The two-stage increase in negative pressure with repeated cavitation for water in a metal Berthelot tube

Abstract

The authors made a stainless steel tube with a copper plug to study the effects of cavitation history on negative pressure for a system of water in a metal Berthelot tube. The water and the copper plug were pre-treated for air purging. The system was alternatively heated and cooled over appropriate temperature ranges many times. In the Berthelot method, the negative pressure generated with failing temperature becomes highest just before cavitation for a single heating and cooling procedure (one temperature cycle). Negative pressures for respective temperature cycles, though scattered, exhibited an increasing trend through two stages, a steep stage for earlier cycles and a gradual stage for later cycles. A similar effect of the cavitation history persisted even in a series of temperature cycles after exchanges of water, so long as the same plug was used for sealing. The negative pressure -76 atm (-7.7 MPa), which is higher than the values ever reported for water in a metal tube, developed at 46 degrees C through two water exchanges after a total of 850 temperature cycles. The two-stage increase was considered to be caused by the successive fading of the weaker cavitation nuclei in the system.

Thermodynamics of Negative Pressures in Liquids

“…Since then, several methods [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] have been developed to generate negative pressures in liquids. The attainable negative pressure can be even of a few hundreds of Mpa [4,23].…”

“…This is because a high pre-pressurization both promotes the disappearance of trapped gas bubbles in the crevices of the walls and helps to diffuse dissolved gas in the liquid. An even more efficient approach [21,22] uses many cycles of pressurizationdepressurization.…”

“…For instance, making the Berthelot tube in a spiral shape [18] enables us to measure the pressure via the deformation of the coil (like in the Bourdon-tube type pressure gauges) -no matter whether the pressure is positive or negative. Similarly, a strain gauge attached to the cell wall [21] can detect the wall deformation (this is the way in which the new electrical pressure gauges -for positive pressure measurements -work too) and thus permit the calculation of the negative pressure from its electrical signal.…”

Thermobarometry for 4′-n-Octylbiphenyl-4-carbonitrile in Metal Tube Berthelot Method and Polymorphism in Crystalline Phase of 4′-n-Octylbiphenyl-4-carbonitrile Found through Cooling Paths in Negative-Pressure Range

“…They were degassed and kept in a vacuum chamber at around 200 C under 10 À1 Pa. Before use, a pre-degassed plug was heated in boiling water for 30 min to exhaust most of the surfacing continuous boiling sites, since they would be the weakest cavitation nuclei after sealing. 3,5,9) 8CB was supplied by Fluoromaterial. Its gel permeation chromatography (GPC) purity is 99.6%, and no further purification was attempted.…”

“…Our experiments showed that (i) cavitation nuclei are gases (air) trapped within tiny ''crevices'' in the metal wall of the tube, (ii) they are exhausted by repeated cavitation events induced by temperature cycles, and (iii) they can be replenished by impurity gases in the bulk of the metal wall. 3,4) Degassing pretreatment for the metal parts yielded À150 bar for water only after ca. 2000 temperature cycles, 5) while their surface pretreatments improved the increasing trends in the negative pressure for earlier temperature cycles; however, the final values rarely exceeded À110 bar.…”