Title of Invention

A REFRIGERANT COMPOSITION FOR A SINGLE STAGE REFRIGERATION SSYSTEM

Abstract A refrigerant composition for a single stage refrigeration system comprising up to 50 molar percent of nitrogen up to 40 molar percent of Methane at least one of the following gases, gas combinations selected from (i) ethane ( up to 45 molar percent) (ii) ethylene up to 45 molar percent) (iii) combination of gases in (i) and (ii) ( up to 45 molar percent) (iv) n-Butane (up to 70 molar percent) (v) Isobutane (up to 70 molar percent) (vi) Argon (up to 70 molar percent) (vii) Helium(up to 70 molar percent) (viii) Hydrogen (up to 70 molar percent) (ix) Neon ( up to 70 molar percent) (x) any combination of gases in (iv) to (ix) (up to 70 molar percent ).
Full Text This invention relates to a refrigerant composition for a single stage refrigeration system.
Our co-pending Application for Patent relates to a refrigerant composition for a single stage refrigeration system under Patent Application No, 415 MAS 03 „
Simple refrigerant systems use a method called vapor compression cycle. The vapor compression cycle is a method in which a compressor such as a piston compressor compresses a low-pressure refrigerant vapor. In the next stage, a condenser condenses the warm compressed vapor, resulting in a partial or complete condensation of the vapor. This condensed refrigerant then passes through a fine capillary tube or other constriction into a larger chamber at low pressure. As the refrigerant enters the large chamber, it evaporates and absorbs heat, resulting in the vapor. This refrigerant vapor is then routed to the intake of the compressor, thus closing the cycle. This is the so-called closed loop refrigeration system.
A single stage refrigerant system is used to achieve temperatures up to -4O0 C. For temperatures in the range of-50°C to -80o C a two stage cascaded vapor compression system has been proposed. This method uses a single refrigerant per stage and two compressors, one for each stage. For still lower refrigeration temperatures, more cascaded stages are required. Typically, four stage cascade vapor compression systems are proposed for reaching cryogenic temperatures, lower than -150°C.
An advance in technology has been achieved by using a single stage compression system with a mixture of refrigerants. This method has been used to achieve temperatures far below those that can be achieved using a cascaded multistage system, for example, the range -100°C to -210°C. This method uses a mixture of several refrigerants each of which with different boiling points.
In mixed gas refrigeration systems, the refrigerant in gaseous form is compressed in a compressor and thereafter cooled to remove the heat of compression to near- ambient temperatures. Partial condensation of the refrigerant may occur in some cases. The refrigerant is then passed through the high pressure side of a regenerative heat exchanger, which is arranged in a cryostat. The high pressure refrigerant leaving the regenerative heat exchanger is throttled to a lower pressure in a throttling device such as an orifice or a capillary tube. The refrigerant is then passed through an evaporator where it absorbs heat from the substance (solid or fluid) being cooled.
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Researchers have proposed several refrigerant compositions. There is still a need for a refrigerant composition that can achieve better efficiency or a greater cooling effect or both.
This disclosure is directed toward a composition of refrigerants for use in single stage refrigeration systems to achieve cryogenic temperature ranges. Applications for such composition of refrigerants include household or commercial refrigeration systems such as refrigerators, electronic circuit cooling, medical applications, cryo-vacuum pumps, storing of biological specimens and tissues at low temperatures, cooling of Gamma-ray, Infra Red and X-ray detectors, cryosurgery and the like.
In one aspect, disclosed herein is a composition of gas cryogenic refrigerant— for use in systems at ambient temperatures preferably above 30 °C and refrigeration temperatures from -173 °C to -210 °C —consisting of 1-50 molar percent of Nitrogen, up to 40 molar percent of Methane, up to 45 molar percent of either or both of Ethane and Ethylene, and up to 70 molar percent of at least one or a combination of n-Butane, Isobutane, Argon, Helium, Hydrogen and Neon.
The new refrigerant compositions proposed herein will result in an efficient cooling system when the ambient temperature is preferably greater than 30 °C. For example, at an ambient temperature of 42 °C (315 K), refrigerating temperature of -188 °C (85 K), with operatmg pressures (high/low) of 20 bar/3 bar, and ensuring that the minimum temperature difference between the hot and the cold streams in the regenerative heat exchanger being set to 0°C in the heat exchanger, the composition shown in Table 1 will result in Exergy efficiency (r\ex) of 42%; Refrigeration of 85 Joules per litre of low pressure refrigerant compressed.

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table 2 shows an example of a refrige ant composition for use at an ambient temperature of 42 "C (315 K), refrigerating temperature of-180 "C (93 K), with operatmg pressures (high/low) of 20 bar/3.5 bar, and ensuring that the minimum temperature difference between the hot and the cold streams in the regenerative heat exchanger being set to 5°C m the heat exchanger, and an isothermal compressor, the refrigerant composition shown in Table 2 will result in, Exergy efficiency (r|„) of 29%; Refrigeration of 74 Joules per litre of low pressure refrigerant compressed.

Table "3 shows an-example of a retVigerant composition tor use at an ambient temperature of 42 °C (315 K), refrigerating temperature 6f -143 *C (130 K), with operating pressures (high/low) of 20 bar/8 bar and ensuring that the minimum temperature difference between the hot and the cold streams in the regenerative heat exchanger being set to O"C in the heal exchanger, and an isothermal compressors tlie refrigerant composition sltown in Table 3 will result in Exergy efficiency (r]ex) of 31,7%; Refrigeration of 74 Joules per litre of low pressure refrigerant compressed.


Table 4 snows an example of a retrigerant composition for use at an ambient temperature of 42 "C (315 K), refrigerating temperature of -178 °C (95 K), with operating pressures (higlVlow) of 20 bar/7 bar, and ensuring that the minimum temperature difference between the hot and the cold streams in the regenerative heat exchanger being set to O"C in the heat exchanger, and an isothermal compressor, the refrigerant composition shown in Table 4 will result in Exergy efficiency (nex) of 27,3%; Refrigeration of 39 Joules per litre of low pressure refrigerant compressed.



We claim:
1. A refrigerant composition for a single stage refrigeration system
comprising
up to 50 molar percent of Nitrogen up to 40 molar percent of Methane
at least one of the following gases, gas combinations selected from (i) ethane (up to
45 molar percent) (ii) ethylene (up to 45 molar percent) (iii) combmation of gases in
(i) and (ii) (up to 45 molar percent) (iv) n-Butane (up to 70 molar percent) (v)
Isobutane (up to 70 molar percent) (vi) Argon (up to 70 molar percent) (vii) Helium
(up to 70 molar percent) (viii) Hydrogen ( 70 molar percent) (ix) Neon (up to 70
molar percent) (x) any combinations of .(v) to (ix) (up to 70 molar percent),
2. A refrigerant composition as claimed in Claim 1 wherein the molar percent of Nitrogen is 1-50, of methane up to 40, of n-Butane 25-60, of Isobutane 25-60, of tiie combination of n-Butane and Isobutane is 25-60.
3. A refrigerant composition for a single stage refrigerating system substantially herem described.
4. A method of refrigerating a substance, in a single stage, by preparing a refrigerant composition, compressing the said refrigerant, cooling the said compressed composition, throttling the said cooled refrigerant, and passing the same, thereafter, through an evaporator for cooling the substance, the said composition being prepared in accordance with any of the preceding Claims.

Documents:

0414-che-2003 abstract.pdf

0414-che-2003 claims-duplicate.pdf

0414-che-2003 claims.pdf

0414-che-2003 correspondence-others.pdf

0414-che-2003 correspondence-po.pdf

0414-che-2003 description (complete)-duplicate.pdf

0414-che-2003 description (complete).pdf

0414-che-2003 form-1.pdf

0414-che-2003 form-19.pdf

0414-che-2003 form-26.pdf


Patent Number 205644
Indian Patent Application Number 414/CHE/2003
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 09-Apr-2007
Date of Filing 19-May-2003
Name of Patentee M/S.INDIAN INSTITITUTE OF TECHNOLOGY
Applicant Address CHENNAI600036
Inventors:
# Inventor's Name Inventor's Address
1 GADHIRAJU VENKATARATHNAM INDIAN INSTITITUTE OF TECHNOLOGY CHENNAI600036
PCT International Classification Number C09K 5/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA