In recent years, the research in the field of thermal hydraulic at a microscale level has been constantly increasing due to the rapid growth of the technology applications that require the transfer of high heat rates in a relatively small space and volume. Such applications spread from compact heat exchangers to cooling systems for computer CPU to micro fluidic devices. Generally, the classical thermal and fluid dynamic theories developed for macro systems are not applicable to fluids in a microscale structure. Investigations on the heat transfer in a capillary are the basis for designing...