THE HEAT CAPACITY AT CONSTANT VOLUME OF THE SYSTEM ETHYLENE NEAR THE CRITICAL TEMPERATURE AND PRESSURE

1938 ◽  
Vol 16b (7) ◽  
pp. 230-241 ◽  
Author(s):  
D. B. Pall ◽  
J. W. Broughton ◽  
O. Maass
Keyword(s):  
Heat Capacity ◽  
Critical Temperature ◽  
Thermal Treatment ◽  
Molecular Interaction ◽  
Liquid State ◽  
Average Density ◽  
Constant Volume ◽  
Critical Range ◽  
Temperature And Pressure

The heat capacity of ethylene at constant volume has been investigated through the critical range, between 6.5° and 27 °C., at an average density slightly greater than the critical. The heat capacity in the immediate neighborhood of the critical temperature is found to be a function of the previous thermal treatment of the system. The results indicate the persistence of a large amount of molecular interaction in ethylene above the critical temperature, and are in agreement with the concept that the liquid state of aggregation can persist above the temperature at which the visible meniscus disappears.

scholarly journals First-Order Phase Transformation at Constant Volume: A Continuous Transition?

Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 31
Author(s):  
Víctor F. Correa ◽  
Facundo J. Castro
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Order Phase Transition ◽  
Pressure Range ◽  
Constant Volume ◽  
Continuous Transition ◽  
First Order ◽  
First Order Phase Transition ◽  
Temperature And Pressure ◽  
First Order Phase

We describe a first-order phase transition of a simple system in a process where the volume is kept constant. We show that, unlike what happens when the pressure is constant, (i) the transformation extends over a finite temperature (and pressure) range, (ii) each and every extensive potential (internal energy U, enthalpy H, Helmholtz energy F, and Gibbs energy G), and the entropy S is continuous across the transition, and (iii) the constant-volume heat capacity does not diverge during the transition and only exhibits discrete jumps. These non-intuitive results highlight the importance of controlling the correct variables in order to distinguish between continuous and discontinuous transitions. We apply our results to describe the transition between ice VI and liquid water using thermodynamic information available in the literature and also to show that a first-order phase transition driven in isochoric condition can be used as the operating principle of a mechanical actuator.

Effects of pressure and temperature on the structure of liquid acetone

1967 ◽  
Vol 45 (2) ◽  
pp. 123-130 ◽  
Author(s):  
W. A. Adams ◽  
K. J. Laidler
Keyword(s):  
Heat Capacity ◽  
Internal Pressure ◽  
Structural Changes ◽  
Constant Volume ◽  
Tait Equation ◽  
Liquid Acetone ◽  
Structure Of Liquid

The compressibility of acetone has been redetermined at temperatures of 25 to 55 °C, and at pressures from atmospheric to 1 kbar. The results have been fitted to the Tait equation, and values of (∂P/∂T)V and of the internal pressure have been calculated. The heat capacity at constant volume has also been deduced as a function of pressure and temperature. The variations in these and other derived quantities have been shown to lead to conclusions about structural changes in the liquid.

High Temperature and High Pressure ESP Performance Testing System Design

2013 ◽  
Vol 457-458 ◽  
pp. 423-427
Author(s):  
Xiao Qing Li ◽  
Xiao Yan Liu
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Heat Exchange ◽  
Liquid State ◽  
Constant Pressure ◽  
Hot Water ◽  
Testing System ◽  
Friction Resistance ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

With the development of oilfield exploration, the performance of electric submersible pump (ESP) has been enhanced very fast. It requires testing techniques develop at the same time. The most outstanding question is the testing of high temperature and pressure ESP. A testing well was drilled in Daqing in 1992. It keeps the water liquid state on 150 centigrade by high pressure. This system can simulate operational mode 3000 meters under the ground. But many new ESPs have been produced these years. The quondam testing system couldnt meet the testing requirement. A new testing system is desiderated eagerly. This paper developed a high temperature and pressure ESP testing experimentation system. Hydraulic/thermodynamic analysis calculation has been carried on. Friction resistance from constant pressure point to the suction inlet of hot water pump and the ESP in heating-forced cycle and experimentation primary cycle are calculated respectively. Keeping the water liquid state on 180 centigrade, constant pressure value was fixed on 2.5 MPa. The heat load is calculated including the heat that the water in the system and the equipment need and the heat loss. In order to protect ESP from emanating too much heat to keep the temperature and pressure of the system steady, heat exchange system has been designed. Cold load and heat exchange square have been calculated. Friction resistance and the size of the cold water cistern have been calculated. These provide necessary academic foundation for the testing experimentation of high temperature and pressure ESP.

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