Author: admin
-
Generalized Compressibility Factor Charts
P-V-T behavior can be generalized in terms of Tc, Pc, and ω. The original correlation was presented by Pitzer, and is given in the form Pitzer correlation. where tables or charts summarized the values of Z0 and Z1 at reduced temperature and pressure. The broad availability of computers and programmable calculators is making this approach somewhat obsolete, but it is worthwhile to…
-
Three-Parameter Corresponding States
If we plot P versus ρ for several different fluids, we find some remarkably similar trends. As shown in Fig. 7.1 below, both methane and pentane show the saturated vapor density approaching the saturated liquid density as the temperature increases. Compare these figures to Fig. 1.4 on page 23, and note that the P versus ρ figure is qualitatively a mirror image of the P versus V figure.…
-
Experimental Measurements
The preferred method of obtaining P–V–T properties is from experimental measurements of the desired fluid or fluid mixture. We spend most of the text discussing theories, but you should never forget the precious value of experimental data. Experimental measurements beat theories every time. The problem with experimental measurements is that they are expensive, especially relative to pushing…
-
Summary
We have seen in this chapter that calculus provides powerful tools permitting us to calculate changes in immeasurable properties in terms of other measurable properties. We started by defining additional convenience functions A, and G by performing Legendre transforms. We then reviewed basic calculus identities and extended throughout the remainder of the chapter. The ability to perform these…
-
Advanced Topics
Hints for Remembering the Auxiliary Relations Auxiliary relations can be easily written by memorizing the fundamental relation for dU and the natural variables for the other properties. Note that {T,S} and {P,V} always appear in pairs, and each pair is a set of conjugate variables. A Legendre transformation performed on internal energy among conjugate variables changes the…
-
Derivative Relations
In Chapters 1–5, we analyzed processes using either the ideal gas law to describe the fluid or a thermodynamic chart or table. We have not yet addressed what to do in the event that a thermodynamic chart/table is not available for a compound of interest and the ideal gas law is not valid for our fluid.…
-
The Fundamental Property Relation
One equation underlies all the other equations to be discussed in this chapter. It is the combined energy and entropy balances for a closed system without shaft work. The only special feature that we add in this section is that we eliminate any references to specific physical situations. Transforming to a purely mathematical realm, we…
-
Homework Problems
5.1. A steam power plant operates on the Rankine cycle according to the specified conditions below. Using stream numbering from Fig. 5.2 on page 201, for each of the options below, determine: a. The work output of the turbine per kg of steam; b. The work input of the feedwater pump per kg of circulated water; c. The flowrate of steam required;…
-
Practice Problems
P5.1. An ordinary vapor compression cycle is to operate a refrigerator on R134a between –40°C and 40°C (condenser temperatures). Compute the coefficient of performance and the heat removed from the refrigerator per day if the power used by the refrigerator is 9000 J per day. (ANS. 1.76) P5.2. An ordinary vapor compression cycle is to be operated on…
-
Summary
Similar to energy balances in Chapter 3, entropy balances can be applied to composite systems. What is new in this chapter is the level of detail and the combination of the energy balance with the entropy balance. Instead of abstract processes like the Carnot cycle, the entropy balance enables us to compute the impacts of each…