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From the point of view of statistical mechanics, the total number of microstates in the combined system 1 + system 2 is , the logarithm of which (times the Boltzmann constant) is the sum of their entropies; thus a flow of heat from high to low temperature, which brings an increase in total entropy, is more likely than any other scenario ...
In thermal fluid dynamics, the Nusselt number ( Nu, after Wilhelm Nusselt [1] : 336 ) is the ratio of total heat transfer to conductive heat transfer at a boundary in a fluid. Total heat transfer combines conduction and convection. Convection includes both advection (fluid motion) and diffusion (conduction). The conductive component is measured ...
Total air temperature is an essential input to an air data computer in order to enable the computation of static air temperature and hence true airspeed . The relationship between static and total air temperatures is given by: where: static air temperature, SAT ( kelvins or degrees Rankine) total air temperature, TAT (kelvins or degrees Rankine ...
is the number of particles (usually atoms or molecules) of the gas. In SI units, p is measured in pascals, V is measured in cubic metres, n is measured in moles, and T in kelvins (the Kelvin scale is a shifted Celsius scale, where 0.00 K = −273.15 °C, the lowest possible temperature).
The Prandtl number ( Pr) or Prandtl group is a dimensionless number, named after the German physicist Ludwig Prandtl, defined as the ratio of momentum diffusivity to thermal diffusivity. [1] The Prandtl number is given as: where: ν {\displaystyle u } : momentum diffusivity ( kinematic viscosity ),
The film temperature is often used as the temperature at which fluid properties are calculated when using the Prandtl number, Nusselt number, Reynolds number or Grashof number to calculate a heat transfer coefficient, because it is a reasonable first approximation to the temperature within the convection boundary layer.
In fluid mechanics, the Rayleigh number ( Ra, after Lord Rayleigh [1]) for a fluid is a dimensionless number associated with buoyancy -driven flow, also known as free (or natural) convection. [2] [3] [4] It characterises the fluid's flow regime: [5] a value in a certain lower range denotes laminar flow; a value in a higher range, turbulent flow.
5 x + 32) °F. The degree Celsius is the unit of temperature on the Celsius temperature scale [1] (originally known as the centigrade scale outside Sweden), [2] one of two temperature scales used in the International System of Units (SI), the other being the closely related Kelvin scale. The degree Celsius (symbol: °C) can refer to a specific ...