Optimisation of waste heat recovery system in paper machine dryer section

In this paper the optimal surface area of an air-to-air plate heat exchanger is determined. The analysis is based on input data obtained by measurement in real operating conditions in board producing paper machine in Belgrade, Serbia. For that purpose effectiveness-NTU method together with previously defined cost functions was applied, taking into account seasonal variations in the parameters of exhaust and fresh atmospheric air. In addition, the total net savings in the consumption of primary energy sources in the factory that can be achieved by applying an optimised system for the use of waste heat were calculated and a simple payback period of the investment was determined.