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Unsteady Natural Convection within an Attic-Shaped Space Subject to Sinusoidal Heat Flux on Inclined Walls

Suvash C. Saha1,*, Ali M. Sefidan2, Atta Sojoudi3

1 School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, NSW, Australia
2 Mechanical Engineering Department, University of Canterbury, Christchurch, New Zealand
3 Mechanical Engineering Department, University of Tehran, Tehran, Iran

* Corresponding Author: Suvash C. Saha. Email:

Energy Engineering 2020, 117(1), 1-17.


Free convection inside an attic enclosure in which sinusoidal heat flux applied on the inclined walls and a constant temperature applied on the base wall has been investigated numerically to demonstrate the primary flow characteristics and heat transfer within the attic enclosure over daily routine cycles. To solve the governing equations, the finite volume technique has been utilized. After performing the grid independency and time step size tests, the roles of Rayleigh number (Ra) and the attic aspect ratio (AR) on the unsteady flow structure and heat transfer phenomenon are explained for a constant Prandtl number (0.72) for the air. Results are illustrated as a form of stream function and isotherms. Moreover, heat transfer is calculated in terms of Nusselt number. The numerical simulations reveal stratified flow within the enclosure during the daytime nonlinear heating stage. However, during night-time, nonlinear cooling stage the flow turns into unstable as the forms of rising and sinking plumes for sufficiently higher Rayleigh number.


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Saha, S. C., Sefidan, A. M., Sojoudi, A. (2020). Unsteady Natural Convection within an Attic-Shaped Space Subject to Sinusoidal Heat Flux on Inclined Walls. Energy Engineering, 117(1), 1–17.

This work is licensed under a Creative Commons Attribution 4.0 International License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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