Heat Transfer Handbook part 123. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | SPECIAL TYPES OF HEAT PIPES 1217 occur. Thus this stage is entirely conduction controlled and solution of the problem is found using any of various solution techniques . the integral method to transient heat conduction equation. Once the heat pipe condenser temperature and pressure decrease below the critical state and the working fluid corresponds to saturation conditions the heat pipe is modeled using a coupled hydrodynamic rewetting model for an advancing liquid in the wick structure along with the heat conductance equation for the remaining dry region. SPECIAL TYPES OF HEAT PIPES Variable Conductance Heat Pipes Heat pipes operate at the saturation temperature of flee working fluids given by the pressure inside the pipe. If the h t r p ut and or condenser coolant conditions change the operating conditions of the heat pipe also change along flie temperature-pressure saturation curve that is a new coupled set of temperature and pressure values are set by the new steady-state operating condition. This mode of heat pipe operation is referred to as a fixed-conductance mode. The interest of variable conductance h t pipes VCHPs is that a VCHP maintains the same operating temperature under varying heat input or condenser cooling conditions. For gas-loaded heat pipes the most common type of vtrrtabte conductance heat pipe this is achieved by connecting the heat pipe with a reservoir containing a noncondensable gas as shown in Fig. . The pressure is set by the reservoir pressure using either active control by pressure regulation or passive control where the volume of the reservoir is large compared with the volume of the haat pipe prcctiaally at teast four to five times larger . During operation the noncondensible gas is swept down the length of the hett pipe by the working fluid vapor to the condenser section. Because condensation of the working fluid does not take place where noncondensable gas is present a portion of the condenser is blocked from .
