Page 414 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 389
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
0 2001 Elsevier Science Ltd. All rights reserved

STUDY ON HEAT TRANSFER BETWEEN GAS FLAME
AND PLATE DURING LINE-HEATING PROCESS

Y. Tomita', N. Osawa', K. Hashimoto', N. Shinkai', J. Sawamura' and K. Matsuoka'

I Department of Naval Architecture and Ocean Engineering, Osaka University,
2-1, Yamadaoka, Suita, Osaka 565-0871 Japan
2Bureau Veritas Japan,
93, Edomachi, Chyuoh-ku, Kobe, Hyogo 65 1-0033 Japan

ABSTRACT
The transient 3-dimensional temperature distribution near the plate surface of the spot heating gas
flame is measured in detail by a high performance L.I.F. measurement system. It has been found that
the thermal-flow field within the combustion flame remains almost unchanged regardless of the
temperature increase in the steel plate. A new hypothesis on the heat transfer during line heating
process is built up based on the result of the L.I.F. experiment. This hypothesis is that the distributions
of gas temperature near plate surface and local heat transfer coefficient depend only on the distance
from the torch. The appropriateness of this hypothesis is proved by performing an inverse heat
conduction analysis of a spot heating experiment.

KEYWORDS
Line heating, Heat transfer, L.I.F., Inverse heat conducting analysis

1 INTRODUCTION

Line heating process, which is one of the most characteristic works in the shipbuilding industry, is
applied to the formation of curved hull plates. This work has not been carried out by the automatic
operation, but by skilled workers. Recently the automatic operation has been strongly desired because
of the decrease in skilled workers. In order to automate this process, heat transfer between flame and
plate has to be evaluated theoretically.
The heat transfer during line heating process is a poorly understood phenomenon. Moshaiov and
Latorre (1 985) studied the temperature distribution of a plate using a distributed heat source moving
along the plate surface. Tsuji and Okunura (1 988) found that the heat flux distribution of flame could
be expressed approximately by superposition of two gaussian distributions. Terasaki et al. (1999)
derived the equations for thermal cycles of line heating. In these theories, a series of experiment is
needed whenever plate size or plate thickness or torch speed changes even if torch nozzle, gas