# External Flow Over Cylinder.xls

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### Description

Purpose of calculation:
Calculate convective heat transfer for a cylinder in cross flow at various velocities. Input cells in blue.
Calculation Reference:
http://en.wikipedia.org/wiki/Churchill%E2%80%93Bernstein_equation
Calculation Validation:
Independently checked against a worked example in the following publication.
Fundamentals of Heat and Mass Transfer by Frank Incropera
/repository/fluids/properties-of-dry-air.xls/
Problem Parameters: Air Temperature, Kinematic viscosity, Thermal diffusivity, Thermal conductivity, Density, Prandtl number, Air Speed, Diameter, Reynolds Number, Nusselt Number (Churchill & Bernstein), Heat Transfer Coefficient, Length of tube, Area of face, Temperature of tube surface, Time period, Heat lost

Calculation Reference
Fundamentals of Heat and Mass Transfer by Frank Incropera
Fluid Mechanics

The general steps and equations involved in calculating convective heat transfer for a cylinder in cross flow at various velocities. Please note that you would need to input the relevant parameters into the equations to obtain the desired results. Here's an outline of the calculation process:

1. Determine the air properties: You mentioned the input parameters for air temperature, kinematic viscosity, thermal diffusivity, thermal conductivity, density, and Prandtl number. These properties are required to analyze the convective heat transfer.

2. Calculate the Reynolds number: The Reynolds number (Re) characterizes the flow regime and is calculated using the air speed, diameter of the cylinder, and kinematic viscosity. The formula for Reynolds number is:

Re = (Air Speed * Diameter) / Kinematic Viscosity

3. Calculate the Nusselt number: The Nusselt number (Nu) correlates the convective heat transfer to the fluid flow characteristics and is a function of the Reynolds number and Prandtl number. The Churchill-Bernstein equation is often used to calculate the Nusselt number for flow over a cylinder:

Nu = 0.3 + (0.62 * Re^0.5 * Pr^(1/3)) / (1 + (0.4 / Pr)^(2/3))^0.25 * (1 + (Re / 282000)^(5/8))^0.8

4. Calculate the heat transfer coefficient: The heat transfer coefficient (h) can be determined using the Nusselt number and thermal conductivity:

h = (Nu * Thermal Conductivity) / Diameter

5. Calculate the heat transfer rate: The heat transfer rate (Q) can be calculated by multiplying the heat transfer coefficient by the length of the cylinder and the temperature difference between the cylinder surface and the surrounding air:

Q = h * Length of Tube * Area of Face * (Temperature of Tube Surface - Air Temperature)

Please input the appropriate values for the air speed, diameter, length of tube, area of face, temperature of the tube surface, and air temperature into the equations mentioned above to perform the calculations and obtain the desired results.

17 Oct 2010
18 Jul 2023
File Size:
96.00 Kb