Heat Pipe Research Paper

2.5 Operating limits The most important heat pipe design consideration is the amount of power the heat pipe is capable of transferring. Heat pipes can be designed to carry a few watts or several kilowatts, depending on the application. Heat pipes can transfer much higher powers for a given temperature gradient than even the best metallic conductors. The maximum heat transport capability of the heat pipe is governed by several limiting factors which must be addressed when designing a heat pipe. There are five primary heat pipe heat transport limitations. These heat transport limits, which are a function of the heat pipe operating temperature, include: viscous, sonic, capillary pumping, entrainment, and boiling. There are various parameters

However, the maximum radius of curvature is limited to the capillary dimension of the wick structure such that the maximum transport occurs when ∆P_(c,max)= ∆P_total . It is important to note that the pressure drop associated with phase transition, ΔPph, is significant only under very high condensation or evaporation rates and represents the jump condition associated with the kinetic energy change in the liquid–vapor process. The phase transition pressure drop is typically negligible [1]. As the capillary pressure at the liquid–vapor interface is due to the curvature of the menisci and the surface tension of the working fluid and is given by the Young– Laplace equation ∆P_c= σ (1/R_1 +1/R_2 )

However, the maximum radius of curvature is limited to the capillary dimension of the wick structure such that the maximum transport occurs when ∆P_(c,max)= ∆P_total . It is important to note that the pressure drop associated with phase transition, ΔPph, is significant only under very high condensation or evaporation rates and represents the jump condition associated with the kinetic energy change in the liquid–vapor process. The phase transition pressure drop is typically negligible