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This paper proposed a type of metal foams filled thermoelectric generator (TEG) for waste heat recovery. Metal foam inserts of three kinds of pore densities (5 PPI, 10 PPI and 20 PPI) were included, considering the heat transfer enhancing features of porous metal mediums. A flow channel detachable prototype was designed to experimentally investigate the influence of metal foams on the performance of thermoelectric waste heat recovery (TWHR) system. The operating parameters were further experimented to improve the thermoelectric power generation efficiency, including hot air inlet temperature, cold water flow rate, metal foam pore density and thermoelectric module (TEM) connecting mode. Moreover, the TWHR performance of the system was evaluated on power generation efficiency, heat exchange effectiveness and waste heat recovery rate, respectively. The results showed that filling metal foams in the flow channels could effectively enhance the performance of the TWHR system. The maximum power generation efficiency was 2.05%, when the TEG was filled with 5 PPI metal foams. It was 29.75% higher than the value of unfilled TEG.