Help request: Insufficient heat exchange capacity
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Dear all**, the liquefied gas at the top of our plant’s stabilizer is cooled using both air cooling and water cooling. The designed cooling temperature through air cooling is 45°C, which does not meet the requirements; therefore, two additional water coolers were added, with a designed cooling range of 47°C to 40°C. However, in hot summer conditions, the actual cooling temperature only reaches 43°C or even 44°C. What can be done to solve this issue? If it is suspected that the circulation flow rate is insufficient and the actual flow rate can be measured, how can the designed flow rate be calculated? If I want to increase the flow rate, to what level do I need to raise it to meet the requirements, and how do I calculate that?
For air cooling, an additional set of atomization devices is added to spray water
The flow rate for general circulating water is typically designed to be 1 meter per second. The idea upstairs is feasible, but it’s best to include measures for reusing the returned water; otherwise, there will be a water curtain right below the air cooler! :lol
Putting the technology aside, I think designs like this need to be traced back to their origins. Is this issue in your equipment present from its original design, or did it arise later on? If it is a congenital issue, the designer should be held accountable. If it was done by someone at home, they too must be held accountable. If the problem arises later on, then it is necessary to investigate issues related to operating conditions or problems with the equipment itself, such as nozzles, water distributors, scaling, and other factors. Nor should design be carried out blindly by adding some equipment just because the requirements are not met. This is not vegetable trading, where you can add more or take less. This is extremely irresponsible behavior. To address this issue, it is necessary to trace it back to its source and categorize the problems; this is the effective way to solve them. Oh, there’s another factor as well, which is one that increases the load on the equipment; it falls into a different category. It would be best to clearly state whether there is room for improvement in the design of air-cooled towers, what their internal structure is, and whether the aforementioned problems may occur, to facilitate discussion. I don’t think there should be any issues with the design; problems are likely caused by equipment failures. We should start investigating from this aspect, rather than by blindly adding equipment. For reference.
Does the air cooler fail to meet the requirements from the start of operation?
I agree with the suggestion from the friend on the fourth floor. According to the poster’s description, there is no mention of the exhaust temperature parameter for the air-cooling section; instead, it is proposed to increase the water flow rate in order to cool the gas. So the more likely explanation is the inherent factor mentioned on the fourth floor, namely that the original water cooling equipment did not meet the standards. If it is liquefied gas condensation, as the original poster mentioned, reducing the temperature from 44 degrees to 40 degrees (it is estimated that some condensation already occurs within this temperature range), simply increasing the water flow rate will not solve the problem. After all, at this point the heat resistance side is the gas side, so the flow rate of water has little impact on the heat transfer coefficient on the water side. Even if the water side temperature is increased by a bit, the impact on the overall heat transfer coefficient is minimal. Therefore, the original design plan that included additional water cooling had issues from the start. So it is recommended to carry out further technical upgrades.
This is a common problem with air coolers: when the temperature difference in summer is too small, it becomes difficult to meet the operational requirements.
Was the air-cooling load overestimated during the design, resulting in the water-cooling load not being sufficient to meet the requirements? If there is no scaling issue, dual air cooling could be tried, but corrosion problems may also arise
How long has it been in use? Generally, a margin of at least 20% is included in the design, unless there are errors in the data or the design itself is flawed. If it is used for a long time, the heat exchanger is also likely to become fouled; it is necessary to consider the actual circumstances to determine this. If it is a problem with the circulation water flow rate, it is recommended to measure the temperature difference between the inlet and outlet of the circulation water.
According to the design you proposed, it shouldn’t cool down to 43°C. Is the circulating water temperature, heat exchanger capacity, flow rate, etc., all related? How much needs to be increased cannot be determined based on the conditions you have listed currently