Internal Flow

In a fully developed flow in a circular tube, what is the critical Reynolds number that typically corresponds to the onset of turbulence?

What is the shape of the velocity profile for a fully developed laminar flow in a circular tube?

For fully developed laminar flow in a smooth circular tube, how is the Moody friction factor 'f' related to the Reynolds number 'ReD'?

How does the thermal entry length (xfd,t) relate to the hydrodynamic entry length (xfd,h) for fluids with a Prandtl number much greater than 1, such as oils?

In a thermally fully developed flow with constant properties, how does the local convection coefficient 'h' vary with axial distance 'x'?

For a fluid being heated in a tube under the condition of uniform surface heat flux, how does the mean temperature 'Tm' vary with axial distance 'x'?

To calculate the total convection heat transfer rate for flow in a tube with a constant surface temperature, what type of average temperature difference should be used?

What is the Nusselt number (NuD) for fully developed laminar flow in a circular tube with a uniform surface heat flux condition?

What is the Nusselt number (NuD) for fully developed laminar flow in a circular tube with a uniform surface temperature condition?

The Dittus-Boelter equation (NuD = 0.023 * ReD^(4/5) * Pr^n) is a common correlation for which type of internal flow?

When using the Dittus-Boelter equation for a fluid being cooled (Ts < Tm), what is the value of the exponent 'n' for the Prandtl number?

What is the primary purpose of using the hydraulic diameter (Dh) in convection calculations for noncircular tubes?

How is the hydraulic diameter (Dh) for a noncircular tube defined?

In a concentric tube annulus, if the inner tube has a diameter Di and the outer tube has a diameter Do, what is the hydraulic diameter Dh?

What is the primary effect of inserting a twisted tape into a tube for heat transfer enhancement?

For which type of flow is heat transfer augmentation by using helically coiled tubes typically employed?

What is the primary reason that heat transfer coefficients in microscale internal flows can be dramatically higher than in conventional-sized channels?

What dimensionless number, analogous to the Nusselt number, is used to characterize convection mass transfer in internal flows?

Calculate the hydraulic diameter for a rectangular duct with side lengths of 40 mm and 160 mm.

Water is flowing in a circular tube with a Reynolds number of 1500. What is the Moody friction factor, f?

In fully developed laminar flow through a square channel with uniform surface temperature, what is the Nusselt number?

What term describes the distance from the entrance of a tube to the location where the velocity profile no longer changes with increasing axial distance?

For laminar flow in a circular tube with a Reynolds number of 1000, what is the hydrodynamic entry length as a fraction of the tube diameter D?

The Sieder and Tate correlation, NuD = 1.86 * (ReD*Pr / (L/D))^(1/3) * (mu / mu_s)^(0.14), is most applicable for which flow condition?

What is the key difference between the mean temperature (Tm) used in internal flow and the free stream temperature (T_infinity) used in external flow?

For a fluid flowing through a tube with a constant surface temperature Ts, which expression describes the variation of the mean temperature Tm(x) with axial distance x?

Under what condition can the Gnielinski correlation (Equation 8.62) for turbulent flow also be used to estimate the effect of wall roughness on the heat transfer coefficient?

For fully developed laminar flow in a rectangular duct with an aspect ratio (b/a) of 2.0 and a uniform heat flux condition, what is the Nusselt number?

In a concentric tube annulus where heat transfer occurs from both the inner and outer surfaces, separate convection coefficients, hi and ho, are defined. Why is this necessary?

For a liquid metal with a Prandtl number less than 0.05 flowing turbulently in a smooth circular tube with constant surface heat flux, which correlation is recommended?

In a thermally fully developed region with uniform surface heat flux, what is the relationship between the surface temperature gradient (dTs/dx) and the mean temperature gradient (dTm/dx)?

When is it generally reasonable to assume that the average Nusselt number for an entire tube is equal to the fully developed value (NuD,fd) for turbulent flow?

In the concentric tube annulus correlations for fully developed laminar flow, what do the influence coefficients theta_i* and theta_o* account for?

According to the provided text, when does the continuum assumption for a gas in internal flow begin to be questionable, based on the hydraulic diameter Dh and mean free path lambda_mfp?

A fluid with a Prandtl number of 7.0 flows through a circular tube. What is the ratio of the hydrodynamic entry length to the thermal entry length (xfd,h / xfd,t) for laminar flow?

Which of the following heat transfer enhancement schemes for internal flow primarily works by increasing the heat transfer surface area?

In fully developed laminar flow through a circular tube, an engineer measures a pressure drop of 800 Pa over a 10 m length. If the tube diameter is doubled while the mean velocity remains the same, what will be the new pressure drop over the same length?

What dimensionless number is analogous to the Prandtl number in convection mass transfer?

In Example 8.6, hot air flows through a duct. If the flow rate were decreased, what would happen to the total heat loss from the duct, assuming the inlet temperature remains the same?

What is the primary physical reason for the existence of a 'fully developed region' in internal flow?

The mass transfer analog of the Dittus-Boelter equation for fully developed turbulent flow is given by ShD = 0.023 * ReD^(4/5) * Sc^0.4. In this equation, what does the Schmidt number (Sc) represent?

For fully developed laminar flow, the velocity at the centerline of a circular tube is how many times the mean velocity?

An engineer is designing a heat exchanger and can choose between a single large tube or several smaller tubes in parallel, with the total cross-sectional area and mass flow rate being the same in both cases. Assuming turbulent flow, why might using several smaller tubes be advantageous for heat transfer?

In a horizontal, thin-walled circular tube, water flows at 0.25 kg/s. The inlet temperature is 15 C and the outlet is 57 C. The tube is 6 m long with a 50 mm diameter and is held at a constant surface temperature of 100 C. What is the log mean temperature difference (LMTD) for this system?

For fully developed turbulent flow in a smooth tube with a Reynolds number of 40,000, what is the approximate Moody friction factor 'f' based on the correlation f = 0.184 * ReD^(-1/5)?

What does the term (P/m_dot*cp) in the differential energy balance (dTm/dx = (P/m_dot*cp) * h * (Ts - Tm)) represent physically?

In a concentric tube annulus, one surface is insulated and the other is held at a constant temperature. Can the Nusselt number for the isothermal surface be determined from the provided tables?

Which property variation is accounted for by the (mu / mu_s)^0.14 term in the Sieder and Tate equation for turbulent flow (Equation 8.61)?

A hot fluid at 103 C enters a 5 m long uninsulated duct with a mass flow rate of 0.050 kg/s and cools to 77 C. What is the total rate of heat loss from the duct? The specific heat of the fluid is 1010 J/kg-K.

In a thermally fully developed flow in a circular tube under constant surface temperature, why is the local convection coefficient constant?