8/2/2019 ETPFGM'10-33
1/4
ETPFGM10
48th European Two-Phase Flow Group Meeting 2010
28th-30th June 2010, Brunel University, London, UK
EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER IN
FLOW BOILING INSIDE A HELICALLY COILED SMALL
DIAMETER TUBE
A. M. El-Sayed, R. K. AL-Dadah1, S. M. Mahmoud, D.K. Aspinwall,
S. L. Soo
School of Mechanical Engineering, University of Birmingham,
Birmingham, B15 2TT.
Helical coils were originally developed for commercial
liquefaction of air, but currently are
also used for boiling applications in petrochemical, cryogenic
[1] and nuclear industries [2]. They
are suitable for boiling in the absence of gravity such as in
space applications where the radial
acceleration imposed on the flow compensates the gravitational
effect [1]. Additionally flow
boiling in micro channels is becoming increasingly important in
many applications involving
devices used for cooling electronic processers and in compact
refrigeration systems and heat
exchangers. Research activity relating to boiling heat transfer
of refrigerants inside helically coiled
small diameter and micro tubes [3-4] which is relevant, is
however limited. This paper initially
reviews previous research and presents experimental data for
flow boiling of refrigerant R134a
inside helically coiled 4 mm diameter tubing.
Figure 1 shows a schematic of the test facility which comprises
a compressor, water cooled
condenser, needle valve for controlling the refrigerant flow
rate and water heated evaporator. The
evaporator incorporated a helically coiled tube (pitch of 7mm
and coil diameter of 30mm) fitted
inside a cylindrical shell with an inside diameter of 50mm.
Measurements of boiling pressure,refrigerant flow rate, refrigerant
and water inlet/outlet temperatures and tube wall temperatures
at
different positions on the coil, were all monitored.
Figure 2 shows the experimental average boiling heat transfer
coefficients plotted against the
heat flux of the helically coiled tube compared to those
predicted by the Chen correlation [5], for a
straight tube of the same diameter. The results showed that
convective boiling was the dominant
mechanism for heat transfer with little dependency on heat flux
and the heat transfer coefficients
varied with mass velocity (G). Furthermore, the coefficients for
the coiled tube were higher than
those of straight tubes. Figure 3 shows good agreement between
the experimental results and those
predicted using Schrock-Grossman and Guo correlations [6] for
helically coiled tubes.
References
[1] Young, M. A. and K. J. Bell (1991). "Review of Two-phase
flow and Heat Transfer
Phenomena in Helically Coiled Tubes." American Institute of
Physics: 1214-1222.
[2] Nariai, H., Kobayashi, M., Matsuoka, T., Friction pressure
drop and heat transfer coefficient of
two-phase flow in helically coiled tube once through steam
generator for integrated type marine
water reactor.
[3] Vashisth, S., V. Kumar, et al. (2008) "A review on the
potential applications of curved
geometries in process industry" Industrial Engineering
Chemistry, 47, pp. 3291-3337.
1 Contact author: Tel: 0121-4143513, Email:
[email protected]
mailto:[email protected]:[email protected]:[email protected]
8/2/2019 ETPFGM'10-33
2/4
[4] Naphon, P. and S. Wongwises (2006) "A review of flow and
heat transfer characteristics in
curved tubes" Renewable and Sustainable Energy Reviews, 10, pp.
463490.
[5] Chen, J.C. (1966) A correlation for boiling heat transfer to
saturated fluids in convective
flow, I & EC Process Design Develop, 5 (3), pp. 322329.
[6] Zhao, L., Guo, Guo, L., Bai, B., Hou, Y., Zhang, X.,
Convective boiling heat transfer and two
phase flow characteristics inside a small horizontal helically
coiled tubing once-through steam
generator, International Journal of Heat and Mass Transfer, 46,
pp. 4779-4788.
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]
