Free Convection Heat Transfer From Upward-Facing Isothermal Horizontal Surfaces

Abstract

Heat transfer by free convection in air from isothermal horizontal surfaces heated and facing upward has been experimentally studied by using a Mach-Zehnder interferometer. The local and the average heat-transfer coefficients and the temperature distributions were determined in the range of Gr Pr from 1.9 × 106 to 1.7 × 108. Measurements were compared with available experimental and theoretical results. Periodical flow instabilities caused random changes, which could reach +45 and −35 percent of mean values in the local Nusselt number and +23 and −15 percent of mean value in the average Nusselt number. The nature of the free convection flow over the heated surface and the separation of the boundary layer were inferred from these random changes in the local and average Nusselt numbers.

Fluid flow and heat transfer of natural convection adjacent to upward-facing, rectangular plates of arbitrary aspect ratios

“…Thereafter, several workers have measured the average Nusselt or Sherwood numbers from the plates with various planforms and sizes. Al-Arabi and El-Riedy [4] and Yousef et al [5] have also given the same 1/4-and 1/3-power heat transfer correlations in the laminar and turbulent regimes, respectively. While, Goldstein and Lau [6] have performed the mass transfer experiments with square naphthalene plates in air, and proposed the 1/5-power correlation.…”

Variability and impact of internal surfaces convective heat transfer coefficients in the thermal evaluation of office buildings

“…These correlations used Fo which is difficult to define in global annual evaluation of building energy performances. Moreover, the correlations proposed look like those presented by Yousef et al [25]. …”

“…• b is a constant [25] Category 3: Function of air flow 3.1. Air change per hour ℎ = ܽ ‫‪ሻ‬ܪܥܣ‪ሺ‬‬ + ܿ • a, b and c are constants [26,27] 3.2.…”

“…NC for ∆T ≤ 5 °C NC (a): For floor surfaces in a buoyant thermal situation. Based on the data of[57],[58] and[25], using[32] mathematical model. Valid for T surf < T air and 10 4 ≤ Ra ≤ 10 12 .…”

Thermal response of unconfined ceilings above growing fires and the importance of convective heat transfer

“…Also, neglect of convection appears to lead to serious underestimates of peak O fluxes when they reach typical hazardous levels of 2W/cm 4 exactly for such a purpose that the details of the convection problem (i.e., the time-dependent temperature and velocity field of the ceiling jet) are likely to play an important role.…”