Isothermic processes isothermal compressibility

The Intercooled Regenerative Reheat Cycle The Carnot cycle is the optimum cycle between two temperatures, and all cycles try to approach this optimum. Maximum thermal efficiency is achieved by approaching the isothermal compression and expansion of the Carnot cycle or by intercoohng in compression and reheating in the expansion process. The intercooled regenerative reheat cycle approaches this optimum cycle in a practical fashion. This cycle achieves the maximum efficiency and work output of any of the cycles described to this point. With the insertion of an intercooler in the compressor, the pressure ratio for maximum efficiency moves to a much higher ratio, as indicated in Fig. 29-36. 

The modulus indicates that heat is absorbed (+), during die isodrermal expansion, but released (—) during die isothermal compression. In the adiabatic processes no heat is supplied or removed from die working gas, and so... 

Isothermal compression is presented here to represent the upper limits of cooling and horsepower savings. It is the equivalent of an infinite number of intercoolers and is not achievable in the practical types of compressors described in this book. For an isothermal process. 

A wide variety of physical properties are important in the evaluation of ionic liquids (ILs) for potential use in industrial processes. These include pure component properties such as density, isothermal compressibility, volume expansivity, viscosity, heat capacity, and thermal conductivity. However, a wide variety of mixture properties are also important, the most vital of these being the phase behavior of ionic liquids with other compounds. Knowledge of the phase behavior of ionic liquids with gases, liquids, and solids is necessary to assess the feasibility of their use for reactions, separations, and materials processing. Even from the limited data currently available, it is clear that the cation, the substituents on the cation, and the anion can be chosen to enhance or suppress the solubility of ionic liquids in other compounds and the solubility of other compounds in the ionic liquids. For instance, an increase in allcyl chain length decreases the mutual solubility with water, but some anions ([BFJ , for example) can increase mutual solubility with water (compared to [PFg] , for instance) [1-3]. While many mixture properties and many types of phase behavior are important, we focus here on the solubility of gases in room temperature IFs. 

The reader interested in the liquefaction technologies can see, for example, ref. [14,15], We will only remind that in most cases, the gas cooling is obtained by the Joule-Thomson process an isothermal compression of the gas is followed by an expansion. This procedure leads to a cooling only if the starting temperatures are lower than the inversion temperature 7] = 6.75 TCI (for a Van der Waals gas), where TCI is the critical temperature. 

Although isothermal compression is desirable, in practice the heat of compression is never removed fast enough to make this possible. In actual compressors only a small fraction of the heat of compression is removed and the process is almost adiabatic. 

Energy is needed to eompress gases. The compression work depends on the thermodynamic compression process. The ideal isothermal compression cannot be realized. Even more energy is needed to compact hydrogen by liquefaction. Low density and extremely low boiling point of hydrogen increases the energy cost of compression or hquefaction. 

During the isothermal compression process 1-2, heat is rejected to maintain a constant temperature Tl. During the isothermal expansion process 3-4, heat is added to maintain a constant temperature Th- There are also heat interactions along the constant-volume heat addition process 2-3 and the constant-volume heat removal process 4-1. The quantities of heat in these two constant-volume processes are equal but opposite in direction. 

The schematic Ericsson cycle is shown in Fig. 4.27. The p-v and T-s diagrams of the cycle are shown in Fig. 4.28. The cycle consists of two isothermal processes and two isobaric processes. The four processes of the Ericsson cycle are isothermal compression process 1-2 (compressor), isobaric compression heating process 2-3 (heater), isothermal expansion process 3-4 (turbine), and isobaric expansion cooling process 4-1 (cooler). 

Compression of hydrogen consumes energy depending on the thermodynamic process. The ideal isothermal compression requires the least amount of energy (just compression work) and the adiabatic process requires the maximum amount of energy. The compression energy W depends on the initial pressure p and the final pressure pf, the initial volume V and the adiabatic coefficient y ... 

Recovery of solvent by isothermal compression. This method was proposed by Claude [14]. It was applied to the recovery of alcohol containing camphor which escapes during the manufacture of celluloid. With alcohol and ether this process entails compressing the vapours to 7 atm, thus causing the condensation of the alcohol and after that rapidly expanding them. Ether is condensed by intensive cooling. The necessary plant was very expensive and there was risk of explosion when the mixture of the air with alcohol and ether was compressed too rapidly. It never attained wide application. 

Figure 4.3 Reversible Camot cycle, showing steps (1) reversible isothermal expansion at th (2) reversible adiabatic expansion and cooling from th to tc (3) reversible isothermal compression at tc (4) reversible adiabatic compression and heating back to the original starting point. The total area of the Camot cycle, P dV, is the net useful work w performed in the cyclic process (see text).

CARNOT CYCLE. An ideal cycle or four reversible changes in the physical condition of a substance, useful in thermodynamic theory. Starting with specified values of die variable temperature, specific volume, and pressure, the substance undergoes, in succession, an isothermal (constant temperature) expansion, an adiabatic expansion (see also Adiabatic Process), and an isothermal compression to such a point that a further adiabatic compression will return the substance to its original condition. These changes are represented on the volume-pressure diagram respectively by ub. he. ctl. and da in Fig. I. Or the cycle may he reversed ad c h a. 

In contrast to isentropy, the process of isothermal compression-expansion, which is accompanied by heat release or heat absorption, is represented by an exergy vector with the slope of < 1 in the regimes of heat absorption and heat release as shown in Fig. 11.10(a). 

Five kilograms of steam in a piston/cylinder device at 150 kPa and 150°C undergoes a mec cally reversible, isothermal compression to a final pressure such that the steam is just saturate Determine Q and W for the process. 

The pure species A and B are isothermally compressed (or expanded, depen on the pressure P) to their equilibrium fugacities in the box. The change in Gibbs energy for this process is given by Eq. (15.9), here written for one mole... 

An ideal gas at 50°C and 1 atm is heated to 500°C at constant pressure, and then isothermally compressed to 10 atm. It is then isobarically cooled to 50°C, and finally is isothermally expanded to back to its initial state. For the overall process, determine AH and AU. 

Because Pex = P throughout the process, this is a reversible compression. In this case iv has a positive sign, because we are performing work on the system. Thus, in the reversible, isothermal compression of the gas, w x = 1.4Pi Vi and since AE = 0,... 

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