A flow reactor or flow reactor component includes a base plate, a first fluid module having first and second major surfaces, an internal process fluid passage, and a heat exchange channel in the first major surface, the first major surface stacked on the base plate; a second fluid module having first and second major surfaces, an internal process fluid passage and a heat exchange channel in the first major surface, the first major surface stacked on the second major surface of the first fluid module, optional additional fluid modules of the same configuration as the first and second fluid modules stacked successively on the second fluid module, and a top plate having a heat exchange channel in a bottom major surface thereof with the bottom major surface stacked on an uppermost fluid module of (1) the second fluid module and (2) the optional additional fluid modules.