Free convection heat transfer and buoyancy-assisted flow over a heated plate inserted horizontally in a vertical channel with time-varying conditions


Saraç B., Aksu E., Demirtaş C., Ayhan T.

Journal of Thermal Analysis and Calorimetry, vol.149, no.5, pp.2255-2271, 2024 (SCI-Expanded)

  • Publication Type: Article / Article
  • Volume: 149 Issue: 5
  • Publication Date: 2024
  • Doi Number: 10.1007/s10973-023-12649-5
  • Journal Name: Journal of Thermal Analysis and Calorimetry
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, Index Islamicus, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.2255-2271
  • Karadeniz Technical University Affiliated: Yes

Abstract

This study investigates time-dependent free convection heat transfer and buoyancy-assisted flow over a horizontal heated

plate within a vertical channel for two distinct scenarios: one stand alone and second involving tilted plates and varying plate

positions. The temperature difference between the plate and air induces buoyant airflow. The study explores the impact of

plate tilt angles and positions on time-dependent heat transfer coefficients due to varying buoyant airflow. The primary focus

of the research for both classes of study is on the effects of the tilt angles (which control the change in flow blockage ratio)

and positions of the heated plate on the time-dependent heat transfer coefficients due to the time-dependent buoyant airflow.

As the blockage ratio increases and the positions of the heated plate in the vertical channel decreases, the influence of timedependent

buoyancy on the time-dependent Nusselt number weakens. The time-dependent Richardson's number varied from

7.4 to 9.6 throughout the tests. Based on the experimental data gathered from corresponding flux geometries and test conditions,

the CFD model was validated. We have also developed a set of empirical correlations for predicting time-dependent

Nusselt numbers for a time-dependent Rayleigh number range of 2000 < Ra < 7500, the dimensionless height of the heated

plate from 0.507 ≤ ϕ ≤ 0.551, and a flow blockage ratio of 0.08 ≤ χ ≤ 0.024. At orientations where γ = π/2 and γ = π/4, it

has been observed that the heat transfer at position ∅1 is higher, whereas at γ = 0 orientation, 1 heat transfer value is lower

compared to the others. When the time required for the heated plate at all positions () to reach thermal equilibrium with the

ambient environment is compared with respect to orientation angles, it has been observed that the γ = π/2 orientation angle

reaches thermal equilibrium in the shortest time compared to the γ = π/0 and γ = π/4 orientation angles.