Kim Nanoscale Research Letters 2011, 6:415 http://www.nanoscalereslett.com/content/6/1/415 Table 2 Summary of studies on CHF of nanofluids in flow boiling Reference [38,77,78] [39] [40,41] [42] Nanofluids Al2O3 (40-50 nm) in water ZrO2 (50-90 nm) Diamond (4 nm) Al2O3 (50 nm) in water Concentration 10-3-10-1 vol.% 10-3-0.5 vo.l% Al2O3 (47 nm) in water 0.01 vol.% Al2O3 (25 nm) in water 10-3-10-1 vol.% Test conditions SS316 tube (5.45 and 8.7 mm I.D.) 1,000-2,500 kg/m2s Inlet subcooling: <20 K SS316 tube (11 mm I.D.) 100-300 kg/m2s Inlet subcooling: 25 and 50 K Rectangular channel (10 × 5 mm2) 1-4 m/s Inlet subcooling: 0 K (saturated) Single side heating: Cu disk (j = 10 mm) SS tube (j = 510 μm) 600-1,650 kg/m2s Inlet temperature: 30-404C Page 3 of 18 CHF enhancement 53% 53% 38% 70% 40% 50% parameters as follows: 1. nanoparticle concentration, 2. nanoparticle material and size, 3. heater size, 4. system pressure, 5. existence of additives, and 6. flow conditions. Influence of nanoparticle concentration CHF enhancement in nanofluids is strongly dependent on nanoparticle concentration. Figure 1 shows the experimental results of You et al. [5] and Kim et al. [18] for the CHF of nanofluids in pool boiling, which was investigated by varying the nanoparticle concentration over a wide range from 10-5 to 10-1 vol.%. Increasing the nanoparticle concentration increased the CHF con- tinuously up to a certain concentration, and thereafter, the CHF remained more or less constant at the maxi- mum enhancement value. This nanoparticle concentra- tion vs. enhancement trend was further confirmed by the experimental studies of Golubovic et al. [19] and Liu et al. [20,21], although their quantitative values differed because of discrepancies in experimental parameters, such as the shape of the heater and the nanoparticle material. Thus, it is reasonable to examine the effects of Figure 1 Effect of nanoparticle concentration on CHF enhancement in nanofluids. (a) Al2O3-water nanofluid on flat Cu plate with 10 × 10 mm2 area [5]; (b) various nanofluids on NiCr wire with 0.2-mm diameter [18].