Low gwp heat transfer compositions

FIELD OF THE INVENTION

0001This invention relates to compositions, and to the use of these compositions in systems that typically utilize the refrigerant R-404A for heating and/or refrigeration (cooling) applications.

BACKGROUND

0002Fluorocarbon based fluids have found widespread use in many commercial and industrial applications, including as the working fluid in systems such as air conditioning, heat pump and refrigeration systems, among other uses such as aerosol propellants, as blowing agents, and as gaseous dielectrics.

0003Heat transfer fluids, to be commercially viable, must satisfy certain very specific and in certain cases very stringent combinations of physical, chemical and economic properties. Moreover, there are many different types of heat transfer systems and heat transfer equipment, and in many cases it is important that the heat transfer fluid used in such systems possess a particular combination of properties that match the needs of the individual system. For example, systems based on the vapor compression cycle usually involve the phase change of the refrigerant from the liquid to the vapor phase through heat absorption at a relatively low pressure and compressing the vapor to a relatively elevated pressure, condensing the vapor to the liquid phase through heat removal at this relatively elevated pressure and temperature, and then reducing the pressure to start the cycle over again.

0004Certain fluorocarbons, for example, have been a preferred component in many heat exchange fluids, such as refrigerants, for many years in many applications. Fluoroalkanes, such as chlorofluoromethanes and chlorofluoroethanes, have gained widespread use as refrigerants in applications including air conditioning and heat pump applications owing to their unique combination of chemical and physical properties, such as heat capacity, flammability, stability under the conditions of operation, and miscibility with the lubricant (if any) used in the system. Moreover, many of the refrigerants commonly utilized in vapor compression systems are either single components fluids, or zeotropic, azeotropic mixtures.

0005Concern has increased in recent years about potential damage to the earth's atmosphere and climate, and certain chlorine-based compounds have been identified as particularly problematic in this regard. The use of chlorine-containing compositions (such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and the like) as refrigerants in air-conditioning and refrigeration systems has become disfavored because of the ozone-depleting properties associated with many of such compounds. There has thus been an increasing need for new fluorocarbon and hydrofluorocarbon compounds that offer alternatives for refrigeration and heat pump applications. By way of example, in certain aspects, it has become desirable to retrofit chlorine-containing refrigeration systems by replacing chlorine-containing refrigerants with non-chlorine-containing refrigerant compounds that will not deplete the ozone layer, such as hydrofluorocarbons (HFCs).

0006Another concern surrounding many existing refrigerants is the tendency of many such products to cause global warming. This characteristic is commonly measured as global warming potential (GWP). The GWP of a compound is a measure of the potential contribution to the green house effect of the chemical against a known reference molecule, namely, CO₂ which has a GWP = 1. For example, the following known refrigerants possess the following Global Warming Potentials: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="29mm" /><colspec colnum="2" colname="col2" colwidth="31mm" /><thead><row><entry valign="top">REFRIGERANT</entry><entry valign="top">GWP (IPCC AR5)</entry></row></thead><tbody><row><entry>R410A</entry><entry>2088</entry></row><row><entry>R-507</entry><entry>3985</entry></row><row><entry>R404A</entry><entry>3943</entry></row><row><entry>R407C</entry><entry>1774</entry></row></tbody></tgroup></table></tables>

0007While each of the above-noted refrigerants has proven effective in many respects, these materials are become increasingly less preferred since it is frequently undesirable to use materials having relatively high GWP. A need exists, therefore, for substitutes for these and other existing refrigerants having undesirable GWPs.

0008There has thus been an increasing need for new fluorocarbon and hydrofluorocarbon compounds and compositions that are attractive alternatives to the compositions heretofore used in these and other applications. For example, it has become desirable to retrofit certain systems, including chlorine-containing and certain HFC-containing refrigeration systems by replacing the existing refrigerants with refrigerant compositions that will not deplete the ozone layer, will not cause unwanted levels of global warming, and at the same time will satisfy all of the other stringent requirements of such systems for the materials used as the heat transfer material.

0009With respect to performance properties, the present applicants have come to appreciate that that any potential substitute refrigerant must also possess those properties present in many of the most widely used fluids, such as excellent heat transfer properties, chemical stability, low- or no- toxicity, low or non-flammability and lubricant compatibility, among others.

0010With regard to efficiency in use, it is important to note that a loss in refrigerant thermodynamic performance or energy efficiency may have secondary environmental impacts through increased fossil fuel usage arising from an increased demand for electrical energy.

0011Furthermore, it is generally considered desirable for refrigerant substitutes to be effective without major engineering changes to conventional vapor compression technology currently used with existing refrigerants, such as CFC-containing refrigerants.

0012Flammability is another important property for many applications. That is, it is considered either important or essential in many applications, including particularly in heat transfer applications, to use compositions which are non-flammable or of relatively low flammability. As used herein, the term "nonflammable" refers to compounds or compositions which are determined to be nonflammable as determined in accordance with ASTM standard E-681, dated 2002. Unfortunately, many HFC's which might otherwise be desirable for used in refrigerant compositions are highly flammable. For example, the fluoroalkane difluoroethane (HFC-152a) is flammable and therefore not viable for use alone in many applications.

0013Applicants have thus come to appreciate a need for compositions that are potentially useful in numerous applications, including vapor compression heating and cooling systems and methods, while avoiding one or more of the disadvantages noted above.

0014<patcit id="pcit0001" dnum="EP2149592A2"><text>EP2149592A2</text></patcit> discloses compositions comprising multi-fluorinated olefins and HFC-32, for use in stationary refrigeration and air conditioning equipment.

0015<patcit id="pcit0002" dnum="WO2013146683A"><text>WO2013146683</text></patcit> discloses refrigerant compositions having a global warming potential (GWP) of 500 or less comprising difluoromethane and/or tetrafluoropropene, carbon dioxide and/or a hydrocarbon having 3 to 4 carbon atoms; and a refrigerating machine oil comprising at least one of a polyol ester, a polyvinyl ether and a polyalkylene glycol.

SUMMARY

0016The present invention relates to a composition comprising (a) 21.5% by weight of HFC-32; (b) 75.5% by weight of 2,3,3,3-tetrafluoropropene; and (c) 3% by weight of CO2.

0017The composition of the present application may be used as a replacement for R-404A.

0018The composition of the present invention may be used in automotive air conditioning systems, residential air conditioning systems, commercial air conditioning systems, residential refrigerator systems, residential freezer systems, commercial refrigerator systems, commercial freezer systems, chiller air conditioning systems, chiller refrigeration systems, transport refrigeration systems, heat pump systems, and combinations of two or more of these. In certain non-limiting aspects, the composition of the present invention may be used as an R-404A replacement in low and medium temperature refrigeration systems. In certain aspects, such systems may be used for storage of frozen or refrigerated goods, such as self-contained or "plug-in" type refrigerators or freezers or "reach-in" type of refrigerators or freezers. Non-limiting examples of such systems include those typically used for indoors or outdoors in places such as restaurants, convenience stores, gas stations, grocery stores, and the like.

0019Additional embodiments, use, and advantages will be readily apparent to the skilled artisan on the basis of the disclosure provided herein.

BRIEF DESCRIPTION OF THE FIGURES

0020<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> provides a graphic illustration of expected versus measured (experimental) capacity and efficiency (COP) in systems having increasing amounts of CO2 between 0% and 9%.</li><li><figref idref="f0002">Figure 2</figref> provides a graphic illustration of the results of experimental energy consumption versus the amount of CO2 in the mixture.</li><li><figref idref="f0003">Figure 3</figref> provides a graphic illustration of the expected versus measured (experimental) compressor discharge pressure versus the amount of CO2 in the mixture.</li><li><figref idref="f0004">Figure 4</figref> provides a graphic illustration of the compressor discharge temperature versus the amount of CO2 in the mixture.</li></ul>

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0021R-404A is commonly used in refrigeration systems, particularly low and medium temperature refrigeration systems such as those defined below. It has an estimated Global Warming Potential (GWP) of 3943, which is much higher than is desired or required. Applicants have found that the composition of the present invention satisfies in an exceptional and unexpected way the need for a new composition for such applications, particularly though not exclusively refrigeration systems, having improved performance with respect to environmental impact while at the same time providing other important performance characteristics, such as capacity, efficiency, discharge temperature, discharge pressure, energy consumption, flammability and/or toxicity. In preferred embodiments the present composition is provided as an alternative and/or replacement for refrigerants currently used in such applications, particularly and preferably R-404A, that at once has a lower GWP value and has a close match in heating and cooling capacity to R-404A in such systems.

HEAT TRANSFER COMPOSITIONS

0022The composition of the present invention is generally adaptable for use in heat transfer applications, that is, as a heating and/or cooling medium, but is particularly well adapted for use, as mentioned above, in refrigeration systems (particularly, though not exclusively, low and medium temperature refrigeration systems) that have heretofore used R-404A. In particular, and as demonstrated herein, applicants have surprisingly and unexpectedly discovered that the composition exhibits improved capacity, efficiency, discharge pressure, discharge temperature, and/or energy consumption, as compared to R-404A in such systems and under the same conditions.

0023Applicants have found that the inclusion of CO2 in the composition of the present invention results in surprisingly and unexpected improvement in the use of such a composition with low and medium temperature refrigeration systems, as compared to R-404A and/or compositions that lack CO2. In particular, the data herein demonstrate surprisingly and unexpected empirical improvement in one or more of the following properties, as compared to expected values using thermodynamic calculations: capacity, efficiency, discharge pressure, discharge temperature, energy consumption and combinations thereof.

0024Applicants have also found that the composition of the present invention is capable of achieving low GWP. By way of non-limiting example, the following Table 1 illustrates the substantial GWP superiority of certain compositions, which are described in parenthesis in terms of weight fraction of each component, in comparison to the GWP of R-404A, which has a GWP of3943. <tables id="tabl0002" num="0002"><table frame="all"><title>TABLE 1</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="30mm" /><colspec colnum="2" colname="col2" colwidth="52mm" /><colspec colnum="3" colname="col3" colwidth="26mm" /><colspec colnum="4" colname="col4" colwidth="29mm" /><colspec colnum="5" colname="col5" colwidth="29mm" /><thead><row><entry align="center" valign="middle"><b>Amount of CO2 (%)</b></entry><entry align="center" valign="middle"><b>Composition</b></entry><entry align="center" valign="middle"><b>Name</b></entry><entry align="center" valign="middle"><b>GWP (AR5 values)</b></entry><entry align="center" valign="middle"><b>GWP (% of R404A)</b></entry></row></thead><tbody><row><entry align="center" valign="middle">-</entry><entry valign="middle">R125/R143a/R134a (0.44/0.52/0.04)</entry><entry align="center" valign="middle">R404A (Baseline)</entry><entry align="center" valign="middle">3943</entry><entry align="center" valign="middle">100%</entry></row><row><entry align="center" valign="middle">0%</entry><entry valign="middle">R32/R1234yf (0.215/0.785)</entry><entry align="center" valign="middle">A0</entry><entry align="center" valign="middle">146</entry><entry align="center" valign="middle">4%</entry></row><row><entry align="center" valign="middle">3%</entry><entry valign="middle">R32/R1234yf/CO2 (0.215/0.755/0.03)</entry><entry align="center" valign="middle">A1</entry><entry align="center" valign="middle">146</entry><entry align="center" valign="middle">4%</entry></row><row><entry align="center" valign="middle">6%</entry><entry valign="middle">R32/R1234yf/CO2 (0.215/0.725/0.06)</entry><entry align="center" valign="middle">A2</entry><entry align="center" valign="middle">146</entry><entry align="center" valign="middle">4%</entry></row><row><entry align="center" valign="middle">9%</entry><entry valign="middle">R32/R1234yf/CO2 (0.215/0.695/0.09)</entry><entry align="center" valign="middle">A3</entry><entry align="center" valign="middle">146</entry><entry align="center" valign="middle">4%</entry></row></tbody></tgroup></table></tables>

HEAT TRANSFER METHODS AND SYSTEMS

0025The present composition is adaptable for use in connection with a wide variety of heat transfer systems in general and refrigeration systems in particular, such as air-conditioning, refrigeration, heat-pump systems, and the like. Generally speaking, such refrigeration systems contemplated in accordance with the present invention include, but are not limited to, automotive air conditioning systems, residential air conditioning systems, commercial air conditioning systems, residential refrigerator systems, residential freezer systems, commercial refrigeration systems, small refrigeration systems, commercial freezer systems, transport refrigeration, chiller air conditioning systems, chiller refrigeration systems, heat pump systems, and combinations of two or more of these.

0026The composition of the present invention may be used in refrigeration systems originally designed for use with an HFC refrigerant, such as, for example, R-404A. Such refrigeration systems may include, but are not limited to, low and medium temperature refrigeration systems, particularly vapor compression refrigeration systems. In certain aspects, such systems may be used for storage of frozen or refrigerated goods, such as self-contained, "plug-in" or hermetic type refrigerators or freezers or "reach-in" type of refrigerators or freezers. Non-limiting examples of such systems include those typically used for indoors or outdoors in places such as restaurants, convenience stores, gas stations, grocery stores, and the like.

0027The composition of the present invention tends to exhibit many of the desirable characteristics of R-404A but has a GWP that is substantially lower than that of R-404A while at the same time having a capacity, efficiency, energy consumption, discharge temperature and/or discharge pressure that is substantially similar to or substantially matches, and preferably is as high as or higher than R-404A.

0028A low temperature refrigeration system is used herein to refer to a refrigeration system that utilizes one or more compressors and operates under or within the following conditions: <ol id="ol0001" compact="compact"><li>a. Condenser temperature from about 20°C to about 50°C, in certain preferred aspects from about 25°C to about 45°C;</li><li>b. Evaporator temperature from about -45°C to about or less than about -10°C, in certain preferred aspects from about -40°C to about -25°C, with an evaporator temperature preferably of about -32°C;</li><li>c. Degree of superheat at evaporator outlet of from about 0°C to about 10°C, with a degree of superheat at evaporator outlet of from about 1°C to about 6°C;</li><li>d. System with a degree of superheat in the suction line of from about 15°C to about 40°C, with a degree of superheat in the suction line of from about 20°C to about 30°C. The superheat along the suction line may also (or alternatively be generated by a heat exchanger between the liquid-line (refrigerant line between condenser and expansion device) and the suction-line (refrigerant line between compressor and evaporator), typically known as suction-line/liquid-line heat exchanger, in order to improve system performance. The suction-line/liquid line heat exchanger provides substantial degree of subcooling at the inlet of the expansion device and degree of superheat at the compressor inlet.</li></ol>

0029A medium temperature refrigeration system is used herein to refer to a refrigeration system that utilizes one or more compressors and operates under or within the following conditions: <ol id="ol0002" compact="compact"><li>a. Condenser temperature of from about 20°C to about 60°C, in certain preferred aspects from 25°C to 45°C;</li><li>b. Evaporator temperature of from about -25°C to about or less than about 0°C, n certain preferred aspects from about -20°C to about -5°C, with an evaporator temperature of about -10°C;</li><li>c. Degree of superheat at evaporator outlet of from about 0°C to about 10°C, with a degree of superheat at evaporator outlet of from about 1°C to about 6°C; and</li><li>d. System with a degree of superheat in the suction line of from about 5°C to about 40°C, with a degree of superheat in the suction line preferably of from about 15°C to about 30°C. The superheat along the suction line may also be generated by a heat exchanger as described in item 3).</li></ol>

0030Examples of such refrigeration systems are provided in Examples 1-3, below. To this end, such systems may include low temperature refrigeration applications (Examples 1 and 2), including commercial freezers or systems that may be used for the storage and maintenance of frozen goods. They may also include medium-temperature commercial applications (Example 3), such as commercial refrigerators, including systems for the storage of fresh goods. The examples below provide typical conditions and parameters that are used for such applications. These conditions, however, are not considered limiting to the invention, as one of skill in the art will appreciate that they may be varied based on one or more of a myriad of factors, including but not limited to, ambient conditions, intended application, time of year, and the like.

0031As used herein the term "refrigeration system" refers generally to any system or apparatus, or any part or portion of such a system or apparatus, which employs a refrigerant to provide heating or cooling. Such air refrigeration systems include, for example, air conditioners, electric refrigerators, chillers, or any of the systems identified herein or otherwise known in the art.

EXAMPLES

0032The following examples are provided for the purpose of illustrating the present invention but without limiting the scope thereof.

EXAMPLE 1: Low-Temp Refrigeration Application - Performance

0033Due to certain characteristics of refrigeration systems, including particularly low temperature refrigeration systems containing or designed to contain R404A refrigerant, it is important in certain embodiments that such systems are capable of exhibiting adequate performance parameters system with respect to R404A. Such operating parameters include: <ul id="ul0002" list-style="bullet" compact="compact"><li>Capacity of at least 90%, and even more preferably greater than 95% of the capacity of the system operating with R404A. This parameter allows the use of existing compressors and components designed for R404A.</li><li>Equal or better efficiency than R404A leading to energy savings with new mixture.</li><li>Equal or lower energy consumption</li></ul>

0034This example illustrates the COP and capacity performance of compositions labeled A0 - A3 when used as a replacement for R404A in a low-temperature refrigeration system. The coefficient of performance (COP) is a universally accepted measure of refrigerant performance, especially useful in representing the relative thermodynamic efficiency of a refrigerant in a specific cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration engineering, this term expresses the ratio of useful refrigeration to the energy applied by the compressor in compressing the vapor and by fans (when applicable). The capacity of a refrigerant represents the amount of cooling or heating it provides and provides some measure of the capability of a compressor to pump quantities of heat for a given volumetric flow rate of refrigerant. In other words, given a specific compressor, a refrigerant with a higher capacity will deliver more cooling power. One means for estimating COP of a refrigerant at specific operating conditions is from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see for example, R.C. Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall, 1988).

0035A commercially available low temperature refrigeration "reach-in freezer" used for refrigeration of frozen food was evaluated with the baseline refrigerant R404A and mixtures A0, A1, A2 to A3. In the case of such a system illustrated in this Example, the condenser temperature operated around 34°C, which generally corresponded to an indoor room temperature of about 25°C. The evaporating temperature was about -35°C, which corresponded to a product temperature of about -18°C. The degree of superheat at evaporator outlet was about 5°C. Such low temperature refrigeration systems are usually equipped with a suction-line/liquid-line heat exchanger. The amount of degree of subcooling and superheat provided by the suction-line/liquid-line heat exchanger typically depends upon the refrigerant thermodynamic properties and the heat transfer goodness of the heat exchanger. A measure of the heat transfer goodness of a suction-line/liquid-line heat exchanger is given by its effectiveness which varies from 0% (minimum heat transfer) to 100% (maximum heat transfer). For this particular example, the effectiveness of the suction-line/liquid-line heat exchanger was about 50%. An additional refrigerant temperature gain along the refrigerant line between the suction-line/liquid-line heat exchanger and the compressor inlet is typically 2°C.

0036The performance evaluations were done using standardized tests as described in ASHRAE standard 72-2005 "Method of Testing Commercial Refrigerators and Freezers" which established requirements and operating conditions for testing those systems. During these tests, cycle pressures and temperatures are measured, as well as power consumption for compressor and fans. These test have a duration of at least 24-h, during which the system cycles ON and OFF. The system also experiences defrost cycles.

0037From these tests, two sets of results were obtained: <ol id="ol0003"><li>1) Taking a data for single cycle, average capacity and COP were obtained by integrating for the duration of the cycle.</li><li>2) Another mean of evaluating performance is by measuring the overall energy consumption over a 24 h period, which may include effects of ON/OFF operation as well as defrost cycles.</li></ol>

0038The Table 2 below shows side-by-side both the expected values, calculated through thermodynamic properties applied to refrigeration cycle, and the "experimental" values, obtained experimentally through the standardized tests, for both Capacity and COP. <figref idref="f0001">Figure 1</figref> illustrates the results of Table 2 in the form of a chart, as a function of the % amount of CO2 in the mixture. Table 3 and <figref idref="f0002">Figure 2</figref> show the performance results in terms of 24h system energy consumption. All results are referenced to R-404A being at 100% for capacity and COP. <tables id="tabl0003" num="0003"><table frame="all"><title>Table 2: Capacity and COP results</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="50mm" /><colspec colnum="3" colname="col3" colwidth="20mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><thead><row><entry namest="col1" nameend="col2" align="center" valign="middle" /><entry namest="col3" nameend="col4" align="center" valign="middle"><b>Capacity [% of R404A]</b></entry><entry namest="col5" nameend="col6" align="center" valign="middle"><b>COP [% of R404A]</b></entry></row><row><entry align="center" valign="middle"><b>Amount of CO2 (%)</b></entry><entry align="center" valign="middle"><b>Name</b></entry><entry align="center" valign="middle"><b>Expected</b></entry><entry align="center" valign="middle"><b>Experimental</b></entry><entry align="center" valign="middle"><b>Expected</b></entry><entry align="center" valign="middle"><b>Experimental</b></entry></row></thead><tbody><row><entry align="center" valign="middle">-</entry><entry align="center" valign="middle">R404A</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry></row><row><entry align="center" valign="middle">0%</entry><entry align="center" valign="middle">A0 * R32/R1234yf (0.215/0.785)</entry><entry align="center" valign="middle">86%</entry><entry align="center" valign="middle">93%</entry><entry align="center" valign="middle">104%</entry><entry align="center" valign="middle">101%</entry></row><row><entry align="center" valign="middle">3%</entry><entry align="center" valign="middle">A1 * R32/R1234yf/CO2 (0.215/0.755/0.03)</entry><entry align="center" valign="middle">96%</entry><entry align="center" valign="middle">96%</entry><entry align="center" valign="middle">103%</entry><entry align="center" valign="middle">102%</entry></row><row><entry align="center" valign="middle">6%</entry><entry align="center" valign="middle">A2 * R32/R1234yf/CO2 (0.215/0.725/0.06)</entry><entry align="center" valign="middle">105%</entry><entry align="center" valign="middle">97%</entry><entry align="center" valign="middle">102%</entry><entry align="center" valign="middle">98%</entry></row><row><entry align="center" valign="middle">9%</entry><entry align="center" valign="middle">A3 * R32/R1234yf/CO2 (0.215/0.695/0.09)</entry><entry align="center" valign="middle">115%</entry><entry align="center" valign="middle">97%</entry><entry align="center" valign="middle">101%</entry><entry align="center" valign="middle">95%</entry></row></tbody></tgroup><tgroup cols="6" rowsep="0"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="50mm" /><colspec colnum="3" colname="col3" colwidth="20mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><tbody><row><entry namest="col1" nameend="col6" align="justify">* Reference Example</entry></row></tbody></tgroup></table></tables><tables id="tabl0004" num="0004"><table frame="all"><title>Table 3: Experimental energy consumption results</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="60mm" /><colspec colnum="3" colname="col3" colwidth="73mm" /><thead><row><entry align="center" valign="middle"><b>Amount of CO2 (%)</b></entry><entry align="center" valign="middle"><b>Name</b></entry><entry align="center" valign="middle"><b>Experimental 24h Energy Consumption [% of R404A]</b></entry></row></thead><tbody><row><entry align="center" valign="middle">-</entry><entry align="center" valign="middle">R404A (baseline)</entry><entry align="center" valign="middle">100%</entry></row><row><entry align="center" valign="middle">0%</entry><entry align="center" valign="middle">A0 * R32/R1234yf (0.215/0.785)</entry><entry align="center" valign="middle">98%</entry></row><row><entry align="center" valign="middle">3%</entry><entry align="center" valign="middle">A1 R32/R1234yf/CO2 (0.215/0.755/0.03)</entry><entry align="center" valign="middle">97%</entry></row><row><entry align="center" valign="middle">6%</entry><entry align="center" valign="middle">A2 * R32/R1234yf/CO2 (0.215/0.725/0.06)</entry><entry align="center" valign="middle">100%</entry></row><row><entry align="center" valign="middle">9%</entry><entry align="center" valign="middle">A3 * R32/R1234yf/CO2 (0.215/0.695/0.09)</entry><entry align="center" valign="middle">104%</entry></row></tbody></tgroup><tgroup cols="3" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="60mm" /><colspec colnum="3" colname="col3" colwidth="73mm" /><tbody><row><entry namest="col1" nameend="col3" align="justify">* Reference Example</entry></row></tbody></tgroup></table></tables>

0039As illustrated in Table 2 and <figref idref="f0001">Figure 1</figref>, the expected capacity should increase linearly with the amount of CO2. However, applicants found unexpectedly that the actual capacity (experimental) increases with the first 3% of CO2 then remains nearly unchanged with higher amounts of CO2. As also illustrated in Table 2 and <figref idref="f0002">Figure 2</figref>, the expected COP should slightly decrease with the increase in the amount of CO2. However, applicants found unexpectedly that the actual COP (experimental) increases upon the addition of CO2 and peaks at around 3% of CO2. It then drops sharply with CO2 amounts above 3%.

0040As illustrated in <figref idref="f0003">Figure 3</figref> and Table 2, the 24h energy consumption unexpectedly reaches a minimum with a mixture of around 3% of CO2.

EXAMPLE 2: Low-Temperature Refrigeration Application - Reliability Parameters

0041Due to certain characteristics of refrigeration systems, including particularly low temperature refrigeration systems containing or designed to contain R404A refrigerant, it is important in certain embodiments that such systems are capable of exhibiting reliable system operating parameters with respect to R404A. Such operating parameters include: <ul id="ul0003" list-style="bullet" compact="compact"><li>High-Side Pressure that is within about 115%, and even more preferably within about 105% of the high side pressure of the system using R404A. This parameter allows the use of existing compressors and components designed for R404A.</li><li>Compressor discharge temperature that does not exceed R404A discharge temperature by more than 15°C, and no more than 10°C. The advantage of such a characteristic is that it permits the use of existing equipment without activation of the thermal protection aspects of the system, which is designed to protect compressor components.</li></ul>

0042Discharge pressure and temperature were estimated for R404A (baseline) and mixtures A0-A3 by the same methods and under the same operating conditions described in Example 1. Those parameters were also measured experimentally using the same reach-in freezer, procedures and standard described in Example 1.

0043The Table 4 below shows side-by-side both the expected values, calculated through thermodynamic properties applied to refrigeration cycle, and the experimental values, obtained experimentally, for discharge pressure and compressor discharge temperature. <figref idref="f0003">Figure 3</figref> and <figref idref="f0004">4</figref> illustrates the results of Table 4 in the form of a chart, as a function of the % amount of CO2 in the mixture. <tables id="tabl0005" num="0005"><table frame="all"><title>Table 4: Results of discharge pressure and compressor discharge temperature</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="50mm" /><colspec colnum="3" colname="col3" colwidth="20mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><thead><row><entry namest="col1" nameend="col2" align="center" valign="middle" /><entry namest="col3" nameend="col4" align="center" valign="middle"><b>Discharge Pressure [% of R404A]</b></entry><entry namest="col5" nameend="col6" align="center" valign="middle"><b>Discharge Temp. [Difference from R404A, in °C]</b></entry></row><row><entry align="center" valign="middle"><b>Amount of CO2 (%)</b></entry><entry align="center" valign="middle"><b>Name</b></entry><entry align="center" valign="middle"><b>Expected</b></entry><entry align="center" valign="middle"><b>Experimental</b></entry><entry align="center" valign="middle"><b>Expected</b></entry><entry align="center" valign="middle"><b>Experimental</b></entry></row></thead><tbody><row><entry align="center" valign="middle">-</entry><entry align="center" valign="middle">R404A (baseline)</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">0</entry><entry align="center" valign="middle">0</entry></row><row><entry align="center" valign="middle">0%</entry><entry align="center" valign="middle">A0 * R32/R1234yf (0.215/0.785)</entry><entry align="center" valign="middle">85%</entry><entry align="center" valign="middle">87%</entry><entry align="center" valign="middle">+8</entry><entry align="center" valign="middle">+1</entry></row><row><entry align="center" valign="middle">3%</entry><entry align="center" valign="middle">A1 R32/R1234yf/CO2 (0.215/0.755/0.03)</entry><entry align="center" valign="middle">96%</entry><entry align="center" valign="middle">103%</entry><entry align="center" valign="middle">+13</entry><entry align="center" valign="middle">+8</entry></row><row><entry align="center" valign="middle">6%</entry><entry align="center" valign="middle">A2 * R32/R1234yf/CO2 (0.215/0.725/0.06)</entry><entry align="center" valign="middle">106%</entry><entry align="center" valign="middle">117%</entry><entry align="center" valign="middle">+17</entry><entry align="center" valign="middle">+12</entry></row><row><entry align="center" valign="middle">9%</entry><entry align="center" valign="middle">A3 * R32/R1234yf/CO2 (0.215/0.695/0.09)</entry><entry align="center" valign="middle">116%</entry><entry align="center" valign="middle">132%</entry><entry align="center" valign="middle">+21</entry><entry align="center" valign="middle">+17</entry></row></tbody></tgroup><tgroup cols="6" rowsep="0"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="50mm" /><colspec colnum="3" colname="col3" colwidth="20mm" /><colspec colnum="4" colname="col4" colwidth="26mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><colspec colnum="6" colname="col6" colwidth="26mm" /><tbody><row><entry namest="col1" nameend="col6" align="justify">* Reference Example</entry></row></tbody></tgroup></table></tables>

0044As illustrated in Table 4 and <figref idref="f0003">Figure 3</figref>, both the expected and the actual (experimental) discharge pressures increased linearly with the amount of CO2. Applicants found unexpectedly, however, that the actual discharge pressure was significantly more sensitive to the amount of CO2 than estimated. The actual discharge pressure reached 105% with CO2 amounts around 3-4% and 115% between 5-6% of CO2.

0045As illustrated in Table 4 and <figref idref="f0004">Figure 4</figref>, both the expected and the actual (experimental) discharge temperature increased steadily with the amount of CO2. Applicants found unexpectedly, however, that the actual discharge temperature was between 7-4°C lower than the estimated values. The actual discharge temperatures are within 10°C of R404A with CO2 amounts below around 4% and within 15°C below around 7% of CO2.

EXAMPLE 3: Medium Temp Refrigeration Application

0046This example illustrates the COP, capacity, discharge pressure and temperature of compositions A0 - A3 when used as a replacement for R-404A in a medium temperature refrigeration system.

0047A typical medium temperature refrigeration application was evaluated with the baseline refrigerant R-404A and mixtures A0, A1, A2 to A3 using the same methods described to estimate the performance in low-temperature application, as described in Example 1. In the case of such a medium temperature refrigeration system illustrated in this Example, the condenser temperature operated around 35°C, which generally corresponded to an indoor room temperature of about 25°C. The evaporating temperature was -10°C, which corresponded to a product temperature of about 0°C. The degree of superheat at evaporator outlet was about 5°C. Such medium temperature refrigeration systems are usually equipped a suction-line/liquid-line heat exchanger as described in Example 1. For this particular example, the effectiveness of the suction-line/liquid-line heat exchanger is about 50%. An additional refrigerant temperature gain along the refrigerant line between the suction-line/liquid-line heat exchanger and the compressor inlet is typically 2°C. The compressor efficiency was about 70%.

0048The Table 5 below shows capacity, COP, discharge pressure and temperature with for the 4 mixtures with respect to R404A values, estimated through thermodynamic properties applied to refrigeration cycle. <tables id="tabl0006" num="0006"><table frame="all"><title>Table 5: Capacity, COP, discharge pressure and temperature at medium temperature</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="22mm" /><colspec colnum="2" colname="col2" colwidth="39mm" /><colspec colnum="3" colname="col3" colwidth="25mm" /><colspec colnum="4" colname="col4" colwidth="21mm" /><colspec colnum="5" colname="col5" colwidth="31mm" /><colspec colnum="6" colname="col6" colwidth="31mm" /><thead><row><entry align="center" valign="middle"><b>Amount of CO2 (%)</b></entry><entry align="center" valign="middle"><b>Name</b></entry><entry align="center" valign="middle"><b>Capacity [% of R404A]</b></entry><entry align="center" valign="middle"><b>COP [% of R404A]</b></entry><entry align="center" valign="middle"><b>Discharge Pressure [% of R404A]</b></entry><entry align="center" valign="middle"><b>Discharge Temp. [Diff. in °C, from R404A]</b></entry></row></thead><tbody><row><entry align="center" valign="middle">-</entry><entry align="center" valign="middle">R404A (baseline)</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">100%</entry><entry align="center" valign="middle">0</entry></row><row><entry align="center" valign="middle">0%</entry><entry align="center" valign="middle">A0 * R32/R1234yf (0.215/0.755)</entry><entry align="center" valign="middle">88%</entry><entry align="center" valign="middle">103%</entry><entry align="center" valign="middle">84%</entry><entry align="center" valign="middle">+5</entry></row><row><entry align="center" valign="middle">3%</entry><entry align="center" valign="middle">A1 R32/R1234yf/CO2 (0.215/0.755/0.03)</entry><entry align="center" valign="middle">98%</entry><entry align="center" valign="middle">102%</entry><entry align="center" valign="middle">95%</entry><entry align="center" valign="middle">+7</entry></row><row><entry align="center" valign="middle">6%</entry><entry align="center" valign="middle">A2 * R32/R1234yf/CO2 (0.215/0.725/0.06)</entry><entry align="center" valign="middle">108%</entry><entry align="center" valign="middle">102%</entry><entry align="center" valign="middle">106%</entry><entry align="center" valign="middle">+10</entry></row><row><entry align="center" valign="middle">9%</entry><entry align="center" valign="middle">* R32/R1234yf/CO2 (0.215/0.695/0.09)</entry><entry align="center" valign="middle">118%</entry><entry align="center" valign="middle">101%</entry><entry align="center" valign="middle">117%</entry><entry align="center" valign="middle">+12</entry></row></tbody></tgroup><tgroup cols="6" rowsep="0"><colspec colnum="1" colname="col1" colwidth="22mm" /><colspec colnum="2" colname="col2" colwidth="39mm" /><colspec colnum="3" colname="col3" colwidth="25mm" /><colspec colnum="4" colname="col4" colwidth="21mm" /><colspec colnum="5" colname="col5" colwidth="31mm" /><colspec colnum="6" colname="col6" colwidth="31mm" /><tbody><row><entry namest="col1" nameend="col6" align="justify">* Reference Example</entry></row></tbody></tgroup></table></tables>

0049As illustrated in Table 5, the expected capacity and COP should increase linearly with the amount of CO2. A closer match in capacity with slightly better COP would happen around 3% of CO2. Both discharge pressure and temperature are also demonstrated to increase steadily with the amount of CO2. Discharge pressure is around a match of R-404A with CO2 amounts of about 3-6%. Discharge temperatures are within 10°C of R404A with CO2 amounts below 6%.