A new approach in pinch technology considering piping costs in total cost targeting for heat exchanger network

The current targeting method for a heat exchanger network identifies an optimum point from material and energy balance prior to design. This optimum point is obtained by tradeoff between energy costs and heat exchangers capital cost. The current method does not consider piping costs associated to heat exchangers. In the targeting method as energy increases, heat exchanger area decreases, but piping size increases as the mass flow rate of utility streams increases. It means by increasing energy costs, heat exchanger cost decreases, however piping costs will increase. So piping costs can affect the total capital cost (heat exchanger costs plus piping costs). As a result considering piping costs in the targeting method may change the global optimality. It is obvious that without the correct initialization of design, the global optimum cost for heat exchanger network cannot be achieved. This paper presents a correlation for estimating piping costs for each stream as their piping size, material of construction and pressure rating. It also develops a method which the allows consideration of piping costs in the current targeting method.