SU813223A1 - Method of measuring heat capacity per unit volume of liquid substances - Google Patents

Description

one

The invention relates to the measurement of the thermophysical properties of liquid substances, in particular to the determination of the volumetric heat capacity ;; thermolabile, chemically aggressive and time-unstable compounds.

The known method for determining the volumetric heat 1 / liquid of liquids, the essence of which is to measure the amount of heat introduced into a kg meter vessel, changes in temperature and volume of an IR sample under investigation. The disadvantages of the method include labor-intensive and temperature measurements, the complexity of processing the results of the experiment, the need for introducing a number of corrections The duration of the experiment is important, due to the need to obtain the dependence of the sample temperature on time, both before and after rekrascheni heat input.

The closest to the invention is the dilatation (etrId | ee. The method for determining the volumetric heat capacity of liquids, which is measured; the weighing vessel with the test liquid is measured from a reference fluid with a known volumetric heat capacity of € 9i; and test liquid Vo, then produce a measurement of the change in the volume of liquids (reference AVyg and test u.Vjr) for the same period of time f, and after termination of thermal expansion, Limit fixes

0 absolute changes in the volumes of the reference D SPD and the studied /, liquids and from the obtained data, calculate the desired value of the volumetric heat capacity using the formula

five

oh ,, c2l

The disadvantages of this method include the need to achieve

0 equilibrium system, which requires measures to prevent its heat exchange with the environment and large measurement intervals, even with forced mixing of liquids,

5 and leads, thus, in the case of unstable compounds to distort the results.

Claims (2)

The purpose of the invention is to reduce the measurement time, which allows determining the volumetric heat capacity of thermolabile chemically aggressive and time-unstable substances. The goal is achieved by measuring the rate and temperature coefficient of the volume expansion of the sample, and measuring the speed and heat flux on the linear portion of the volume expansion from a time point of 1-1.5 s from the moment the heat input starts and heat capacity is calculated from where C is the volumetric heat capacity, p is the temperature coefficient of the volume distribution, W is the velocity of the volumetric expansion, Q is the heat flux introduced into the interface, The installation for carrying out the method contains a glass dilatomet A 115.78 cm® cell with an electrically integrated rotor inside the test cell filled with a substance that is separated from the atmosphere by a mercury gate, which communicates with the atmosphere through a calibrated glass-capillary section, 0267 cm, and a photoelectric tracking system. complete with a KSP-4 type recorder, which allows to record on the chart tape the dependence of the volume change of the sample over time by moving the meniscus of mercury in a calibrated capillary; devices for measuring by the voltmeter – amp method The electric power meter, the power source of the heater are battery / l battery. Benzene was taken as the control substance. The method is carried out as follows. After filling the dilatometric cells, they first switch on the diagrams of the tape of the KSP-4 recorder (with a Vo drawing speed of 15.0 mm / s} I and then supplying the electric heater, and after 1-1.5 s after completion of the heater heating, the voltage and current in the electric heater circuit are measured, which allows to calculate the power of the electrical heating and thus the heat flux into the sample Q Figure 1b shows the kinematic curves for the recording of the heat dissipation of benzene, corresponding to different heat supply in the coordinates i, the displacement of the meniscus of mercury in the capillary and L, the displacement of the diagram tape, which is identical to the time t-). Three initial thermal expansion j can be distinguished on the curve, corresponding to heating the heater for 1-1.5 s, intermediate (linear curve section), corresponding to adiabatic expansion of the sample, and the stage at which heat loss through the walls of the dilatometric cell begins to play the role. The linear portion of the curve allows the calculation of the rate of volume expansion of the sample. Under these experimental conditions (see Fig. 1), optimal results by definition of W can be obtained with a heat flux of 10-50 W. After the thermal expansion of the sample reaches the third stage, which in the range of supplied heat fluxes of 1090 W corresponds to these conditions by a time of 10–5 s, the electric heating is disconnected and, using the experimental data obtained, the values of Q and W are calculated. by / & , calculate the volumetric heat capacity by the formula. Comparison of the results of the measured values of the volumetric heat capacity shows the best agreement with the HHSvsi reference values of the volumetric heat capacity. The method of determining the volumetric heat capacity of liquid substances by detecting the heat flux introduced into the sample and the volume expansion initiated by it, characterized in that, in order to reduce the measurement time, the velocity and temperature coefficient of volume expansion of the sample are determined, and the measurement of the rate of volume expansion and heat flux carried out from the moment of input of the heat flux and the heat capacity is determined by calculation. Sources of information taken into account in the examination 1.Kirillnv VA and Sheindlin A.E. Investigation of the thermodynamic properties of a substance M, -L ,, 1963, p. 326-334, 2. Authors certificate of the USSR (J 43891, class, G 01 N 25/20, 1976, (prototype). t3 fn