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10 TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT - ĐẠI HỌC ĐÀ NẴNG
Fig.4. Comparison of mean Nusselt number
of the hot fluid flow in case 3 between
our numerical prediction and literature data
E. Validation
Our computational approach is validated in this
part. It is noted that the calculations are carried out
Fig.2. Structured mesh of case 2 with the finite volume method [16] through the
commercial software Ansys-Fluent®. Convection
terms in momentum, energy, turbulent kinetic energy,
and turbulent losses were discretized with the second-
order upwind scheme. The variables are set converged
-6
at 10 .
To validate the numerical accuracy, numerical
prediction of dependence of mean Nusselt numbers of
the hot fluid flow on Reynolds numbers of the hot
fluid flow for case 3 was compared with analytical
data. It can be seen from Fig. 4 that our numerical
prediction is consistent with that reported by Jerry
Taborek [17]. The maximum error between our
numerical prediction and that of Jerry Taborek [17] is
10.5% at Reh = 17000. Thus, these comparisons
clearly indicate that the numerical accuracy is
promising.
4. RESULTS AND DISCUSSIONS
In this part, temperature distribution, heat transfer
rate, effectiveness for case 1, 2, 3 is reported and
analyzed. Additionally, comparisons between these are
also made.
A. Temperature distribution
In the scope of the survey with Reynolds numbers
of the hot fluid flow Re h from 5000 to 17000, effects
of Reynolds numbers of the hot fluid flow on
temperature at outlet of the hot and cold fluid flow for
the three cases are shown in Fig. 5. It can be seen that
temperature at outlet of the hot fluid flow and the cold
fluid flow increases with Reynolds numbers of the hot
fluid flow increases in all cases. Based on Eq. (16),
velocity of the hot fluid flow in the inner pipe
Fig.3. Mesh sensitivity study increases with Reynolds numbers of the hot fluid flow
for three cases at Reh = 14000 increases, thus temperature at outlet of the hot fluid
flow also increases. Besides, heat transfer efficiency of
the double pipe heat exchanger increase with Reynolds
numbers of the hot fluid flow increases, this lead to
temperature at outlet of the cold fluid flow increases.
ISBN: 978-604-80-9779-0
