nusselt number การใช้

• A larger Nusselt number corresponds to more active convection, with turbulent flow typically in the 100 1000 range.
• On the other hand, correlations for the peripherally averaged Nusselt number for constant wall temperature are very useful.
• The equation yields the surface averaged Nusselt number, which is used to determine the average convective heat transfer coefficient.
• Both correlations utilize the Nusselt number and are only valid when the Reynolds number is greater than 10, 000.
• These correlations are the mass transfer analogies to heat transfer correlations of the Nusselt number in terms of the Reynolds number and Prandtl number.
• A Nusselt number close to one, namely convection and conduction of similar magnitude, is characteristic of " slug flow " or laminar flow.
• This becomes the ratio of conductive thermal resistance to the convective thermal resistance of the fluid, otherwise known as the Nusselt number, Nu.
• In the situation of laminar flow in circular tubes, several dimensionless numbers are used such as Nusselt number, Reynolds number, and Prandtl.
• For this purpose, correlations for the peripherally averaged Nusselt number are, if none, of little use when keeping heat flux conditions constant.
• Using the mass-heat transfer analogy, the Nusselt number is replaced by the Sherwood number, and the Prandtl number is replaced by the Schmidt number.
• It should not be confused with Nusselt number, which employs the thermal conductivity of the fluid and hence is a comparative measure of conduction and convection, both in the fluid.
• Depends on different flow conditions ( laminar, turbulent, shapes of entrance, etc . ), the Nusselt number has different dependence on Reynolds number, Prandtl number and the friction factor of the flow.
• This increases to 3.57 with a heat transfer surface temperature of 100 癈 ( viscosity 2.82?0 & minus; 4 Pa穝 ), making a significant difference to the Nusselt number and the heat transfer coefficient.
• In contrast to the definition given above, known as " average Nusselt number ", local Nusselt number is defined by taking the length to be the distance from the surface boundary to the local point of interest.
• In contrast to the definition given above, known as " average Nusselt number ", local Nusselt number is defined by taking the length to be the distance from the surface boundary to the local point of interest.
• The film temperature is often used as the temperature at which fluid properties are calculated when using 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.
• For a correlation for a given geometry ( e . g . spheres, plates, cylinders, etc . ), a heat transfer correlation ( often more readily available from literature and experimental work, and easier to determine ) for the Nusselt number ( Nu ) in terms of the Reynolds number ( Re ) and the Prandtl number ( Pr ) can be used as a mass transfer correlation by replacing the Prandtl number with the analogous dimensionless number for mass transfer, the Schmidt number, and replacing the Nusselt number with the analogous dimensionless number for mass transfer, the Sherwood number.
• For a correlation for a given geometry ( e . g . spheres, plates, cylinders, etc . ), a heat transfer correlation ( often more readily available from literature and experimental work, and easier to determine ) for the Nusselt number ( Nu ) in terms of the Reynolds number ( Re ) and the Prandtl number ( Pr ) can be used as a mass transfer correlation by replacing the Prandtl number with the analogous dimensionless number for mass transfer, the Schmidt number, and replacing the Nusselt number with the analogous dimensionless number for mass transfer, the Sherwood number.
• For heat transfer, where " Nu " is the Nusselt number, " Re " is the standard Reynolds number based on the inner diameter of the tube, " Re "'is the specific Reynolds number based on the wiping frequency, " Pr " is the Prandtl number, " Fa " is the Fanning friction factor, " L " is the length of the tube, " D " is the inner diameter of the tube, " n " is the number of blades and the dots account for any other relevant dimensionless parameters.