Reynold’s number

For turbulent flow across tube banks, a modified Fanning equation and modified Reynold s number are given. 

Re = Modified Reynold s number Do = Outside tube diameter, ft p = Viscosity, Ib/ft sec centipoises x 0.000672... 

Viscosity Correction Using Reynold s Number Method of API RP520... 

Co is a function of the velocity of approach, hole diameter/tray-thickness ratio, Reynold s number through the... 

Tube side Determine heat transfer coefficient from Figure 10-46 (using tube-side curve) at Reynold s number calculated for pressure drop evaluation. If the hj calculated exceeds 300 for organics (Figure 10-103), use a value of 300 and correct to outside coefficient, hj. ... 

From calculated Reynold s number = 10,200 Read Figure 10-46, jjj = 45... 

Reynold s number, expressed in units suitable for application. 

The friction factor in Equations 2-54 and 2-55 is a function of the surface roughness of the pipe and the Reynold s number. Typical surface roughnesses of new commercial pipes are shown in Table 2-9. Old or corroded pipes may have a significantly higher roughness. 

In subcritical flow the discharge coefficient is affected by the velocity of approach as well as the type of choke and the ratio of choke diameter to pipe diameter. Discharge coefficients for subcritical flow are given in Figure 2-24 as a function of the diameter ratio and the upstream Reynolds number. Since the flow rate is not initially known, it is expedient to assume C = 1, calculate Q, use this Q to calculate the Reynold s number, and then use the charts to find a better value of C. This cycle should be repeated until the value of C no longer changes. 

In order to estimate an upper bound for attainable TZ s, consider a LG with lattice spacing Iq, speed-of-sound Cg, kinematic viscosity v. Reynold s number is then given by... 

Reynold s number It is a dimensionless number that is significant in the design of any system in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid. It is equal to the density of a fluid, times its velocity, times a characteristic length, divided by the fluid viscosity. This value or ratio is used to determine whether the flow of a fluid through a channel or passage, such as in a mold, is laminar (streamlined) or turbulent. 

For very small values of Reynold s numbers (negligible convective diffusion), elementary calculations lead to... 

Equation (e) is merely a definition of the mass flow rate. Equation (/) is a standard correlation for the friction factor for turbulent flow. (Note that the correlation between /and the Reynold s number (Re) is also available as a graph, but use of data from a graph requires trial-and-error calculations and rules out an analytical solution.)... 

As flow is, by definition, unpredictable, there is no single equation that defines the rate of turbulent flow as there is with laminar flow. However, there is a number that can be calculated in order to identify whether fluid flow is likely to be laminar or turbulent and this is called Reynold s number (Re). 

If one were to calculate the units of all the variables in this equation, you would find that they all cancel each other out. As such, Reynold s number is dimensionless (it has no units) and it is simply taken that... 

Other factors do intervene. Significant solar heating of the soil surface, so that the soil becomes warmer than the air, causes vertical thermal convection currents to develop within the boundary layers. This introduces turbulence or instability that acts to move the chemical signature up into the free air. When the molecules are moved into the free flow of the air, the effect is to reduce the concentration by dilution. Conversely, when the soil surface is cooler than the air, thermal convection is inhibited, with the result that the molecules are effectively trapped in the boundary layer. This effect is strengthened by the cooling of the air adjacent to the surface, which increases its viscosity. Higher viscosity lowers the Reynold s number, thus decreasing boundary layer thickness. 

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