Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Cooling water systems are generally designed with a set of
heat exchangers arranged in parallel. This arrangement results
in higher cooling water flowrate and low cooling water return
temperature thus reducing cooling tower efficiency. Previous
research on cooling water systems has focused mainly on heat
exchanger network thus excluding the interaction between heat
exchanger network and the cooling towers. This paper presents
a technique for synthesis and optimization of cooling water
systems which incorporates the performances of the cooling
towers involved. The study focuses mainly on cooling systems
consisting of multiple cooling towers that supply a common set
of heat exchangers. The heat exchanger network is synthesized
using the mathematical optimization technique. This technique
is based on superstructure in which all opportunities for cooling
water reuse are explored. The cooling tower model is used to
predict the thermal performance of the cooling towers. Two
case studies are presented to illustrate the performance of the
proposed technique. The first case results in nonlinear
programming (NLP) formulation and the second case yields
mixed integer nonlinear programming (MINLP) problem. In
both cases the cooling towers operating capacity is
debottlenecked without compromising the heat duties of the
associated heat exchangers [1].
