Liquid can sustain mechanical tension as its pressure drops below the vapor-liquid coexistence line and becomes less than zero, until it reaches the stability limit-the pressure at which cavitation inevitably occurs. For liquid water, its stability limit is still a subject of debate: the results obtained by researchers using a variety of techniques show discrepancies between the values of the stability limit and its temperature dependence as temperature approaches 0 °C. In this work, we present a study of the stability limit of water by the metastable vapor-liquid equilibrium (MVLE) method with nanoporous silicon membranes. We also report on an experimental system which enables tests of the temperature dependence of the stability limit with MVLE. The stability limit we found increases monotonically (larger tension) as temperature approaches 0 °C; this trend contradicts the centrifugal result of Briggs but agrees with the experiments by acoustic cavitation. This result confirms that a quasi-static method can reach stability values similar to that from the dynamic stretching technique, even close to 0 °C. Nevertheless, our results fall in the range of ∼ -20 to -30 MPa, a range that is consistent with the majority of experiments but is far less negative than the limit obtained in experiments involving quartz inclusions and that predicted for homogeneous nucleation.

The design and analysis of plant-inspired loop heat pipes (LHPs) that would exploit nanoporous membranes to allow for operation with large capillary pressures and superheated liquid are presented. The operating concepts of this superheated loop heat pipe (SHLHP) resemble the transpiration process in vascular plants: reduction of pressure in leaves drives sap flow up from the roots and overcomes gravity, viscous drag, and reduced chemical potential of water in subsaturated soils. We present a model for steady-state operation and a linear response analysis of both the conventional and superheated designs. Our analysis shows that these SHLHPs could: (1) extend the limitations of conventional LHPs imposed by thermodynamic properties of the working fluid, (2) provide efficient heat transfer over long distances and against large accelerations, and (3) allow for operation in a subsaturated state that would eliminate the thermal resistance and entrainment effect of the liquid film of conventional designs. V C 2013 American Institute of Chemical Engineers AIChE J, 60: [762][763][764][765][766][767][768][769][770][771][772][773][774][775][776][777] 2014