Convection Heat Transfer Of CO2 Research Articles

Study of convection heat transfer of CO2 at supercritical pressures during cooling in fluted tube-in-tube heat exchangers

The heat transfer characteristics of CO2 at supercritical pressures during cooling in two fluted tube-in-tube heat exchangers and a smooth tube-in-tube heat exchanger are investigated. Both the overall heat transfer and the local heat transfer coefficients are analyzed at various CO2 mass flow rates, inlet pressures, and flute pitches. The results demonstrate that the smaller hydraulic diameter of a fluted tube has a higher heat transfer coefficient at any pressure. The fluid is more disturbed in the fluted tube with a smaller flute pitch where the temperature gradient of CO2 near the wall is larger, resulting in greater Nusselt number. The overall heat transfer coefficients of the fluted tubes are 2–3 times that of the smooth tube. A new correlation is developed by considering the fluid properties and the fluted tube structure effects for the convective heat transfer calculation of supercritical CO2 in the fluted tube during cooling.

A numerical investigation on how to efficiently utilise carbon dioxide in convection-based energy systems

Owing to the environmentally benign nature and the special property variation at supercritical pressure, greenhouse gas carbon dioxide is regarded as the best retrofit to meet the future demand on long-term environmental-friendly working fluids. However, how to efficiently utilise carbon dioxide to reduce energy consumption and mitigate global warming is still an unsolved problem. In this paper, the natural convection heat transfer of carbon dioxide under supercritical pressure condition in a small cavity is studied for the first time. The potential of carbon dioxide as working fluid is quantitatively estimated in terms of enhancing heat transfer and reducing the cost of heat exchangers. It is found that the operating conditions including the temperature, temperature difference and pressure all have significant effects on heat transfer rate due to the special property variations of the CO2 fluid. Furthermore, a heat transfer correlation is proposed for the first time to quantitatively describe the natural convection heat transfer of CO2 at supercritical pressure in a small cavity.

A numerical investigation on how to efficiently utilise carbon dioxide in convection-based energy systems

Owing to the environmentally benign nature and the special property variation at supercritical pressure, greenhouse gas carbon dioxide is regarded as the best retrofit to meet the future demand on long-term environmental-friendly working fluids. However, how to efficiently utilise carbon dioxide to reduce energy consumption and mitigate global warming is still an unsolved problem. In this paper, the natural convection heat transfer of carbon dioxide under supercritical pressure condition in a small cavity is studied for the first time. The potential of carbon dioxide as working fluid is quantitatively estimated in terms of enhancing heat transfer and reducing the cost of heat exchangers. It is found that the operating conditions including the temperature, temperature difference and pressure all have significant effects on heat transfer rate due to the special property variations of the CO2 fluid. Furthermore, a heat transfer correlation is proposed for the first time to quantitatively describe the natural convection heat transfer of CO2 at supercritical pressure in a small cavity.