Condensed liquid drainage

Air recirculation Condenser liquid drainage Subcooling reflux Vapor-bound condensers... 

Ablauf fliissigkeitt /. discharge liquid, drainage liquid, -bahn, m. Ablasshahn. -dl, n. expressed oil run oil. -rohr, n., -rohre, /. outlet tube, waste pipe, -trichter, m. draining funnel, condensing funnel (inverted funnel with tubulated rim for carrying off condensed vapors). 

In cases where the quantity of material to be distilled is such that there is a danger of drainage of droplets of condensed liquid from the cold finger, a small collection cup may be attached to the cold finger by means of platinum wire suitably fused to the two glass surfaces (Fig. 2.114). Alternatively the Wheaton-Hickman flask (Aldrich) (Fig. 2.115) may be used note in this case the screw thread joint. 

W. E. McEver and H. Hwangbo, Surface Tension Effects in a Space Radiator Condenser with Capillary Liquid Drainage, AIAA 18th Thermophysics Conf., Montreal, 1983. 

Pressure transmitters should be mounted above the measurement nozzle so that any condensed liquid can drain back. The line to the transmitter should be sufficiently large to permit proper drainage. 

A common form of turbine pump is the vertical pump, which has the pump element mounted at the bottom of a column that serves as the discharge pipe (see Fig. 10-46). Such units are immersed in the liquid to be pumped and are commonly used for wells, condenser circulating water, large-volume drainage, etc. Another form of the pump has a shell surrounding the pumping element which is connected to the intake pipe. In this form, the pump is used on condensate service in power plants and for process work in oil refineries. 

Liquid hydrocarbons accumulated in non-condensible blowdown drums, originating from safety valves, closed drain headers, knockout drum drainage, etc. Facilities are normally provided at the drum for weathering volatile liquids and cooling hot liquids before disposal. 

Select 3-in. nozzle, head loss less than 0.00035 ft (negligible). Use large nozzle to ensure free drainage of unit and no vapor binding in oudet line. Actually a 1-in. connection would safely carry the liquid flow with a head of about 0.08 ft of liquid. A condenser must be free draining and capable of handling surges. 

In conventional compressed air systems, vapor and liquid removal is limited. Most two-stage compressors will include an intercooler between stages. On air-cooled units for 100 to 200psig service, the air between stages is not cooled sufficiently to cause substantial liquid drop out and provision is not usually made for its removal. Water-cooled intercoolers used on larger compressors will usually cool sufficiently to condense considerable moisture at cooler pressure. Drainage facilities must always... 

Where heat transfer is taking place at the saturation temperature of a fluid, evaporation or condensation (mass transfer) will occur at the interface, depending on the direction of heat flow. In such cases, the convective heat transfer of the fluid is accompanied by conduction at the surface to or from a thin layer in the liquid state. Since the latent heat and density of fluids are much greater than the sensible heat and density of the vapour, the rates of heat transfer are considerably higher. The process can be improved by shaping the heat exchanger face (where this is a solid) to improve the drainage of condensate or the escape of bubbles of vapour. The total heat transfer will be the sum of the two components. 

Receivers are commonly made of steel tuhe with welded dished ends, and are located horizontally. Small receivers may he vertical, for convenience of location. The liquid drain pipe from the condenser to the receiver should he amply sized, and any horizontal runs sloped to promote easy drainage. Shut-off valves in this line should not he in a horizontal outlet from the condenser, since their slight frictional resistance will cause liquid hack-up in the condenser. Oudet pipes from the receiver may he from the bottom or, by means of an internal standpipe, may leave at the top. A valve is invariably fitted at this point. 

Operated in this manner, the shell-and-tube type is a flooded evaporator (see Figure 7.3) and has oil drainage pots if using ammonia, or a mixture bleed system if the refrigerant is one of the halocarbons. The speed of the liquid within the tubes should be about 1 m/ s or more, to promote internal turbulence for good heat transfer. End cover baffles will constrain the flow to a number of passes, as with the shell-and-tube condenser. (See Section 6.4.)... 

The reason is condensate backup. The condensate backup causes subcooling that is, the liquid is cooled below its bubble point, or saturated liquid temperature. Perhaps a rat has lodged in the condensate outlet pipe. The rat restricts condensate drainage from the shell side. To force its way past the dead rat, the propane backs up in the condenser. The cold tubes in the bottom of the shell are submerged in liquid propane. The liquid propane is cooled below its bubble-point temperature. 

Vertical in-tube condensers are often designed for reflux or knock-back application in reactors or distillation colnmns. In this case, vapor flow is upward, countercurrent to the liquid flow on the tube wall the vapor shear acts to thicken and retard the drainage of the condensate film, reducing the coefficient. Neither the flnid dynamics nor the heat transfer is well miderstood in this case, bnt Soliman, Schuster, and Berenson [/. Heat Transfer, 90, 267-276... 

During shutdown, it is necessary to drain the trays and seal pans of unevaporated liquid and steam condensate. At least two drain holes are needed for each tray or seal pan, at 0.50 in. minimum diameter and preferably 0.75 in. to avoid plugging. As a rule of thumb, a 0.75 in. hole will deliver about 2gpm of liquid during tower drainage. 

A sudden rush of liquids from equipment into the drainage system would cause compression of entrapped gases in the sewer ahead of the stream and a vacuum behind the stream. Such pulsation drains all the traps and permits permeation of odors and sewer gases. The breather system, by proper installation of vents, is always installed according to code. In order to prevent the back rush of liquids, a ball check is installed ahead of a condenser. Both check valve and subsequent trap should be accessible for cleanout. The bell of the trap extends down from the perforated or gridded floor screen and covers a portion of the drain pipe extending above the bottom of the drain pit. More commonly the floor drains, drain screen, bell, and outside case of the pit are cast iron. 

If liquid accumulates (e.g., due to poor drainage) in the condensing side of the condenser, the flooded surface subcools condensate. This robs the condenser of condensation area and lowers the overall heat transfer rate. This mechanism is responsible for "liquid removal problems in condensers. 

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