HYDROCARBON FUEL IN HORIZONTAL PARALLEL CHANNELS WITH NONUNIFORM HEAT FLUX BOUNDARY

Supercritical fluid flow instability is a crucial issue in regenerative active cooling technology. In this study, the supercritical cyclohexane flow in nonuniform heat flux parallel horizontal channels was investigated experimentally. The nonuniform heat flux (Qratio = Q1/Q2 = 1,1.2, and 1.5) boundary effect on the flow maldistribution caused by flow excursion was examined at supercritical pressure. Some important conclusions are summarized. A flow distribution interval was defined to describe the flow distribution in parallel tubes. Because the outlet fluid temperature is close to the pseudocritical temperature, flow excursion occurs in the corresponding channel and then causes an uneven flow distribution in parallel channels. The heating ratio is one of the crucial factors that influence the flow distribution results. Because the Qratio range is from 1 to 1.2, the flow distribution becomes more uneven with an enhanced Qratio. The flow distribution results are almost the same for Qratio = 1.2 and Q Qratio = 1.5. Compared with uniform heating, the system pressure has a greater effect on the flow distribution under a nonuniform heat flux between parallel tubes. The flow excursion instability boundary was obtained using two dimensionless parameters. These conclusions can provide guidance for the design of regenerative cooling systems.