Heat Transfer Enhancement in a Gas-Cooled Condenser Using Carbon Foams

摘要

Significant heat transfer enhancement by using carbon foam in the cold head of a cryocooler for liquefaction ofncryogens is demonstrated. The development of an effective, lightweight and compact cold head for liquefaction ofngaseous hydrogen and its subsequent densification to subcooled liquid hydrogen will require a condenser with highnheat transfer coefficient and low pressure drop on the gas side. High-thermal-conductivity carbon foam is used tonenhance the heat transfer coefficient. For convenience, as a first effort, this work uses air and vapor/liquid FC-87 tonsimulate heliumand gaseous/liquid hydrogen, respectively.Experiments are conducted on carbon block foamand annalternative flow configuration called “corrugated” carbon foam, which has a lower flow resistance. Results of thesenexperiments showthat, comparedwith block carbon foam, corrugated carbon foamhas amuch lower pressure dropnand a significant improvement in heat transfer performance. Experimental results of air and vapor/liquid FC-87nshowthat carbon-foam-based heat sinks can be 18 times better than conventional air-channel heat sinks at lowspeedn(1 m=s).