Process effluents recovery can be a tremendous source of revenue as well as a smart way to reduce their environmental footprint for industrial processes. Reusing effluents for heating purposes or reducing resource consumption can lead to substantial operating costs savings if the capital investments required to implement recovery networks are depreciated over an adequate period of time. This paper presents a mixed-integer linear programming model to design mass allocation and heat exchanger networks simultaneously. Mass streams are characterized by their composition and properties. A superstructure is presented to define the interactions between mass allocation and heat exchanger networks. Non-isothermal mixing can occur before and after the heat exchanger network. The objective function is the total annualized costs of both networks. It takes into account the annual operating costs for energy and mass requirements and the capital costs of the heat exchanger network. Two literature case studies are presented to demonstrate the model performances.