Experimental study on evaporation heat transfer of CO2/DME mixture refrigerant in a horizontal smooth tube

Onaka, Yoji; Miyara, Akio; Tsubaki, Koutaro

doi:10.1016/j.ijrefrig.2010.06.014

Cited by 19 publications

(5 citation statements)

References 21 publications

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“…Despite the excellent heat-transfer properties of supercritical CO 2 at the transcritical state, the high operating pressure and low coefficient of performance (COP) thereof still limit its popularisation and application. Considering this, many scholars have tried to add other materials in supercritical CO 2 to prepare zeotropic refrigerants for improvement [8][9][10][11][12][13][14]. Numerous theoretical and experimental studies (Zhang et al [6]; Onaka et al [7]; Sarkar et al [8]; Ali et al [9]; and Kim [10,11]) reveal that the mixture of refrigerant R170 or R744 with CO 2 as a heat-transfer medium can improve the COP and reduce the operating pressure of a system.…”

Section: Introductionmentioning

confidence: 99%

“…Considering this, many scholars have tried to add other materials in supercritical CO 2 to prepare zeotropic refrigerants for improvement [8][9][10][11][12][13][14]. Numerous theoretical and experimental studies (Zhang et al [6]; Onaka et al [7]; Sarkar et al [8]; Ali et al [9]; and Kim [10,11]) reveal that the mixture of refrigerant R170 or R744 with CO 2 as a heat-transfer medium can improve the COP and reduce the operating pressure of a system. Dai et al [14] evaluated the heat-transfer properties of ten working media including R41, R161, R134a, and R152a blended with CO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive evaluation on the thermal-hydraulic performance of supercritical CO2/R41 in a micro-fin tube

Dai

Wang

et al. 2022

THERM SCI

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A three-dimensional flow and heat-transfer theoretical model was established for a 5-mm micro-fin tube to explore the heat-transfer and flow characteristics of supercritical CO2/R41 therein under different pressures, mass fluxes, and components. The research attempts to provide reference for selecting components of working media and setting the pressure and mass flux in different application scenarios. Results show that the closer the temperature of the working medium to the critical temperature, the larger the local convective heat transfer coefficient (CHTC). The CHTC at the critical temperature is 8 to 16 times higher compared with that at the non-critical temperature. The maximum CHTC is greater and the temperature corresponding to the maximum CHTC is lower when the mixed working medium is at a pressure closer to the critical pressure. The maximum CHTC under 7.0 MPa is twice that at 8.0 MPa. As the mass flux increases from 400 to 800 kg/(m2?s), the CHTC at the non-critical temperature increases by 1.7 times, while the comprehensive evaluation results of heat transfer and pressure drop decrease significantly. When the CO2 fraction increases from 20.5% to 75%, the maximum CHTC is increased by 2.6 times.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comprehensive evaluation on the thermal-hydraulic performance of supercritical CO2/R41 in a micro-fin tube

Dai

Wang

et al. 2022

THERM SCI

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“…However, mixtures of CO2 and DME (CO2/DME) use lower operating pressures than CO2 trans-critical heat pumps while also suppressing the flammability of DME (Koyama et al, 2006;Onaka et al, 2008). The condensation (Afroz et al, 2008) and evaporation (Onaka et al, 2010) heat transfers of CO2/DME mixtures flowing in horizontal smooth tubes have been experimentally studied for various mass fluxes. The results showed that the heat transfer coefficient increased with increasing DME mass fraction and that the pressure drops of CO2/DME mixtures were lower than that of pure DME (Afroz et al, 2008;Onaka et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Modeling of the Heat Transfer in a Supercritical Co2/Dme Mixture Flowing in Cooled Helically Coiled Tubes

Ba¹,

Chen²,

Li³

2021

Frontiers in Heat and Mass Transfer

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The heat transfer of supercritical CO2/DME mixtures was modeled in this study for a mass ratio of 95/5 for cooling in horizontal helically coiled tubes. The CO2/DME heat transfer coefficient was higher in the high-temperature zone than with pure CO2. The heat transfer of CO2/DME (95/5) was predicted for various mass fluxes, heat fluxes and pressures. The CO2/DME heat transfer coefficient increased with the mass flux due to the increased turbulent diffusion, and first increased but then decreased with the heat flux. The peak heat transfer coefficient of CO2/DME shifted toward the high-temperature region as the operating pressure increased. The effects of buoyancy and the centrifugal force were also analyzed to better understand the heat transfer mechanisms in helically coiled tubes. The gravitational buoyancy effect on the heat transfer decreased with mass flux while increased with heat flux. Higher heat fluxes strengthened the centrifugal buoyancy effect on the heat transfer at the beginning of the cooling process but weakened the centrifugal buoyancy effect later in the cooling process. The present study gives insight into the flow and heat transfer processes in helically coiled tubes which is useful for heat exchanger designs and refrigerant selection.

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“…However, for transcritical heat pump system, it is challenged by the much higher heat rejection pressure than the traditional freon one in subcritical cycle [2]. The theoretical and experimental researches have proved that on mixing suitable second component with carbon dioxide, the heat rejection pressure can be reduced [3][4][5][6]. From the perspective of environmental protection, extensive application, or the economic pressures during refrigerant replacement process, certain freons have been investigated as the second components.…”

Section: Introductionmentioning

confidence: 99%

Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

et al. 2015

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As an eco-friendly working fluid, carbon dioxide or R744 is expected to substitute for the existing working fluids used in heat pump systems. It is, however, challenged by the much higher heat rejection pressure in transcritical cycle compared with the traditional subcritical cycle using freons. There exists a worldwide tendency to utilize blend refrigerants as alternatives. Therefore, a new binary blend R744/R161 in this research is proposed in order to decrease the heat rejection pressure. Meanwhile, on mixing R744 with R161, the flammability and explosivity of R161 can be suppressed because of the extinguishing effect of R744. A transcritical thermodynamic model is developed, and then the system performances of heat pump using R744/R161 blend are investigated and compared with those of pure R744 system under the same operation conditions. The variations of heat rejection pressure, heating coefficient of performance, unit volumetric heating capacity, discharge temperature of compressor and the mass fraction of R744/R161 are researched. The results show that R744/R161 mixture can reduce the heat rejection pressure of transcritical heat pump system.

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Experimental study on evaporation heat transfer of CO2/DME mixture refrigerant in a horizontal smooth tube

Cited by 19 publications

References 21 publications

Comprehensive evaluation on the thermal-hydraulic performance of supercritical CO2/R41 in a micro-fin tube

Comprehensive evaluation on the thermal-hydraulic performance of supercritical CO2/R41 in a micro-fin tube

Modeling of the Heat Transfer in a Supercritical Co2/Dme Mixture Flowing in Cooled Helically Coiled Tubes

Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

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