Abstract
A combination of two passive heat transfer enhancement techniques using a microfin structure and nanofluids was investigated numerically. TiO2/water nanofluids flowing inside a square minichannel with a microfin structure (SMM) were observed as a practical application. Increased heat transfer performance was investigated by observing the Nusselt number, friction factor, and performance evaluation criterion (PEC). Velocity and temperature profiles were also demonstrated at a laminar developing flow regime. The SMM used in this work had six microfins (N = 6) and TiO2/water nanofluids with various nanoparticle concentrations of 0.005, 0.01, and 0.1 vol.%. By combining nanofluids as working fluids and SMM as a passive heat transfer enhancement, the maximum PEC value of 1.2 was achieved at Re = 380 with a volume fraction of 0.01 vol.%. It is obvious that compared to water flowing inside the square minichannel microfin, the heat transfer can be increased by using only a nanofluid with a volume fraction of 0.01%. The combination of a microfin and nanofluids as working fluids is strongly recommended due to its excellent performance in terms of heat transfer and economic considerations.
Highlights
Many efforts have been made to improve the heat transfer performance in heat exchangers, such as reducing the geometry of the hydraulic diameter, generating turbulence, and using nanofluids [1,2,3,4,5]
The technique of heat transfer enhancement by combining a microfin and nanofluids to improve the thermal performance of single phases on micro/minichannels has been investigated in previous studies [23,24,25]
The pressure interpolation scheme used in this work was the pressure staggering option (PRESTO) scheme
Summary
Many efforts have been made to improve the heat transfer performance in heat exchangers, such as reducing the geometry of the hydraulic diameter, generating turbulence (using insert devices, winglets, turbulators, etc.), and using nanofluids [1,2,3,4,5]. The technique of heat transfer enhancement by combining a microfin and nanofluids to improve the thermal performance of single phases on micro/minichannels has been investigated in previous studies [23,24,25]. Numerical convective heat transfer analysis of Cu/water nanofluids by comparing single-phase and two-phase models under conditions of constant surface temperature has been conducted [32]. The effect of adding nanofluids with different volume fractions and a microfin structure with a square minichannel on heat transfer enhancement was numerically investigated. A heat transfer dual (or hybrid) passive enhancement technique, that is, using nanofluids and a microfin structure inside a square minichannel, was for the first time investigated numerically, in order to measure effective performance increase
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