In this work the potential application of grey programming (GP) and grey system to process design is analyzed. GP is a simple technique to consider uncertainty. The design of flexible heat-exchange network is used as an example. Complete methodologies is developed, which include the grey composite curve, the determination of the grey minimum utility consumption, and the determination of grey number of interchangers units. The utilized techniques consider grey linear programming (GLP) and grey mixed-integer linear programming (GMILP).