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Formula for the calculation of the Prandtl number of air and water. For air with a pressure of 1 bar, the Prandtl numbers in the temperature range between −100 °C and +500 °C can be calculated using the formula given below. The temperature is to be used in the unit degree Celsius.
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 ).
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or ... the total number of microstates in the combined system 1 + system 2 ...
History Anders Celsius's original thermometer used a reversed scale, with 100 as the freezing point and 0 as the boiling point of water.. In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale that was the reverse of the scale now known as "Celsius": 0 represented the boiling point of water, while 100 represented the freezing point of water.
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 ...
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.
Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 5 Pa (100 kPa, 1 bar ). NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). [3] This standard is also called normal temperature and pressure (abbreviated as NTP ).
Mach number is a function of temperature and true airspeed. Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is found from Bernoulli's equation for M < 1 (above):