A gas turbine engine heat exchange system includes a first microchannel heat exchanger (MCHX) configured to transfer heat between a first air stream and a working fluid. The first MCHX includes a plurality of air-passage layers. Each of the air-passage layers includes a plurality of etched air-passage microchannels that are configured to allow passage of the first air stream therethrough. The first MCHX also includes a plurality of working fluid layers. Each working fluid layer includes a plurality of etched working fluid microchannels that are configured to allow passage of the working fluid therethrough.