EP0591430A1 - Improved cooling medium for use in a thermal energy storage system - Google Patents
Improved cooling medium for use in a thermal energy storage systemInfo
- Publication number
- EP0591430A1 EP0591430A1 EP92914815A EP92914815A EP0591430A1 EP 0591430 A1 EP0591430 A1 EP 0591430A1 EP 92914815 A EP92914815 A EP 92914815A EP 92914815 A EP92914815 A EP 92914815A EP 0591430 A1 EP0591430 A1 EP 0591430A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- surfactant
- energy storage
- thermal energy
- cooling medium
- storage system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000004146 energy storage Methods 0.000 title claims abstract description 23
- 239000002826 coolant Substances 0.000 title claims abstract description 21
- 239000004094 surface-active agent Substances 0.000 claims abstract description 63
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000000693 micelle Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 8
- -1 alkyl dimethyl benzyl ammonium salt Chemical class 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- LVGUZGTVOIAKKC-UHFFFAOYSA-N 1,1,1,2-tetrafluoroethane Chemical compound FCC(F)(F)F LVGUZGTVOIAKKC-UHFFFAOYSA-N 0.000 claims description 2
- UJPMYEOUBPIPHQ-UHFFFAOYSA-N 1,1,1-trifluoroethane Chemical compound CC(F)(F)F UJPMYEOUBPIPHQ-UHFFFAOYSA-N 0.000 claims description 2
- NPNPZTNLOVBDOC-UHFFFAOYSA-N 1,1-difluoroethane Chemical compound CC(F)F NPNPZTNLOVBDOC-UHFFFAOYSA-N 0.000 claims description 2
- 229940051271 1,1-difluoroethane Drugs 0.000 claims description 2
- GTLACDSXYULKMZ-UHFFFAOYSA-N pentafluoroethane Chemical compound FC(F)C(F)(F)F GTLACDSXYULKMZ-UHFFFAOYSA-N 0.000 claims description 2
- RWRIWBAIICGTTQ-UHFFFAOYSA-N difluoromethane Chemical compound FCF RWRIWBAIICGTTQ-UHFFFAOYSA-N 0.000 claims 2
- 238000001816 cooling Methods 0.000 claims 1
- 230000015572 biosynthetic process Effects 0.000 abstract description 15
- NDKGUMMLYBINOC-UHFFFAOYSA-N 1,2-dichloro-1-fluoroethane Chemical compound FC(Cl)CCl NDKGUMMLYBINOC-UHFFFAOYSA-N 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 239000000839 emulsion Substances 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- CYRMSUTZVYGINF-UHFFFAOYSA-N trichlorofluoromethane Chemical compound FC(Cl)(Cl)Cl CYRMSUTZVYGINF-UHFFFAOYSA-N 0.000 description 3
- FRCHKSNAZZFGCA-UHFFFAOYSA-N 1,1-dichloro-1-fluoroethane Chemical compound CC(F)(Cl)Cl FRCHKSNAZZFGCA-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000003507 refrigerant Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229940029284 trichlorofluoromethane Drugs 0.000 description 2
- OHMHBGPWCHTMQE-UHFFFAOYSA-N 2,2-dichloro-1,1,1-trifluoroethane Chemical compound FC(F)(F)C(Cl)Cl OHMHBGPWCHTMQE-UHFFFAOYSA-N 0.000 description 1
- VOPWNXZWBYDODV-UHFFFAOYSA-N Chlorodifluoromethane Chemical compound FC(F)Cl VOPWNXZWBYDODV-UHFFFAOYSA-N 0.000 description 1
- RJCQBQGAPKAMLL-UHFFFAOYSA-N bromotrifluoromethane Chemical compound FC(F)(F)Br RJCQBQGAPKAMLL-UHFFFAOYSA-N 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- 150000005826 halohydrocarbons Chemical class 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/02—Materials undergoing a change of physical state when used
- C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
- C09K5/063—Materials absorbing or liberating heat during crystallisation; Heat storage materials
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/02—Materials undergoing a change of physical state when used
- C09K5/04—Materials undergoing a change of physical state when used the change of state being from liquid to vapour or vice versa
Definitions
- halogenated hydrocarbons which are used as the guest molecules are not water iscible. Clathrates will not form unless the guest and host (lattice) compounds are in contact. In an attempt to bring the guest molecule and water into closer contact, various surfactants have been added.
- U.S. Patent No. 4,540,501 discloses using a nonionic fluorosurfactant having the chemical formula F(CF 2 CF 2 ) 3 - ⁇ CH 2 CH 2 ⁇ (CH 2 CH,0) g .
- Zonyl® Fluorosurfactant and Unidyne DS-401 have been added to water-l,l,l-tetrafluoroethane clathrate forming thermal energy storage medium in Formation of Gas Hydrate or Ice by Direct-Contact Evaporation of CFC Alternatives.
- Halohydrocarbons such as HCFC-141(b) which contain hydrogen, and are believed to pose less of a threat to the ozone layer, and are thus proposed as the guest molecule in clathrate formation according to the present invention.
- the present invention provides a cooling medium for use in a thermal energy storage system comprising water, a guest molecule and a surfactant having a critical micelle concentration in an amount less than about twice the critical micelle concentration.
- the critical micelle concentration is less than about lxlO "3 and more preferably between lxlO"*M and 1 10 " ⁇ .
- a thermal energy storage unit which uses the cooling medium and a process for using the thermal energy storage unit are also disclosed.
- the guest molecules of the present invention may be any compound'capable of forming a clathrate with water. Suitable guest molecules generally have an average diameter of less than about 7 A.
- Clathrates of the present invention are formed from the guest molecule, and water. Depending on the size of the guest molecule between 5 to 17 water molecules per guest molecule are needed to form a clathrate. Preferably the amount of each the guest molecule and water is at least equal to the ratio necessary to form clathrate. More preferably, an excess of water is used to maintain a slurry, and ensure continuous and efficient heat transfer. For example, where HCFC- 141(b) is used, 20 moles of water is used for each 1 mole of HCFC-141(b).
- the optimum concentration of surfactant necessary to provide maximum mixing is not greater than about twice the critical micelle concentration, preferably less than about 1.5 times the cmc and most preferably less than about the cmc.
- the cmc it may be desirable to exceed the cmc in order to acheive a particular effect.
- the concentration of surfactant may still be quite low-as compared to conventional surfactant concentration even though it is above the cmc.
- the competition between the surfactant and the guest molecule is proportionately less severe, even at concentrations which are above the cmc.
- surfactants with critical micelle concentrations below about lxlO"*M are preferred.
- Emulsions formed according to the present invention are stable at room perature, and remain emulsified for as long as two days with minimum drainage.
- the clathrate is formed in a storage tank/crystallizer.
- the pressure in the crystallizer is decreased by means of a compressor, as described in more detail in U.S. Patent No. 4,540,501, and heat is removed until the tempera*-nre of formation for the clathrate is reached. Ti sressure and temperature are maintained until all of t ⁇ clathrate is formed.
- the clathrate is circulated through the heat exchanger via the recirculation loop. Clathrate is circulated through the heat exchanger, decomposed, and the water and guest molecule mixture is returned to the crystallizer.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
- Thermal Sciences (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Medicinal Preparation (AREA)
- Detergent Compositions (AREA)
Abstract
Liquide de refroidissement pour système de stockage de l'énergie thermique comprenant de l'eau, une molécule hôte et un agent tensioactif dont la concentration critique pour la formation de micelles est inférieure à environ 2 fois cette concentration critique. De préférence, la concentration critique pour la formation de micelles est inférieure à environ 1x10-3M ou mieux, elle est située entre 1x10-4M et 1x10-6M. Est également décrite une unité de stockage de l'énergie thermique faisant appel à ce liquide de refroidissement et un procédé d'utilisation de cette unité de stockage de l'énergie thermique.A thermal energy storage system coolant comprising water, a host molecule, and a surfactant whose critical concentration for micelle formation is less than about 2 times this critical concentration. Preferably, the critical concentration for micelle formation is less than about 1x10-3M or better still is between 1x10-4M and 1x10-6M. Also described is a thermal energy storage unit using this coolant and a method of using this thermal energy storage unit.
Description
IMPROVED COOLING MEDIUM FOR DSE IN A THERMAL ENERGY 1TORAGE SYSTEM
This application is a continuation-in-part of Application Serial No. 722,428, filed on June 27, 1992.
Background of the Invention
Thermal energy storage systems contain a cooling medium, which is frozen during the off peak, evening hours. During the daytime, heat from the surrounding area is used to melt the cooling medium. The removal of heat to drive the decomposition causes the surrounding area to become cooler.
U.S. Patent No. 4,540,501 discloses a thermal energy storage system which uses clathrates as the cooling medium. Clathrates are hydrates which use a non-stoichiometric number of water molecules per guest molecule. The guest molecule fills the interior of the lattice, stabilizing the clathrate. This stabilization allows the water lattice structure to form at temperatures significantly higher than the temperature of ice formation (0°C) . The guest molecule must be highly insoluble in water, and must have a molecular size which is less than 7 A.
The halogenated hydrocarbons which are used as the guest molecules are not water iscible. Clathrates will not form unless the guest and host (lattice) compounds are in contact. In an attempt to bring the guest molecule and water into closer contact, various surfactants have been added. U.S. Patent No. 4,540,501 discloses using a nonionic fluorosurfactant having the chemical formula F(CF2CF2)3-βCH2CH2θ(CH2CH,0)g.11H when the guest molecule is a refrigerant chosen ro brominated, chlorinated and luorinated hydrocarbons including CC12F2, CC13F, CBrF3, CHC12F, CHCIF2, CH2C1F and CH3CC1F2. U.S. Patent No. 4,821,794 discloses the use of Zonyl® Florosurfactants in amounts between 1 to 5000 ppm generally, and the use of Zonyl* FSN with
trichlorofluoromethane in the amount of about 200 to 300 ppm. Zonyl® Fluorosurfactant and Unidyne DS-401 have been added to water-l,l,l-tetrafluoroethane clathrate forming thermal energy storage medium in Formation of Gas Hydrate or Ice by Direct-Contact Evaporation of CFC Alternatives. F. Isobe and Y.H. Mori, Int. J. Refrig., vol. 15, No. 3 (1992), pgs. 137 - 142. Proc. Inter. Soc. Enerσy Convers. Enσ. Conf.. Akiya et al., 1991, 26th(6) 115-119 used two unspecified surfactants in concentrations up to 500 ppm to enhance the rate of formation of the clathrate from a water - 1,1-dichloro-l-fluoroethane cooling medium.
However, for the known guest molecules relatively large quantities of surfactant have been used (up to and in excess of 1000 ppm) and some of the guest molecule will associate with the surfactant instead of forming a clathrate with water. This decreases the efficiency of the thermal enerσy storage system. Prior to the present invention there has been no teaching in the art of how to select a surfactant for a particular cooling medium or how to determine the amount of surfactant which will insure optimum mixing with a minimum of guest molecule association. Furthermore, many of the guest molecules presently being used are CFCs such as trichlorofluoromethane (CFC-11) . The use of these compounds is becoming disfavored because of the detrimental effect to the ozone layer. Thus it is a goal of the present invention to find a cooling medium which poses less of a threat to the ozone layer. Halohydrocarbons such as HCFC-141(b) which contain hydrogen, and are believed to pose less of a threat to the ozone layer, and are thus proposed as the guest molecule in clathrate formation according to the present invention.
Description of the Figure
FIGURE 1 shows the relationship between the surfactant concentration and the surface tension of water for the surfactant DRSC®. Figure 2 shows the relationship between surfactant concentration (DRSC«) and the interfacial tension for 1,1-dichloro-l-fluoroethane/water solution.
Detailed Description of the Invention The present invention provides a cooling medium for use in a thermal energy storage system comprising water, a guest molecule and a surfactant having a critical micelle concentration in an amount less than about twice the critical micelle concentration. Preferably the critical micelle concentration is less than about lxlO"3 and more preferably between lxlO"*M and 1 10"^. A thermal energy storage unit which uses the cooling medium and a process for using the thermal energy storage unit are also disclosed. The guest molecules of the present invention may be any compound'capable of forming a clathrate with water. Suitable guest molecules generally have an average diameter of less than about 7 A. Preferably, the guest molecule is a refrigerant selected from the group consisting of hydrochlorofluorocarbons, hydrofluorocarbons, and mixtures thereof. Examples of preferred hydrochlorofluorocarbon guest molecules include l-fluoro-l,l-dichloroethane, and chlorodifluoromethane. Examples of preferred hydrofluorocarbon guest molecules include 1,1,1,2- tetrafluoroethane, 1,1,1-trifluoroethane, difluorormethane, pentafluoroethane, and 1,1- difluoroethane. The configuration of the thermal energy storage system of the present invention is the similar to that of U.S. patent No. 4,540,501.
To form a clathrate the guest molecule and water must be dissimilar and be in contact with each other, the more intimate the contact, the more efficient the clathrate formation will be. Accordingly, emulsions of water and the guest molecule are highly desirable.
Clathrates of the present invention are formed from the guest molecule, and water. Depending on the size of the guest molecule between 5 to 17 water molecules per guest molecule are needed to form a clathrate. Preferably the amount of each the guest molecule and water is at least equal to the ratio necessary to form clathrate. More preferably, an excess of water is used to maintain a slurry, and ensure continuous and efficient heat transfer. For example, where HCFC- 141(b) is used, 20 moles of water is used for each 1 mole of HCFC-141(b).
The concentration of free surfactant in water affects the properties of the water and particularly the surface tension, which is shown for DRSC® in Figure 1. For multiphase systems, such as the guest molecule/water mixtures, which are used in thermal energy storage systems the interfacial tension between the guest molecule and water may be measured. The effect of DRSC* at varying concentrations on a 1,1- dichloro-1-fluoroethane/water is shown in Figure 2.
The properties of both solution change rapidly between about 25 ppm and about 125 ppm. Beyond that range of concentration, properties change more gradually. This narrow concentration range in which properties change rapidly is called the critical micelle concentration or cmc. After the cmc has been exceeded water surface tension decreases only slightly by adding more surfactant. Because water-guest molecule mixing increases as the surface tension of water decreases, maximum water-guest molecule mixing is achieved near
the cmc. Moreover, after about 200 ppm (twice the cmc) of the DRSC® surfactant has been added there is virtually no change in either the surface or interfacial tension. Thus, regardless of what surfactant is used, the optimum concentration of surfactant necessary to provide maximum mixing is not greater than about twice the critical micelle concentration, preferably less than about 1.5 times the cmc and most preferably less than about the cmc. By limiting the amount of surfactant used to less than about twice the cmc it is possible to use small amounts of surfactants, especially if the critical micelle concentration is small (less than about 10"3M) .
Each surfactant has a unique cmc, which depends upon its structure. Generally surfactants with longer hydrocarbon chains have lower critical micelle concentrations. The lower the cmc, the less surfactant is necessary to achieve maximum mixing. Thus, preferably surfactants of the present invention have critical micelle concentrations which are below 1x10' 3M, and preferably between lxl0"*M and .1x10"^. Critical micelle concentrations for many surfactants are listed in "Critical Micelle Concentrations of Aqueous Surfactant Systems'* by Mukerjee and Mysels [Nat. stand. Ref. Data Ser. , Nat. Bur. Stand. (U.S) 36, Feb. 1971. Many ways of determining the cmc of surfactants are described by Mukerjee et al. Moreover, because the present invention provides a large number of suitable surfactants, surfactants which produce only gradual changes in surface or interfacial tension over varying surfactant concentrations, and thus have poorly defined cmcs are not preferred. An example of a surfactant having a poorly defined cmc is Zonyl® FSN.
Most preferably, a surfactant having a cmc less than lxl0"*M is used in an amount about equal to or
slightly in excess of the cmc. By choosing surfactants having low cmcs and limiting the amount of surfactant to the cmc, inefficiencies due to guest molecule association with the aggregated surfactant and competition between the surfactant and guest molecule may be minimized. When any non-polar substance is in contact with water, the water molecules become arranged or organized in a cluster around the non-polar moiety. It is believed that clathrates are formed by the crystallization of this cluster. Similarly, when a surfactant is present, water molecules cluster around the surfactant, forming surfactant aggregates. This competition between the potential guest molecules and surfactant molecules for water molecules decreases the amount of clathrate which can be formed with a given amount of water molecules. Thus it is preferable to minimize the amount of surfactant used.
In some situations, it may be desirable to exceed the cmc in order to acheive a particular effect. When the cmc is low, the concentration of surfactant may still be quite low-as compared to conventional surfactant concentration even though it is above the cmc. Thus, the competition between the surfactant and the guest molecule is proportionately less severe, even at concentrations which are above the cmc. Thus, surfactants with critical micelle concentrations below about lxlO"*M are preferred.
An example of a surfactant species which has been found particularly effective in enhancing emulsion formation where HCFC-141(b) is used as the guest molecule is the surfactant DRSC« (alkyl dimethyl benzyl ammonium salt of octaphenyl phosphoric acid, commercially available from Allied-Signal, Inc.). The physical properties of DRSC* are shown in Table 1, below.
The cmc for DRSC® is between about 50 ppm and about 125 ppm, which was determined by measuring the surface tension of water as increasing amounts of DRSC® were added. Thus, less than about 200 ppm of the DRSC® is required to insure emulsion formation between water and the chosen guest molecule. Preferably less than 100 ppm DRSC® is used. The losses of the guest molecule (HCFC-141(b)) due to association with the surfactant decrease as the amount of surfactant used is decreased, thereby increasing the efficiency of clathrate formation, and the thermal energy storage system.
Agitation is not required to ensure clathrate formation of the cooling medium of the present invention. However, agitation may be used to further encourage clathrate formation.
Emulsions formed according to the present invention are stable at room perature, and remain emulsified for as long as two days with minimum drainage. The clathrate is formed in a storage tank/crystallizer. The pressure in the crystallizer is decreased by means of a compressor, as described in more detail in U.S. Patent No. 4,540,501, and heat is removed until the tempera*-nre of formation for the clathrate is reached. Ti sressure and temperature are maintained until all of tϋώ clathrate is formed. The clathrate is circulated through the heat exchanger via the recirculation loop. Clathrate is circulated through the heat exchanger, decomposed, and the water
and guest molecule mixture is returned to the crystallizer.
Example A solution of DRSC® having a concentration of 25 ppm was made by adding 0.025 ml of DRSC® to 1 liter of water. 300 ml of the surfactant solution was poured into a 500 ml jar, and 30 ml of 141(b) was added. The jar was capped and shaken vigorously for l minute. An emulsion formed in the jar, which was stable and remained emulsified for two days without noticeable drainage.
The sealed jar was placed in a freezer at 40°F. A considerable amount of snowflake-like crystals (the clathrate) was observed in the jar after 1.0 hour. The jar was left in the freezer overnight. By morning crystals had formed in the jar, indicating that clathrate had formed.
Accordingly, DRSC®, which has a low cmc, is a suitable aid for clathrate formation, forming clathrate at low surfactant concentrations. Because only a small amount of surfactant is required (twice the cmc or less) , there is less surfactant to associate with the guest molecule (here HCFC-141(b)) , and thus the clathrate formation process, and the thermal energy storage system are more efficient.
Claims
1. A thermal energy storage system having a crystallizer compartment containing a clathrate forming cooling medium, a means for circulating the cooling
5. medium through a heat exchanger and a means for lowering the temperature in said crystallizer compartment; the improvement comprising: using as said clathrate forming cooling medium a mixture comprising water, a guest molecule and a 0 surfactant in an amount less than twice said surfactant's critical micelle concentration.
2. The thermal energy storage system of claim 1 wherein said surfactant is used in an amount up to said surfactant's critical micelle concentration.
3. The thermal energy storage system of claim 1 wherein said critical micelle concentration is between lxlO'*M and lxlO_6M.
4. The thermal energy storage system of claim l wherein said guest molecule is selected from the group consisting of hydrochlorofluorocarbons and hydrofluorocarbons.
5. The thermal energy storage system of claim 4 wherein said guest molecule is selected from the group consistingof 1,1-dichloro-l-fluororethane, l-fluoro-l,l- dichloroethane chlorodifluoromethane, 1,1,1,2- tetrafluoroethane, 1, 1, 1-trifluoroethane, difluoromethane, pentafluoroethane and 1,1- difluoroethane.
6. The thermal energy storage system of claim 1 wherein the surfactant is alkyl dimethyl benzyl ammonium salt of octaphenyl phosphoric acid.
7. The thermal energy storage system of claim 6 wherein the amount of said surfactant used is less than 200 ppm.
8. A process for thermal energy storage wherein a cooling medium is induced to form a clathrate, and heat is removed from the surroundings to melt the clathrate;
the improvement comprising: using as said cooling medium a mixture comprising water, a guest molecule and a surfactant having a critical micelle concentration less than lxlO"3M in an
5. amount less than twice said critical micelle concentration.
9. The process of claim 8 wherein said surfactant has a critical micelle concentration between lxlO"M and lxlO_sM. 0
10. The process of claim 9 wherein said surfactant is alkyl dimethyl benzyl ammonium salt of octaphenyl phosphoric acid.
11. The process of claim 18 wherein the amount of said surfactant used is less than 200 ppm.
12. A cooling medium for use in a thermal energy storage system comprising water, a guest molecule and a surfactant having a critical micelle concentration in an amount is less than twice said critical micelle concentration.
13. The cooling medium of claim 12 wherein said critical micelle concentration is less than lxl0'3M.
14. The cooling medium of claim 13 wherein said critical micelle concentration is between lxl0'*M and lxlO_6M.
15. The cooling medium of claim 14 wherein the surfactant is alkyl dimethyl benzyl ammonium salt of octaphenyl phosphoric acid.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/722,428 US5159971A (en) | 1991-06-27 | 1991-06-27 | Cooling medium for use in a thermal energy storage system |
| US722428 | 1991-06-27 | ||
| US89972292A | 1992-06-23 | 1992-06-23 | |
| US899722 | 1992-06-23 | ||
| PCT/US1992/005368 WO1993000412A1 (en) | 1991-06-27 | 1992-06-24 | Improved cooling medium for use in a thermal energy storage system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0591430A1 true EP0591430A1 (en) | 1994-04-13 |
Family
ID=27110592
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP92914815A Withdrawn EP0591430A1 (en) | 1991-06-27 | 1992-06-24 | Improved cooling medium for use in a thermal energy storage system |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0591430A1 (en) |
| JP (1) | JPH06508679A (en) |
| AU (1) | AU659663B2 (en) |
| CA (1) | CA2111831A1 (en) |
| WO (1) | WO1993000412A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999029800A1 (en) * | 1997-12-11 | 1999-06-17 | Alliedsignal Inc. | A cold pack comprising an aqueous clathrate composition |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4332690A (en) * | 1979-04-23 | 1982-06-01 | Mitsubishi Denki Kabushiki Kaisha | Heat storage system comprising a phase change medium and a nucleating agent |
| US4540501A (en) * | 1984-09-12 | 1985-09-10 | The United States Of America As Represented By The United States Department Of Energy | Gas hydrate cool storage system |
| US4821794A (en) * | 1988-04-04 | 1989-04-18 | Thermal Energy Storage, Inc. | Clathrate thermal storage system |
| WO1993004139A1 (en) * | 1991-08-27 | 1993-03-04 | Allied-Signal Inc. | Improved thermal energy storage system and process for thermal energy storage and transfer |
-
1992
- 1992-06-24 CA CA 2111831 patent/CA2111831A1/en not_active Abandoned
- 1992-06-24 EP EP92914815A patent/EP0591430A1/en not_active Withdrawn
- 1992-06-24 AU AU22956/92A patent/AU659663B2/en not_active Ceased
- 1992-06-24 JP JP5501658A patent/JPH06508679A/en active Pending
- 1992-06-24 WO PCT/US1992/005368 patent/WO1993000412A1/en not_active Application Discontinuation
Non-Patent Citations (1)
| Title |
|---|
| See references of WO9300412A1 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2111831A1 (en) | 1993-01-07 |
| JPH06508679A (en) | 1994-09-29 |
| AU2295692A (en) | 1993-01-25 |
| WO1993000412A1 (en) | 1993-01-07 |
| AU659663B2 (en) | 1995-05-25 |
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