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Enhancements of thermal conductivities with Cu, CuO, and carbon nanotube nanofluids and application of MWNT/water nanofluid on a water chiller system.

Liu M, Lin MC, Wang C - Nanoscale Res Lett (2011)

Bottom Line: Dynamic effect, such as nanoparticle dispersion may effectively augment the system performance.It is also found that the dynamic dispersion is comparatively effective at lower flow rate regime, e.g., transition or laminar flow and becomes less effective at higher flow rate regime.Test results show that the coefficient of performance of the water chiller is increased by 5.15% relative to that without nanofluid.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, National Chiao Tung University, Hsinchu, Taiwan. ccwang@mail.nctu.edu.tw.

ABSTRACT
In this study, enhancements of thermal conductivities of ethylene glycol, water, and synthetic engine oil in the presence of copper (Cu), copper oxide (CuO), and multi-walled carbon nanotube (MWNT) are investigated using both physical mixing method (two-step method) and chemical reduction method (one-step method). The chemical reduction method is, however, used only for nanofluid containing Cu nanoparticle in water. The thermal conductivities of the nanofluids are measured by a modified transient hot wire method. Experimental results show that nanofluids with low concentration of Cu, CuO, or carbon nanotube (CNT) have considerably higher thermal conductivity than identical base liquids. For CuO-ethylene glycol suspensions at 5 vol.%, MWNT-ethylene glycol at 1 vol.%, MWNT-water at 1.5 vol.%, and MWNT-synthetic engine oil at 2 vol.%, thermal conductivity is enhanced by 22.4, 12.4, 17, and 30%, respectively. For Cu-water at 0.1 vol.%, thermal conductivity is increased by 23.8%. The thermal conductivity improvement for CuO and CNT nanofluids is approximately linear with the volume fraction. On the other hand, a strong dependence of thermal conductivity on the measured time is observed for Cu-water nanofluid. The system performance of a 10-RT water chiller (air conditioner) subject to MWNT/water nanofluid is experimentally investigated. The system is tested at the standard water chiller rating condition in the range of the flow rate from 60 to 140 L/min. In spite of the static measurement of thermal conductivity of nanofluid shows only 1.3% increase at room temperature relative to the base fluid at volume fraction of 0.001 (0.1 vol.%), it is observed that a 4.2% increase of cooling capacity and a small decrease of power consumption about 0.8% occur for the nanofluid system at a flow rate of 100 L/min. This result clearly indicates that the enhancement of cooling capacity is not just related to thermal conductivity alone. Dynamic effect, such as nanoparticle dispersion may effectively augment the system performance. It is also found that the dynamic dispersion is comparatively effective at lower flow rate regime, e.g., transition or laminar flow and becomes less effective at higher flow rate regime. Test results show that the coefficient of performance of the water chiller is increased by 5.15% relative to that without nanofluid.

No MeSH data available.


Related in: MedlinePlus

Pressure drop vs. flow rate subject to the influence of MWNT/water nanofluid at 0.1 vol.%.
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Figure 8: Pressure drop vs. flow rate subject to the influence of MWNT/water nanofluid at 0.1 vol.%.

Mentions: The associated pressure drop vs. flow rate for the nanofluid and base fluid is shown in Figure 8. For both the water base fluid and the MWNT/water nanofluid, the pressure drop increases with the increase of flow rate from 60 to 150 L/min. However, negligible difference in pressure drop amid the MWNT/water nanofluid and the base fluid water is seen. The results are in line with the calculation made by Behzadmehr et al. [26]. Their two-phase modeling shows that adding 1% nanopowder results in an increase of the Nusselt number by more than 15% without appreciable increase of pressure drop. It is attributed to the absorption of turbulence caused by the nanopowders. Furthermore, Lu et al. [28] also reported that a novel and stable CNT/polystyrene hybrid miniemulsion is used as a water-based lubricant additive. The anti-wear performance and load-carrying capacity of the base stock are significantly raised and the friction factor is decreased. As a consequence, the present nanofluid with MWNT reveals negligible pressure drop penalty pertaining to the system performance of the water chiller.


Enhancements of thermal conductivities with Cu, CuO, and carbon nanotube nanofluids and application of MWNT/water nanofluid on a water chiller system.

Liu M, Lin MC, Wang C - Nanoscale Res Lett (2011)

Pressure drop vs. flow rate subject to the influence of MWNT/water nanofluid at 0.1 vol.%.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211363&req=5

Figure 8: Pressure drop vs. flow rate subject to the influence of MWNT/water nanofluid at 0.1 vol.%.
Mentions: The associated pressure drop vs. flow rate for the nanofluid and base fluid is shown in Figure 8. For both the water base fluid and the MWNT/water nanofluid, the pressure drop increases with the increase of flow rate from 60 to 150 L/min. However, negligible difference in pressure drop amid the MWNT/water nanofluid and the base fluid water is seen. The results are in line with the calculation made by Behzadmehr et al. [26]. Their two-phase modeling shows that adding 1% nanopowder results in an increase of the Nusselt number by more than 15% without appreciable increase of pressure drop. It is attributed to the absorption of turbulence caused by the nanopowders. Furthermore, Lu et al. [28] also reported that a novel and stable CNT/polystyrene hybrid miniemulsion is used as a water-based lubricant additive. The anti-wear performance and load-carrying capacity of the base stock are significantly raised and the friction factor is decreased. As a consequence, the present nanofluid with MWNT reveals negligible pressure drop penalty pertaining to the system performance of the water chiller.

Bottom Line: Dynamic effect, such as nanoparticle dispersion may effectively augment the system performance.It is also found that the dynamic dispersion is comparatively effective at lower flow rate regime, e.g., transition or laminar flow and becomes less effective at higher flow rate regime.Test results show that the coefficient of performance of the water chiller is increased by 5.15% relative to that without nanofluid.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, National Chiao Tung University, Hsinchu, Taiwan. ccwang@mail.nctu.edu.tw.

ABSTRACT
In this study, enhancements of thermal conductivities of ethylene glycol, water, and synthetic engine oil in the presence of copper (Cu), copper oxide (CuO), and multi-walled carbon nanotube (MWNT) are investigated using both physical mixing method (two-step method) and chemical reduction method (one-step method). The chemical reduction method is, however, used only for nanofluid containing Cu nanoparticle in water. The thermal conductivities of the nanofluids are measured by a modified transient hot wire method. Experimental results show that nanofluids with low concentration of Cu, CuO, or carbon nanotube (CNT) have considerably higher thermal conductivity than identical base liquids. For CuO-ethylene glycol suspensions at 5 vol.%, MWNT-ethylene glycol at 1 vol.%, MWNT-water at 1.5 vol.%, and MWNT-synthetic engine oil at 2 vol.%, thermal conductivity is enhanced by 22.4, 12.4, 17, and 30%, respectively. For Cu-water at 0.1 vol.%, thermal conductivity is increased by 23.8%. The thermal conductivity improvement for CuO and CNT nanofluids is approximately linear with the volume fraction. On the other hand, a strong dependence of thermal conductivity on the measured time is observed for Cu-water nanofluid. The system performance of a 10-RT water chiller (air conditioner) subject to MWNT/water nanofluid is experimentally investigated. The system is tested at the standard water chiller rating condition in the range of the flow rate from 60 to 140 L/min. In spite of the static measurement of thermal conductivity of nanofluid shows only 1.3% increase at room temperature relative to the base fluid at volume fraction of 0.001 (0.1 vol.%), it is observed that a 4.2% increase of cooling capacity and a small decrease of power consumption about 0.8% occur for the nanofluid system at a flow rate of 100 L/min. This result clearly indicates that the enhancement of cooling capacity is not just related to thermal conductivity alone. Dynamic effect, such as nanoparticle dispersion may effectively augment the system performance. It is also found that the dynamic dispersion is comparatively effective at lower flow rate regime, e.g., transition or laminar flow and becomes less effective at higher flow rate regime. Test results show that the coefficient of performance of the water chiller is increased by 5.15% relative to that without nanofluid.

No MeSH data available.


Related in: MedlinePlus