Liquid line

The constants Cj and C9 are both obtained from Fig. 2-40 Ci, usually from the saturated liquid line and C2, at the higher pressure. Errors should be less than 1 percent for pure hydrocarbons except at reduced temperatures above 0.95 where errors of up to 10 percent may occur. The method can be used for defined mixtures substituting pseiidocritical properties for critical properties. For mixtures, the Technical Data Book—Fehvleum Refining gives a more complex and accurate mixing rule than merely using the pseiidocritical properties. The saturated low pressure value should be obtained from experiment or from prediction procedures discussed in this section for both pure and mixed liquids. 

Inlet Line. Unstable circulation can result if the inlet line to a vertical theimosyphon reboiler is too large. The tubes of a vertical thermosyphon reboiler fire individually. The tubes can backfire excessively if the liquid inlet line is too large. They don t have to backfire all the way into the tower to cause problems, just to the inlet tubesheet. It is common to put flanges in the inlet liquid line so an orifice can be added later, if required, to provide proper dampening effect. 

Airstream neutralization of acid aerosols by NH3 present in the airway-lumen reduces the health risk associated with acid particles by reducing the acid concentration prior to particle deposition.- In addition, the liquid lining of the respiratory tract probably acts as a chemical buffer," further reducing the health hazard posed by inspired acid particles. Principal factors controlling airstream neutralization of acid aerosols, which is considered to be a diffusion-limited process, are particle surface area, and particle... 

Whenever two-phase flow is encountered in facility piping it is usually in flowlines and interfield transfer lines. Some designers size liquid lines downstream of control valves as two-phase lines. The amount of gas involved in these lines is low and thus the lines are often sized as singlephase liquid lines. Oversizing two-phase lines can lead to increased slugging and thus as small a diameter as possible should be used consistent with pressure drop available and velocity constraints discussed in Volume 1. 

Refrigerant Liquid Line to Economizer/Storage Vessel... 

The safety relief valve will protect the liquid-wetted areas of the storage vessel. The metal temperature will not significantly exceed the liquid temperature, which will be absorbing the latent heat of vaporization. However, above the liquid line no such cooling will take place. The metal temperature at the top of the vessel could therefore exceed safe limits. 

The corrosion conditions can be different at the fluid line from the bulk condition. Aqueous liquids have a concave meniscus, which creates a thin film of liquid on the vessel wall immediately above the liquid line. Some corrosion processes, particularly the diffusion of dissolved gases, are more rapid in these conditions. Additionally, the concentration of dissolved gases is highest near the liquid surface, especially when agitation is poor. Locally high corrosion rates can therefore occur at the liquid line, leading to thinning in a line around the vessel. This effect is reduced if the liquid level in the vessel varies with time. Any corrosion tests undertaken as part of the materials selection procedure should take this effect into account. 

On double seal installations, be sure the sealing liquid lines are connected, the pressure control valves are properly adjusted, and the sealing liquid system is operating before starting the equipment. 

Such a valve is a metering device and may not provide positive shut-off when the compressor is stopped. Under these circumstances, refrigerant will continue to leak into the evaporator until pressures have equalized, and the liquid level might rise too close to the suction outlet. To provide this shut-off, a solenoid valve is needed in the liquid line. 

A low-pressure switch can also be used in conjunction with a thermostat and a solenoid valve in the pump-down circuit. In this method of control, the thermostat does not stop the compressor but de-energizes the liquid line solenoid valve to stop the supply of refrigerant to the evaporator. The compressor continues to run and pumps down the evaporator until stopped by the low-pressure switch. When the thermostat again calls for cooling, it opens the solenoid valve, liquid enters the evaporator and the low-pressure switch will close again to restart the compressor. This method is used to ensure that the evaporator is kept clear of liquid when the plant is off. If there is any leak at the solenoid valve, it will cause the... 

Pipeline sight glasses can be used to indicate whether gas is present in a pipe which sould be carrying only liquid. The main application in refrigeration is in the liquid line from the receiver to the expansion valve. If the equipment is running correctly, only liquid will be present and any gas bubbles seen will indicate a refrigerant shortage (see also Chapters 11 and 33). 

In order to admit the initial refrigerant charge into the circuit, or add further if required, a charging connection is required. The safest place to introduce refrigerant will be ahead of the expansion valve, which can then control the flow and prevent liquid reaching the compressor. The usual position is in a branch of the liquid line, and it is fitted with a shut-off valve and a suitable connector with a sealing cap or flange. A valve is needed in the main liquid line, just upstream from the branch and within reach. For the method of use, see Chapter 11. 

Separation vessels can be inserted in a liquid line. Liquid will fall to the bottom and pass through an expansion device to an evaporator. High pressure gas will rise to the top of the vessel and can then be used for heating or for hot gas defrost of another heat exchanger. 

Example 11.1 R.22 condenses in a circuit at 34°C and is subcooled to 30°C before it leaves the condenser. How much liquid lift can be tolerated before bubbles appear in the liquid line ... 

The same effect will occur where the liquid line picks up heat on a horizontal run, where it may be in the same duct as hot pipes, or pass through a boilerhouse. If the sight glass flashes even with the addition of refrigerant, the possibility of such extra heating should be investigated. To cure this, insulate the pipe. 

Flashing liquids, 134-146 Flow coefficients, Gv, for valves, 81 Friction loss, 68 Incompressible fluid, 71 Laminar flow, 77, 78, 86 Liquid lines, chart, 92 Long natural gas pipe lines, 120 Non-water liquids, 99 Pipe, 71... 

Figure 8.1 Phase diagram for CCF. Point (a) is the critical point and point (b) is the triple point. Line ab gives the vapor pressure of the liquid, line be gives the vapor pressure of the solid, and line bd gives the melting temperature as a function of pressure.

The total vapor pressure line in Figure 6.5 for ( yic-C6HmCH3 +. Y2C-C6H12) at T = 308.15 K is reproduced as the upper line in Figure 8.13. This line is often known as the bubble-pressure curve. We will refer to it as the liquid line. The straight line relationship for this line as predicted by equation (8.16) is evident. 

The liquid line and vapor line together constitute a binary (vapor + liquid) phase diagram, in which the equilibrium (vapor) pressure is expressed as a function of mole fraction at constant temperature. At pressures less than the vapor (lower) curve, the mixture is all vapor. Two degrees of freedom are present in that region so that p and y2 can be varied independently. At pressures above the liquid (upper) curve, the mixture is all liquid. Again, two degrees of freedom are present so that p and. v can be varied independently/... 

In Figure 8.15, a two-phase (liquid + vapor) region is again enclosed by a liquid line and a vapor line. However, the lines have inverted from those in the pressure against mole fraction phase diagram, with the vapor line now on top and the liquid line on the bottom. At temperatures below the liquid line, only liquid is present while above the vapor line, only vapor is present. 

The relative positions of the three lines shown in Fig. 7.25 are different for each substance. One possibility—which depends on the strength of intermolecular interactions in the condensed phases—is for the liquid line to lie in the position shown in Fig. 7.26. In this case, the liquid line is never the lowest line, at any temperature. As soon as the temperature has been raised above the point corresponding to the intersection of the solid and gas lines, the direct transition of the solid to the vapor becomes spontaneous. This plot is the type that we would expect for carbon dioxide, which sublimes at room temperature. 

Shape and form of the specimen support should assure free contact of the specimen with the corroding solution, the liquid line, or the vapor phase, as shown in Fig. 25-5. If clad alloys are ejq)osed, special procedures are required to ensure that only the cladding is ejq)osed (unless the purpose is to test the ability of the cladding to protect cut edges in the test solution). Some common supports are glass or... 

C. F. L. Goudy. How flow improvers can reduce liquid line operating costs. Pipe Line Ind, 74(6) 49-51, June 1991. 

---