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Heat flux can be directly measured using a single heat flux sensor located on either surface or embedded within the material. Using this method, knowing the values of k and x of the material are not required. The multi-dimensional case is similar, the heat flux goes "down" and hence the temperature gradient has the negative sign:
Estimates of the total heat flow from Earth's interior to surface span a range of 43 to 49 terawatts (TW) (a terawatt is 10 12 watts). [13] One recent estimate is 47 TW, [1] equivalent to an average heat flux of 91.6 mW/m 2, and is based on more than 38,000 measurements.
In meteorology, the term 'sensible heat flux' means the conductive heat flux from the Earth's surface to the atmosphere. [6] It is an important component of Earth's surface energy budget. Sensible heat flux is commonly measured with the eddy covariance method.
However, one needs to select if the heat flux is based on the pipe inner or the outer diameter. If the heat flux is based on the inner diameter of the pipe, and if the pipe wall is thin compared to this diameter, the curvature of the wall has a negligible effect on heat transfer. In this case, the pipe wall can be approximated as a flat plane ...
This is a vector quantity, its components being determined in terms of the normal (perpendicular) direction to the surface of measurement. This is sometimes called energy flux density, to distinguish it from the first definition. Radiative flux, heat flux, and sound energy flux density [3] (also sound intensity) [4] are specific cases of this ...
For a uniform wall heating flux, the modified Rayleigh number is defined as: ... q″ o is the uniform surface heat flux; k is the thermal conductivity. [7] Other ...
Heat fluxes across the stable vapor layers are low but rise slowly with temperature. Any contact between the fluid and the surface that may be seen probably leads to the extremely rapid nucleation of a fresh vapor layer ("spontaneous nucleation"). At higher temperatures still, a maximum in the heat flux is reached (the critical heat flux, or CHF).
On-site heat flux measurements are often focused on testing the thermal transport properties of for example pipes, tanks, ovens and boilers, by calculating the heat flux q or the apparent thermal conductivity. The real-time energy gain or loss is measured under pseudo steady state-conditions with minimal disturbance by a heat flux transducer ...