12_GapConductance_web

12_GapConductance_web - ENU 4134 – Gap Conductance D...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ENU 4134 – Gap Conductance D. Schubring Fall 2011 Learning Objectives I 3-d Evaluate models for gap conductance (“evaluate” meaning both getting a result and considering if the model is physical) I 5-a Develop familiarity with terminology and mathematical symbols common to nuclear TH, including those symbols which do not map one-to-one to terminology I 5-b Use correlations and/or models to analyze problems in nuclear thermal hydraulics Gap Conductance (1) In a typical LWR, the second biggest Δ T is across the gas gap. At BOL, this is a narrow (order of 100 μ m) space between the UO 2 fuel and Zircalloy cladding. It is filled with an inert gas, usually helium. The gap gets smaller as the reactor first comes to temperature; both the width and composition of the gap vary with burnup. Width: fuel swelling and cracking leads to shrinking gap and fuel-clad contact. Composition: fission gases displace some of the helium and reduce conductance through the gap. Gap Conductance (2) The term gap conductance can be confusing. It is possible to formulate this Δ T using a parameter with dimensions of W K- 1 , W m- 1 K- 1 , or W m- 2 K- 1 . Strictly, thermal conductance should have dimensions of W K- 1 , but modeling with dimensions of W m- 2 K- 1 is conventional (consider as a heat transfer coefficient) q 00 g = htc g ( T fo- T ci ) (1) Since the thickness of the gap δ g << D , the gap is usually modeled without regard to curvature effects.modeled without regard to curvature effects....
View Full Document

This note was uploaded on 10/22/2011 for the course ENU 4134 taught by Professor Schubring during the Fall '11 term at University of Florida.

Page1 / 13

12_GapConductance_web - ENU 4134 – Gap Conductance D...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online