Provided is a process and device for exchanging heat energy between three or more streams in a microchannel heat exchanger which can be integrated with a microchannel reactor to form an integrated microchannel processing unit. The combining of a plurality of integrated microchannel devices to provide the benefits of large-scale operation is enabled. In particular, the microchannel heat exchanger enables flexible heat transfer between multiple streams and total heat transfer rates of about 1 Watt or more per core unit volume expressed as W/cc.