Studies on isobaric specific heat capacity of liquid under high pressure

流体的热物理性质，例如热容和焓，对于各种过程计算是重要的。虽然这些性质可以通过实验PVT数据或状态方程计算，但很难可靠地估计这些PVT性质的一阶和二阶导数的误差。因此，直接实验测定热容是可行的。在这种量热计中，液体在恒定压力下通过一个温度计、一个加热器和第二个温度计的稳定流动。通过测量流量、输入到加热器的功率以及量热计的入口和出口处的液体温度，可以计算样品液体的表观热容。通常有一些热损失，因此应进行适当的校正以获得真实的热容。该热量计可在230 ~ 420 K和40 MPa压力范围内准确、方便地测量纯液体及其混合物的等压热容Cp。测量的不确定度估计在2.1以内<plus-minus>。首先，对文献中报道的HCFC 123（CH_3CHCl_2）的等压比热容进行了测量，以验证该装置和方法的可靠性。测量温度为310.2和320.2K，压力为1.0MPa。在实验不确定度范围内，本结果与文献值一致。在303 ~ 323 K和1.0MPa压力范围内测定了HCFC 141 b（CH_3CCl_2F）的热容。在此实验条件下，获得的热容随压力的增加而单调下降。

Thermophysical properties of fluids, such as heat capacity and enthalpy, are important for various process calculations. Although, these properties can be calculated by the experimental PVT data or the equation of state, it is very difficult to estimate reliably the errors in the first and second derivatives of these PVT properties. Therefore, the direct experimental determination of heat capacity is desirable.A new adiabatic flow calorimeter was designed and constructed. In this calorimeter, steady flow of liquid past a thermometer, a heater and second thermometer under a constant pressure. By measurement of the flow rate, of power input to the heater and of liquid temperatures at inlet and outlet of the calorimeter, the apparent heat capacity of the sample liquid may be calculated. Usually there are some heat losses, therefore an adequate correction should be made to obtain the true heat capacity. This calorimeter can measure the isobaric heat capacity, Cp, of pure liquids and their mixtures precisely and conveniently in the temperature range from 230 to 420K and pressures up to 4OMPa. The uncertainty of the measurements is estimated to be within <plus-minus>2.1At first, the isobaric specific heat capacity of HCFC123 (CH_3CHCl_2) whose heat capacity data were reported in the literature was measured to confirm a reliability of this apparatus and procedure. Measurements were carried out at the temperature 310.2 and 320.2K and pressure 1.0MPa. The present results agree with the literature values within the experimental uncertainty. The heat capacity of HCFC14lb (CH_3CCl_2F) was measured at temperature from 303 to 323K and pressures up to 1.0MPa. In this experimental conditions, heat capacities obtained decreased monotonously with increasing pressure.