Sample Film Coefficient
INSTED®/Database contains ballpark values of the heat transfer (or film) coefficients for the following:
- forced convection
- free convection
- boiling water
- condensation of water vapor at one atmosphere
- Shell and Tube heat exchanger systems (over all U-values)
- Concentric Tubes heat exchanger systems (over all U-values)
For forced and free convection, knowing the heat transfer coefficient, calculate the heat transfer rate using the following formula:
Q = hA(Ts - Tf)
Where Q is the heat transfer rate in Watts (W), h is the heat transfer coefficient in (W/m2K), A is the surface area (m2), Ts is the temperature of the surface in (K) and Tf is the “free stream” temperature in (K).
The overall heat transfer coefficient for various duties and configurations for Shell and Tube heat exchanger systems is also available in INSTED/Database. The heat load, Q, is defined as:
Q = UADT,
where U is the overall heat transfer coefficient, A is the heat transfer area, and DT is the mean temperature difference (single-phase) or some suitable average value (multi-phase).
It is often desirable to obtain a quick estimate of the size of the Shell and Tube system required for a particular duty and configuration. If the value of the overall heat transfer coefficient is known, the equation given above for the heat load may be used to calculate this size.
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