【Q&A Question 020】May 10, 2016

Some tubes become supercooled, resulting in an increase in the condensed liquid phase and higher resistance, which leads to uneven distribution； Differences in the air-cooling locations result in uneven overall flow. In colder weather, the lower flow rates lead to overall undercooling, which in turn causes a higher overall pressure drop and further limits the flow rate, resulting in flow deviation ； The presence of a small amount of debris within the tube bundle reduces the flow area, and colder weather leading to increased subcooling further exacerbates uneven flow distribution ；

Insufficient installation level, fouling and blockage of the air-cooled tube bundle, damage and dents on the surface of the tube bundle, freezing on the side with lower temperature

Reason: 1. Uneven distribution of air cooling openings； 2. Low traffic volume ； 3. The design of the distribution pipes is unreasonable

The main reasons are as follows (excluding the issue of excessive blockage in the equipment itself): 1. Some tube bundles are under-cooled, resulting in an increase in the liquid phase of condensate and thus higher resistance, which leads to uneven distribution； 2. Differences in the locations of air cooling lead to uneven overall flow; in colder weather, the lower flow rates result in overall undercooling, which in turn causes a higher overall pressure drop and further limits the flow rate, leading to flow deviation ； 3. The presence of a small amount of debris within the tube bundle reduces the flow area, and colder weather leading to increased subcooling further exacerbates uneven flow distribution ； By adjusting the distribution of the total flow rate, control is achieved; this usually results in an increase in the total pressure drop, so it’s important to do it in moderation. Ensure proper anti-freezing protection for the subcooled air-cooled tube bundles to prevent equipment damage due to freezing at temperatures below zero degrees. Covering it with an insulating tarp, reducing the fan’s speed, or changing the direction of the airflow are all viable options.

Decrease in ammonium salt crystallization or circulating hydrogen volume

1. Low load 2. Blockage inside the pipe 3. Cold weather, resulting in uneven heat distribution and thus resistance

Air-cooling fouling, asymmetry when starting the air-cooled system

A high amount of impurities in the medium, or in the case of standby air cooling, blockages in certain tube bundles due to scaling as well as low loads that result in low flow rates in some of those tube bundles, can all lead to flow deviation

1. Some tube bundles are blocked and not flowing properly； 2. Unreasonable design ； 3. Influence of valve opening degree.