Heat Transfer Mechanisms in Supercritical Fluids

Supercritical fluids, which exist above their critical temperature and pressure, exhibit unique thermophysical properties that combine liquid-like densities with gas-like diffusivities. Close to the pseudo-critical line, rapid variations in specific heat, thermal conductivity and density give rise to enhanced heat transfer but also to regions of heat transfer deterioration. In forced convection systems, buoyancy forces induced by steep density gradients can either augment or suppress turbulence in the near-wall region, altering thermal boundary-layer structure. The result is a delicate balance between mixed convection, real-fluid effects and turbulent transport that governs local heat flux, pressure drop and overall energy efficiency. Applications range from supercritical water reactors and high-efficiency power cycles to microfluidic cooling systems and carbon-capture heat pumps. Understanding the interplay of pseudo-boiling phenomena, turbulent mixing and buoyancy-driven transport is therefore critical for optimising designs and ensuring safe, reliable operation under transcritical and supercritical conditions.

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Heat Transfer Mechanisms in Supercritical Fluids publication trend

The graph below shows the total number of articles in heat transfer mechanisms in supercritical fluids across all publications each year (not limited to Nature Index journals).

Technical terms

Supercritical fluid: A substance at temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.

Pseudo-critical temperature: The temperature at which specific heat peaks under supercritical pressure, marking intensified thermodynamic fluctuations.

Heat transfer deterioration (HTD): A local reduction in convective heat transfer coefficient due to anomalous near-wall property gradients or buoyancy-induced laminarisation.

Nusselt number (Nu): A dimensionless parameter representing the ratio of convective to conductive heat transfer across a boundary layer.

Buoyancy force: A body force arising from density differences in a gravitational field, which can modify flow turbulence and heat transport.

References

1. Experimental investigations on heat transfer of CO2 under supercritical pressure in heated horizontal pipes. Energy (2022).
2. Thermodynamics-informed neural network for recovering supercritical fluid thermophysical information from turbulent velocity data. International Journal of Thermofluids (2023).
3. Structure of the thermal boundary layer in turbulent channel flows at transcritical conditions. Journal of Fluid Mechanics (2022).