The present work experimentally investigates the characteristics of convective heat transfer
in horizontal shell and coil heat exchangers in addition to friction factor for fully
developed flow through the helically coiled tube (HCT). The majority of previous studies
were performed on HCTs with isothermal and isoflux boundary conditions or shell and
coil heat exchangers with small ranges of HCT configurations and fluid operating conditions.
Here, five heat exchangers of counter-flow configuration were constructed with different
HCT-curvature ratios (d) and tested at different mass flow rates and inlet
temperatures of the two sides of the heat exchangers. Totally, 295 test runs were performed
from which the HCT-side and shell-side heat transfer coefficients were calculated.
Results showed that the average Nusselt numbers of the two sides of the heat exchangers
and the overall heat transfer coefficients increased by increasing coil curvature ratio.
The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side
and of 224.3–92.6% for the shell side when d increases from 0.0392 to 0.1194 within the
investigated ranges of different parameters. Also, for the same flow rate in both heat
exchanger sides, the effect of coil pitch and number of turns with the same coil torsion
and tube length is remarkable on shell average Nusselt number while it is insignificant on
HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is
obtained in the HCT-Fanning friction factor (fc) when d increases from 0.0392 to 0.1194.
Correlations for the average Nusselt numbers for both heat exchanger sides and the
HCT Fanning friction factor as a function of the investigated parameters are obtained. |
