Common Operating Problems with Condensers

Inerts accumulation, condensate removal, and condenser fouling are by far the most common problems that adversely affect condenser operation (381). One author (28) states that more than half of all condenser problems are due to poor venting. Fouling in condenser- usually occurs on the coolant side and will not be dealt with here. Other problems occasionally also affect condenser performance. 

Inerts. Accumulation of even a small fraction of noncondensables can impair condensation heat transfer. The mechanism by which noncondensables accumulation reduces heat transfer is described in Sec. 15.10. Inerts problems are most common in shell-side condensation, where gases can segregate in pockets, and are difficult to remove unless sufficient pressure drop is used to force them to the vent outlet (291, 381). Cross-flow condensers are particularly prone to inerts accumulation. Numerous cases where inerts venting was a problem have been reported (28,134, 239, 381). Adequate venting facilities are needed at all locations where noncondensables are likely to accumulate. Guidelines for venting are presented in Sec. 15.9. 

An inert blanketing problem in a condenser shell can often be diagnosed by measuring surface temperature. Areas blanketed by inerts tend to be considerably cooler. If safety regulations permit, feeling the shell by hand at different spots can sometimes be an effective surface thermometer. 

Condensate removal. If condensate is removed at an insufficient rate, or if the condenser traps condensate, heat transfer area will become flooded. This will lower condenser heat transfer rates, as described in Sec. 15.10. Numerous case histories of troublesome condensate removal have been reported (134, 290, 381). 

A condensate removal problem in shell-side condensers can sometimes be detected by surface temperature measurements. Where safety permits, feeling the exchanger by hand can be effective. Regions where condensate builds up tend to be considerably cooler. 

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Where the MU water supply to cast-iron boilers does not precisely keep up with steam generation demands, the water level can quickly decrease and the problems become even more acute. Conversely, where MU does precisely keep up with steaming rates and is supplied to a common condensate receiver-FW tank via automatic level control, the tank can easily overfill when condensate finally drains back under on-off operating conditions. This gives rise to a loss of valuable hot, treated water from the system and the start of another chain of cause and effect problems. 

High humidity is a significant cause of reliability problems because many corrosion mechanisms require water to operate. A humid environment is an excellent source of water, even when it is not condensing. Polymers commonly used in PCBs are hygroscopic that is, they absorb moisture readily from the environment. This phenomenon is reversible the moisture can be driven out of the PCB by baking it. The amount of moisture absorbed and the time to reach equilibrium with a humid environment depend on the laminate material, its thickness, the type of solder mask or other surface coating, and the conductor pattern. 

One common problem arising when AFM experiments are run in air is that there might be a 2-50 nm thick contamination layer on the sample surface, which usually includes water that also can condense in the gap between the tip and the surface, even if it is absent elsewhere. If a contamination layer exists, capillary forces will pull the tip toward the surface with a strength that can be greater than the van der Waals forces, and will depend on the sample, the humidity and the tip shape. Contamination can be observed as hysteresis in the force distance curve since the tip will remain wetted up to larger separations as it is withdrawn from the surface but can be avoided by operating in vacuum, in dry gas or in a liquid. 

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