Donald R. Mulholland, Porter J. Perkins
naca-tn-1588
May 1948
The icing protection obtained from an internally air-heated propeller blade partitioned to confine the heated air forward of 25-percent chord was investigated in the NACA Cleveland icing research tunnel. A production-model hollow steel propeller was modified with an internal radial partition at 25-percent chord and with shank and tip openings to admit and exhaust the heated air.
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http://naca.central.cranfield.ac.uk/reports/1948/naca-tn-1588.pdf