System and method for measuring void fraction of inside of heat conduction member

A system for measuring a void fraction of an inside of a heat conduction member, the system comprising:

• a heating device configured as a heat source to heat an evaporation end of the heat conduction member;
• a cooling device configured for cooling a condensation end of the heat conduction member;
• at least one pair of electrode pads respectively attached to two opposite surfaces of the heat conduction member;
• and
• an LCR meter electrically connected to the at least one pair of the electrode pads for measuring impedances of the heat conduction member, wherein each of the impedances is converted into the void fraction that corresponds to a measured position of the heat conduction member;
• wherein a relation between the void fraction of the heat conduction member and capacitance values measured by the LCR meter is:
• α={[(Cw d(Cm−Cs)]/[ε0 A (2Cs+Cw−2Cm)]−εL}/(εv−εL);
• wherein α is the void fraction of the heat conduction member, Cm is the capacitance value measured by the LCR meter, Cw is the capacitance value between the electrode pads and the surfaces of the heat conduction member, Ce is the capacitance value of a working fluid inside the heat conduction member, Cs is a stray capacitance of a circuit, ε0 is a vacuum permittivity, εv is a relative permittivity of water vapor, εL is a relative permittivity of liquid water, εv and εL are functions of temperature and pressure, A is an electrode area, and d is a distance between one pair of the electrode pads;
• wherein, since the pressure has a negligible effect on εv and εL, εv and εL are taken as the functions of the temperature.