Pavel A. Pavlov

Vapour-liquid critical temperatures and pressures of normal alkanes with from 19 to 36 carbon atoms, naphthalene and m-terphenyl determined by the pulse-heating technique

Abstract The paper presents the results of measuring the critical temperatures and the critical pressures of normal alkanes: nonadecane, eicosane, docosane, tetracosane, hexacosane, octacosane, triacontane, hexatriacontane, and also naphthalene and m-terphenyl. The pulse-heating method of a wire probe immersed in the liquid under investigation applicable to thermally unstable substances has been used. Equations of state of a polymeric fluid of the van der Waals and Redlich-Kwong type have been written in a ‘self-consistent-field’ approximation. Dependences of the critical constants of chain molecules on the number of links have been obtained. Equations for calculating the critical temperatures and pressures of normal alkanes have been derived. The results of calculations are compared with experimental data.

Critical temperatures and pressures of 1-alkanols with 13 to 22 carbon atoms

Abstract The paper gives the results of measuring the critical temperatures and pressures of thermally unstable 1-alkanols CnH2n+1OH with a number of carbon atoms n=13–18,20,22. The method of pulse heating of a wire probe located in the liquid under investigation has been used. Equations that correlate the critical temperatures and pressures of 1-alkanols with the number of carbon atoms in a molecule have been obtained. The results of measurements are compared with the values predicted by various methods. The acentric factors of 1-alkanols have been calculated.

Acoustic method of measuring critical properties of thermally unstable substances

Abstract An acoustic method of measuring critical temperatures and pressures of thermally unstable substances is described. In the cell with the liquid under investigation there is a wire probe, 0.02 mm in diameter, which is heated by electric-current pulses with a duration of 0.025 to 0.25 ms. At the moment of liquid boiling-up in the layer that surrounds the probe, one can observe an acoustic wave, which is registered by a ceramic piezoelectric element on a base (PbZrO 3 +PbTiO 3 ). The probe temperature at the moment of boiling-up is determined from its resistance. With an increase of the pressure in the cell with the substance under investigation the amplitude of an acoustic signal decreases. The cessation of boiling-up and disappearance of the acoustic signal show that the critical state is reached. A more precise critical pressure is found by linear extrapolation of the amplitude of the acoustic signal to zero in an amplitude–log (pressure) plot. The paper reports the experimental critical temperatures T c and the critical pressures p c of reference substances: n -hexane, n -heptane, n -decane, benzene, and of thermally unstable n -alkanes: docosane and tetracosane, and also the critical curve of the system n -hexadecane–benzene. The critical constants of reference substances were measured by this acoustic method with an error that does not exceed 0.015 T c and 0.015 p c .

Estimation of the critical constants of long-chain normal alkanes

Correlations between the critical constants of normal alkanes and the number of carbon atoms in a molecule have been considered. In an approximation of a self-consistent field for a polymeric fluid, an equation of state of the van der Waals type has been written, and the dependences of the critical constants of chain molecules on the number of mers have been obtained. It has been found that for an infinitely long alkyl chain, the limiting values of the critical temperature, the critical pressure, and the critical density are equal to, respectively, 1135 K, 0 M Pa, and 0 kg · m−3. A method of pulse heating of a wire probe immersed in the substance under investigation has been used to measure the dependence of the temperature of the attainable superheatT* of low-density polyethylene on the pressure p and the duration of heating pulset*. Extrapolation has been used to obtain an estimation of the attainable-superheat temperature of polyethyleneT*(p=0,t*=0)= 1175 K, which can be treated as the “critical” temperature of polyethylene.

Explosive cavitation in superheated liquid argon

The kinetics of explosive boiling-up of liquid argon has been investigated at negative pressures created by the reflection of a compression pulse 3-5 mus long from the free surface of a liquid by the method of liquid pulse heating on a thin platinum wire (with a rate of temperature increase of about 1 Kmus). The limiting superheats T(*) (stretches p(*)), the effective nucleation rate J(*), and the derivative G(T)=(d ln JdT)(T=T(*) ) have been determined by experimental data on the thermal perturbation of a wire probe and the results of solution of the problem on the initial stage of explosive boiling-up of a liquid. The experimental data are compared with homogeneous nucleation theory.

Bubble Nucleation in Polymeric Liquids Under Shock Processes

AbstractThis paper studies the phenomenon of spontaneous boiling-up of polymeric liquids on heating at rates

Dynamics of vapor film formation upon rapid superheating of liquid

(\dot T)

Homogeneous nucleation in liquid nitrogen at negative pressures

up to 107 K·s−1. A model of the thermal equation of state for (polymer + monomer) systems and a procedure for determination of the spontaneous boiling-up temperature T* for polymeric liquids, taking decomposition into account, are proposed. The experimental data on T*