Abstract:
We have obtained an extensive data set of heat transfer
coefficient (HTC) measurements in (R-218, C3F8)/(R-116, C2F6)
zeotropic refrigerant blends. A horizontal thin-wall tube with a
circular cross-section and diameter of 4 mm was used as an
evaporator. The data covers heat fluxes from 3.5 to 10 kW.m-2,
mass fluxes from 91 to 264 kg.m-2s-1 and C2F6 fractions from 0
to 25% molar. Various flow regimes were clearly identified via
the HTC measurements on both the top and bottom of the tube.
Boiling liquid was observed to pool at the bottom of the tube at
low mass fluxes, while an annular flow regime was achieved at
higher mass fluxes. The C3F8/C2F6 saturated fluorocarbon blends
are zeotropic, exhibiting the usual behaviour where the HTC of
the blend is lower than those of its pure components. A
comparison between the data and several models of flow boiling
heat transfer is presented. The comparison includes a flow map
that predicts various flow boiling regimes inside a horizontal
pipe.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
