A waste cold recovery from the exhausted cryogenic nitrogen by using thermoelectric power generator

Waste energy appears in the form of waste heat as well as waste cold. Among all, cryogenic nitrogen is the most common cold source and is extensively used in the industry and laboratories. An intuitive way to recover waste cold is applying TEGs (thermoelectric power generators) due to the observed huge temperature difference between the exhausted cryogenic fluid and the ambience. The purpose of this work is to investigate such a waste cold recovery system analytically and experimentally. Confirmed through a model analysis and by experimental measurements, the system works successfully and cascade TEG modules are suggested for accessing more temperature difference and thus generating more power. However, the measured power generation rates are less than the predictions. The ice frozen over the thermal spreader, which is not taken into consideration in the model, must take the responsibility. Still, a power generation rate as high as 0.93 W was obtained by the proposed prototype with four two-layer cascade TEG modules and a mass flow rate of cryogenic nitrogen of 3.6 g/s.