Heat transfer modification induced by a localized thermal disturbance in a differentially-heated cavity

Abstract

Numerical investigation of a natural convection flow with a localized thermal disturbance is presented here. The configuration of a differentially heated cavity is considered with air as working fluid. In this study, the initial flow regime is steady and close to the transition to unsteadiness. Different cases of local wall temperature disturbances are tested in a thin area at the onset of the hot vertical boundary layer. These cases are distinguished by the time-averaged temperature of this area (higher or lower than the hot wall temperature) and by their temporal evolution (steady or periodic). In cases with a periodic disturbance, the imposed frequency corresponds to the first frequency emerging in the unsteady regime. The results show the spread of temperature fluctuations across the whole cavity with the periodic disturbance, in particular near the upper corner of the cavity. The hot steady disturbance trigs the onset of time-dependent flow. Moreover, the local modification of the hot wall temperature has an impact on global heat transfer: about 16% downstream the disturbance area and about 2% on the opposite cold wall.

Heat transfer enhancement of a natural convection flow in an enclosure submitted to a small extent thermal disturbance: Influence of location and frequency

“…130×260 control volumes are chosen following a mesh convergence study. More details and validation tests can be found in [32].…”

“…The introduced obstacle induced a decrease of the downstream heat transfers, and the temperature oscillation of the pipe amplified the fluctuations of the unsteady flow. Recently, a localized time variation of the imposed temperature on a part of the hot wall has been studied by [32].…”

Natural convection in vertical enclosures with conjugate boundary conditions

“…In contrast, the maximum heat transfer occurs at a particular aspect ratio with the constant temperature boundary conditions. Recent studies by Chorin, Moreau & Saury (2018) and Thiers, Gers & Skurtys (2020) explored the use of a localized thermal disturbance on a vertical wall to trigger time-dependent flow with unsteady disturbances in an otherwise stable system to enhance the heat transfer.…”