Experimental Analysis of a Capillary Pumped Loop for Terrestrial Application

This paper reports on an experimental study of a capillary pumped loop for terrestrial application (CPLTA) that has been tested using ethanol, methanol, and N-pentane as working fluids. This CPLTA, designed for integrated power electronics cooling in railways, is capable of transferring total heat power of more than 5 kWwhen filled with methanol. First, experiments carried out under transient conditions show the high stability of this device for all the conditions tested, particularly with regard to a harsh rail cycle. Second, steady-state results convincingly show that conductance of the evaporator is independent of secondary fluid temperature, but strongly dependent on the nature of the fluid and the saturation temperature at the reservoir. A theoretical analysis has been undertaken in order to establish the thermodynamic operating curves of all tests carried out in steady-state condition by calculating the pressure difference between the reservoir and the evaporator; from these curves onemay determine the evaporation temperature, as well as the conductance restricted to the single evaporator, thereby underscoring the differences between the fluids. Finally, these results confirm that methanol is the maximally performing fluid for such devices, but also that N-pentane is useful with regard to the lowest heat powers applied, due to its lower density when compared with other fluids.