Shell and tube heat exchanger with helical baffles and graphene nanofluid: a CFD analysis of its performance and characteristics

Abstract

Heat exchangers are a heavily used equipment in both industry and daily lives. The most famous example of an industrial application for heat transfer is the shell and tube heat exchanger, being a classic model used even nowadays. This type of heat exchanger varies in size, in tubes profile, quantities, fluid direction and in its geometry, especially in the baffles and its varieties, which can help to increase thermal efficiency and to reduce pumping costs. The field of study of heat exchangers is not new to science, but when the baffle geometry is changed for a determined application, the performance can vary widely. On the other hand, nanofluids are still a new field of research. Nanofluids can be defined as a blend of a nanoparticles, fluid and other chemicals to stabilize the moisture. The literature has reviewed nanofluids as a promising way to improve heat transfer in the same heat exchanger. This present study has the aim to investigate and compare three different heat exchanger’s baffle geometry and three graphene based nanofluids for the optimal heat transfer performance and overall equipment performance. The study was conducted through Ansys CFX software with nine different inputs for each geometry. The geometries studied were continuous helical (CH) with the setups of 360o and 1080o; segmented helical (SH) baffles, both for the same sized heat exchanger with a counterflow configuration. The cold fluid inputs were (0.051 kg/s, 0.1kg/s and 0.2kg/s) at 25oC. The hot fluid inputs were (60oC, 50oC and 40oC) for 0.05kg/s. The nanofluid was made based in Graphene nanoparticle (GNP) and water, and were only allocated in the hot domain, with its total weight (wt.) concentrations as (0.0125%, 0.025% and 0.05%). The results have shown that for overall equipment performance, the SH configuration has shown the best results for any given hot inlet temperature, and the result is amplified when the hot inlet temperature is low. On the other hand, when the best thermal performance is to be achieved, the 1080CH baffle configuration has performed better than any other, showing a very relevant finding about continuous baffles for the inputs presented in this work. For all different inputs, the 360CH shown the worst overall equipment performance. The study also has shown that the best performance working fluid was the 0.025% wt. graphene, which has shown to be the tipping point for higher nanofluid concentration.