A new microchannel heat exchanger configuration using CNT-nanofluid and allowing uniform temperature on the active wall

Abstract

The present study presents a three-dimensional numerical analysis using the finite element method of nanofluid enhanced heat transfer in micro heat exchanger equipped with triangular fins. The new configuration based on an existent system where a jet impingement supplies a microchannel structure. A modification of the heat exchanger geometry in the z-direction is added allowing a uniform wall temperature profile. The micro heat exchanger is assumed to be well insulated. The hot fluid (water) flows in the lower channel with a fixed velocity (uw_in = 20 mm/s) and cold fluid (CNT-water nanofluid) flows in the upper channel which is equipped with triangular fins with a velocity (unf_in) ranged from 5 to 45 mm/s. The nanofluid is considered homogeneous with temperature-dependent thermophysical properties and the CNT nanoparticles volume fraction is varied from 0 to 5%. The results are presented in term of thermal and flow fields, heatlines, overall heat transfer coefficient, thermal effectiveness, and thermal performance factor (TPF). It was found that the performances of the heat exchanger are significatively improved using the CNT nanofluid and the triangular fins. But the TPF increase with the CNT volume fractions and decreases with the fin’s height.

Keywords

• Heat transfer
• Flow structure
• Micro heat exchanger
• Triangular fins
• Nanofluid