|Title of Invention||
A process for changing the temperature profile of a stream of substance
|Abstract||The invention relates to the use of mixtures consisting of 1,1,1,3,3-pentafluorobutane (R365mfc) and at least one further partially fluorinated hydrocarbon from the group 1,1,1,2-tetrafluoroethane (R134a), pentafluoroethane (R125), 1,1,1,3,3-pentafluoropropane (R245fa) and 1,1,1,2,3,3,3-heptafluoropropane (R227ea) as the working fluid in high-temperature heat pumps. The refrigerant mixtures used according to the invention have a high temperature glide.|
|Full Text||The present invention relates bo a process for changing the temperature profile of a stream of a substance, - It also relates to the process of mixtures.consisting of 1,1,1, 3, 3-pentaf liiorobutane
(R3 65mfc). and at least one further partially fluorinated
hydrocarbon as heat transfer medium or refrigerant, preferably as the working fluid in high-temperature heat pumps.
For ecological reasons, in particular with regard to the effect on the ozone layer, increasingly environmentally acceptable substitutes are being used in refrigeration and air conditioning which may be used instead of CFCs, such as R12, R502 and partially halogenated CFCs such as R22. Only for the field of high-temperature heat pumps is there no suitable refrigerant available at present. In the past, R114, a chlorofluorocarbon (CFC), has been used for such applications with high condensation temperatures of 100°C and above. Since this working fluid comes under the ozone-depleting substances mentioned in the Montreal Protocol and may no longer be used, a suitable substitute must be found.
Unpublished European Patent Application EP 99 20 0762.5 discloses a mixture containing 1,1,1,3,3-pentafluorobutane and at least one non-combustible partially fluorinated hydrocarbon with more than 3 carbon atoms and its suitability as refrigerant or heat transfer medium. No statements are made therein about the suitability of these mixtures for high-temperaiture heat pumps.
The object of the invention is to provide suitable compositions which in contrast to the refrigerants known
hitherto have a high temperature glide and a high critical temperature.
The criteria for selecting the mixture are the refrigeration and heat performance coefficients, the temperature glide in the condenser and in the evaporator and also the end compression temperatures.
The present invention relates to a process for changing the temperature profile of a stream of a substance which comprises passing the Stream through a high temperature heat pump filled with a mixture containing or consisting of 1,1 1,3 3 penta fluorobutane (R365mfc) and at least one further-partially fluorinated hydrocarbon from the group consisting of 1,1,1,2 tetrafluoroethane (R134a) , pentaf luoroethane (R125) , 1,1,1,-3, pentafluoropropane (R245fa) and 1,1,1, 2,3,3,3-heptafluoropropane (R227ea) as refrigerants or heat transfer media.
In particular compositions which contain 1,1,1,3,3-pentafluorobutane and at least one constituent from the group 1,1,1,2-tetrafluoroethane, pentafluoroethane and 1,1,1,2,3,3,3-heptafluoropropane are expedient.
In one embodiment, the mixtures according to the invention may be binary, i.e. R365mfc with a further constituent, or ternary, i.e. R3 65mfc with two further constituents, compositions.
Preferred binary compositions contain 1,1,1,3,3-pentafluorobutane and as second constituent 1,1,1,2-tetrafluoroethane or pentafluoroethane or 1,1,1,3,3-pentafluoropropane or 1,1,1,2,3,3,3-heptafluoropropane.
Preferred ternary compositions contain 1,1,1,3,3-pentafluorobutane, 1,1,1,2-tetrafluoroethane and 1,1,1,2,3,3,3-heptafluoropropane or 1,1,1,3,3-pentafluorobutane, 1,1,1,2-tetrafluoroethane and 1,1,1,3,3-pentafluoropropane.
The mixtures used according to the invention contain 40 to 95 mass % 1,1,1,3,3-pentafluorobutane and at least one partially fluorinated hydrocarbon from the group 1,1,1,2-tetrafluoroethane, pentafluoroethane, 1,1,1,3,3-pentafluoropropane and 1,1,1,2,3,3,3-heptafluoropropane in amounts of from 5 to 60 mass %.
Table 1 shows characteristic variables of the refrigerants for high-temperature heat pumps.
Table It Refrigerants for high-temperature heat pumps
In a preferred embodiment, the following compositions are used as binary mixtures:
95 - 90 mass % R365mfc and 5-10 mass % R134a
95 - 70 mass % R365mfc and 5-30 mass % R227ea
95 mass % R365mfc and 5 mass % R125
95 - 40 mass % R365mfc and 5-60 mass % R245fa.
In another preferred embodiment, the following compositions are used as ternary mixtures:
90 - 40 mass % R365mfc and 5-40 mass % R227ea and 5-20 mass % R134a
90 - 40 mass % R365mfc and 5-40 mass % R245fa and 5-20 mass % R134a.
Over the entire concentration range from 4 0 to 95 mass % R365mfc and 5 to 60 mass % of the partially fluorinated
hydrocarbon, the total of the constituents being 100 mass %, these mixtures exhibit zeotropic behaviour.
It has been found that R365mfc with the aforementioned constituents forms a zeotropic mixture.
"Zeotropic" in the context of the invention is understood to mean that in the equilibrium state steam and liquid have different compositions throughout the entire concentration range, since the boiling points of the individual mixture constituents are different. The evaporation and condensation processes do not take place at a constant temperature, but at a gliding temperature.
"Temperature glide" is understood to mean the difference between the boiling and dewpoint temperatures at constant pressure. This effect can be utilised in heat transmission in heat exchangers if the heat transfer on the thermal sink or heait source likewise takes place under a gliding temperature. The energy losses can thus be reduced, in particular in the condenser.
In cold steam processes, the heat is given off in the condenser and the heat is absorbed in the evaporator. In industrial utilisation, the heat dissipation and absorption may take place on a heat transfer medium or cooling medium. The heat transfer medium or cooling medium in that case undergoes a significant temperature step change.
The compositions according to the invention are advantageously suitable as refrigerants for industrial applications in which a stream of a substance must be cooled by a significant temperature step change >15 K.
One further field of use of such zeotropic mixtures is high-temperature heat pumps for condensation temperatures of 70 to 120°C.
The compositions according to the invention are thus advantageously suitable as refrigerants in heat pumps which distribute the heat via a secondary circuit, usually water, the secondary circuit having a significant temperature difference between the outward and return flow temperatures.
In particular the compositions according to the invention are suitable as refrigerants in heat pumps which in addition to a great temperature step change additionally require a high condensation temperature, e.g. in the range of 70 to 120°C.
The suitability of the mixtures according to the invention as refrigerants for high-temperature heat pumps will be illustrated by a calculation of a refrigerant circuit by way of an example.
The Carnot cycle is used as a comparison process for all types of refrigerating machinery. It consists of what are called isentropes and isotherms. The isentropes describe the state upon compression and expansion. The dissipation of heat in the condenser and the absorption of heat in the evaporator take place at constant temperatures and are represented by isotherms.
Zeotropic mixtures upon heat dissipation and heat absorption in the heat exchangers have what is called a temperature glide, i.e. the liquefaction and evaporation temperatures are not constant owing to the different compositions at the same pressure. With zeotropic mixtures, the temperature in the condenser is reduced due to the temperature glide and the evaporation temperature increases.
Due to the so-called temperature control of the heat transfer medium and cooling medium in the condenser and evaporator, this property of zeotropic mixtures can be exploited industrially. The reaction takes place in practice with counter-current heat exchangers. The theoretical
calculation can be made using what is called the Lorenz cycle. The Lorenz cycle takes into account the supply and removal of the heat at gliding temperature. As in the Carnot cycle, the isentropes describe the states of compression and expansion. For the isotherms of the Carnot cycle in the evaLporation and liquefaction generalising polytropes are provided, as shown in Fig. 1. (Fig Removed)
Figure 1: Carnot and Lorenz cycle in a temperature (T)/entropy(s) diagram
Points 1 to 4 in Figure 1 describe the respective processes in the T/s diagram. The temperature absorption and dissipation of the heat transfer medium and cooling medium are shown.
In the Carnot cycle, the driving temperature difference between heat transfer medium or cooling medium and refrigerant changes. In the Lorenz cycle it remains constant between heat transfer medium or cooling medium and refrigerant. The temperature glide of zeotropic mixtures can be utilised by the temperature control of the heat transfer medium or cooling medium, i.e. constant driving temperature difference. The difference in the heat-exchanger entry and
exit temperatures should in this case correspond to the temperature of the respective glide. Theoretically higher performance coefficients are then obtained for zeotropic refrigerant mixtures compared with single-component refrigerants.
The heat performance coefficient for the zeotropic mixture R365mfc/R227ea in the composition 75/25 mass % and for the refrigerant R114 will calculated in an example of application below. Process heat at a temperature of 20°C is aveiilable as heat source. This temperature is supplied to the evaporator with a cooling medium. The cooling medium is cooled to 10°C in the evaporator. In the condenser, water at a temperature of 80°C is heated to a low-pressure steam temperature of 100°C. The superheating of the theoretical circuit is 15K, the subcooling 5K and the isentropic efficiency 0.8.
The refrigerant mixture enters the evaporator at a temperature of 8.3°C and leaves the evaporator at a temperature of 11.7°C. The evaporator glide is 3.4 K. The average evaporation temperature for the zeotropic refrigerant R365mfc/R227ea is 10°C. The refrigerant mixture enters the condenser at a temperature of 109°C and leaves the condenser at a temperature of 90°C. The condenser glide is 19.8 K. The average condenser temperature is 100°C. The calculated heat performance coefficient is 2.40. In comparison with this, the heat performance coefficient for the same application with the refrigerant R114 is 2.3. The evaporation and condensation take place at constant temperatures.
Table 2 shows characteristic calculated data.
Table 2: Comparison of performance data at a liquefaction temperature of 100°C, subcooling of 5 K, an evaporation temperature of 10°C, superheating of 15 K at an isentropic efficiency of 0.8 (Table Removed)
1. A process for changing the temperature profile of a stream of a substance
which comprises passing the stream through a high temperature heat pump filled
with a mixture containing or consisting of 1,1,1,3,3-penta-fluorobutane
(R365mfc) and at least one further partially fluorinated hydrocarbon from the
group consisting of 1,1,1,2-tetrafluoroethane (R134a) , pentafluoroethane (R125) ,
1,1,1,3,3-pentafluoropropane (R245fa) and 1,1,1,2,3,3,3-heptafluoropropane
(R227ea) as refrigerants or heat transfer media.
2. A process as claimed in claim 1, wherein the mixture contains or consists of
40 to 95 mass % R365mfc and at least one further partially fluorinated
hydrocarbon from the group R134a, R125, R245fa and R227ea in quantities from
5 to 60 mass % as refrigerants or heat transfer media.
3. A process as claimed in claim 1 or 2 wherein the mixture contains or consists of refrigerants with high temperature glide.
4. A process as claimed to anyone of Claims 1 to 3 wherein the mixture contains or consists of refrigerants having a high condensation temperature.
5. A process as claimed in claim 4 wherein the condensation temperature is
6. A high-temperature heat pump, filled with a refrigerant as claimed in
anyone of Claims 1 to 5.
7. A process for changing the temperature profile of a stream of a substance
substantially as herein before described with reference to the accompanying
8. A high-temperature heat pump substantially as herein before described with reference to the accompanying drawings.
|Indian Patent Application Number||00889/DELNP/2003|
|PG Journal Number||37/2008|
|Date of Filing||06-Jun-2003|
|Name of Patentee||Solvay Fluor Und Derivate Gmbh,|
|Applicant Address||Hans-Bockler Allee-20,D-30173 Hannover,|
|PCT International Classification Number||C09K 9/04|
|PCT International Application Number||PCT/EP01/12957|
|PCT International Filing date||2001-11-09|