Compact and efficient microchannel heat exchangers (MCHEs) are widely employed in aerospace, automotive, electronics cooling and renewable-energy systems. MCHEs always exhibit characteristics of low weight, reduced material usage, rapid response to load changes and compatibility with additive manufacturing. This study employs numerical method to investigate a tubular MCHE with one-layer, two-layer and three-layer configurations under high-temperature conditions. The heat transfer rate per unit pumping power is regarded as the comprehensive performance evaluation criterion. The compressed air is used as working medium while the effects of channel size, channel orientation, flowrate and temperatures on the comprehensive performance are investigated. Then, the spiral MCHE is proposed due to the positive effect of plug flow behavior on heat transfer. Result showed that raising the inlet temperature markedly increases the pressure drop across all configurations. For the circular-channel MCHEs, an inlet temperature of 300 °C produces a pressure drop 48.9–57.4 % higher than at 200 °C and 16.5-20.9 % higher than at 100 °C. On the other hand, spiral MCHEs exhibit a remarkably higher pressure drop along the flow direction than the straight circular-channel orientation. Nonetheless, the inherently larger heat-transfer surface area of the spiral geometry improves overall thermo-hydraulic performance by 12–50%. The merits and demits of plug flow characteristics and centrifugal force on the heat transfer enhancement and pressure loss contribution are both explained. As a result, the best orientation is proposed while the non-uniform spiral MCHE can achieve the best comprehensive performance.