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Research Papers: Heat Exchangers

# Thermal and Hydraulic Performance of Counterflow Microchannel Heat Exchangers With and Without Nanofluids

[+] Author and Article Information
Hamid Reza Seyf

Islamic Azad University, Karaj Branch, P.O. Box 31375-1746, Karaj, Tehran 3158777878, Iranhamid_seyf2001@yahoo.com

Islamic Azad University, Takestan Branch, Takestan, Qazvin 3158777878, Iran

J. Heat Transfer 133(8), 081801 (May 02, 2011) (9 pages) doi:10.1115/1.4003553 History: Received July 25, 2010; Revised December 14, 2010; Published May 02, 2011; Online May 02, 2011

## Abstract

This paper analyzes the thermal and hydraulic performance of a counterflow microchannel heat exchanger (CFMCHE) with and without nanofluid as working fluid. A 3D conjugate heat transfer simulation is carried out using a finite volume approach to evaluate the effects of inlet Reynolds number, Brownian motion, and volume fraction of nanoparticles on the pumping power, effectiveness, and performance index of CFMCHE. The accuracy of the code has been verified by comparing the results with those available in the literature. A single phase approach is used for the nanofluid modeling. The base fluid used in the analyses as a basis for comparison was pure water. Two types of nanofluids, namely, water-$Al2O3$ with a mean diameter of 47 nm and water-CuO with a mean diameter of 29 nm, each one with three different volume fractions, are utilized. In addition, two temperature dependent models for the thermal conductivity and viscosity of nanofluids that account for the fundamental role of Brownian motion are used. Calculated results demonstrate that the effectiveness and performance index of CFMCHE decrease with increasing Reynolds number. Moreover, it is observed that the relative enhancements in the pumping power become more prominent for higher values of Reynolds numbers. It was also found that the performance index and pumping power are not sensitive to volume fraction at higher and lower Reynolds numbers, respectively.

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## Figures

Figure 1

Schematic of the CFMCHE, computational domain, and coordinate system

Figure 2

Computational grid in CFMCHE

Figure 3

Comparison of variation in wall temperature distribution along a counterflow heat sink with different total flow rates

Figure 4

The temperature in CFMCHE at three different Reynolds numbers with water as working fluid

Figure 5

Effect of volume fraction on the effectiveness of the CFMCHE

Figure 6

Effect of volume fraction on the pumping power of the CFMCHE

Figure 7

Effect of volume fraction on the performance index of the CFMCHE

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