传热学The highlight of the past half century of international heat transfer community.ppt

The highlight of the past half century of international heat munity-
What is the essence of enhancing heat transfer:
Field Synergy Principle and Its Applications
Professor: TAO Wen-Quan, HE Ya-LingCenter of Thermal & Fluid ScienceSchool of Energy &Power EngineeringXi’an Jiaotong University
December 20, 2002
Contents

of Guo’s Concept
by Numerical Tests
of Field Synergy Principle
to PTR Analysis
Research Needs
Interesting Example

1. Introduction

Enhancement of heat transfer generally means the
increase in heat transfer rate. From:
Newton’s law of cooling:
Overall heat transfer equation :
It can be seen that by increasing , the
heat transfer rate can be increased.
By enhancement techniques we mean the methods
or ways by which the value of k or h can be increased. This is the one of the topical subjects in the heat
munity in the last half century.
Figure 1 Publications on the enhanced heat transfer
Great achievements have been obtained in
developing heat transfer enhancement technology,
and according to Bergles[2] three generation
techniques were developed. They are now
widely adopted in many engineering fields. The
continuous size reduction of domestic air-
conditioner is an example of the application of
such achievements.
1950s:
Figure 2 First generation of heat transfer technique
1980s
Figure 3 Second generation of heat transfer techniques
Figure 4 The longitudinal vortex generator
Figure 5 Wavy fin with the longitudinal vortex generator