Present paper deals with numerical modeling of heat transfer in a tube with two types of twisted tape inserted in
a circular tube. Single twisted tape and double twisted (coaxial) tape as two enhancing elements are added to the
circular tube. A numerical investigation conducted to explore the effects of these elements on the pressure drop
(ΔP), convective heat transfer coefficient (h) and entropy generation (S). The results demonstrate that increasing
the Reynolds number has a positive effect on the convective heat transfer coefficient in all cases due to enhance
the flow swirling which improves the heat transfer on the tube wall. The results represent that the coaxial tape in
the lower twisted ratio (TR) has a better performance than single tape while the opposite is true for a high
twisted ratio. The results of pressure drop for two studied cases reveal that pressure drop in the coaxial tape is
higher than single tape in all TRs and with increasing TRs the pressure drop experience a decrement. It can be
concluded that the lower TR in two types of inserts leads to the lower total entropy generation. Also, the results
of exergy destruction rate and second law efficiency demonstrate coaxial tape exhibit better performance than
single tape.
A genetic algorithm based multi-objective optimization for coaxial tape implemented. The results of optimization
displays, the best performance can be achieved in the case TR, Reynolds number and heat flux are 3.46,
9008.93 and 97894.1 W/m2, respectively.