Compressibility curves, generalized factor

Each compressor unit and condition has its own specific horsepower point or requirement for operation. However, the general characteristic shape will he about the same, and for a reasonable range of conditions, the general shape and effect of varying a particular condition can be relatively established even for gases of other k values. Of course, the curves can be recalculated and drawn for the particular gas under consideration. The peaks will be in about the same ratio. Note that Figures 12-26 and 12-27 were established using a bhp/MMCFD correction factor at a mean pressure of 200 psia for the lower compression ratios where this correction is required. ... 

It is worth to be noted that (1 /a)h (rja) is the result of the dilation of h (r) by the factor a in which the area under the curve is conserved. The result in reciprocal space is a compressed function H. This property of the Fourier transform is the generalization of Bragg s law. 

The conclusion just reached forms the bams of the generalized, or reduced, compresmbility curves (Fig. 4). From actual experiments on a numbw of gases, the mean observed compressibility factors at various temperatures and pressures have been derived, and the values of k are plotted against the corresponding reduced pressures, with the reduced temperature as parameter. From these curves it is posmble to derive, with a fair degree of accuracy, the value of either the pressure, volume or temperature of any gas, if the other two variables are given. The determination of the volume can be achieved directly from Fig. 4, but the evaluation of either pressure or temperature is not quite as simple.f... 

As discussed in Section 2.5.4, the simple two-parameter corresponding states principle indicates that a generalized equation of state for all substances can be created using only two specific parameters, for example, T, and P. The success of this approach is restricted to simple, spherical molecules like Ar, Kr, Xe, or CH4, where vapor pressure and compressibility factor can be reasonably described. For other molecules, the simple two-parameter corresponding states principle leads to significant errors. A large improvement has been achieved with the introduction of a third parameter which describes the vapor pressure curve (extended three-parameter principle of corresponding states). The most common parameter of this kind is the so-called acentric factor, which is defined as... 

When minimum movement capability is required, the arch is sometimes filled with soft rubber using a suitable adhesive. The maximum amount of movement (axial extension and compression, lateral deflection and angular rotation) that an expansion joint is capable of absorbing is called the rated movement. This rating depends on various factors, such as the size of the expansion joints, the thickness of the tube, arch or convolution, and the type and properties of rubber compound and fabric used in construction. Rated movements are established by manufacturers of expansion joints theoretically, or are based on actual load deflection curves of each size of joint. Rubber expansion joints are generally subjected to hydraulic and vacuum tests at 1.5 times the operating pressure. No internationally accepted standard technical specification for rubber expansion bellows is available, since they are mostly custom built to specific operational requirements. The Expansion Joint Manufacturers Association in New York has laid down standards for rubber expansion joints, which are called EJMA standards [2]. 

---