Buoyancy-Driven Flow in Fluid-Saturated Porous Media near a Bounding Surface by Hitoshi Sakamoto & Francis A. Kulacki

Author:Hitoshi Sakamoto & Francis A. Kulacki
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Fig. 4.8Fluid side heat flux and error profile with alternating heat flux (brass plate with k = 111 W/mK)

Figure 4.8 shows that heat flux into the fluid is estimated to be less than 6000 W/m2, everywhere except the leading edge region. The error is due to the longitudinal conduction. It is always less because axial conduction is always toward the leading edge and the temperature gradient is always increasing toward it. There is an inflection point in the heat flux profile and the error profile, and this can be explained by the correspondence between decreasing heat transfer coefficient and increasing temperature difference as functions of distance from the leading edge. The maximum error occurs near the leading edge, implying that that the Nusselt correlation should not be applied in that region. The analysis must be refined to draw more accurate conclusions, or the actual heat flux into the fluid cannot be assumed to be known. In the vicinity of the leading edge, conduction dominates heat transfer from the wall to the fluid, and thus the heat flux should be less than what is estimated by the laminar boundary layer approximation. The heat flux goes to a minimum approximately at x = 0.04 m. The error is approximately 2.5%. This may be adversely affected by the leading edge region. The error remains less than 2.5% for 0.08 < x < 0.20 m. It then increases toward the trailing edge and is approximately 2% there. Based on this analysis here, we assume the corresponding uncertainty at 3%.

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