Some modular heat-transfer systems can have an array of at least one heat-transfer element being configured to transfer heat to a working fluid from a heat dissipator. A manifolded heat exchanger can be configured to receive heated working fluid from a plurality of heat-transfer elements and to reject heat to a working fluid of a second fluid circuit. In some embodiments, the heat exchanging manifold can split an incoming flow of working fluid from the second fluid circuit into two or more streams having different bulk flow directions. In some instances, heat exchanger portions of the heat exchanging manifold are configured to provide counter flow heat exchange between the working fluid of the first fluid circuit and the working fluid of the second fluid circuit.