Impact of Non-Condensable Gases on Two-Phase Heat Transfer in Aero Engine Heat Exchangers

Several of the revolutionary flight propulsion concepts studied today comprise heat exchangers as essential components. This could be either as part of unconventional gas turbine cycles as the Water-Enhanced Turbofan concept (WET) or as part of the thermal management system of electrified propulsion systems. Two-phase heat exchangers as condensers can contribute to significant improvements. Often the condensing medium is mixed with components that cannot condense in the present temperature range. A common case is the condensation of steam in the presence of air. This presence of non-condensable gases can lead to a significant reduction in the condenser’s heat transfer performance. Therefore it is crucial to assess its effect in conceptual design. Two well-established literature methods for modeling the non-condensable-gas-effect are compared with a far simpler alternative approach. The observed deviations in overall heat transfer rate using this latter approach do not exceed 6.6%, whereas modeling complexity and computation time are reduced. This observation enables an efficient assessment of condensation in the early phase of flight propulsion concept evaluation.