# Experimental data of free convection heat transfer for 12.7 and 25 um horizontal wires in rarefied atmospheres

## Description

When free convection is to be calculated for very thin wires in rarefied atmospheres, the Rayleigh number becomes very small. At these small Rayleigh numbers, available correlations are no longer applicable and there is also a lack of published experimental data. Therefore, new tests were performed using 12.7 and 25 um horizontal wires at low pressures. The wires were heated using electrical current and the temperature of the wires was calculated using the electrical resistance temperature coefficient. The heat transfer parameters and non-dimensional numbers were obtained using usual theoretical analysis. The gathered experimental data show that the Knudsen number must be incorporated in order to reliably describe the heat transfer in above-mentioned conditions. Data are in CSV format with utf-8 encoding. The header of each columns is the variable's name as follows: Gr: Grashof number Pr: Parndtl number Nu: Nusselt number Kn: Knudsen number h: heat transfer coefficient ( W/(m**2 K) ) Tw: wire's temperature (K) Ti: air's temperature (K) p: pressure (Pa) d: wire's diameter (m) L: wire's length (m)

## Files

## Steps to reproduce

Wire's temperature was measured at diferent sub-atmospheric pressures. The Nusselt number was calculated, as well as Rayleigh and Knudsen numbers.