Natural convection in vertical parallel plates with an unheated entry or unheated exit

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Numerical Heat Transfer. Part A, Applications; (United States)

DOI:https://doi.org/10.1080/10407789408955961· OSTI ID:7235266

Lee, K T ^[1]

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1. Oriental Institute of Technology, Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

This study aims to investigate the effects of the unheated entry or unheated exit section on the free convection heat transfer in air flow in vertical parallel plate channels resulting from the thermal boundary conditions of uniform heat flux (UHF) and uniform wall temperature (UWT). Results of average Nusselt number and dimensionless volume flow rate are presented in terms of the ratio of the length of heated section to the full channel length and a Rayleigh number, ranging from the limit for the fully developed flow to that for single-plate behavior. Analytical equations for dimensionless volume flow rate and average Nusselt number for both unheated restrictions and both thermal boundary conditions have been developed for the fully developed flow limit. The numerical solutions are shown to approach asymptotically the approximate solution for fully developed flow as the Rayleigh number approaches 1 or less. An important finding of the study is that an unheated exit characterizes greater total heat transfer and volume flow rate than an unheated entry does. The presence of the unheated entry or unheated exit severely affects the convection process, especially at low Rayleigh number. A notable effect of an unheated exit on convection characteristics was found for the case of UHF at high Rayleigh number.

• OSTI ID: 7235266
• Journal Information: Numerical Heat Transfer. Part A, Applications; (United States), Journal Name: Numerical Heat Transfer. Part A, Applications; (United States) Vol. 25:4; ISSN 1040-7782; ISSN NHAAES
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400* -- Engineering-- Heat Transfer & Fluid Flow
ANALYTICAL SOLUTION
CONVECTION
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ENERGY TRANSFER
HEAT TRANSFER
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NATURAL CONVECTION
NUMERICAL SOLUTION
ORIENTATION