Note: Descriptions are shown in the official language in which they were submitted.
WO 93/14173 PCr/GB92/02382
212618~ -
CO~POSITIONS USEFaL AS REFRIGERANTS.
ThB present in~ention relates generally to
refrigerant compositions for cooling and heating
applications and to the use of such compositions in
heat transfer devices. More particularly, the pre~ent
invention is concerned with refrigerant composi~ions
1~ which are designed to rep}ace dichlorodifluoromethane
(Refrigerant R-12).
~ echa~ical refrigerstion systems a~d relsted heat
transfer deYices such as heat pumps and
air-conditioning sy~ems are well known. In such
devices, a refrigerant liquid of a sultable boiling
point evaporates at low pressure taking heat from
surrounding zone. The resulting vapour ~s then
compre~sed a~d passed to a conden~er where it condenses
a~d give~ off heat to a seco~d zone. the condensate
being returned through an e~pansion ~alve to the
evaporator, so completing the c~cle. The mechanical
energy required for compressing the vspour and pumping
the liquid may be provided by an electric motor or an
internal combustion engine.
In addition to having a suitable boiling point and
a high latent heat of vaporisation, the properties
preferred of a refrigerant include }ow toxic~ty, non-
flammability, non-corrosivity, high stability and
freedom from ob3ectionable odour.
~itherto, heat transfer device~ have tended to use
fuLly and partially halogenated chlorofluorocarbon
re~rigerants. Particular mention may be made of -
dichlorodifluoromethane (Refrigerant R-12) which
possesse~ a suitable combination of properties and has
or many ye~rs been the most widely used refrigerant.
:
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In recent years, howeYer, there has been -:
increasing international concern that the fully and
partially halogenated chlorofluorocarbons may be
damaging the earth's protective ozone layer and ~here ~
is general agreement that their manufacture and use ::
should be severely restricted and eventually phased out
completely.
Whilst heat ~ransfer devices of the type to which
the present invention relates are essentially closed
systems, loss of refrigera~t to the atmosphere can
occur due to leakage during operation of the equipment
or during maintenance procedure~. It is imporsant,
therefore, to replace fully and partially halogenated
c~lorofluorocarbon refrigerants by materials having
subs~antially lower, preferably zero, ozone depl~tion
potential~.
In addition to the possibility of ozone depletion,
it has been suggested that sig~lfica~ concentratio~s
of chlorofluorocarbon refrigerants in the atmosphere
might contribute to global warming (the so-called
greenhouse effect). It is desirable, therefore, to use
refrigerants which have relatively short atmospheric
lifetimes as a result of their ability to react with
other atmospheric constituents such as hydroxyl
radicals.
The present invention provides a refrigerant
composition which may be used as a replacement for
Refrigerant R-12. The compo~ition contains refrigerant -
compounds which ha~e e3sentially zero ozone depletion
pot2ntials and comparatively low direct global warming
potentials. --:
~ccordingly, the present invention provides a
re~rigerant composition comprising a mi~ture of
1,1,1,2-tetrafluoroethane (Cr3CH2F) and at least one
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fluorinated ether selected from trifluoromethyl meehyl
ether (CF30C83) and fluoromethyl trifluoromethyl ether
( CF30C~2F )
Refrigerant compositions in accordance with rhe
present invention typically contain from 5 to 952 by
weight of 1,1,1,2-tetrafluoroethane and from 95 to 5Z
by weight of the ether. Additionally, the refrigerant
compositions of the invention may contain other
refrigerant compounds which have low and pre~erably ~-
zero ozone depletion potentials, for e~ample other
hydrofluoroalksne~ and/or other fluorin~ted ethers -`
containing residual hydrogen atoms. Esamples of other
1~ hydrofluoroalk~nes which msy be incorporsted in the
refrigerant compositions of the invention include
difluoromethane (R-32), l,l.l-~rifluoroethane (R-143a),
1.1,2,2-tetrafluoroethane ~R-134), pentafluoroethane
(R-125) and l,l-difluoroethane ~R-152a). E~amples of
other fluorinated ethers which ma~ be included in the
refrigerant composition~ of the invention are the
fluorinated dimethyl ethers containing re~idual
h~drogen stDms~
Although the refrigerant compositlons of the
invention may comprise other refrigerant compounds, the
preferred refrigerant compositions of the invention -~
consist ess~ntially of 1,1,1.2-tetrafluoroethane and at
least one fluorinated ether selected from
trifluoromethyl methyl ether and fluoromethyl -
trifluoromethyl ether.
Although the refrigerant compositions of ehe
invention may be zeotropic they are preferably
azeotropic or azeotrope-like.
In one embodiment of the present invention, the
refrigerant composition compri~es a mixture of
1,1,1,2-tetra~luoroethane and fluoromethyl
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21261~ - 4 -
trifluoromethyl ether. A specific composition of this -~
type is one which consists essentially of the stated
components. Such compositions will typically comprise
from 25 to 75 2 by weigh~ of 1,1,1,2-tetrafluoroethane
and from 75 to 2~ ~ by weight of fluoromethyl
trifluoromethyl ether. Refrigerant compositions of the
invention comprising 1,1,1,2-tetrafluoroethane and
fluoromethyl trifluoromethyl ether a~ essential
compone~ts may suit bly replace Refrigera~t R-12 in
many applications. Ho~èver, such compositions may be
particularly useful as a replacement for R-12 in heat
pumps and automotive air conditioners. Heat pumps snd
automotive air conditioners operate with high discharge
temperatures, typically around 80 C, which tends to
result in fairly high pressures in the co~denser. B~
using blends of 1,1,1.2-tetrafluoroethane and
fluoromethyl trifluoromethyl ether as the working fluid
in such s~tems, it is possible ~o achieve lower
conden~er pressures at these high discharge
temperatures than is possible when Refrigerant R-12 or
1,1,1,2-tetrafluoroethane (the generally accepted
replacement for Refrigerant R-12) are u~ed. Our
research indicates thst at a discharge temperature of
80C a condenser pressure of around 17.7 bar is
attainable when using a refrigerant composition
comprising 25 Z by weight of 1,1,1,2-tetrafluoroethane
and 75 Z by weight of fluoromethyl trifluoromethyl
ether.
Table 1 shows the performance of a number of
refrigerant compositions of the invention comprising
1,1,1,2-tetrafluoroethane (R-134a in the Table) and
fluoromethyl trifluoromethyl ether (E-134a in the
Table). The percentage by weight of each component in
the refrigerant compositions evaluated is gi~en in the
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- 5 -
second row of the Table. Thus, refrigerant compo3itions
respectively comprising 75 Z by weight of
1,1,1,2-tetrafluoroethane and 25 2 by weight of
fluoromethyl trifluoromethyl ether; 50 ~ by weight of
1,1,1.2-tetrafluoroethane snd 50 2 by weight of
fluoromethyl trifluoromethyl ether; and 25 Z by weight
of 1,1,1,2-tetrafluoroe~ha~e and 75 ~ by weight of
fluoromethyl trifluoromethyl ether were evaluated. The
opera~ing conditlons which were 3elected for the
evaluation are represe~tative of those esisting in a
domestic refrigeration ~ystem. Specifically, these
conditions were as follows:
Evaporator Temperature: -25C
Condenser Temperature: 40C
Superheat: 45C
Subcooling: lO~C
Cooling Duty: 1 ~W
Isentropic Compressor Efficiency: 75
The performance parameters of the refrigerant
compositions which are presented in the Table, i.e.
conden~er pressure, evaporator pressure, discharge
~5 temperature, return gas temperature, volumetric flow,
system efficiency (coefficient of performance, b~ which
is meant the ratio of cooling duty achieved to
mechanical energy supplied to the compre~or),
refrigeration capacity (cooling du~y per unit swept
volume of the compressor)~ and the glide in the
evaporator ~the temperature range over which the
refrigerant composition boils in the evapora~or), are
all art recognised parameters.
The performance of Refrigeran~ R-12 and
1,1,1,2-tetrafluoroethane, which is the generally
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- 6 -
accepted replacement for Refrigerant R-12, under
identical opersting condi~ions are also shown in Table
1 by way of comparison. -
From Table 1, it is apparent that refrigerant .
compositions according to the invention comprising
1,1.1,2-tetrafluoroethane and fluoromethyl
trifluoromethyl ether can e~hibit a performance in a
refrigera~ion s~stem which is not too far removed from
that of Refrigerant R-12. Furthermore, the gl~de in the
e~aporator was o~ly 0. 29C for all ~he miYed refrigerant
compositions evaluated showing that such compositions
are azeotrope like.
In a prefer~ed embodiment of the pre~ent -:~
inventio~, the refrigerant composition comprises a
mixture of 1,1,1,2-tetrafluoroethane and .:
trifluoromethyl methyl ether, optio~ally together with :~
fluoromethyl trifluoromethyl ether and/or at least one ~:~
other fluorinated e~her containing residual hydrogen :~
atoms snd/or at least one other hydrofluoroalkane.
Particulsrly preferred refrigerant compositions are
mixtures consisting essentiallr of
191,1,2-tetrafluoroethane and trifluoromethyl methyl
ether. :
2S Refrigerant compositions comprising a mixt~re of
l,l,l,Z-tetrafluoroethane and trifluoromethyl methyl
ether have been found to eshibit a similar performance
to Refrigerant R-12 in a refrigeration cycle. In
consequence, such compositions may be used in plaoe of
Re~rigerant R-12 which is at present widely used as 8
working fluid in refrigeration systems and related heat
trans~er devices. Purthermore, compositions comprising
1,1,1,2-tetrafluoroethane a~d trifluoromethyl methyl
ether benefit from the particularly short atmo~pheric
lifetlme of trifluoromethrl methyl ether (ca 3.6 years)
W093l14173 PCT/GB92~02382
212618i
and, thus, can exhibit a low direct global warming
pOt ential.
Preferred refrigersnt composition3 based on
1,1,1,2-tetrafluoroethane and trifluoromethyl methyl
ether comprise from 5 to 75 ~ by weight of ~-
1,1,1,2-tetrafluoroethane and from 95 to 25 Z by weight
of trifluoromethyl methyl` ether. Particularly preferred
refri~erant compositions of this t~pe compriRe from 5 ~;
to 60 ~ by we~ght of 1,1,1,2-tetrafluoroethane and from
95 to 40 2 by weight o~ trifluoromethyl mQthyl ether,
with compositio~s comprising from 25 to 50 ~ b~ weight
of 1,1,1~2-te~rafluoroe~hane and from 75 to 50 2 by
weight of trifluoromethyl methyl ether being especially
preferred. The preferred compositions are therefore
characterised b~ the presence of a 3ubsta~tial amount
of trifluoromethy} methyl ether which confers on the
composition a lower direct global warming pote~tial.
~owe~er, surprisingly such compositlons also e2hibit a
performance ~n a refrigeration system which is
comparable to Refrigerant R-12.
Trifluoromethyl methyl ether is slightly flammable
and our reRearch suggests that mixed refriBerant
compositions comprising in e~cess of 40 ~ by weight of
this ether and less than 60 Z by weight of
1,1,1.2-tetrafluoroethane may also be flammable. It is
believed that the potential flammability o~ such
refrigerant compositions may not be a problem in
practice, bearing in mind that heat transfer devices
are e~sentially closed systems and that~certain
devices, such as domestic refrigeration systems, only
contain small quantities of the refrigerAnt. Moreover,
the benefit of using a refrigerant composition
comprising a large amQunt of trifluoromethyl methyl
ether opposite reduced global warming potential may
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outweigh any possible disadvantage opposite
flammability. ~owever, if flammability is a concern,
then compositions containing from 70 to 95 ~ by weight
of 1,1,1,2-tetrafluoroethane and from 30 to 5 2 by
weight of trifluoromethyl methyl ether are preferred,
with compositio~s containing from 70 to 85 ~ by weight
of 1.1~1,2-tetrafluoroethane and from 30 to 15 Z by
weight of trifluoromethyl methyl ether being
particularly pre~erred, in view of their
non-flam~ability.
Tsble 2 shows the performance of a number of
refrigerant compositions of the i~Yention comprising
1,1.1,2-tetrafluoroethane (R-134a in the Table) and
trif}uoromethyl methyl ether (E-143a in the Table). The
percentage by weight of each component in the
refrigerant compo~itions evaluated is given in the
~econd row of the Table. Thus, refrigeran~ compositions
respectively comprising 75 Z by weight of
1.1,1,2-tetrafluoroethane and 25 Z by weight of
tri~luoromethyl methyl ether; 50 2 by weight of
1,1,1,2-tetrafluoroethane and 50 ~ by weight of
trifluoromethyl methyl ether; and 25 Z- by weight of
1,1,1~2-tetrafluoroethane and 75 Z by weight of
trifluoromethyl methyl ether were evaluated. The
operating contitions which were selected for the
evaluation are representative of those existing in a
dome~tic refrigeration system. Specifically, the e
conditions were a~ follows:
Evaporator Temperarure: -25C
Condenser Temperature: 40C
Superheat: 45 D C
Subcooli~g: 10C
Cool~ng Duty: 1 XW
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212618~ ~ `
g `. .
Isentropic Compressor Efficiency: 7S
- '' '~
The perfor~ance parameters of the refrigerant ~-
compositions ~hich are presented in the Table, i.e.
~ condenser pressure, evaporator pressure, discharge
temperature, return gas temperature, volumetric flow,
system efficiency (coefficient of performance, by which
is meant the ratio of cooling duty ach$eved to
mechanical energy supplied to the compressor)~
refrigeration capacity (cooling duty per unit swept
vslume of the compressor), and the glide in the
evaporator tthe temperature range o~er which the
refrigerant composition boils in the evaporator~, are
all art recognised parameters.
T~e performance of Refrigerant R-12 a~d --
1,1,1,2-~etrafluoroethane, which is the generally
accepted replacement for Refrigerant R-12, under
identical operating conditions are also ~hown in Table
2 by ~ay of comparison.
~rom Table 2, lt is apparent that refrigerant
composition~ accordlng to the invention comprising
1,1,1,2-tetrafluoroethane and trifluoromethyl methyl
ether csn eshibit a performance in a refrigeration
system which i5 comparable to that of Refrigerant R-12. ~-
Furthermore, the glide in the evaporator was -~
essentially zero for all the mixed refrigerant
compositions tested showing that such cvmpositions are
azeotrope like.
The refrigerant compositions of the invention may
be prepared by a simple mixing process. -
The compssitions are useful in all types of
compression cycle heat tsansrer de~iceR. Thus, they
may be used to pzovide cooli~g by a method involving
conden~ing the refrigerant composition and thereafter
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~1261~ `
- 1 0 _ ,
evaporating it in a heat e~change relationship with a
body to be cooled. They may also be used to provide
hesting by a method in~olYing condensing the
refrigerant composition in a heat exchange relationship -~
with B body to be heated and thereafter evaporating it.
The compositions of the invention provide a good
compromi3e between capacity and efficiency combined
with low atmospheric lifetime and esse~tially zero
ozone depletion. They are especially suitable for
applications currently sa~isfied by Refrlgerant R-12,
for e~ample domestic refrigeration. automobile
air-conditioning and refrig~rated food transport.
:-
~-
W093/14173 PCT/GB92~02382
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ll- 212618~ ~
TABLE 1
REFRIGERANT R-12R-134a R-134a/E-134a
. .. _ ... , ..
% BY WEIGHT 100 100 75/25 50/50 25/75
, . .......... . . . , . .
CONDENSER
1 PRESSURE ~Bar)9.6010.10 9.04 8.07 7.28
O , . . ....... ..
EVAPORATOR
PRESS~RE (Bar)1.23 1.07 1.01 0.94 0.8B
DISC~AR~E
TEMPERAT~RE (C)120.8110,9 106.5 100.8 96.2
RET~RN GAS
TEMPERATURE ~C)20.020.0 20.I 20.1 20.1
VOLUMETRIC
FLOW (M3l3 x 102) 0.140 0.150 0.169 0.187 0.206
, . .
COOLING DUTY PER
UNIT SWEPT
VOL~ME (~Wtm3) 7I4 F67 592 534 485 ~-
COEFFICIENT OF
PERFORMANCE 1.90 1.86 1.87 1.86 1.83
BOILING BP* -29.8 -26.2 -25.31-23.91 -21.90
POINT (C) DP~ -29.8_Z6.2 -25.07-23.51 -22.26
GLIDE IN _
EVAPORATOR (C) O O 0.2 0.2 0.2
* BP - Bubble Point
** DP - Dew Point
3~
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21261~S 12 -
TABLE 2
REFRICER _ R-12 R-134a R-134alE-143a
.. . .. . , _ .. . , . . _ .
~ ~Y WEIG~T 100 100 75125 50~50 25/75 .:
~ . ___ :'
CONDENSER . :-:
PRESS~RE (Bar) 9 63 10.10 9.58 9 2D ~.85 -
EVAPORAT9R
P~ESS~RE ( Bar ) 1. 23 1. 07 1. 02 1. 00 O.97
.. . - . . . . - . _
DISC~ARGE
TE~PERATURE (C) 120.8 110.9 110.0 107.5 105.1
___ _ _-- .
R~T~RN GAS ~:
TE~PERAT~RE (C) 20.0 20.0 20.0 29.0 20.0 .
. . . - ... -............ :::VOLU~ETRIC
FLOW (M31~ s lOZ ) 0.140 0.150 0.162 0.170 0-176
. . . _ . . . . , -
COOLI~G D~TY PE~
UNIT SWEPT
VOLUME ~W/m3) 714 667 617 588 56B
COEFFICIENT OF
PERFORMANCE 1.90 1.86 1.85 1.85 1.85
. . _ . . . ~ .
BOILING BP~ -29.8 -26.2 -25.61 -24.94 -24.45
POINT ~C) DP*~ -29.8 -26.2 -25.54 -24.88 -24.42
. . . _
GLIDE IN
EVAPORATOR (C) O O _ O i O
* BP D Bubb1e Point
** DP - Dew Point
