Microheat Pipe

Khmstalev D, Faghri A (1994) Thermal analysis of microheat pipe. J Heat Transfer ASME... 

Lee M, Wong M, Zohar Y (2003) Integrated microheat-pipe fabrication technology. J Microelectromech Syst 12(2) 138-146... 

As a fundamental investigation on heat pipes, Tchikanda et al. [54] derived analytical expressions for the mean velocity of a liquid flowing in an open rectangular microchannel. The flow is driven by pressure gradients and shear stress on the liq-uid/vapor interface. Koizumi et al. [55] developed a microheat pipe with asymmetric cross-section and observed boiling two-phase flow. 

Figure 13.6 Schematic of the microheat pipe showing its operational principle...

Figure 13.7 Various microheat pipe profiles (square, rectangular, modified rectangular, circular outer and triangular inner, circular outer and square inner, tapered)...

Microheat pipes are subjected to the same operating limits as the conventional heat pipe. The capillary limitation is the most important operating limit of the microheat pipe. 

Figure 13.7 shows various shapes of microheat pipe profiles used in literature. The hydraulic radius/diameter is used to describe the size of an internal duct. Hydraulic radius is defined as / , = —, where A is the cross-sectional area and P is the perimeter. Similarly, the capillary radius is used to describe the liquid-vapor interface as = capillary radius = reciprocal of the mean curvature of the liquid-vapor interface. For microheat pipe, > 1. 

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