Oscillating Flow and Heat Transfer of Single Phase in Capillary Tubes

Abstract

For an operating OHP, as shown in Fig. 3.1, when heat is added to the evaporator section, the heat is transferred from the wall to the working fluid inside by evaporation and forced convection. The thermally excited oscillating motion carries the heat to the condenser section where the heat is rejected by condensation and forced convection. During the heat transfer process from the evaporator to the condenser, while some of the heat is transferred through the phase changer heat transfer, i.e., the evaporation heat transfer in the evaporator and the condensation heat transfer in the condenser, most of the heat is transferred by thermally excited convection, i.e., the forced convection heat transfer from the wall to the working fluid in the evaporator and from the working fluid to the wall in the condenser. For an OHP, fluid inside should be formed as a train of liquid plugs and vapor bubbles. Liquid plugs and vapor bubbles are separated distinctly. The heat transfer process due to the thermally excited oscillating motion in an OHP is similar to the forced convection of a single phase oscillating flow either between the liquid phase and wall or between the vapor phase and wall. Therefore, in this chapter, single phase oscillating flow and its heat transfer process will be introduced. First, the concepts of reciprocating and pulsating flow are presented; fluid flow and heat transfer of fully developed and developing laminar oscillating flows in a pipe are then discussed; and finally, fluid flow and heat transfer of turbulent pulsating flow will be introduced.