High pressure measurements of density, velocity of sound, and bulk moduli of pentane and 2-methylbutane and their mixtures

Abstract

Dil a torne tri c and ultrasonic meas urem e nt s we re mad e o n m ixtures of pe ntan e a nd 2-m eth ylbutane to give density, re la tive vo lum e , isoth e rm a l bu lk modu lu s, ve loc it y of sou nd , a nd ad iabati c b ulk modulu s to press ure of 24 kilobars (2.4 X l Q9N/m' ).K e y word s : Bulk mod ulu s; co mpre ss ibility; den s it y; dil ato me tri c me as uremen ts; hi gh pressure ; liquid s ; 2-me th ylbuta ne ; pentan e ; ultras oni cs _ . IntroductionThi s r e port s upple me nts a prev ious r eport [IP whi c h gave th e r es ults of measure me nts of mixtures of 2-methylbutane and aviatio n in strum e nt oil to 20 kilobars.2 Mixtures of pe ntan e and 2-methylbutane are used as hydrostati c pressure fluid s to 50 kilobars [2]. Th ese press ures are well above th e freezing pressures of th e individual fluid s. A s tud y was undertaken to de termin e th e properties of th e mixtures as a fun c ti on of pressure at room te mpe rature . Th e freezing press ure at room te mpe rature, give n b y R eeves e t al [4] , is 15 kbar for pe ntan e and is 21 kb ar for 2-methylbutan e . The freezin g press ure of pe ntane was meas ured to be 17.55 ± 0.67 kbar by Gelles [5]. Our ex perim e nts show the press ure r eq uire d at 22°C for initiation of freezing to be 25 kbar for pentane and 29 kbar for 2-m eth ylbutan e with equilibrium fr eezing I press ures of 18.2 ± 0.5 kbar and 22.5 ± 0.5 kbar res pectively.The equilibrium freezin g press ures were d ete rmined by over-pressurizin g th e fluid sufficiently to initiate freezing, then r educin g th e pressure to partially m elt th e solid, and then in creasing the press ure to partially refreeze the liquid in contact with th e solid. The ave rage of the meltin g press ure and thi s refreezing press ure is take n as e quilibrium freezin g press ure. Attempts to determin e freezin g press ures of various mixtures of th e pe ntan es we re un s uccessful. One 1 Fi gures in brac ket s indi cat e th e lit e rature refe re nces at th e e nd of thi s pape r. 2 I kilobar = 108 N/ m2, mixture of 90 per ce nt pentane-lO per ce nt 2-methylbutan e a ppeare d to freeze at 27 kba r but fiv e other attempts to freeze simila r mixtures were un s uccessful at press ures of 30 to 39 kbar. One mixture of 75 perce nt pe ntane-25 percent 2-meth ylbutane ap peared to freeze at 33 kbar but a seco nd mixture failed to freeze at 39 kbar. Oth er mixtures s howe d no freezin g at 39 to 44 kbar. While no sati sfac tory freezing determ in ation s were made for th e mixtures th e pro perti es de te rmin e d for th e mixtures as well as th e pure s ubs tan ces to 24 kbar are prese nted. Th e pure pe ntan es are in the s upe rcoole d (s uperpress urized) state above their equilibrium freezin g press ures. Low-Pressure Measurements (AtmosphericPressure)The densities of the mixtures were dete rmin ed by weighing known volumes of the fluid s . Th e same 10 MHz transducer and electroni c equipm e nt whi c h are used for the high press ure ultrasoni c meas ure me nts, described in refere nce [3], wer...

Short Fundamental Equations of State for 20 Industrial Fluids

“…The vapor-phase speeds of sound of Ewing and Goodwin (1991) and the equation agree within 0.03 %, and the liquid-phase speeds of sound of Walter et al (1992), Houck (1974), and Kling et al (1953) show general agreement to within 3 %, except for one isotherm at 290 K.…”

PρT and saturation properties of isopentane at T= (280–440) K and up to 200 MPa

“…Our results and those of the literature data sets of Bridgman [2], Mopsik [6], and Houck and Heydemann [7,8] We calculated numerically the isothermal compressibility ratios T α and volume expansion coefficients β based on the present PρT measurements given in table 3 by the following equations;…”

“…MPa from the Lemmon-Span model (REFPROP ver.9.1 [14] for isopentane). •, this work; □, Bridgman [2]; △, Mopsik [6]; ×, Houck and Heydemann [7,8]. …”

“…For ρ′, our results are also in good agreement with those of Gallagher et al [15] and Holcomb et al [16] [14] for isopentane). •, this work; ◇, Young and Thomas [1]; □, Bridgman [2]; ＊, Isaac et al [3]; +, Silberberg et al [4]; △, Mopsik [6]; ×, Houck and Heydemann [7,8]. MPa from the Lemmon-Span model (REFPROP ver.9.1 [14] for isopentane).…”

High-pressure viscoelastic properties and equation of state of liquids derived from Brillouin data

“…The zero-pressure value of K T is 0.489 GPa [25] and the only unknown parameter is Kj|p=o-Zero-pressure values of M r typically range from 0.2 to 0.4 GPa for simple organic liquids [26]. We model the pressure dependence of M r with a linear expansion in P: M r {P) s =M r o + M' r oP.…”