Heat integration (HI) is an important aspect of chemical process design owing to significant energy saving. This strategy can be applied to complex of closely located plants, referred as Inter-Plant Heat Integration, to further reduce energy consumption. It is known that heat exchanger network (HEN) synthesis is regarded as a NP-hard problem. The non-linearity of models generally makes it difficult to obtain global optimal solutions, even local solutions without initial points. It is significant to develop a model which is easy to solve. In this paper, a new transshipment type model for IPHI directly using process streams is developed, while simultaneously optimizing the total annual cost of intra-plant and interplant HEN, including the piping and pumping cost. Thus, the interconnection between intra-plant and inter-plant HENs can be considered during optimization. New formulations are developed to keep track of the transportation of process streams across plants, so as to calculate the piping and pumping cost and compare different inter-plant heat integration opportunities. Case studies show that better results with lower TAC can be obtained, compared to literature. Besides, owing to the characteristic of more structures embedded in the model, results with unique structures can be obtained by the proposed model.