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Title:
FLUIDS FOR USE IN SORPTION REFRIGERATORS AND HEAT PUMPS
Document Type and Number:
WIPO Patent Application WO/1984/002715
Kind Code:
A1
Abstract:
Working fluid for an absorption refrigerating machine comprises trifluoroethanol as refrigerant and defined nitrogen-containing heterocyclic compounds as absorbents.

Inventors:
VELTWISCH DIETER (DE)
Application Number:
PCT/GB1983/000347
Publication Date:
July 19, 1984
Filing Date:
December 22, 1983
Export Citation:
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Assignee:
BRITISH PETROLEUM CO PLC (GB)
International Classes:
C09K5/04; F25B15/00; (IPC1-7): C09K5/04
Foreign References:
GB2080821A1982-02-10
DE1044843B1958-11-27
US2149948A1939-03-07
GB1357947A1974-06-26
Other References:
PATENT ABSTRACTS OF JAPAN, Volume 5, No. 156 (C-74) (828) 6 October 1981, & JP, A, 5688485 (Sanyo) see Abstract
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Claims:
*Claims:
1. A mixture of substances suitable for use in an absorption heat transfer machine which mixture comprises 2,2,2trifluoroethanol and that it also contains at least one of (a) an imidazolidone derivative of the general formula (I) 10 in which each of R1 and R2 are hydrogen or C1C4 alkyl and R1, R2 are the same or different and R3 is C1C4 alkyl (b) an imidazole derivative of the general formula (II) 20 in which at least one of R^ and R5 is C^C4 alkyl and the 'other is hydrogen or C1C alkyl *' (c) a pyrazole derivative of general formula (III) ' *& 25.
2. in which R6 is hydrogen or CjC4 alkyl and R7 is C1C4 alkyl. (d) a pyridazine derivative of the general formula (IV) in which R8 is hydrogen or C1C alkyl (e) a pyridone derivative of the general formula (V) 40 (V) R3 in which each of R9 and R10 is hydrogen or 0^04 alkyl and R9, R10 are the same or different (f) a quinoline derivative of the general formula (VI) in which at least one of R^ and R 2 is C^C4 alkyl and the other Is hydrogen or C1C4 alkyl and/or (g) a lactam derivative of the general formula (VII) in which m is 1, 2,.
3. or 4, and (a) when m » 1, R13 is C1C.
4. lkyl and 14 is hydrogen or C1C alkyl; (b) when m » 2 or 4, each of R13 and R1^ Is hydrogen or C1C.
5. lkyl and R*3 and *4 may be the same or different; (c) when m » 3, at least one of R13 and Rl is C1C.
6. lkyl and the other is hydrogen or C1C alkyl. gυ EAfT OM " 2 A mixture of substances according to claim 1 which comprises 2,2,2trifluoroethanol and at least one of Nmethyl£caprolactam, Nmethyl2piperidone, Nmeth l2pyridone, 1methylimidazole, Nbutylimidazole, 1 ,2dimeth limidazole, l,3dimethyl2imidazolidone and 3methylpyridazine.
7. 3 An absorption process for transferring heat against a temperature gradient using a refrigerant which is 2,2,2trifluoroethanol and an absorbent according to either claims 1 or 2. OMPl Λ . IPO.
Description:
FLUIDS FOR USE IN SORPTION REFRIGERATORS AND HEAT PUMPS

The present invention relates to absorption heat transfer machines for transferring heat against a temperature gradient, and to working fluids for use therein.

Machines which transfer heat against a temperature gradient i.e. from a relatively cold heat source to a heat sink at higher temperatures are well known. These machines may be described as refrigerating machines. Refrigerating machines working on the absorption principle are well known. In such absorption heat transfer machines a pair of working substances is used which may be described as a refrigerant and an absorbent. The heat transfer process takes place in a closed system. Heat is taken into the system from outside by evaporation of the refrigerant in an evaporator. The evaporated refrigerant then passes to an absorber in which the refrigerant is absorbed in an absorbent which is poor in refrigerant. Heat is produced by the absorption and is given up to an external coolant. The liquid absorbent, now rich in refrigerant, is passed to a second evaporator (the generator) where heat is supplied to drive out the refrigerant from the absorbent. The resulting solution poar in refrigerant is returned to the absorber. The refrigerant Vapour is cooled and liquefied by heat exchange with an external coolant and then returned to the evaporator.

Refrigerating machine's may be used either to withdraw heat from material which it is desired to cool in which case they may be termed as refrigerators. Alternatively they may be used to introduce heat into material which it is desired to heat eg the air inside a house.

OMPl

Machines intended for heating may be the conventional heat pumps in which heat at a relatively high temperature provides the energy to transfer heat from a relatively low temperature heat source to a heat sink at an intermediate temperature. Alternatively heat may be supplied from a heat source at an intermediate temperature and transferred to a heat sink at a relatively high " temperature by making use of the energy obtained by the transfer of some of the heat down a temperature gradient from the heat source at intermediate temperature to a second heat sink at a lower temperature. Such machines may be described as heat transformers.

Working fluid pairs (refrigerant and absorbent) for use in absorption refrigerating machines should in particular satisfy the following requirements:

(a) the difference in boiling temperature between the refrigerant and the mixture of refrigerant and adsorbent should be as great as possible,

(b) the mixture of refrigerant and absorbent should not be solid in the range of compositions and working temperatures used,

(c) the mixture of refrigerant and absorbent should be thermally stable,

(d) the expenditure of energy required for rectifying the mixture evaporated from the generator in order to separate the absorbent from the refrigerant should be low,

(e) the viscosity of the mixture of refrigerant and absorbent in the range of working temperatures and compositions should be low.

GB 2080821 discloses mixtures of trifluoroethanol as refrigerant and various substances as absorbents in absorption refrigeration systems. „-.

-^

The suitability of a refrigerant-absorbent pair cannot be r determined from the properties of the individual component's. In particular, it is not possible to predict the stability of the refrigerant-absorbent pair.

The present invention relates to a mixture of substances suitable for use in an absorption heat transfer machine, which mixture comprises 2,2,2-trifluoroethanol and an absorbent characterised in

that the absorbent is at least one of

(a) an Imidazolidone derivative of the general formula (I)

in which each of Rl and R2 is hydrogen or C j -C4 alkyl and *, R^ are the same or different and R 3 is C1-C4 alkyl

(b) an imidazole derivative of the general formula (II)

is in which at least one of 4 and R^ is C1-C4 alkyl and the other is hydrogen or C1-C4 alkyl

(c) a pyrazole derivative of general formula (III)

in which R° is hydrogen or C1-C4 alkyl and R 7 is C1-C4 alkyl. (d) a pyridazine derivative of the general formula (IV)

in which R 8 is hydrogen or C1-C alkyl

(e) a pyridone derivative of the general formula (V)

in which each of R 9 and R 10 is hydrogen or C1-G4 alkyl and R 9 , R 10 are the same or different

(f) a quinoline derivative of the general formula (VI)

in which at least one of R 11 and R 12 is C1.-C4 alkyl and the other is hydrogen or 0^-04 alkyl, and/or

(g) a lactam derivative of the general formula (VII)

(CH 2 ) (VII)

.-»

.*•*

in which is 1, 2, 3 or 4, and (a) when to - 1, R 13 is C1-C4 alkyl and R 1 ^ is hydrogen or C1-C alkyl; (b) when m » 2 or 4, each of * 3 and R 1 * Is hydrogen or C^-C4 alkyl and R* 3 and Rl* may be the same or different; (c) when m - 3, at least one of 13 and R is C1-C4 alkyl and the other is hydrogen or C^-C alkyl. According to a further aspect of the present invention there Is provided a process for transferring heat against a temperature gradient using a refrigerant which is 2,2,2-trifluoroethanol and an absorbent characterised in that the absorbent is at least^one of (I) to (VII). The C1-C4 alkyl may be straight chain or branched. / Examples of absorbents which may be used are:

(a) Formula (I): l,3-dime h l-2-imidazolidone (R* » methyl;

R 2 =» hydrogen, R 3 ■ methyl).

(b) Formula (II): N-methylimidazole (R* - methyl, R5 » hydrogen) N-n-butylimidazole (R^ n-butyl, R.5 » hydrogen)

1,2-dimethylimidazole (R^ =■ methyl; R 5 ■ methyl)

tjUREATT

(c) Formula (III) : 3-methylpyτazole (R 6 = « hydrogen, R 7 - methyl)

(d) Formula (IV) : pyridazine (R 8 = hydrogen)

3-methylpyridazine (R 8 ■ methyl)

(e) Formula (V): N-meth l-2-pyridone (R 9 =» methyl, R 10 - hydrogen)

(f) Formula (VI): 6-methyl quinoline (RU » methyl; R^ =» hydrogen

(g) Formula (VIII): N-methyl- -caprolactam (R 13 = » hydrogen,

R14 „ methyl, m - 3) N-methyl-2-piperidone (R 13 ■ hydrogen, Rl4 =■ methyl, m » 2)

5-methyl-2-pyrrolidone (R 13 » methyl, 14 « hydrogen, 1) The composition of the working fluid will of course vary in different parts of the heat transfer process. However the absorbent preferably is 50-95% by weight of the total weight of working fluid (refrigerant plus absorbent) in the heat transfer process as a whole.

The mixture of refrigerant and absorbent Introduced into the machine may contain various additives such as corrosion inhibitors, stabilisers and/or surface active agents. These will generally remain in the absorbent unless they are volatile.

The present invention will now be illustrated by reference to the following experiment.

Measurements were carried out on various absorbents and on mixtures containing trifluoroethanol (TFE) and various absorbents. The stability of the mixtures was also determined by sealing samples into a glass ampoule and heating for 100 hours at 200°C. The samples were then examined by gas chromatography to test for the presence of decomposition products. None were found. 4

The results are given in the Table. f The suitability of the absorbents for use with trif luoroethanol in absorption heat transfer machines can be seen from the results. The compounds N-meth l-£-caprolactame, N-meth l-2-piperidone, N-methyl-2-pyridone, 1-methyl-imidazole, N-butyl-imidazole, 1 ,2-dimeth l-imidazole, 1 ,3-dimethyl-2-imidazolidone and 3-methyl- pyridazine are especially suitable if a high temperature lift effect and a high temperature level of the high grade heat are desired.

OMPL

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