Frictional Flow Characteristics of Water Flowing Through Rectangular Microchannels

Transition from laminar to turbulent flow in liquid filled microtubes

“…It is concluded that the magnitude of spatial variations due to roughness are within the noise level, if they exist at all. This implies that although microscale effects are plausible, the differences in microscale and macroscale transition to turbulence in a circular tube are not nearly as large as originally thought by Mala and Li 11 and Peng et al 10 It is concluded that the effects of surface roughness are negligible in the current study.…”

“…Peng et al 10 based on measured friction factor versus Reynolds number data, report that transition to turbulence occurs as low as Reynolds numbers of 200-700 in rectangular channels with hydraulic diameter 133 to 367 µm, and Mala and Li, 11 again based on measured friction factor versus Reynolds number data, report a departure from expected linear behavior in tubes that may indicate anomalous transition at Reynolds number of 300-900. Other researchers attribute a reduction in expected flowrate to the polar nature of certain liquid molecules for Re∼1-20, D h ∼ 57 µm; 12 or they attribute nonlinear pressure drop to surface roughness.…”

Toward a Better Understanding of Friction and Heat/Mass Transfer in Microchannels-- A Literature Review

“…Although these results give a value of ReC (= 2,770) that is close to the estimated values from published results ( The two studies by Peng et af. [ 10,11] complement one tnother in thm the geometric details of the chwrnek and the Re range (SO to 3,000) were the same. The documented tcmsition Reynolds numbers in these studies are significantly lower~hun those for smooth channels of large D~, even lower (hm (he VOIUCS in the Ii(eraturc for very rough channels.…”

“…Peng et al [10,11] indicated that the Re = 200-700 range represented the upper bound for Iaminar flow transition to turbulence, and that fulIy turbulent ,flow occurred in the 400 to 1500 Re range. Based on their heat transfer results, Peng and Peterson [22] gave Re c 400 for laminar flow, 400< Re < 1,000 for the transition region, and Re > 1,000 for fully turbulent flow.…”

Investigation of heat transfer in rectangular microchannels

“…Heat fluxes as high as 790 W/cm 2 were achieved with the chip temperature maintained below 110C. Peng et al [2,8] experimentally investigated the flow and heat transfer characteristics of water flowing through rectangular stainless steel microchannels with hydraulic diameters of 133 to 367 m at channel aspect ratios of 0.33 to 1. Their fluid flow results were found to deviate from the values predicted by classical correlations and the onset of transition was observed to occur at Reynolds numbers from 200 to 700.…”