Mixed Convection Heat Transfer in Enclosed Systems

Mixed convection in enclosed systems arises when both buoyancy‐driven and externally forced flows contribute to heat transfer within a confined geometry. Such systems range from electronic cooling enclosures to solar receivers and process furnaces. The interplay between natural and forced convection is governed by parameters including the Reynolds, Richardson and Prandtl numbers, as well as geometric features such as cavity shape, aspect ratio and the presence of internal obstacles. Numerical and experimental studies typically employ finite‐volume or finite‐element methods to resolve coupled momentum, continuity and energy equations under the Boussinesq approximation. Key objectives include maximising the heat‐transfer coefficient, minimising entropy generation and controlling flow patterns through features such as moving walls, magnetic fields or nanoparticle suspensions. Advances in nanofluid formulations have extended the design space, allowing tailored thermal conductivities and viscosities, while optimised obstacle placement or fin geometry can augment convective pathways. Applications span electronics cooling, thermal energy storage, building climate control and high‐temperature industrial processes, where precise control of temperature distributions and flow uniformity is essential for performance and reliability.

Research from Nature Portfolio

Recent studies have explored entropy production and heat‐transfer optimisation in trapezoidal enclosures filled with nanofluids and containing a central solid cylinder. By varying the Reynolds and Richardson numbers alongside nanoparticle volume fraction and cylinder size, researchers demonstrated that both geometry and fluid suspension strongly influence streamlines, isotherms and isentropic contours. Optimised cylinder placement and radius can raise the average Nusselt number by over 30% and reduce irreversible losses, as quantified by the Bejan number. This work highlights the potential for coupled geometrical and material design to balance buoyancy‐driven and pressure‐driven effects, offering guidelines for minimising entropy generation in compact thermal devices.

Mixed Convection Heat Transfer in Enclosed Systems publication trend

The graph below shows the total number of articles in mixed convection heat transfer in enclosed systems across all publications each year (not limited to Nature Index journals).

Technical terms

Mixed convection: Heat transfer regime in which buoyancy and forced‐flow effects are of comparable magnitude, typically characterised by the Richardson number.

Richardson number (Ri): Dimensionless ratio of buoyancy to inertial forces; Ri ≫ 1 indicates natural‐convection dominance, Ri ≪ 1 indicates forced‐convection dominance.

Reynolds number (Re): Dimensionless inertial‐to‐viscous force ratio governing flow regime, with higher values indicating turbulent or stronger forced flow.

Nusselt number (Nu): Dimensionless heat‐transfer coefficient comparing convective to conductive heat flux across a boundary.

Bejan number (Be): Ratio quantifying the share of entropy generation due to heat transfer relative to total entropy production.

Hartmann number (Ha): Dimensionless measure of magnetic‐field influence on electrically conducting fluid flow, affecting convective heat transfer in magnetohydrodynamic systems.

References

1. Entropy production and mixed convection within trapezoidal cavity having nanofluids and localised solid cylinder. Scientific Reports (2021).
2. Mixed Convection of Hybrid Nanofluid in an Inclined Enclosure with a Circular Center Heater under Inclined Magnetic Field. Coatings (2021).
3. Mixed Convection inside a Duct with an Open Trapezoidal Cavity Equipped with Two Discrete Heat Sources and Moving Walls. Mathematics (2022).
4. Nanofluid mixed convection inside wavy cavity with heat source: A non-homogeneous study. Case Studies in Thermal Engineering (2022).