科研之友
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摘要
Indirect channels like the serpentine tubes are widely utilized in many engineering applications such as chemical and petrochemical industries, air conditioning and refrigeration systems, and modern energy conversion. Nanofluids are advanced and potential coolants, which can provide appropriate thermal performance in heat exchange devices. In this paper, fluid flow and heat transfer characteristics of Cu-water nanofluid inside five serpentine tubes with variable straight section lengths are experimentally investigated. The concentrations of 0%, 0.1%, and 0.4% wt. of stabilized Cu-water nanofluid are examined with variation of flow rates in the range of 1-5 l/min. The Cu-water nanofluids are produced by a one-step method, namely electro-exploded wire (EEW) technique, and the thermo-physical properties of the nanofluids required for the analysis are systematically measured. To obtain accurate results, a highly precise test loop with the ability to produce a constant wall temperature condition is designed and fabricated. It is found that creating short straight section lengths at the beginning of the serpentine tubes enhances both the heat transfer coefficient and pressure drop values. However, this technique improves the overall thermal-hydraulic performance of the serpentine tubes about 10%. Also, the results show that Cu-water nanofluids flow inside all the studied serpentine tubes increase the heat transfer rate. The maximum performance evaluation criterion (PEC) of 1.18 is obtained for the 0.4% wt. nanofluid inside the serpentine tube with Low to High straight section lengths.
- 出版日期2015-2
