Heat transfer enhancement for heat exchanger network retrofit

Heat exchanger networks (HEN) play important roles in a chemical plant. In a plant lifetime, it may be required to retrofit a HEN several times in ord er to improve the energy efficiency or to accommodate the increase in throu ghput. The network pinch method developed by Asante and Zhu [1] can identif y bottlenecks, which limit the increase in heat recovery for an existing HE N and also indicate promising structure changes to overcome the bottlenecks . As a result of HEN retrofit, additional surface area is required for some h eat exchangers. There are a number of options to provide additional area, s uch as installing new shells or new units, adding new tubes to an existing bundle, etc. if heat transfer enhancement (HTE) is applied, additional area can be reduced significantly This can result in a great reduction in capit al cost and implementation time for modifications. However in practice, hea t transfer enhancement techniques have not been applied extensively, partic ularly in the petroleum refining industry. Several main aspects need to be addressed when HTE is taken into considerat ion for HEN retrofit. The first is how to determine which heat exchangers a re suitable to apply HTE in the network and the second issue is to determin e what level of augmentation of heat transfer performances is required. The last is about how to select a particular enhancement technique that can fu lfil the enhancement requirement. A new strategy for applying HTE in HEN retrofit at the conceptual design st age has been developed. The above issues can be addressed properly by this new method. The new procedure is demonstrated using a case study.