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Abstract
This work addresses the effect of temperature on the thermophysical properties (i.e., density, viscosity, thermal conductivity, and specific heat capacity) of alumina–water nanofluid over a wide temperature range (25°C–75°C). Low concentrations (0–0.5% v/v) of alumina nanoparticles (40 nm size) in distilled water were used in this study. The pressure drop and the effective heat transfer coefficient of nanofluids were also estimated for different power inputs and at different flow rates corresponding to Reynolds numbers in the range of 1500–6000. The trends in variation of thermophysical properties of nanofluids with temperature were similar to that of water, owing to their low concentrations. However, the density, viscosity, and thermal conductivity of nanofluids increased, while the specific heat capacity decreased with increasing the nanoparticle concentration. The convective heat transfer coefficient of the nanofluid and the pressure drop along the test section increased with increasing the particle concentration and flow rate of nanofluid. Results showed that the heat transfer coefficient increases, while the pressure drop decreases slightly with increasing the power input. This is because of the fact that increasing power input to heater increases the bulk mean temperature of nanofluids, resulting in a decreased viscosity. The prepared nanofluids were found to be more effective under turbulent flow than in transition flow.
NOMENCLATURE
| CP | = | specific heat capacity (J/kg-°C) |
| d | = | pipe diameter (m) |
| DSC | = | differential scanning calorimetry |
| f | = | friction factor |
| h | = | heat transfer coefficient (W/m2-°C) |
| k | = | thermal conductivity (W/m-°C) |
| L | = | length of test section (m) |
| = | mass flow rate (kg/s) | |
| Nu | = | Nusselt number |
| PID | = | proportional-integral-derivative |
| Q | = | heat transfer rate (J/s) |
| Re | = | Reynolds number |
| T | = | temperature (°C) |
| t | = | time (s) |
| u | = | fluid velocity (m/s) |
| W | = | power input to heater (W) |
Greek Symbols
| Δp | = | pressure drop (Pa) |
| ΔT | = | temperature difference (°C) |
| ϵ | = | pipe roughness (m) |
| μ | = | fluid dynamic viscosity (Pa-s) |
| ρ | = | density (kg/m3) |
| φ | = | particle volume fraction |
Subscripts
| b | = | bulk mean value |
| bf | = | base fluid (water) |
| cal | = | calculated |
| en | = | enhancement |
| exp | = | experimental |
| i | = | inside |
| in | = | input |
| nf | = | nanofluid |
| np | = | nanoparticles |
| o | = | outside |
| s | = | surface |
| w | = | water |
Additional information
Notes on contributors
Richa Saxena
Richa Saxena is an assistant professor in the Department of Petroleum Engineering, DIT University, Dehradun, Uttarakhand, India. She received her M.Tech. degree from Thapar University, Patiala, India, in 2013 and B.Tech. degree from Moradabad Institute of Technology, Moradabad, India, in 2010. She worked on heat transfer and pressure drop characteristics of nanofluids during her master's degree as her thesis work.
Dasaroju Gangacharyulu
Dasaroju Gangacharyulu is a professor in the Department of Chemical Engineering, Thapar University, Patiala, India. He is also the Controller of Examinations for the university. He has more than 20 years of experience in teaching, research and industry. He has specialized in heat transfer and fluid flow, nanofluids, heat pipes, hydrogen energy, energy management, energy storage, design of heat exchangers, thermal engineering, process design, process modeling, and simulation. His research interests include heat transfer enhancement using nanofluids and energy conservation and integration.
Vijaya Kumar Bulasara
Vijaya Kumar Bulasara is an assistant professor in the Department of Chemical Engineering, Thapar University, Patiala, India. He received his M.Tech. and Ph.D. degrees in chemical engineering from Indian Institute of Technology, Guwahati, India, in the years 2008 and 2011, respectively. He has specialized in heat transfer in nanofluids, design of heat exchanger networks, electroless plating, reaction engineering and catalysis, adsorption, and membrane separation. His research interests include heat transfer enhancement using nanofluids and wastewater treatment. He is an editorial board member for the International Journal of Chemical Research, Journal of Catalyst & Catalysis, and Trends in Chemical Engineering.