Multi tubes in tube helically coiled heat
exchanger is proposed as a compact heat exchanger. Effects
of heat exchanger geometric parameters and fluid flow
parameters; namely number of inner tubes, annulus hydraulic
diameter, Reynolds numbers and input heat flux, on performance
of the heat exchanger are experimentally investigated.
Different coils with different numbers of inner tubes,
namely 1, 3, 4 and 5 tubes, were tested. Results showed that
coils with 3 inner tubes have higher values of heat transfer
coefficient and compactness parameter (¯hAh). Pressure
drop increases with increasing both of Reynolds number
and number of inner tubes. Correlations of average Nusselt
number were deduced from experimental data in terms of
Reynolds number, Prandtl number, Number of inner coils
tubes and coil hydraulic diameter. Correlations prediction
was compared with experimental data and the comparison
was fair enough.