Experimental characterization of thermionic surface cooling in thermionic discharge

TL;DR

This study experimentally investigates thermionic surface cooling during plasma discharges at 1 Torr, demonstrating significant cooling capacity and potential for thermal protection in high-temperature applications like hypersonic vehicles.

Contribution

The paper provides the first direct experimental evidence of thermionic cooling during plasma discharges, quantifying its capacity and demonstrating its potential for thermal management.

Findings

Surface cooling initiated at plasma ignition observed directly.

Cooling capacity estimated at 1.6 ± 0.2 MW/m^2.

Thermionic cooling shows promise for high-temperature thermal protection.

Abstract

In this work, the thermionic cooling effect during thermionic discharges with parallel plate electrodes at 1 Torr is investigated. Time-resolved observation of electron emission and surface temperature is realized in addition to the typical steady state characterization. Surface cooling by the electron emission, initiated by plasma ignition, is directly captured at its onset and an estimated cooling capacity of 1.6 \pm 0.2 MW/m^2 is observed. The present work provides experimental evidence of considerable surface cooling achieved by thermionic cooling. This result indicates that thermionic cooling can be a promising thermal protection method at elevated temperatures, such as those encountered by hypersonic vehicle leading edges in flight.