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UNSTEADY THERMAL ENTRANCE HEAT TRANSFER IN LAMINAR PIPE FLOWS WITH STEP CHANGE IN AMBIENT TEMPERATURE.

Author(s) : LIN T. F., HAWKS K. H., LEIDENFROST W.

Type of article: Article

Summary

A FULLY IMPLICIT UPWIND FINITE DIFFERENCE NUMERICAL SCHEME HAS BEEN PROPOSED TO INVESTIGATE THE CHARACTERISTICS OF THERMAL ENTRANCE HEAT TRANSFER IN LAMINAR PIPE FLOWS SUBJECT TO A STEP CHANGE IN AMBIENT TEMPERATURE. A MODIFIED NUSSELT NUMBER IS INTRODUCED. THE UNSTEADY AXIAL VARIATIONS OF MODIFIED NUSSELT NUMBER, BULK FLUID TEMPERATURE, AND WALL TEMPERATURE AND THE TRANSIENT TEMPERATURE PROFILES AT CERTAIN AXIAL LOCATIONS ARE PRESENTED FOR VARIOUS OUTSIDE HEAT TRANSFER COEFFICIENTS. THE RESULTS CAN BE COMPREHENSIVELY EXPLAINED BY THE INTERACTION BETWEEN THE UPSTREAM CONVECTIVE HEAT TRANSFER AND THE DIFFUSION HEAT TRANSFER IN THE RADIAL DIRECTION. STEADY STATE IS REACHED WHEN THE AXIAL CONVECTION BALANCES THE RADIAL DIFFUSION.

Details

  • Original title: UNSTEADY THERMAL ENTRANCE HEAT TRANSFER IN LAMINAR PIPE FLOWS WITH STEP CHANGE IN AMBIENT TEMPERATURE.
  • Record ID : 1984-1390
  • Languages: English
  • Source: Wärme Stoffübertrag. - vol. 17 - n. 3
  • Publication date: 1983
  • Document available for consultation in the library of the IIR headquarters only.

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