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Spray cooling characteristics of nanofluids for electronic power devices.

Hsieh SS, Leu HY, Liu HH - Nanoscale Res Lett (2015)

Bottom Line: The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein.The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm.The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan.

ABSTRACT
The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein. The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm. The effects of nanoparticle volume fraction and mass flow rate of the liquid on the surface heat flux, including critical heat flux (CHF), are explored. Both steady state and transient data are collected for the two-phase heat transfer coefficient, boiling curve/ cooling history, and the corresponding CHF. The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

No MeSH data available.


Related in: MedlinePlus

DI water and nanofluids: (a)hvsq″, (b)hnano(nanofluid)/hDI(DI water) vsq″.
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Fig10: DI water and nanofluids: (a)hvsq″, (b)hnano(nanofluid)/hDI(DI water) vsq″.

Mentions: Figure 8 presents a comparison on heat transfer of the present nanofluids with that of DI water. Surprisingly, the heat transfer enhancement is not clearly noted at the same mass flux, which means that the nanofluids with different volume fraction under study is not superior to that of DI water. This result quite coincides with some of previous studies [12-14]. However, the trend seems opposite due to the following reasons: there are two possible major mechanisms to involve nanofluid heat transfer during spray cooling. (i) Fluid mechanics; high volume fraction nanofluid has a higher duration time when it impacts upon the heater surface which deteriorate the heat transfer; however, (ii) the thermal conductivity of the nanofluid, most likely, increases with the increased volume fraction of the nanofluid for this study. The net heat transfer effect is based on the counter balance of the above two factors. Due to the different nanofluids as well as different concentration and different operating conditions (e.g. temperature, etc.) from the previous published papers [12-14]), it seems that they may come out different conclusions. Figure 9 displays the h vs. q″ distribution for DI water with different Weber numbers and for nanofluids of Ag and MCNT with different volume fractions. Note that the h here indicates a local value (function of heat flux). This h increases as the heat flux increases in the power (exponent) of nearly 0.59 ± 0.04 for DI water, as shown in Figure 9a. This value is quite similar to that in Hsieh et al. [3] also included in Figure 9a. Similarly, the same h vs q″ trend is obtained as illustrated in Figure 9b with a slightly smaller exponent (0.55) found for Ag and MCNT nanofluids. However, the heat transfer coefficient value h is generally much higher than that of DI water and is about 4.3 W/cm2K for Ag nanofluids at q″ = 100 W/cm2 and G = 11.9 × 10−4 kg/cm2s, for example. On the other hand, h (at the same q and G) is about 3.8 W/cm2K for DI water. A more detailed h and comparison of (hnano/hDI) as a function of heat flux was plotted and shown in Figure 10a,b, respectively. It was found that there seems to be no significant difference in the heat transfer coefficient between DI water and MCNT nanofluid. In fact, in Figure 10b, for a given heat flux, hnano is lower than hDI in most cases. But, nevertheless, it can also be seen that two different trends (one is a positive and one is a negative slope) are found for the dependence of h on q″. From Figure 10a,b, one may conclude that the application of nanofluids’ cooling is very suitable for high power devices because h increases as q increases when the cooling demand of the power devices exceeds about 80 W/cm2. Furthermore, the effect of nanofluids with different volume fractions can be seen, although some fluctuations with an average value of 1.1 to 1.2 for MCNT and Ag nanofluids, respectively, were also observed, as illustrated in Figure 10b.Figure 8


Spray cooling characteristics of nanofluids for electronic power devices.

Hsieh SS, Leu HY, Liu HH - Nanoscale Res Lett (2015)

DI water and nanofluids: (a)hvsq″, (b)hnano(nanofluid)/hDI(DI water) vsq″.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385298&req=5

Fig10: DI water and nanofluids: (a)hvsq″, (b)hnano(nanofluid)/hDI(DI water) vsq″.
Mentions: Figure 8 presents a comparison on heat transfer of the present nanofluids with that of DI water. Surprisingly, the heat transfer enhancement is not clearly noted at the same mass flux, which means that the nanofluids with different volume fraction under study is not superior to that of DI water. This result quite coincides with some of previous studies [12-14]. However, the trend seems opposite due to the following reasons: there are two possible major mechanisms to involve nanofluid heat transfer during spray cooling. (i) Fluid mechanics; high volume fraction nanofluid has a higher duration time when it impacts upon the heater surface which deteriorate the heat transfer; however, (ii) the thermal conductivity of the nanofluid, most likely, increases with the increased volume fraction of the nanofluid for this study. The net heat transfer effect is based on the counter balance of the above two factors. Due to the different nanofluids as well as different concentration and different operating conditions (e.g. temperature, etc.) from the previous published papers [12-14]), it seems that they may come out different conclusions. Figure 9 displays the h vs. q″ distribution for DI water with different Weber numbers and for nanofluids of Ag and MCNT with different volume fractions. Note that the h here indicates a local value (function of heat flux). This h increases as the heat flux increases in the power (exponent) of nearly 0.59 ± 0.04 for DI water, as shown in Figure 9a. This value is quite similar to that in Hsieh et al. [3] also included in Figure 9a. Similarly, the same h vs q″ trend is obtained as illustrated in Figure 9b with a slightly smaller exponent (0.55) found for Ag and MCNT nanofluids. However, the heat transfer coefficient value h is generally much higher than that of DI water and is about 4.3 W/cm2K for Ag nanofluids at q″ = 100 W/cm2 and G = 11.9 × 10−4 kg/cm2s, for example. On the other hand, h (at the same q and G) is about 3.8 W/cm2K for DI water. A more detailed h and comparison of (hnano/hDI) as a function of heat flux was plotted and shown in Figure 10a,b, respectively. It was found that there seems to be no significant difference in the heat transfer coefficient between DI water and MCNT nanofluid. In fact, in Figure 10b, for a given heat flux, hnano is lower than hDI in most cases. But, nevertheless, it can also be seen that two different trends (one is a positive and one is a negative slope) are found for the dependence of h on q″. From Figure 10a,b, one may conclude that the application of nanofluids’ cooling is very suitable for high power devices because h increases as q increases when the cooling demand of the power devices exceeds about 80 W/cm2. Furthermore, the effect of nanofluids with different volume fractions can be seen, although some fluctuations with an average value of 1.1 to 1.2 for MCNT and Ag nanofluids, respectively, were also observed, as illustrated in Figure 10b.Figure 8

Bottom Line: The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein.The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm.The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan.

ABSTRACT
The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein. The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm. The effects of nanoparticle volume fraction and mass flow rate of the liquid on the surface heat flux, including critical heat flux (CHF), are explored. Both steady state and transient data are collected for the two-phase heat transfer coefficient, boiling curve/ cooling history, and the corresponding CHF. The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

No MeSH data available.


Related in: MedlinePlus