A thermal contact model encompassing near-field effects of multi-interface TEGs in hypersonic conditions

High efficiency heat harvest of hypersonic vehicles claims elaborate design of thermoelectric (TE) conversion process. A thermoelectric generator (TEG) contains multi-interfaces in the heat transfer path and the interfacial thermal contacts with certain amount of nanoscale effects have significant influence on its TE conversion process. In this paper, a thermal contact model encompassing near-field thermal radiation (NFTR) effects of TEGs with heterogeneous interfaces between substrates, electrodes and TE legs is established and experimentally validated in hypersonic conditions. First, a real-topology-based thermal contact resistance (TCR) prediction model is developed and the far-and near-field radiative heat transfer at heterogeneous interfaces is considered by the fluctuational electrodynamics, and the model is validated by direct and indirect experimental measurements. Second, the effects of average interfacial temperature, clearance distance and opposite heat transfer paths on the thermal radiation are analyzed, and the influences of average interfacial temperature, loading pressure and clearance mediums on the TCR are then clarified. Third, the TCR is equivalently considered in a TEG perfor-mance evaluation model and the NFTR effects is quantitatively counted. The result shows that: with the consideration of the NFTR, the TCRs between TE legs and electrodes, substrates and electrodes decrease by about 3.90% to 17.0% and 0.510% to 6.40% under vacuum clearance, 1.30% to 5.50% and 0.220% to 2.00% under air clearance, respectively; and the maximum output power of the TEG increases by about 8.02% and 1.29% under vacuum and air clearance (0.1 MPa, 650 K), respectively.