Experimental study on a closed-loop pulsating heat pipe (CLPHP) charged with water-based binary zeotropes and the corresponding pure fluids

Pulsating heat pipe (PHP) is a relatively new and promising addition to the family of passive two-phase energy transport devices. By charging with water-methanol, water-ethanol and water-acetone zeotropic mixtures at various volume mixing ratios, a vertical closed-loop PHP has been experimentally investigated with heat input ranged from 10 W to 100 W. It was found that because of the zeotropic properties in phase transition and the complex molecular interactions between the components, the PHPs charged with the mixtures were quite more complex than those with pure fluids. At small or medium filling ratios, most of the binary mixtures had better anti-dry-out performance than at least one of the pure fluids (even both) due to the phase-change-inhibition effect (PCIE) of zeotropic mixtures where the vaporization of the high boiling point component (water) will be suppressed by the higher pressure of its counterpart abundant in the vapor slugs. At large filling ratios and high heat input, the thermal performances of the PHP charged with mixtures were generally not as good as that with the pure water possibly due to the PCIE, the flow retardance caused by the resistance to additional mass transfer and the possible increase in dynamic viscosity of the mixtures.