Calculation of thermal expansion pressure of liquids in closed systems
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Dear experts, there is a problem for which I can’t find a way to calculate it. When a closed container is filled with water and the water is heated, the water expands due to the heat, but the confined space of the container limits this expansion, resulting in pressure being applied to the container. How can this pressure value be calculated?
PV=nRT, where P is pressure, V is volume, n is the amount of substance, R is a constant, and T is the thermodynamic temperature
This is called the Clapeyron equation: PV = (m/M)RT. P represents the pressure of the gas, measured in pascals; V is the volume of the gas; m is the mass of the gas; M is the molar mass of the gas, and (m/M) represents the number of moles. R is the universal gas constant, R=8.31 J/mol; T is the temperature of the gas, measured in Kelvin.
This applies to ideal gases; it doesn’t apply to liquids, right?
Coefficient of thermal expansion of water, container size, elastic modulus of metal, Poisson’s ratio
This post was last edited by 2005011lcj on 2021-3-2 at 16:56. It can be calculated using the PR equation. This problem can be simplified to calculating pressure given temperature and molar volume.
This post was last edited by 2005011lcj on 2021-3-4 at 14:36. We don’t know why it was said that I didn’t answer the question; we neither know nor dare to ask. Then I’ll answer using a different method. Assume that at normal temperature and pressure (20°C, gauge pressure of 0), a container is filled with water; the density of water in this case is approximately 998.2 kg/m3. Since it is a sealed container, both its volume and mass remain constant, so it can be assumed that the density of water also remains unchanged, thus it is still 998.2 kg/m3. Now, the temperature of the water in the container gradually increases to 40°C. In the refrigerant property function of chemical calculation apps, it is necessary to continuously adjust the pressure in order to carry out calculations such that the resulting density gets as close as possible to 998.2 kg/m3 – this value represents the pressure at that point. The pressure at this time is approximately 14 MPa (gauge pressure).
This post was last edited by xyq1983 on 2021-3-4 13:20. Does it have nothing to do with the coefficient of thermal expansion of liquids? I’m not quite sure. Below is the PR equation – isn’t the PR equation used to calculate VLE equilibrium?