19 wherein the desiccant regenerater and glycol recovery
means includes an air to desiccant contacter mesh downstream from
the heat source means, and spray bar means applying weakened glycol
base desiccant thereto for interface contact with the outgoing relief
exhaust air, said weakened desiccant being transported to said spray
bar means by pump means from a sump underlying the heat absorber
section of the heat-pipe means, there being a heat exchanger means
transferring heat out of the strengthened desiccant heated by regeneration
and pre-heating the weakened desiccant for regeneration by the heated
exhaust relief air, a dual purpose glycol recovery coil downstream
from said air to desiccant contacter mesh and spray bar means, and
through which coil the weakened glycol base desiccant passes at
a temperature below the dew point of the glycol therein and above
the dew point of the water vapor entrained in the exhaust relief
air, whereby entrained glycol vapors are condensed for recirculation
with the strengthened glycol base desiccant, and an eliminator pack
downstream from the air to desiccant contacter mesh and through
which the relief air exhausts, for collection of glycol droplets
condensed thereby for recirculation with the strengthened glycol
base desiccant.
Description BACKGROUND OF THE INVENTION
This invention relates to air pre-conditioning wherein a portion
of the outside air intake is efficiently dehumidified. Heretofore,
the desiccants employed have been expensive and because of their
nature the dehumidifying section of air conditioning equipment has
been fabricated of exceedingly expensive corrosive resistant materials.
Accordingly, it is a primary object of this invention to provide
a relatively inexpensive and substantially non-corrosive desiccant
that is economically effective and which is adapted to use in relatively
inexpensive equipment made of commercial grade materials such as
protectively treated steel and the like. Cost effective stand-alone
installation of a dehumidifier is an object of this invention, all
of which is accomplished without change to the downstream refrigeration
and/or heating equipment.
It is an object of this invention to employ Glycol as a desiccant
and to enhance its moisture absorption capacity by adding to it
a Polymer. Suitable soluble compounds from the glycol family are
Tri ethylene glycol and/or tetra ethylene glycol, a preferred compound
being Polyethyleneglycol. Additives such as Fructose, Silica gel,
Alumina silicates, and the like can be included to enhance the liquid
carrying capacity of the glycol.
There are a number of polymer materials known to be useful as desiccants
to absorb water moisture and to be regenerated for repeated use,
it being an object of this invention to enhance a liquid glycol
with a liquid polymer, for use as a desiccant. Such polymers which
are feasible to be used with glycol desiccants are as follows:
Polystyrene Sulfonic acid lithium salt
Polystyrene sulfonic acid sodium salt
Polyacrylic acid ammonium salt
Poly (methacrylic acid) sodium salt
Poly (n-vinylacetamide vinyl sulfonate) sodium salt
Polyacrylic acid sodium salt
Cellulose sulfonate sodium salt
Methyl cellulose
The preferred desiccant additive is sulfonated Lithium SO.sub.3
Li, PSSALS in a solution and at a viscosity that can be pumped and
sprayed with a heat range of 80.degree. F. to 225.degree. F. db.
The sorption properties of this Lithium polymer salt solution is
enhanced 4% to 15% of weight fraction gain by adding it to Tri ethylene
glycol (TEG) 10% (by weight). In practice, the improved performance
is greater than the algebraic addition prediction for the mixture.
And, it is clear that the moisture absorption capacity of the TEG-
PSSALS mixture is far superior as it produces unexpected results
when compared with known prior art desiccants.
It is a liquid glycol desiccant enhanced with a liquid polymer
material with which this invention is particularly concerned, and
to this end it is an object to provide the same in the form of an
improved hygroscepic desiccant fluid.
Water vapor sorption by polymers is a recognized advantage, the
water uptake capability being most important. Ion-dipole interaction
is to be considered, reference being made to FIGS. 3a, 3b and 3c
of the drawings, which illustrate the comparisons between the use
of Lithium, Sodium and Potassium. It becomes apparent that the Lithium
ion Li+ accommodates a far greater amount of water of the three,
due to its small cationic size as compared with either Sodium Na+
of Potassium K+. The atomic weight and corresponding cationic size
of various elements are to be considered as follows:
______________________________________ Li Lithium 6.9 Na Sodium
23 K Potassium 39 Ca Calcium 40 Cs Cesium 133 ______________________________________
Therefore, is it an object of this invention to employ the better
of the known salts in the sulfonation of the aforementioned polymers
employed as a hygrosopic liquid, especially as a desiccant additive
to glycol. Accordingly, Polystyrene Sulfonate Acid Lithium Salt
solution or PSSALS is the preferred embodiment use herein (see FIG.
7).
Air conditioning involves generally, an outside air supply, a supply
air discharge into a building interior, return air intake from the
building interior, and a relief air discharge. The polymer enhanced
glycol solution air pre-conditioner of the present invention is
adapted to the outside air intake of the existent air conditioning
equipment. It is an object of this invention to advantageously employ
a portion of the outside supply air intake for desiccant treatment.
It is also an object of this invention to advantageously employ
a heat-pipe to extract heat after dehumidification and to dissipate
that heat. The air dehumidifier intake section herein disclosed
replaces an air intake or power section of usual equipment and is
preferably attached to a blower section unit that separates the
relief air from the return air, as shown.
An air conditioning system involves the discharge of relief air
that is replaced by outside supply air. The volume ratio of these
two columns of air varies as a result of variations leakage from
the conditioned air space involved, the relief air being stale interior
air retrieved at a place or places of higher interior temperature
and where stale air exists. Consequently, relief air is substantially
warmer than supply air (the conditioned air), it being an object
of this invention to advantageously employ warmer relief air before
its discharge as exhaust air, by dissipating its usable heat energy
through a heat exchanger into outside air. It is still another object
of this invention to advantageously employ the heat energy rejected
by the heat-pipe, as will be described.
It is an object of this invention to directly process the weakened
higher viscosity desiccant through a multi-effect reflux boiler
concentrator, using the direct application of heat with a counter
flow of desiccant from which water vapor is driven out of the weakened
water saturated liquid and desiccant enriched vapor is condensed
and returned to the contactor section or sections as strengthened
desiccant.
It is an object of this invention to control the temperature of
liquid refrigerant returned to the refrigeration compressor, so
that compressor capacity is maximized. In practice, this is accomplished
with a heat exchanger that desuperheats and condenses the refrigerant
vapor, and simultaneously recovers heat from recirculated glycol
or polymer enhanced glycol which is then distributed to a spray
header and moisture extracted by heated exhaust air.
It is also an object of this invention to efficiently regenerate
the-glycol-polymer enhanced desiccant solution (a mixture), a portion
of which could be lost as a result of vaporization, by providing
a reflux boiler to enrich the desiccant by condensing the glycol
vapors and avoiding their loss.
It is still another object of this invention to implement heat-pipes
so as to function as a dehumidification contacter (heat in) and
to function as a regeneration (heat out) heat source for reconstituting
a strong desiccant mixture of glycol based polymer enhanced desiccant.
The heat in ends of the heat-pipes operate in the incoming outside
air OSA, while the heat out ends of the heat-pipes operate in the
outgoing relief air RE, there being heater means to raise the relief
air to an effective regenerative temperature. Additionally, the
heat of condensation from the dehumidification process is recovered
for desiccant regeneration, and the AC heat of compression is also
recovered for desiccant regeneration.
SUMMARY OF THE INVENTION
A polymer enhanced glycol solution provided as the desiccant in
the form of an improved hygroscopic liquid that can be processed
and transported most efficiently in cost effective dehumidification
equipment. Of the known salts that may be used in the formation
of such a desiccant is preferably one of small cationic size such
as Lithium, Sodium or Potassium. These polymer materials do not
readily vaporize and are reasonably stable for the purpose intended,
and they are sulfonated and retained in solution and liquid state
for transport between and effective processing at the contactor
section and regenerater section of the dehumidifier. The preferred
additive is sulfonated Lithium, for its small dipole configuration
as illustrated in FIG. 3a of the drawings, a cost effective material
that is, for example, approximately two thirds the cost of a comparable
aqueous Lithium Chloride solution, when prepared for the purpose
under consideration. And, by employing either a glycol or a polymer-salt
solution as specified herein, corrosive effect upon the equipment
is minimized to the extent that cost effective materials can now
be used in their construction. Accordingly, commercial grade low
cost materials can be used to replace high cost prior art materials.
The aforesaid employment of polymer-salt additive for dehumidification
is advantageously accomplished with 70% to 90% glycol by weight,
preferably Tri ethylene glycol (TEG) so as to provide a desiccant
solution that has an increased moisture adsorption capacity. In
practice, moisture adsorption capacity is increased at least 4%
and up to approximately 15%, by weight of the moisture laden desiccant
mixture.
A feature of this invention is that the dehumidified air discharge
is through heat-pipe means that removes heat added to the outside
intake air in the preceeding process of adsorption. Another feature
of this invention is the use of relief air discharge over the heat
rejecter portion of the heat-pipe means whereby heat energy in the
relief air is advantageously employed and supplemented by a controllable
heat source to operate the regenerater section of the dehumidifier.
It is still another object of this invention to combine a dehumidifier
and a heat-pipe for simultaneous dehumidification and heat rejection
from outside air, ahead of refrigeration or heating by downstream
equipment. In accordance with this invention, the heat absorber
section of the heat-pipe means serves as the adsorption section
of the dehumidifier, its heat transfer surface being wetted with
the desiccant, preferably with the glycol enhanced sulfonated Lithium
solution mixture, as described herein. In the summer mode of operation,
outside dehumidified air is pre-cooled. In the winter mode of operation,
outside dehumidified air is permitted to add heat through inherent
removal by the heat-pipe. The downstream air conditioning equipment
operates in either the summer or winter mode.
The regeneration of weakened desiccant can be conducted on a unit
basis with a regenerater section assigned to each contacter section,
or on a central service basis with a common return to and supply
from a remoted regenerator unit of most efficient design. Further,
a most significant feature of this invention is the higher viscosity
of the glycol enhanced polymer salt solution used as the desiccant,
wherein a multi stage reflux boiler efficiently regenerates the
desiccant solution mixture without the loss of the glycol which
is subject to vaporization.
The foregoing and various other objects and features of this invention
will be apparent and fully understood from the, following detailed
description of the typical preferred forms and applications thereof,
throughout which description reference is made to the accompanying
drawings.
THE DRAWINGS
FIG. 1 is a longitudinal plan view illustrating the system of the
present invention, with the preconditioner installed ahead of a
downstream air conditioner.
FIG. 2 illustrates a multiplicity of downstream air conditioner
units serviced by a stand alone air preconditioner.
FIGS. 3a, 3b and 3c illustrate the comparison in the cationic size
of Lithium, Sodium and Potassium ions, the preferred salts used
herein to form the polymer-salt solution as desiccant.
FIG. 4 illustrates the air preconditioner of the present invention
in a first embodiment form wherein regeneration of the desiccant
is by means of an external reflux boiler.
FIG. 5 illustrates the air preconditioner of the present invention
in a second embodiment form wherein regeneration of the desiccant
is by means of internal heat transfer.
FIG. 6 is an elevational diagram of the glycol recovery means shown
in FIG. 5.
FIG. 7 is a diagram that illustrates a Lithium anionic polymer.
FIG. 8 is a transverse elevational view illustrating the "heat
in" and "heat out" sides of the heat-pipes as they
are employed in this system.
FIG. 9 is a diagramatic elevational view of the reflux boiler as
it is used in the first embodiment disclosed herein.
FIG. 10 is a fragmentary section of a heat-pipe configuration as
it is employed herein.
And, FIG. 11 is an enlarged sectional view showing the finned feature
of the heat-pipes.
PREFERRED EMBODIMENTS
Referring now to the drawings, FIG. 1 illustrates typical refrigeration
air conditioning equipment comprised of a power return section a
filter section 11 a coil section 12 a blower section 13 and a
diffuser and final filter section 14. The necessary refrigeration
compressor and condenser (not shown) are included in the coil section
12 or they are external. The power section 10 is preferably a blower
section that includes means that separates return air RA into recirculated
supply air SA which is supplemented by incoming outside air OSA
air and into relief air.sub.RE which is exhausted to outside atmosphere.
That is, a portion of the conditioned interior air is discharged
as relief air RE, and it is replaced by new incoming outside air
OSA. In practice, the discharge temperature of incoming outside
air OSA into the power return section 10 is proximate to the outside
air temperature, while the discharge temperature of relief air is
that of the warmer interior air. The sections 10-14 discharge supply
air SA into the conditioned interior at a temperature set by thermostat
control means (not shown). The downstream air conditioning equipment
is state of the art, having an intake duct at 15 to receive dehumidified
outside air, and a discharge duct 16 to deliver conditioned supply
air into a building structure. The power return section 10 is in
open communication with the intake duct 15 and receives dehumidified
outside air OSA therefrom. The power section 10 is characterized
by damper means or the like (not shown) that separates a portion
of the return air for discharge to atmosphere via a discharge duct
17 corresponding in capacity to an intake duct 18 (see FIG. 1),
ducts 17 and 18 opening at the interface of power section 10 with
the dehumidifier contactor and regenerator means D later described.
In accordance with this invention, the structure of the dehumidifier
sections are of commercial grade materials that require the desiccant
to be substantially non-corrosive, and to this end I have provided
a glycol-polymer solution in the form of a hygroscopic liquid. As
specified above, there are a number of elements and their atomic
weights to be considered, and among which are the following:
______________________________________ Li Lithium 6.9 Na Sodium
23 K Potassium 39 Ca Calcium 40 Cs Cesium 133 ______________________________________
These materials when added to the anionic polymer solutions, as
described herein, will vary in their corrosiveness, it being determined
that some well within tolerance for contact with commercial grade
materials such as steel that is protectively coated as by a paint
or sealant, plating, or galvanized and the like, without undue corrosive
action. The selected material or element is also selected for its
cationic size (see FIGS. 3a, 3b and 3c), a material having the smaller
ion size being preferable order to accomodate a greater number of
water clusters in surrounding hydration spheres, as is illustrated.
Accordingly, Lithium Li is preferred, since its atomic weight size
are very and cationic small, and because its corrosiveness is known
to be tolerable when using the commercial grade materials specified
herein. For a comparison, Helium H has a lower atomic weight of
one (1) and therefore a smaller cationic size, but when sulfonated
into a salt solution its corrosive action is intolerable for a cost
effective structure of the type under consideration.
______________________________________ Polystyrenesufonic PSSALS
acid lithium salt Polystyrenesulfonic PSSASS acid sodium salt Polyacrylic
PAAAS acid ammonium salt Poly(mehtacrylic acid) PMAASS sodium salt
Poly(vynylacetamide, vinyl PVAVSSS sulfonate) sodium salt Poly acrylic
acid PAASS sodium salt Cellulose sulfate CSSS sodium salt Methyl
cellulose MS ______________________________________
These solutions have suitable sorption, adsorption and stability
properties.
Present commercially available liquid glycols are as follows:
Tri ethylene glycol
Tetra ethylene glycol
Penta ethylene glycol
Neopentyl glycol
Penta erythritol
Present commercially available additives to the foregoing polymers
and glycols to enhance their liquid carrying capacity are materials
as follows:
Fructose
Silica gel
Alumina silicates
Polysatyrene sulfonic acid lithium salt PSSALS
Poly n-vinylacetamide vinyl
sulfonate lithium salt PNVSLA
In accordance with this invention, liquid glycols are enhanced
as desiccants by the agition thereto of polymer materials. The preferred
polymers are PSSALS and PNVSLA materials which increase the moisture
carrying capacity substantially. The preferred glycol is Polyethylene
Glycol.
Polyethylene Glycols are found in a family of 11near polymers formed
by the addition reaction of ethylene oxide. The generalized formula
for Polyethylene Glycols is:
where "n" is the average number of repeating oxyethylene
groups. The repeating ether linkages and terminal hydroxyl groups
give rise to the water solubility of the Polyethylene Glycols. Each
polyethylene Glycol or PEG is designated by a number that represents
its average molecular weight. For example, PEG 600 consists of a
distribution of polymers of varying molecular weights with an average
of 600 which corresponds to an average number of repeating oxyethylene
groups ("n") of 13. Polyethylene Glycols are available
in average weights ranging from 200 to 8000. All Polyethylene Glycols
are water soluble. At 20.degree. C. the liquid PEGs form clear aqueous
solutions in all proportions, and a wide range of substances are
soluble in Polyethylene Glycol, as disclosed herein. Also, the hydroxyl
functionality of the Polyethylene Glycols allows them to exhibit
hygroscopicity, which is their ability to attract and retain moisture.
In accordance with this invention, a liquid sorbent material is
provided by mixing a sorbent solid such as gels of Silica and/or
Alumina, zeolites, clays, organic polymer salts such as polystyrene
sulfonic acid sodium salt (PSSA-Na) with Triethylene Glycol (TEG)
or preferably Polyethylene Glycol (PEG), or other amines. An unexpected
and advantageous feature is that certain amounts of the additive
of solid sorbent (soluble or insoluble) to a given quantity of liquid
sorbent results in a composite mixture which is still liquid and
exhibits a sorption capacity greater than the algebraic sum of the
individual sorptior, capacities of its components. The individual
constituent materials and compounds exhibit sorptive properties
towards a variety of chemical vapors and gases, and moisture (water
vapor) sorption is most important herein in the untilization of
these liquid composites in humidity control air conditioning. And,
the affinity of these sorbent mixtures for other vapors such as
volatile organic compounds (VOCs) is also significant and highly
utilitarian in air conditioning. The result is new compositions
of matter characterized by composite mixtures of solid ant liquid
sorbent materials. In practice, a 4% to 15% increase in TEG moisture
adsorption capacity has been attained by adding 10% PSSA--Li, or
PSSA--Na. Commensurately improved performance results in the dehumidifying
system equipment, which is conducive to down-sizing said equipment.
Also, lower vapor pressures prevail in these polymer enhanced glycol
mixtures, together with reduction of oxidation of the equipment
structure. The aforesaid increased percentage in sorbent capacity
is made in comparison to state of the art Tri ethylene chloride
(LiCL) solutions.
According to the foregoing, the preferred desiccant additive is
sulfonated Lithium SO.sub.3 Li, PSSALS in a solution and at viscosity
that can be pumped and sprayed within a heat range of 80.degree.
F. to 225.degree. F. db. The sorption properties of this Lithium
polymer-salt solution is substantial and cost effective and provides
a non-vaporizing desiccant that is reasonably stable.
Referring now to the air preconditioning apparatus and to FIG.
4 of the drawings, the dehumidifier of means D or contacter section
22 is a means that involves both the aforesaid relief air discharge
duct 17 and the OSA intake duct 18 these two ducts being of substantially
the same air flow capacity, as shown. Discharge duct 17 exhausts
relief air RE to atmosphere at 20 while the separate and essentially
parallel duct 18 receives outside air OSA at 21. In accordance with
this invention, there is adsorption means for removal of humidity
from the outside air OSA flowing therethrough in the form of a heat-pipe
means P for removing heat from the outside air OSA entering through
the duct 18 and for rejecting said heat into the relief air RE exhausting
through the duct 17. Accordingly, the heat absorber section 22 of
the heat-pipe means P forms the dehumidifier contacter section in
the flow of outside air OSA from the entry at 21 to the downstream
discharge at duct 15. And, the heat rejecter section 23 of the heat-pipe
means P exhausts heated relief air RE to atmosphere at 20.
The dehumidifier contactor section 22 heats the incoming outside
air OSA as a result of the desiccant adsorption of water vapor,
during which said outside air is cooled by the heat absorber section
22 of the heat-pipe means P. A distribution means or spray bar 25
supplied with strong glycol-polymer solution desiccant from a pump
26 wets the heat-pipe section 22 through which the air column flows.
A sump 27 collects the fall of weak liquid desiccant from the heat
pipe fins, and from which the desiccant is recirculated through
a reflux boiler B for regeneration, as will be described by means
of pimp 26. The desiccant supply is subject to depletion due to
evaporation of its water content when operated in the humidification
mode, and it is replenished by a float control valve 28 supplied
with make-up desiccant, as shown in FIG. 8.
The heat-pipe means P cools the incoming outside air OSA flowing
through the dehumidifier contacter section, by absorbing heat therefrom
at its heat absorber section 22 and it heats the outgoing relief
air RE by rejecting heat at its heat rejecter section 23. Accordingly,
the heat absorber section 22 is in duct 18 while the heat rejecter
section 23 is in duct 17.
The heat-pipe P is characterized by a hot end for absorption of
heat and by a cold end for rejection of heat. In other words, there
is a "heat in" end and a "heat out" end, for
the normal summer cooling mode, which is inherently reversed for
the normal winter heating mode. In carrying out this invention,
the cold "heat out" rejecter section 23 is placed in the
relief air RE exhaust duct 17 and the hot "heat in" absorber
section 22 is placed in the outside air OSA inlet duct 18. A feature
of this invention is that the heat absorber section 22 is the dehumidifier
means D with the section 23 rejecting heat to exhaust air at 20.
Accordingly, there is a heat transfer function that occurs between
and from duct 18 to duct 17 so as to reduce the induction air temperature
during dehumidification by the desiccant, and to increase the relief
air RE temperature that is exhausted. In practice, transfer of heat
energy from the incoming column of OSA air to the outgoing column
of RE air is by means of a multiplicity of heat-pipe tubes, the
cold end sections 23 in the form of heat dissipaters placed in the
duct 17 and the hot end sections 22 in the form of heat absorbers
placed in the duct 18 and functioning as the contacter for dehumidifying
incoming air.
In accordance with this invention, the heat-pipes P are lengths
of heat conductive tubing 33 sealed at their opposite ends, having
interior fitting tubular wicks 34 and charged with a fluid refrigerant
35 a temperature responsive liquid-to-gas fluid (see FIG. 10).
A temperature differential between the ends of each pipe causes
the fluid refrigerant to migrate in its liquid state by capillary
action to the warmer end where evaporation to its gaseous state
takes place and thereby absorbs heat. The resultant gaseous refrigerant
vapor then returns through the hollow interior of the tube, where
it gives up the heat carried thereby, by condensing into the wick
in order to repeat the cycle. The heat transfer process is efficent,
since the heat pipes are sealed and have no moving parts, and therefore
require little or no attention. The, heat-pipes are finned for most
efficient heat energy transfer and for expansive contacter area
(see FIG. 11).
In accordance with this invention, control of the heat-pipe means
P involves evaporative cooling of the heat rejection section 23
thereof as and when required, to increase the cooling effect of
the heat absorber section 22. As shown in FIG. 8 a spray bar 36
supplied with an evaporative liquid such as water from sump 37 by
a recirculating pump 38 wets the finned air contacting exterior
of the heat rejecter section 23 of the heat-pipe. In practice, the
evaporative liquid is cold makeup water that has a sensible cooling
effect as well as evaporative. A thermostat 24 senses temperature
as a control means that determines coiling requirements. Referring
to FIG. 4 the dehumidifier contacter means D involves the finned
"heat in" section 22 of the heat-pipe means P. Section
22 of the heat-pipe functions as a dehumidifier by being sprayed
with desiccant from a spray bar 25 supplied by a pump 26 drawing
desiccant from the sump 27 as shown in FIG. 8. The spray bar 25
is horizontally disposed as shown, and the heat-pipe means P incorporates
the dehumidifier features as described. A humidistat 24' in the
conditioned space S (see FIG. 2) determines the humidification and
dehumidification requirements and thereby controls the operational
mode of the system.
The FIG. 4 embodiment features external regeneration of weakened
desiccant, as by a reflux boiler means B, the details of which are
shown in FIG. 9 of the drawings. This first embodiment can be combined
with downstream refrigeration equipment as shown in FIG. 1 or it
can be free standing alone as shown remote in FIG. 2. As hereinabove
described, the weakened glycol based desiccant is collected by the
sump 27 and is recirculated by the pump 26 to the spray bar 25.
As shown in FIG. 4 recirculation of the weakened desiccant is through
the regeneration boiler means B where it is subjected to heat in
order to drive out the moisture adsorbed thereby during dehumidification
of the incoming outside air OSA. As a result of the heat application
for regeneration, there is a substantial amount of glycol vapor
released from its liquid desiccant state, it being an object herein
to recover the vaporized glycol and bring it to its liquid state
for recirculation to the spray bar 25 as above described. To this
end this invention provides regeneration in the form of the reflux
boiler means B that subjects the weakened moisture or water saturated
desiccant to a heat range within the dew points of water and the
glycol that is employed. For example, between 212.degree. F. to
boil off the water and 345.degree. F. (or less) to prevent boiling
off the glycol or that portion of the enhanced glycol desiccant
employed.
Referring now to the reflux boiler means B for desiccant regeneration
as shown in FIG. 9 of the drawings, there is a multi-stage liquid
to vapor separator column 40 each stage being comprised of a liquid
holding tray 41 with percolating means 42 through which liquid glycol
desiccant drops to the next lower tray and from which released water
vapor rises to a header 43. The, lower sump end 44 of the column
is subjected to the high heat within the 212.degree. F. to 345.degree.
F. range, each successively higher tray being subjected to a lesser
temperature, and the uppermost tray being subjected to the lower
heat within the 212.degree. F. to 345.degree. F. range. A feature
of the reflux boiler means B is the separate condensing chamber
means 45 in open communication with the header 43 and maintained
at the 212.degree. F. dew point of water. The upper chamber portion
houses a condensing coil 46 through which a coolant is recirculated
through an outside heat rejecting coil 47 by a pump 48. Water-vapor
condenses on the coil 46 and drops into the water discharge sump
portion 47 of the condensing chamber 45. The uppermost separator
tray 41 is supplied with water for percolation by an overflow 50
from the sump portion 49. Regenerated glycol desiccant, purged of
water, is recovered at the sump end discharge 51 heated to 345.degree.
F. below the dew point of the glycol.
The FIG. 5 embodiment features internal regeneration of weakened
desiccant. That is, the glycol desiccant is regenerated and its
vapors recovered in combination with the heat-pipe dehumidifier
and its components. This second embodiment can be combined with
downstream refrigeration equipment as shown in FIG. 1 or it can
be free standing alone as shown remote in FIG. 2 of the drawings.
The heat-pipe dehumidification of the outside air OSA is the same
here as above described with respect to the first embodiment, while
the regeneration of weakened desiccant benefits from the heat of
compression recovered from the downstream air conditioning refrigeration
equipment; and benefits from the heat of condensation recovered
from the process of dehumidification.
As shown in FIG. 2 there is at least one and preferably a multiplicity
of conditioned air spaces S in each of which there is a fan and
coil unit A/C that refrigerates and distributes mixed return air
RE and preconditioned outside air OSA. Remote compressor-condenser
units C serve each fan unit by recirculating pressurized refrigerant
through an expansion valve 60 and through a coil 61. A fan 62 delivers
the supply air SA into the air space S. And, the coil 61 discharges
the depressurized refrigerant to a compressor 63 from which the
heat of compression is normally rejected by a condenser coil 64.
However and in accordance with this invention, the heat of compression
is recovered partially or exclusively by means of a condenser coil
65 and employed in the desiccant regeneration process.
In accordance with this invention, first stage heating of the relief
air RE passing through the preconditioner duct 17 is performed by
the heat of rejection from the cold "heat out" ends of
the heat-pipes P, bringing the air column temperature up to approximately
70.degree. F. to 77.degree. F.
In accordance with this invention, a substantial amount of heat
of compression from the downstream refrigeration units is recovered
by delivering the compressed and heated refrigerant through a heat
dissipating condenser coil 65 positioned in the preconditioner air
intake duct 17 for second stage heating of relief air RE, bringing
the air column temperature up to approximately 77.degree. F. to
100.degree. F. The condenser coil 65 can be an auxiliary coil in
series from the normal condenser coil 64 or it can replace said
coil 64. In practice, the refrigeration condenser coil 65 is placed
in the relief air duct following the cold "heat out" ends
of the heat-pipes P so as to raise the air column temperature drawn.
therethrough by a fan 66. As shown, a fan 67 delivers the outside
air OSA through the duct 18 both fans being located in the free
standing preconditioner unit.
Third stage heating of the relief air RE to approximately 140.degree.
F. to 190.degree. F. is by means of a gas fired furnace means F
or the like (see FIG. 5), through which the column of relief air
RE passes to an air to desiccant contacter mesh or packing 68 wetted
with the weakened desiccant by means a of a spray bar 69. The relief
air passes through the contacter mesh 68 and exits therefrom with
entrained water vapor and trace amounts of glycol vapor resulting
from desorption of the desiccant.
Referring now to the desiccant flow circuit as shown in FIGS. 5
and 6 weakened and heated desiccant is delivered by the pump 26
from the sump 27 of the dehumidifier contacter heat-pipe ends 22.
Delivery of the weakened desiccant heated by the heat of condensation
is through a heat exchanger 70 that precools the strengthened desiccant
heated by the regeneration process. A feature is the delivery of
the weakened desiccant thorugh a dual purpose glycol recovery coil
71 in the heated relief air RE column downstream from the contacter
mesh 68 maintained by thermal and flow balance at a temperature
below the dew point of the glycol, and above the dew point of the
water vapor entrained in the relief air RE. The glycol recovery
coil 71 is finned and from which the glycol vapors condense and
drop into a sump 73 that underlies the regeneration mesh 65 the
coil 71 and the downstream eliminator pack 74 that collects the
last and very little remaining glycol droplets which then drop from
said mesh and into the sump. The weakened desiccant heated by the
heat of condensation during the dehumidification process adsorbs
heat from the hot regenerated desiccant when delivered through the
heat exchanger 70 by a pump 26 and also absorbs heat from the heated
relief air RE when passing through the glycol recovery coil 71.
The hot desiccant within a 95.degree. F. to 110.degree. F. range
is then discharged into the regeneration mesh 62 by the spray bar
69. A pump, 75 returns the heated and regenerated desiccant through
the heat exchanger 70 where it is precooled and delivered to the
spray bar 25 for repeating the process cycle of dehumidification
of incoming outside air OSA.
Having described only the typical preferred forms and applications
of my invention, I do not wish to be limited or restricted to the
specific details herein set forth, but wish to reserve to myself
any modifications or variations that may appear to those skilled
in the art, as set forth within the limits of the following claims. |