Heat Exchanger Network Area Targeting Considering Stream Passage through Shell or Tubes

An optimal heat recovery network requires optimum values of area and energy targets. Current heat exchanger network targeting methods do not consider the optimal passage of each stream through the shell or tubes side of the exchanger during the network cost estimation. They usually pre-set the passage of the streams through shell or tubes ahead of targeting [1]. However, considerations of appropriate passage of streams through the shell or tubes side can considerably affect the network costestimation. This paper introduces a new area targeting procedure which utilizes the optimal passage of each stream in all enthalpy intervals. The procedure evaluates two possible options for each stream split pass through each exchanger in the spaghetti network. One option is the hot stream passing through the shell while cold stream passes through tubes. The next option is that the hot strea m passes through tubes and cold stream passes through the shell side. Therefore, two different exchanger area requirements can be estimated. From these two configurations, the one with less area requirement leads to the lower network cost. During this optimization process, the optimal distribution of each stream pressure drop within enthalpy intervals is fully utilized. The proposed targeting procedure is applied for a case study and comparison of the results with previous methods [1] shows reduction of around 18% in the network area. In another case study, the area-energy trade off has been performed using the new procedure and a reduction of 12.4% and 14.5% in minimum network area requirement and total annual cost was observed respectively. It is concluded that the new procedure can considerably alter the area–energy trade off.

Keywords:

Heat Exchanger Network , Pinch Technology , Area Targeting , Shell & Tube Exchanger , Pressure Drop , Cost Optimization