Correlations for Convective Heat Transfer

11 pages
70 views

Please download to get full document.

View again

of 11
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Share
Description
Correlations for Convective Heat Transfer In many cases it's convenient to have simple equations for estimation of heat transfer coefficients. Below is a collection of recommended correlations for single-phase convective flow in different geometries as well as a few equations for heat transfer processes with change of phase. Note that all equations are for mean Nusselt numbers and mean heat transfer coefficients. The following cases are treated: 1. 2. 3. 4. 5. 6. 7. 8. ã ã Forced Convection Fl
Tags
Transcript
  Correlations for Convective Heat Transfer In many cases it's convenient to have simple equations for estimation of heat transfer coefficients.Below is a collection of recommended correlations for single-phaseconvective flow in different geometries as well as a few equations for heat transfer processes withchange of phase. Note that all equations are for mean Nusselt numbers and mean heat transfercoefficients. The following cases are treated:1.   Forced Convection Flow Inside a Circular Tube2.   Forced Convection Turbulent Flow Inside Concentric Annular Ducts3.   Forced Convection Turbulent Flow Inside Non-Circular Ducts4.   Forced Convection Flow Across Single Circular Cylinders and Tube Bundles5.   Forced Convection Flow over a Flat Plate6.   Natural Convection7.   Film Condensation8.   Nucleate Pool Boiling ã   List of Symbols ã   References 1 Forced Convection Flow Inside a Circular Tube All properties at fluid bulk mean temperature (arithmetic mean of inletand outlet temperature).Nusselt numbers Nu 0 from sections 1-1 to 1-3 have to be corrected fortemperature-dependent fluid properties according to section 1-4. 1-1 Thermally developing, hydrodynamically developed laminarflow (Re < 2300) Constant wall temperature:(Hausen)  Constant wall heat flux:(Shah) 1-2 Simultaneously developing laminar flow (Re < 2300) Constant wall temperature:(Stephan)Constant wall heat flux:which is valid over the range 0.7 < Pr < 7 or if Re Pr  D  /   L < 33 also for Pr > 7. 1-3 Fully developed turbulent and transition flow (Re > 2300) Constant wall heat flux:(Petukhov, Gnielinski)whereConstant wall temperature:For fluids with Pr > 0.7 correlation for constant wall heat flux can be used with negligibleerror.  1-4 Effects of property variation with temperature Liquids, laminar and turbulent flow:Subscript w: at wall temperature, without subscript: at mean fluid temperatureGases, laminar flow:Nu = Nu 0  Gases, turbulent flow:Temperatures in Kelvin 2 Forced Convection Flow Inside Concentric Annular Ducts, Turbulent (Re > 2300)  Dh = Do - DiAll properties at fluid bulk mean temperature (arithmeticmean of inlet and outlet temperature).Heat transfer at the inner wall, outer wall insulated:(Petukhov and Roizen)Heat transfer at the outer wall, inner wall insulated:(Petukhov and Roizen)  Heat transfer at both walls, same wall temperatures:(Stephan) 3 Forced Convection Flow Inside Non-Circular Ducts, Turbulent (Re > 2300) Equations for circular tube with hydraulic diameter 4 Forced Convection Flow Across Single Circular Cylinders and Tube Bundles  D = cylinder diameter, u m = free-stream velocity, all properties at fluid bulk meantemperature. Correction for temperature dependent fluid properties see section 4-4. 4-1 Smooth circular cylinder (Gnielinski)whereValid over the ranges 10 < Re l < 10 7 and 0.6 < Pr < 1000
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks
SAVE OUR EARTH

We need your sign to support Project to invent "SMART AND CONTROLLABLE REFLECTIVE BALLOONS" to cover the Sun and Save Our Earth.

More details...

Sign Now!

We are very appreciated for your Prompt Action!

x