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A characterization of gas-to-gas micro heat exchangers has been performed in terms of pressure drop behavior and heat transfer performance. The gas-to-gas micro heat exchangers differ by partition wall material, partition wall thickness and flow arrangement. The pressure drop behavior has been analyzed due to the pressure losses in different sections of the gas-to-gas micro heat exchangers. Increased pressure losses in front of and behind the micro channels have been detected due to modified geometries in the inlet and outlet distribution chambers. The heat transfer performance has been determined in terms of thermal effectiveness. The comparison among different partition wall materials and partition wall thicknesses showed no significant criteria of the influence of thermal conductivity on the thermal effectiveness. An assessment due to an overall heat exchanger effectiveness has been performed to compare the gas-to-gas micro heat exchangers. For this purpose, the overall exergy loss has been calculated by combination of thermal effectiveness and pressure losses. A strong impact of the exergy loss due to pressure drop has been detected which influences the overall exergy loss of the gas-to-gas micro heat exchangers.

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Micro heat exchangers have been revealed to be efficient devices for improved heat transfer due to short heat transfer distances and increased surface-to-volume ratios. Further augmentation of the heat transfer behaviour within microstructured devices can be achieved with heat transfer enhancement techniques, and more precisely for this study, with passive enhancement techniques. Pin fin geometries influence the flow path and, therefore, were chosen as the option for further improvement of the heat transfer performance. The augmentation of heat transfer with micro heat exchangers was performed with the consideration of an improved heat transfer behaviour, and with additional pressure losses due to the change of flow path (pin fin geometries). To capture the impact of the heat transfer, as well as the impact of additional pressure losses, an assessment method should be considered. The overall exergy loss method can be applied to micro heat exchangers, and serves as a simple assessment for characterization. Experimental investigations with micro heat exchanger structures were performed to evaluate the assessment method and its importance. The heat transfer enhancement was experimentally investigated with microstructured pin fin geometries to understand the impact on pressure loss behaviour with air.

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