Low GWP refrigerant blends

Abstract

Non-ozone depleting and non-flammable refrigerant compositions with GWPs less than 1050 which may replace HFC404A, HFC507 and HFC410A in refrigeration and air-conditioning systems.

Claims

1. A nonflammable, zeotropic refrigerant composition consisting essentially of one of the following compositions: TABLE-US-00090 (a) R125 9.5% carbon dioxide   9% R1234ze  58% R227ea   7% R32 9.5% R134a   7% wherein the percentages are by mass; TABLE-US-00091 (b) R125 11% carbon dioxide 11% R1234ze 57% R227ea  7% R32 11% R134a  3% wherein the percentages are by mass; TABLE-US-00092 (c) R125 18% carbon dioxide 11% R1234ze 44% R227ea  6% R32 17% R134a  4% wherein the percentages are by mass; TABLE-US-00093 (d) R125 11% carbon dioxide 11% R1234ze 55% R227ea  7% R32 11% R134a  5% wherein the percentages are by mass; TABLE-US-00094 (e) R125 13% carbon dioxide 11% R1234ze 53% R227ea  7% R32 13% R134a  3% wherein the percentages are by mass; TABLE-US-00095 (f) R125 13% carbon dioxide 11% R1234ze 55% R227ea  7% R32 13% R134a  1% wherein the percentages are by mass; TABLE-US-00096 (g) R125 14% carbon dioxide 11% R1234ze 51% R227ea  7% R32 14% R134a  3% wherein the percentages are by mass; TABLE-US-00097 (i) R125 10.5% carbon dioxide   11% R1234ze   57% R227ea    7% R32 10.5% R134a    4% wherein the percentages are by mass; TABLE-US-00098 (j) R125 10.5% carbon dioxide   11% R1234ze   58% R227ea    7% R32 10.5% R134a    3% wherein the percentages are by mass; TABLE-US-00099 (k) R125 11.5% carbon dioxide   10% R1234ze   57% R227ea    7% R32 11.5% R134a    3% wherein the percentages are by mass; TABLE-US-00100 (l) R125 11.5% carbon dioxide   10% R1234ze   56% R227ea    8% R32 11.5% R134a    3% wherein the percentages are by mass.

2. A nonflammable, zeotropic refrigerant corn position consisting essentially of one of the following compositions: TABLE-US-00101 (a) R125 19% carbon dioxide 10% R1234ze 44% R227ea  3% R32 17% R134a  7% wherein the percentages are by mass; TABLE-US-00102 (b) R125 18% carbon dioxide 11% R1234ze 44% R227ea  7% R32 17% R134a  3% wherein the percentages are by mass; and TABLE-US-00103 (c) R125 18% carbon dioxide 11% R1234ze 44% R227ea  6% R32 17% R134a  4% wherein the percentages are by mass.

Description

Example 1

(1) Refrigerant compositions shown in Table 1 were assessed as replacements for R410A in existing and new equipment.

(2) TABLE-US-00081 TABLE 1 Refrigerant # Chemical name R410A Blend 1 Blend 2 R125 pentafluoroethane  50 18.7 18   R134a 1, 1, 1, 2-tetrafluoroethane   0  7.4  4.2 R744 carbon dioxide   0 10.3 10.9 R1234yf 2, 3, 3, 3-tetrafluoroprop-1-ene   0 0  0  R227ea 1, 1, 1, 3, 3 ,3-hexafluoropropane   0 3   5.8 R1234ze (E) E-1, 3, 3, 3-tetrafluoroprop-1-ene   0 43.3 43.8 R32 difluoromethane  50 17.2 17.4 GWP 2088

(3) A Toshiba reversible, split air-conditioning unit, Model RAS-137SAV-E3, containing 0.8 kg R410A was used to cool a room and monitored using temperature and pressure sensors positioned as indicated in FIG. 1 with a current meter to record the compressor electric power consumption. Data collected is shown in Table 2a.

(4) (I(A) is the current in amps consumed by the compressor.

(5) T1 is the sensor located in the airstream leaving the evaporator.

(6) T2 is the sensor located within in the room.

(7) T3 is the sensor located in the airstream at the condenser outlet.

(8) T4 is the sensor located in the airstream entering the condenser.

(9) T5 is the sensor located on the refrigerant discharge from the compressor.

(10) P1 is the suction pressure of the compressor.

(11) TABLE-US-00082 TABLE 2a Refrigerant: R410A Mode: Cooling T1 T2 T3 T4 T5 P1 I Time (° C.) (° C.) (° C.) (° C.) (° C.) (barg) (A) (min) 31 28.2 27.1 26.3 45.7 14.39 0.18 0 16.4 27.2 34.6 26.9 49.1 8.5 3.22 5 14.5 26.4 34 27.6 50.5 8.8 3.29 10 12.8 25.9 35.2 28.7 49.8 8.5 3.35 15 11.9 25.6 34.6 28.5 48.5 8.3 3.37 20 11 25.3 34.6 28.6 48.4 8 3.39 25 10.5 25.1 34.4 28.8 48.7 7.9 3.34 30

(12) The R410A was replaced by 0.8 kg of Blend 1 with the composition shown in Table 1 and the device again run to cool the room. The data collected is shown in Table 2b.

(13) TABLE-US-00083 TABLE 2b Refrigerant: Blend 1 Mode: Cooling T1 T2 T3 T4 T5 P1 I Time (° C.) (° C.) (° C.) (° C.) (° C.) (barg) (A) (min) 27.7 27.9 28.6 26.5 27.6 11.85 0 0 20 26.9 29.1 27.3 41.5 3.66 4 5 14.9 25.9 32.4 29.2 52.6 5.72 2.95 10 13.9 25.5 31.6 28.8 53.7 5.72 2.9 15 13.5 25.3 31.6 28.6 53.5 5.61 2.87 20 13.1 25.2 32.3 28.9 53.4 5.55 2.9 25 12.8 25 32.1 29.3 53.2 5.46 2.98 30 12.5 24.9 31.9 29 53.1 5.41 2.93 35

(14) Blend 1 was then removed from the device which was then recharged with 0.8 kg of Blend 2. The device was again to cool the room and the data collected is shown in Table 1 c.

(15) TABLE-US-00084 TABLE 2c Refrigerant: Blend 2 Mode Cooling T1 T2 T3 T4 T5 P1 I Time (° C.) (° C.) (° C.) (° C.) (° C.) (barg) (A) (min) 30 29.8 31.3 29.6 39.2 13.58 0 0 17.6 28.2 32.5 30 55.2 5.6 4.4 5 14.7 27.3 34.3 30.2 57.6 5.33 4.43 10 13.8 26.9 34.6 30.6 57.5 5.15 4.42 15 13.1 26.5 34.6 30.5 57.9 4.97 4.39 20 12.3 26.2 34.5 30.8 58.1 4.86 4.36 25 12 26 34.8 31.8 58.7 4.81 4.43 30

(16) The data shows that both Blend 1 and Blend 2 are effective retrofit replacements for R410 in a typical split air conditioning unit. Blend 1 is especially preferred because it has a lower current consumption and thus a lower power consumption than R410A. In other words, Blend 1 is more efficient than R410A.

Example 2

(17) Refrigerant compositions containing R1234ze(E) and R1234yf, shown in Table 2, were assessed as potential replacements for R410A in air conditioning units by modelling their performances using cycle simulations based on thermodynamic data generated by NIST's REFPROP v10. The results demonstrated that Blends 3 to 6 are acceptable replacements for R41 OA. Flow rates were similar so that the capillary expansion tubes commonly found in smaller split air conditioning units will continue to operate properly, thus avoiding costly modifications. The maximum operating pressures, which occurred in the condenser, were not more than 2 bar greater than that of R410A under comparable conditions, which is within the typical rating of a split air-conditioning unit. The discharge temperatures were 15° C. or less above that of R410A, avoiding thea nal decomposition of lubricants or damage to other components. The GWPs of the blends were all less than 1000, so 1 tonne of a blend can replace more than 2 tonnes of R410A and remain within the EU imposed GWP cap.

(18) TABLE-US-00085 TABLE 3 R410A Blend 3 Blend 4 Blend 5 Blend 6 R125 0.5 19 18 17 17 R134a 0 7 4 10 14 R744 0 10 11 11 11 R1234yf 0 0 0 22 41 R227ea 0 3 6 3 0 R1234zeE 0 44 44 22 0 R32 0.5 17 17 17 17 2088 980 998 952 912 Input Parameters Cooling duty kW 1 1 1 1 1 Condenser Midpoint C. 45 51 51 51 50 Subcool kJ/kg 5 5 5 5 5 External air temperature C. 35 35 35 35 35 Evaporator Midpoint C. 7 15 15 15 15 Superheat C. 5 5 5 5 5 Compressor Isentropic efficiency 0.7 0.7 0.7 0.7 0.7 Electric motor efficiency 0.9 0.9 0.9 0.9 0.9 Volumetric efficiency 0.9 0.9 0.9 0.9 0.9 Output Results Condenser Pressure bara 27.30 26.33 27.02 28.31 29.30 Dew point C. 45.06 60.29 60.76 59.19 57.11 Bubble point C. 44.94 41.71 41.24 42.81 42.89 Mid point C. 45 51 51 51 50 Glide K 0.1 18.6 19.5 16.4 14.2 Exit temperature C. 39.9 36.7 36.2 37.8 37.9 Heat out kW 1.30 1.34 1.34 1.35 1.34 Evaporator Pressure bara 9.93 7.88 8.08 8.69 9.45 Entry temperature C. 6.96 1.46 0.97 2.40 3.38 Dew point C. 7.04 16.54 17.03 15.60 14.62 Mid point C. 7 9 9 9 9 Glide K 0.1 15.1 16.1 13.2 11.2 Exit temperature C. 12.0 21.5 22.0 20.6 19.6 Heat in kW 1 1 1 1 1 Compressor Entry temperature to C. 12.0 21.5 22.0 20.6 19.6 casing Entry temperature to C. 25.7 38.3 38.9 36.6 34.5 compressor Discharge temperature C. 82.4 96.5 97.3 94.2 90.6 Compression ratio 2.7 3.3 3.3 3.3 3.1 Total power input kW 0.30 0.34 0.34 0.35 0.34 Swept volume m{circumflex over ( )}3/h 0.65 0.78 0.77 0.74 0.70 System Suction specific volume kJ/m{circumflex over ( )}3 4960 4135 4224 4356 4622 COP cooling 3.32 2.95 2.94 2.89 2.95 Mass flow rate kg/s 0.00613 0.00622 0.00622 0.00655 0.00673

Example 3

(19) Refrigerant composition blend 7 shown in Table 4 was assessed as a replacement for R404A in existing unit.

(20) TABLE-US-00086 TABLE 4 Refrigerant # Chemical name R410A Blend 7 R125 Pentafluoroethane  44 11.4 R134a 1, 1, 1, 2-tetrafluoroethane   4  3.3 R143a 1, 1, 1-trifluoroethane  52 0  R744 carbon dioxide   0 10.4 R1234yf 2, 3, 3, 3-tetrafluoroprop-1-ene   0 0  R227ea 1, 1, 1, 3, 3, 3-hexafluoropropane   0  7.4 R1234ze (E) E-1, 3, 3 ,3-tetrafluoroprop-1-ene   0 56.1 R32 Difluoromethane   0 11.4 GWP 2088 733 
Testing a composition in an actual unit may take several days to assess the performance. Initial screening of candidates is therefore typically carried out by using a computer program to model the Rankine refrigeration cycle using as input the thermodynamic properties of the composition and important operating parameters to generate key performance criteria as output. This type of program is widely employed throughout the refrigeration industry. The performances of R404A and Blend 7 were modelled under similar conditions typical of a commercial refrigeration freezer cabinet with a cycle model using NIST's REFPROP v10 providing thermodynamic data. Since Blend 7 has very wide temperature glides in the evaporator and condenser the midpoint temperatures of the glide ranges were selected to be representative of the evaporating and condensing temperatures. The input and output parameters are summarised in Table 5.

(21) TABLE-US-00087 TABLE 5 Input R404A Blend 7 Cooling duty kW 1 1 Condenser Midpoint 35 35 Subcool kJ/kg 5 5 Evaporator Midpoint C −35 −35 Superheat C 10 10 Compressor Isentropic efficiency 0.7 0.7 Electric motor efficiency 0.9 0.9 Output Condenser Pressure bara 16.1 16.4 Dew point C 47.5 Bubble point C 34.8 22.5 Midp9int C 35 35 Glide K 0.4 25.1 Exit temperature C 29.8 17.5 Evaporator Pressure bara 1.65 1.19 Entry temperature C −35.2 −41.8 Dewpoint C −3478 −28.2 Midpoint C −35 −35 Glide K 0.49 13.5 Exit temperature C −24.8 −18.2 Heat in kW 1 1 Compressor Entry temperature to casing C −24.8 −18.2 Entry temperature to C −15.0 −4.3 compressor Discharge temperature C 83.0 121.4 38.4 Compression ratio 9.8 13.8 Total power input kW 0.73 0.70 Swept volume m.sup.∧3/h 4.10 4.53 System Suction specific volume kJ/m.sup.∧3 790.7 715.5 90.5 COP cooling 1.4 1.4 Mass flow rate kg/s 0.00898 0.00615 68.4
Although Blend 7 has much lower GWP than R404A and its maximum (discharge) pressure is acceptable as a retrofit for R404A, the model results indicated that the performance of Blend 7 was inferior to R404A in certain key respects.
The compressor discharge temperature is 38.4° C. higher for Blend 7 than for R404A which would seriously reduce reliability and operating life of the compressor. The mass flow rate of Blend 7 is 68.4% lower than for R404A, so, for a freezer or other refrigeration unit with a fixed capillary tube expansion device, the flow rate of Blend 7 would be too large, potentially flooding the evaporator which might result in too high an evaporation temperature and also flooding of the evaporator risking liquid returning to the compressor, which might cause damage.
The very wide evaporator glide of 13.5 K would result in the evaporator refrigerant exit temperature (−18.4° C.) being above the maximum temperature needed to needed to maintain frozen food below −18° C.
The very wide condenser glide of Blend 7 (25.1 K) resulted in a condenser exit temperature of 17.5° C. compared to 29.9° C. for R404A. On the basis that the exit temperature needed to be at least approximately 5 K above the ambient air temperature to for adequate heat transfer from the refrigerant to the air, than R404A may be cooled by ambient air at 25° C. and below, while Blend 7 would only work if the ambient temperature was below 12° C., an unrealistic value for a commercial freezer cabinet in a supermarket.
The calculated suction cooling capacity of Blend 7 was only 68.4%. This indicated that R404A, would not be able to reach and maintain food in the required temperature range of −23° C. to −18° C., especially at high ambient. The calculations predicted that Blend 7 could not be a retrofit replacement for R404A. Surprisingly we have found that Blend 7 is a good retrofit for R404A in a real unit. Contrary to what is predicted using the conventional calculations.

(22) An AHT freezer display cabinet, Model Paris 250(-) type LE228, containing 0.276 kg R404A, was loaded with 182 kg of ice contained in 50×1.5 L, 1×3 L and 13×8 L plastic bottles to simulate a typical freezer contents. The freezer was run until it reached and maintained a steady temperature as recorded by its in-built temperature sensor. The ambient air temperature, the compressor gas discharge temperature, the suction pressure, the discharge pressure, the suction gas temperature just before the compressor and the current draw by the unit were also measured. The results are recorded in Table 6 after the freezer had been operating for 29.7 hours.

(23) The R404A was then replaced by a similar weight of Blend 7 and the results recorded after 29.8 hours of operation

(24) TABLE-US-00088 TABLE 6 R404A Blend 7 Room temperature ° C. 14.2 14.0 Refrigerant suction temperature ° C. 16.8 17.0 Refrigerant discharge temperature ° C. 68.9 71.1 Freezer temperature (unit thermostat) ° C. −25.5 −28.0 Temperature top of freezer ° C. −22.0 −21.2 Suction pressure barg −0.02 0.13 Discharge pressure barg 11.8 14.1 Current draw amp 2.39 2.66 Running time hour 29.7 29.8
The results show that Blend 7 is able to maintain the freezer temperature at or below below its design rating of −18 to −23° C. achieved with R404A. The fact that Blend 7 is maintaining a lower temperature than R404A indicates that it has a better cooling capacity than R404A and thus will be acceptable for high ambient temperatures.
Surprisingly the discharge temperature of Blend 7 was only 2.2° C. higher than that of R404A, in contrast to the much greater difference predicted from the model calculation.
Although the current draw (a measure of the electrical power input) is about 11% higher for Blend 7 this is acceptable.
The operating period of 29.8 hours showed that Blend 7 had reached a steady state and there was no indication of malfunctioning that might be associated with a flooded evaporator problem.

Example 4

(25) The performances of Blends 8 to 12, whose compositions are shown in Table 7, were modelled for a typical low temperature refrigeration system using a Rankine Cycle program with thermodynamic data generated by NIST's REFPROP v10. The perfoiinance of R404A is included for comparison. The results in Table 7 indicate that these novel blends are acceptable replacements for retrofitting in R404A equipment.

(26) TABLE-US-00089 TABLE 7 Component Blend 8 Blend 9 Blend 10 Blend 11 Blend 12 R125 0.11 0.13 0.12 0.14 0.14 R143a 0 0 0 0 0 R134a 0.03 0.03 0.05 0.03 0.05 carbon dioxide 0.11 0.11 0.09 0.11 0.11 R1234yf 0 0 0.3 0 0.48 R227ea 0.07 0.07 0.05 0.07 0.08 R1234ze 0.57 0.53 0.28 0.51 0 R32 0.11 0.13 0.11 0.14 0.14 GWP 701 777 690 816 872 Results Input Cooling duty kW 1 1 1 1 1 Condenser Midpoint C. 35 35 35 35 35 Subcool K 5 5 5 5 5 Evaporator Midpoint C. −35 −35 −35 −35 −35 Superheat C. 5 5 5 5 5 Compressor Isentropic efficiency 0.7 0.7 0.7 0.7 0.7 Electric motor efficiency 0.9 0.9 0.9 0.9 0.9 Volumetric efficiency 0.9 0.9 0.9 0.9 0.9 Output Condenser Pressure bara 16.6 17.3 17.1 17.6 20.1 Dew point C. 47.9 47.4 45.3 47.1 44.5 Bubble point C. 22.1 22.6 24.7 22.9 25.5 Mid point C. 35 35 35 35 35 Glide K 25.7 24.8 20.5 24.3 19.0 Exit temperature C. 17.1 17.6 19.7 17.9 20.5 Evaporator Pressure bara 1.20 1.28 1.34 1.32 1.74 Entry temperature C. −42.0 −42.1 −40.3 −42.1 −40.2 Dew point C. −28.0 −27.9 −29.7 −27.9 −29.8 Mid point C. −35 −35 −35 −35 −35 Glide K 13.93 14.20 10.63 14.26 10.48 Exit temperature C. 23.0 22.9 24.7 22.9 24.8 Compressor Entry temperature to C. −23.0 −22.9 −24.7 −22.9 −24.8 casing Entry temperature to C. −9.3 −9.0 −12.0 −8.9 −12.1 compressor Discharge temperature C. 116.2 117.8 106.2 118.5 107.5 Compression ratio 13.8 13.4 12.7 13.3 11.6 Total power input kW 0.70 0.71 0.71 0.71 0.73 Swept volume m{circumflex over ( )}3/h 4.49 4.26 4.27 4.16 3.49 System Suction specific volume kJ/m{circumflex over ( )}3 721 760 759 779 927 COP cooling 1.42 1.42 1.40 1.41 1.37 Mass flow rate kg/s 0.00626 0.00623 0.00687 0.00622 0.00701