|Title of Invention||
A REFRIGERANT COMPOSITION FOR A SINGLE STAGE REFRIGERATION SYSTEM
|Abstract||A refrigerent composition for a single stage refrigeration a system -415 Che B3 A refrigerent composition for a single stage refrigeration system Comprising less than 30 molar percent of nitrogen less than 20 molar percent of methane characteria at least one of the following gases selected from (i) ethane up to 45 molar percent (ii) ethylene up to 45 molar percent (iii) combination of gases in and (ii) tup iv 45 molar percent (iv) propane up to 70 molar percent (v) propylane 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 of (iv) to (ix)up to 70 molar percent|
This invention relates to a refrigerant composition for a single stage refrigeration system.
Simple refrigeration 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 a 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 larger 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 -40°C. For temperatures in the range -50 °C to -80 °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 multi¬stage 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 leavmg 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.
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 below 30 °C and refrigeration temperatures from -173 °C to -210 °C —consisting of less than 30 molar percent of Nitrogen, less than 20 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 Propane, Propylene, Argon, Helium, Hydrogen and Neon.
In a further aspect. Ethane or Ethylene need not be used in the composition.
The new refrigerant compositions proposed herein will result in an efficient cooling system when the ambient temperature is preferably less than 30 °C. For example, at an ambient temperature of 27 °C (300 K), refrigerating temperature of -185°C (88 K), with operating pressures (high/low) of 20 bar/2.4 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 in the heat exchanger, and an isothermal compressor, the composition shown in Table 1 will result in Exergy efficiency (r\ex) of 30%; Refrigeration of 61 Joules per litre of low pressure refrigerant compressed.
N itrogen 28.1 mo lar percent
Methane 19.8 molar percent
Ethane 7.2 molar percent
Propane 44.9 molar percent
Table 2 shows an example of a reliigerant composition at an ambient temperature of 27 °C (300 K), refrigerating temperature of -191°C (82 K), witJr operating pressures (high/low) of 20 bar/2.5 bar, and ensuring tliat the minimum temperature difference between the hot and the cold streams in the regenerative heat exchanger being set to 5°C in the heat exchanger, and an isothermal compressor, the composition shown in Table 2 will result in Exergy efficiency (nex) of" 16%; Rejfigeration of 32 Joules per litre of low pressure refl'igerant compressed,
Nitrogen 27.4 molar percent
Methane 17.3 molar percent
Propane _ 45.1 mo lar percent
Neon 10.2 molar percent
As shown in Table 2, under some conditions, ethane may be'completely :-excluded from the refrigerant composition.
Our co-pending Application for Patent No. 414 CHE 2003 relates to a retngerant composition for a single stage refrigeration system.
1 ..A refrigerant composition for a single stage refrigeration system compirsing
less than 30 molar percent of nitrogen less that 20 molar percent of methane characterised by at least one of the following gases selected from (1) ethane cup 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) propane up to 70 molar percent (v) propylene up to 70 molar percent (vi) Argon up to 70 molar percent (viii) 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)
2„ A reiriaeranl con^v^'siiion as t.lauued n\ (Jiauii I vvhcrem the miliar perceni nj niiix^iien ts less tiian 50, oi'methane icss than 20 of propane 27-60. ol fTrc!p\letic 25-60, ol'thc ceirnhfri:i!!
4, A methtM.] of rdrigeralnm a subsiaiKC. m a snigSe stage. b\' prcpann.u i> reingeranl convpossiiou. eoinpressiug ihc said rctngerani. coohng Ihe said eoniprcssed compositKiii. ihroitfnig the said eoi4ed refrigerant aiid passnig the same. Ihereatter, through an evaporator for coolmg (he snhsianee. eJiaraelensed in dial the said composHion is pieparcd ui accordance with am of ihe piecedmg (71aniis.
|Indian Patent Application Number||415/CHE/2003|
|PG Journal Number||30/2009|
|Date of Filing||19-May-2003|
|Name of Patentee||M/S. INDIAN INSTITUTE OF TECHNOLOGY|
|Applicant Address||IIT P.O, CHENNAI 600 036|
|PCT International Classification Number||N/A|
|PCT International Application Number||N/A|
|PCT International Filing date|