An environmentally friendly heat transfer medium matched with a constant temperature and humidity air conditioning system

Abstract

The invention belongs to the field of precise regulation of environmental temperature and humidity, discloses an environmentally friendly heat transfer working medium matched with a constant temperature and humidity air conditioning system, proposes three components including 3,3,3-trifluoropropylene (CH2=CHCF3), monofluoroethane (CH3CH2F) and trifluoroiodomethane (CF3I), and further mixes a performance regulator, wherein the performance regulator is one of 1,1,2,2-tetrafluoroethane (CHF2CHF2), trans-1,3,3,3-tetrafluoropropylene (trans-CHF=CHCF3) and hexafluoropropylene (CF3=CF3), thereby forming a quaternary mixed heat transfer working medium with excellent comprehensive performance, so as to replace the high greenhouse effect working medium commonly used in existing air conditioners, and is specially used in constant temperature and humidity air conditioning units. Compared with R134a and R410A widely used in current ordinary air conditioners, the GWP value of the present invention is greatly reduced, which is very consistent with the "dual carbon" development strategy. Moreover, the operating pressure is comparable to that of R134a, meeting the basic requirements of the "direct injection substitution" working fluid substitution method. It has the technical advantage of being compatible with some components of the current R134a system, and the refrigeration cycle performance coefficient is higher than that of R134a and R410A, with significant energy-saving significance. The exhaust temperature is not high, which is of positive significance for optimizing the compression process.

Description

Technical Field

[0001] The present invention belongs to the field of precise regulation of ambient temperature and humidity, and relates to an environmentally friendly heat transfer medium matched with a constant temperature and humidity air-conditioning system, and specifically to a mixed heat transfer medium matched with a vapor compression refrigeration cycle. Background Art

[0002] The 2021 Nobel Prize in Physics was awarded to Hasselmann and Manabe Tokuro for their "physical modeling of the Earth's climate to quantify variability and reliably predict global warming." The problem of global warming has become increasingly serious and has attracted widespread attention at home and abroad. It is generally believed that this is related to human activities and greenhouse gas emissions. To achieve sustainable development, in December 2015, the 21st United Nations Climate Change Conference adopted the Paris Agreement, establishing an international climate change mechanism arrangement based on the "Nationally Determined Contributions" target after 2020. All parties pledged to control the increase in global average temperature to below 2°C and strive for a temperature control target of 1.5°C. In October 2016, the Kigali Amendment was formally adopted at the 28th Conference of the Parties to the Montreal Protocol, which included 18 hydrofluorocarbons (HFCs) in the scope of control and stipulated a specific phase-out timetable. In June 2021, the Chinese government formally submitted its instrument of acceptance of the Kigali Amendment. Starting from 2024, the production and use of HFCs for controlled purposes in my country will be frozen at the baseline level, reduced by 10% in 2029, 30% in 2035, and 50% in 2040, and is expected to not exceed 20% of the baseline by 2045.

[0003] Many HFCs are widely used in the field of heating, ventilation and air conditioning (HVAC) because they do not damage the ozone layer, have excellent thermal properties, are widely available, and have good safety and applicability. HFCs are the main substitutes for ozone-depleting substances and have made significant contributions to protecting the ozone layer. In particular, R134a (CF3CH2F) and R410A (a mixture of CF2H2 and CF3CF2H in equal mass ratios) are currently widely used in a variety of refrigeration heat pumps and air conditioning devices. However, the global warming potential (GWP) of R410A and R134a is 2088 times and 1360 times that of CO2, respectively (calculated over 100 years). In the context of "dual carbon", from the perspective of sustainable development of energy and technology, it is necessary to study new environmentally friendly heat transfer fluids.

[0004] The main products of the applicant for this invention are cooling towers and constant temperature and humidity air conditioners, with a variety of products using R410A and R134a as heat transfer fluids. Constant temperature and humidity air conditioners are an important type of precision control equipment for ambient temperature and humidity, primarily used in situations where there are strict requirements for indoor ambient temperature, humidity fluctuations, and regional deviations, such as electronic component production workshops, biological culture equipment, medical clean rooms, data center computer rooms, high-grade storage rooms, and laboratories. Constant temperature and humidity air conditioners have higher control accuracy requirements than conventional vehicle air conditioners and household air conditioners. Ordinary constant temperature and humidity air conditioners can simultaneously or independently maintain temperature fluctuations within the regulated closed area within ±1°C to ±0.5°C and humidity fluctuations within ±5% to ±2%; high-precision constant temperature and humidity air conditioners can simultaneously or independently maintain temperature fluctuations within ±0.5°C to ±0.3°C and humidity fluctuations within ±2%; some ultra-high-end units have a temperature control accuracy of up to ±0.1°C.

[0005] The inventors analyzed that: First, compared with the complex external environmental conditions that commonly used heat pump air conditioners have to face, especially the significant temperature and humidity fluctuations and extremely low evaporation temperatures in severe winter, the evaporation temperature during operation of constant temperature and humidity air conditioners is generally above zero degrees, and the operating condition fluctuation range is smaller. This can provide greater choice for the fine screening of new matching environmentally friendly heat transfer fluids and the comprehensive consideration of multiple factors.

[0006] Secondly, to achieve the required stability and accuracy of the outlet air temperature of constant temperature and humidity air conditioning units, heat compensation is typically designed. Given the high energy consumption associated with electric heating methods, constant temperature and humidity air conditioning units are typically designed with reheaters, which involve the issue of splitting (non-equal division) and re-combining the working medium. Failure to consider the gas-liquid phase relationships between the components of the mixed working medium can seriously affect the unit's actual operating performance.

[0007] Third, the condensation heat of conventional air conditioners is directly released into the environment, but constant temperature and humidity air conditioners usually recycle and utilize part of the condensation heat. The number of devices and the total process through which the heat transfer medium passes will increase, so the heat exchange capacity and flow transport properties at medium and high temperatures need to be considered in detail.

[0008] Fourthly, a significant difference from household air conditioners is that constant temperature and humidity air conditioners are used by businesses. On the one hand, the greenhouse effect of the working medium may affect the carbon emissions of the user. On the other hand, constant temperature and humidity units typically operate continuously for long periods of time, and their overall energy efficiency, when accumulated over time, will have a significant impact, both from an economic and carbon emissions perspective.

[0009] Fifth, considering the constant temperature and humidity air conditioning environment, a leak of the working fluid not only affects the unit's performance and operational stability, but also poses a significant risk to precision components and high-purity production processes. To reduce the likelihood of leaks, in addition to strengthening the air conditioning unit's inherent sealing, optimization strategies should be developed based on the physical and chemical properties of the working fluid.

[0010] In summary, based on previous research, the present invention proposes an environmentally friendly heat transfer fluid specifically matched with a constant temperature and humidity air-conditioning system. Summary of the Invention

[0011] In response to the shortcomings of the existing technology and development needs, the present invention proposes a quaternary mixed heat transfer working medium containing 3,3,3-trifluoropropylene (CH2=CHCF3), monofluoroethane (CH3CH2F) and trifluoroiodomethane (CF3I), and further mixing it with a performance regulator, thereby forming a quaternary mixed heat transfer working medium with excellent comprehensive performance, which can replace the high greenhouse effect working medium commonly used in existing air conditioners and is specifically used in constant temperature and humidity air conditioning units.

[0012] In order to achieve the above object, the technical solution adopted by the present invention is:

[0013] An environmentally friendly heat transfer medium for constant temperature and humidity air conditioning systems. The mixed heat transfer medium comprises 3,3,3-trifluoropropene (a first component), monofluoroethane (a second component), and trifluoroiodomethane (a third component), along with a performance modifier, mixed using conventional physical mixing methods according to the component mass ratios. Based on 100% of the total mass of the mixture, the first component, 3,3,3-trifluoropropene, accounts for 20% to 80% of the total mass of the mixture; the second component, monofluoroethane, accounts for 8.0% to 30.0% of the total mass of the mixture; and the third component, trifluoroiodomethane, accounts for 10% to 40% of the total mass of the mixture. The performance regulator is one of 1,1,2,2-tetrafluoroethane (CHF2CHF2), trans-1,3,3,3-tetrafluoropropylene (trans-CHF=CHCF3) and hexafluoropropylene (CF3=CF3). Different performance regulators are selected according to the needs of different specific constant temperature and humidity air-conditioning units. The performance regulator accounts for 2.0% to 10.0% of the total mass of the mixture.

[0014] The key physical and chemical properties of the 3,3,3-trifluoropropene, monofluoroethane, trifluoroiodomethane, 1,1,2,2-tetrafluoroethane, trans-1,3,3,3-tetrafluoropropene, and hexafluoropropene are shown in Table 1:

[0015] Table 1 Important physical and chemical properties of several substances

[0016]

[0017] The development of heat transfer fluids for air conditioning systems has entered the stage of addressing global warming, with replacements typified by hydrofluorocarbons (HFCs) such as R410A, R134a, and R404A. This shift away from the previously targeted and now-solved issue of ozone depletion, typified by HFCs such as R22 and R142b. Consequently, the development of new, environmentally friendly heat transfer fluids requires a corresponding evolution in their technical solutions and design. Recent research and development efforts, both domestically and internationally, indicate that a single working fluid with comprehensive performance that is universally applicable to most refrigeration and air conditioning systems has yet to be developed. The current mainstream approach is to comprehensively consider the working fluid's basic thermal properties, environmental impact, safety risks, cycle performance, cost and energy efficiency when used in refrigeration and air conditioning systems, and develop tailored solutions tailored to the specific refrigeration and air conditioning system and its operating conditions. The environmentally friendly heat transfer medium matched with the constant temperature and humidity air-conditioning system proposed in the present invention is designed based on the working characteristics of the constant temperature and humidity air-conditioning system. It is based on three main components that complement each other in performance, and a performance regulator is added to enhance performance or expand the scope of application.

[0018] The functions of the first, second, and third main components and the performance-adjusting agent of the present invention are analyzed as follows: The first component, 3,3,3-trifluoropropene, is a HFO (fluoroolefin) substance, a new generation of environmentally friendly synthetic heat transfer media. It is ozone-safe and has a very low greenhouse gas potential. Its standard boiling point is very close to that of R134a, and its operating pressure under the same temperature conditions is very similar to that of R134a. Its excellent overall thermodynamic properties make it considered to have great development potential in the HVAC field. Given these advantages, and considering the operating conditions of constant temperature and humidity air conditioning systems, the present invention uses 3,3,3-trifluoropropene as the first component. The addition of monofluoroethane as the second component enhances the mixture's heat transfer capacity at lower temperatures and its short-term compatibility with lower-cost lubricants. Furthermore, monofluoroethane is an HFC-type substance not restricted by the Kigali Amendment. Preliminary field measurements indicate that the mixture of the first and second components is flammable, requiring the addition of a flame retardant to reduce its explosion risk. The present invention incorporates trifluoroiodomethane as a third component, owing to its high flame retardancy, low greenhouse effect, and suitable thermal properties. Finally, to further adjust the overall performance of the mixed working fluid to meet the requirements of constant temperature and humidity air conditioning operation under various operating conditions, the addition of performance modifiers such as 1,1,2,2-tetrafluoroethane, trans-1,3,3,3-tetrafluoropropylene, or hexafluoropropylene is proposed. The choice of 1,1,2,2-tetrafluoroethane as a modifier is based on its being an isomer of the alternative R134a (1,1,1,2-tetrafluoroethane). It also offers the following advantages: 1,1,2,2-tetrafluoroethane has a greenhouse effect approximately 20% lower than R134a; 1,1,2,2-tetrafluoroethane exhibits flame retardancy; and 1,1,2,2-tetrafluoroethane has a standard boiling point closer to that of the flame-retardant main component, R13I1 (compared to the alternative R134a). Trans-1,3,3,3-tetrafluoropropylene was chosen as the modifier because it is of the same family as the first component and has a similar boiling point. Furthermore, it is reported that its production capacity is planned to be expanded, which is expected to further reduce costs. Finally, hexafluoropropylene was chosen as the modifier because it is of the same family as the first component, is environmentally friendly, has excellent flame suppression capabilities, and has a very suitable boiling point.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The new heat transfer working medium proposed in the present invention is suitable for constant temperature and humidity air-conditioning systems, and its GWP value (calculated over 100 years) is about 1.3 to 113.8. Compared with the currently widely used R134a and R410A, this represents a huge reduction (up to 99.9%), which is very consistent with the "dual carbon" development strategy.

[0021] (2) The new multi-component mixed working medium proposed in the present invention is composed of three main components and one performance adjustment component. Its operating pressure is comparable to that of R134a in a wide concentration ratio range, meeting the basic requirements of the "direct injection replacement" working fluid replacement method and having the technical advantage of being compatible with some components of the current R134a system.

[0022] (3) The new quaternary mixed heat transfer medium proposed in the present invention has a refrigeration cycle performance coefficient higher than that of R134a and R410A, and has significant energy-saving significance.

[0023] (4) The new quaternary mixed heat transfer medium proposed in the present invention has a lower compression ratio than R134a and R410A, and the exhaust temperature is not high, which has positive significance for optimizing the compressor. DETAILED DESCRIPTION

[0024] To further elaborate on the content and features of the present invention and to facilitate those skilled in the art to better understand the present invention, some specific embodiments of the present invention are given below. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0025] Specific Example 1: The first component (3,3,3-trifluoropropylene) accounts for 20% of the total mass of the mixture, the second component (monofluoroethane) accounts for 30% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 40% of the total mass of the mixture, and the fourth component (1,1,2,2-tetrafluoroethane) accounts for 10% of the total mass of the mixture. This quaternary mixture using 1,1,2,2-tetrafluoroethane as a modifier has a relative molecular mass of approximately 88.1 g / mol, a critical temperature of approximately 102.7°C, and a critical pressure of approximately 4421.0 kPa.

[0026] Specific Example 2: The first component (3,3,3-trifluoropropylene) accounts for 80% of the total mass of the mixture, the second component (monofluoroethane) accounts for 8% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 10% of the total mass of the mixture, and the fourth component (1,1,2,2-tetrafluoroethane) accounts for 2% of the total mass of the mixture. This quaternary mixture using 1,1,2,2-tetrafluoroethane as a modifier has a relative molecular mass of approximately 93.5 g / mol, a critical temperature of approximately 103.0°C, and a critical pressure of approximately 3745.0 kPa.

[0027] Specific Example 3: The first component (3,3,3-trifluoropropylene) accounts for 50% of the total mass of the mixture, the second component (monofluoroethane) accounts for 20% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 25% of the total mass of the mixture, and the fourth component (1,1,2,2-tetrafluoroethane) accounts for 5% of the total mass of the mixture. This quaternary mixture using 1,1,2,2-tetrafluoroethane as a modifier has a relative molecular mass of approximately 89.8 g / mol, a critical temperature of approximately 102.2°C, and a critical pressure of approximately 4083.4 kPa.

[0028] Specific Example 4: The first component (3,3,3-trifluoropropene) accounts for 20% of the total mass of the mixture, the second component (monofluoroethane) accounts for 30% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 40% of the total mass of the mixture, and the fourth component (trans-1,3,3,3-tetrafluoropropene) accounts for 10% of the total mass of the mixture. This quaternary mixture using 1,3,3,3-tetrafluoropropene as the regulating agent has a relative molecular mass of approximately 88.9 g / mol, a critical temperature of approximately 100.7°C, and a critical pressure of approximately 4304.5 kPa.

[0029] Specific Example 5: The first component (3,3,3-trifluoropropene) accounts for 80% of the total mass of the mixture, the second component (monofluoroethane) accounts for 8% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 10% of the total mass of the mixture, and the fourth component (trans-1,3,3,3-tetrafluoropropene) accounts for 2% of the total mass of the mixture. This quaternary mixture using 1,3,3,3-tetrafluoropropene as the regulating agent has a relative molecular mass of approximately 93.6 g / mol, a critical temperature of approximately 102.7°C, and a critical pressure of approximately 3727.9 kPa.

[0030] Specific Example 6: The first component (3,3,3-trifluoropropene) accounts for 50% of the total mass of the mixture, the second component (monofluoroethane) accounts for 20% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 25% of the total mass of the mixture, and the fourth component (trans-1,3,3,3-tetrafluoropropene) accounts for 5% of the total mass of the mixture. This quaternary mixture using 1,3,3,3-tetrafluoropropene as the regulating agent has a relative molecular mass of approximately 90.2 g / mol, a critical temperature of approximately 101.36°C, and a critical pressure of approximately 4034 kPa.

[0031] Specific Example 7: The first component (3,3,3-trifluoropropene) accounts for 20% of the total mass of the mixture, the second component (monofluoroethane) accounts for 30% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 40% of the total mass of the mixture, and the fourth component (hexafluoropropylene) accounts for 10% of the total mass of the mixture. This quaternary mixture using hexafluoropropylene as a modifier has a relative molecular mass of approximately 90.6 g / mol, a critical temperature of approximately 99.1°C, and a critical pressure of approximately 4271.3 kPa.

[0032] Specific Example 8: The first component (3,3,3-trifluoropropene) accounts for 80% of the total mass of the mixture, the second component (monofluoroethane) accounts for 8% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 10% of the total mass of the mixture, and the fourth component (hexafluoropropylene) accounts for 2% of the total mass of the mixture. This quaternary mixture using hexafluoropropylene as a modifier has a relative molecular mass of approximately 94.0 g / mol, a critical temperature of approximately 102.4°C, and a critical pressure of approximately 3721.7 kPa.

[0033] Specific Example 9: The first component (3,3,3-trifluoropropene) accounts for 50% of the total mass of the mixture, the second component (monofluoroethane) accounts for 20% of the total mass of the mixture, the third component (trifluoroiodomethane) accounts for 25% of the total mass of the mixture, and the fourth component (hexafluoropropylene) accounts for 5% of the total mass of the mixture. This quaternary mixture using hexafluoropropylene as a regulator has a relative molecular mass of approximately 91.1 g / mol, a critical temperature of approximately 100.6°C, and a critical pressure of approximately 4017.6 kPa.

[0034] The ability of a constant temperature and humidity air conditioning system to regulate ambient temperature and humidity primarily relies on the unit's refrigeration cycle characteristics. A theoretical single-stage vapor compression refrigeration cycle model was established, operating in an isentropic compression mode with equal enthalpy values ​​before and after throttling. Under operating conditions of an evaporating temperature of 10°C, a condensing temperature of 50°C, a compressor suction temperature of 20°C, and a condenser outlet subcooling temperature of 10°C, a comparative analysis was conducted to determine the key technical performance differences between Specific Examples 1 to Specific Examples 9 and R134a for refrigeration systems. Key parameters of interest included the refrigeration cycle coefficient of performance (COP), condensing pressure, exhaust temperature, cooling capacity per unit volume, and compression ratio. The comparative results are listed in Table 2.

[0035] Table 2 Differences in refrigeration cycle performance between the specific embodiments of the present invention and R134a

[0036]

[0037] The refrigeration cycle coefficient of performance (COP) of Examples 1 through 9 of the present invention is generally slightly higher than that of R134a. This means that, for the same cooling capacity, refrigeration systems using the novel mixture of the present invention consume less power, resulting in significant energy savings. The compression ratios of Examples 1 through 9 are all lower than those of R134a (relatively -7.0% to -9.8%), which has positive implications for compressor optimization. The compressor exhaust temperatures of Examples 1 through 9 are not significantly different from those of R134a (relatively -3.5% to +6.8%), with the maximum absolute difference being approximately 4°C. No additional effort is required in terms of lubricant viscosity selection or system overheating prevention. The condensing pressures of Examples 2, 3, 5, 6, 8, and 9 of the present invention are essentially equivalent to those of R134a. A brief analysis by those skilled in the art will demonstrate that the proposed quaternary mixture meets the basic requirements for "drop-in replacement" for R134a across a wide range of concentration ratios, establishing the pressure requirements for compatible use of some components in existing R134a units. Generally, working media with higher operating pressures have greater refrigeration capacity per unit volume. Specific Examples 1, 4, and 7 of the present invention aim to increase refrigeration capacity per unit volume by reducing the working chamber volume of the compressor. If the refrigeration system's pressure resistance permits, the operating pressure can be appropriately increased to achieve a greater refrigeration capacity per unit volume. Comparative results show that, compared to R134a, Specific Examples 1, 4, and 7 of the present invention exhibit a greater increase in refrigeration capacity per unit volume at the same condensing pressure increase ratio, resulting in superior performance.

[0038] A theoretical single-stage vapor compression refrigeration cycle model was established, operating in an isentropic compression mode with equal working fluid enthalpy before and after throttling. Under operating conditions of an evaporation temperature of 10°C, a condensing temperature of 50°C, a compressor suction temperature of 20°C, and a condenser outlet subcooling temperature of 10°C, a comparative analysis was conducted on the key technical performance differences between Examples 1 to 9 and R410A used in refrigeration systems. Key parameters of interest included the refrigeration cycle coefficient of performance (COP), condensing pressure, exhaust temperature, unit volumetric cooling capacity, and compression ratio. The comparative results are listed in Table 3.

[0039] Table 3 Differences in refrigeration cycle performance between the specific embodiments of the present invention and R410A

[0040]

[0041] The cycle coefficient of performance (COP) of Examples 1 through 9 of the present invention is significantly higher than that of R410A (+8.9% to +10.6%). This means that if the novel mixed refrigerant of the present invention is used instead of R410A, the refrigeration system consumes less power while meeting the same cooling capacity requirement, resulting in significant energy savings. The condensing pressure and compressor exhaust temperature of Examples 1 through 9 of the present invention are significantly lower than those of R410A. The condensing pressure is reduced by more than half, and the exhaust temperature can drop by up to 20%. Furthermore, the compression ratio is also reduced. This reduces the temperature and pressure requirements of the refrigeration cycle equipment, facilitating material selection, preparation, cost reduction, and the design and implementation of risk reduction measures. It should be noted that, compared to R410A, the reduced operating pressure of Examples 1 through 9 of the present invention under the described operating conditions also results in a significant reduction in unit volumetric cooling capacity. Although the reduction in the latter is less significant than that of the former, it is prudent to not directly use the novel mixed refrigerant of the present invention in compressors originally designed for R410A.

[0042] Based on the aforementioned operating conditions, assuming that constant temperature and humidity air conditioners using specific embodiments 1 to 9 of the present invention, R134a, and R410A as heat transfer media have the same cooling capacity, then relying on the aforementioned single-stage vapor compression refrigeration theoretical cycle model, a comparative value of the theoretical required circulation volume of the heat transfer medium can be obtained. Furthermore, the reduction in the equivalent global warming potential (GWP) can be obtained based on this. The comparative analysis results are listed in Table 4. Compared with R134a and R410A, specific embodiments 1 to 9 of the present invention can reduce the global warming potential (GWP) by up to 99.9%, and the environmental protection effect of the present invention is quite significant.

[0043] Table 4 GWP reduction capability of specific embodiments of the present invention

[0044]

[0045] The above specific embodiments 1 to 9 are for further explaining the content and features of the present invention and are intended to facilitate those skilled in the art to better understand the present invention.

Claims

1. An environmentally friendly heat transfer medium matched with a constant temperature and humidity air conditioning system, characterized in that: A quaternary mixed heat transfer working medium specially matched to a vapor compression constant temperature and humidity air conditioning refrigeration cycle, comprising a first component 3,3,3-trifluoropropylene, a second component monofluoroethane, a third component trifluoroiodomethane and a performance regulator, wherein the performance regulator is one of 1,1,2,2-tetrafluoroethane CHF2CHF2, trans-1,3,3,3-tetrafluoropropylene trans-CHF=CHCF3 and hexafluoropropylene CF3=CF3, and is obtained by mixing according to the mass ratio of the components using a conventional physical mixing method; The first component 3,3,3-trifluoropropene accounts for 20%-80% of the total mass of the mixture; The second component, fluoroethane, accounts for 8.0% to 30.0% of the total mass of the mixture; The third component, trifluoroiodomethane, accounts for 10% to 40% of the total mass of the mixture; The performance modifier accounts for 2.0% to 10.0% of the total mass of the mixture.

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