Reasons for poor heat exchange performance of heat exchangers
Thread Content
I would like some advice. Recently, I replaced the heat exchanger with a new one that is identical to the old one, which had been in use for 7 or 8 years. At first, the heat exchange performance was good, but after about a week of operation, it deteriorated. I’m wondering what could be causing this issue. The process gas flows through the shell side (as it needs to be cooled), while the cooling fluid flows through the tube side (ethylene glycol).
Since the heat exchange efficiency was good at first, it’s only possible that the operating conditions have changed or there is a blockage on the tube side (ethylene glycol side).
There is a flow meter on the ethylene glycol side, and the flow rate is very high.
It is recommended to use two heat exchangers in parallel, with filters installed in front of the heat exchangers. Additionally, there is also the issue of pressure and flow rate; if the gas pressure is relatively high, should considering a tubular flow path be taken into account? Also, has ethylene glycol evaporated to form gas, thereby creating a gas zone in the shell side and reducing the heat exchange area? ? ? Check whether the exhaust valve installed above the shell side is open to see if any gas is being discharged Or is it a cooler leak (gas phase leaking into the liquid phase)? ? ?
According to the poster’s description, since the old equipment has been in use for seven or eight years, it should meet the required performance standards. If a new device of the same type is used, its heat exchange efficiency starts to decline after just one week of operation. If the process conditions remain unchanged (this requires comparing the actual operating parameters with the recorded data), then the problem must lie with the new device. Moreover, the poster replied on the 3rd floor that there is a flow meter on the ethylene glycol side, and the flow rate is high, but this does not shed any light on the issue. It is necessary to compare the ethylene glycol flow rates recorded in the operation logs of the old equipment; if all operating parameters are the same (it is also possible to increase the ethylene glycol flow rate and try again), then one can only turn to the new equipment (even if it is manufactured according to the drawings, it may not be exactly the same). Other types of heat exchange equipment could also be considered.
It is recommended to consider the following aspects: Will the process materials be condensed? Is it the incorrect baffle that causes some of the process material to take a short circuit? Is there insulation on the outer surface of the shell side for the process gas? If there is no insulation, touch the surface of the heat exchanger to check whether it is hot on top and cold at the bottom Check the temperature difference at the inlets and outlets of the cooling medium and process materials?
If the operating conditions remain unchanged, the view from the 6th floor is supported: the moon bows between the baffle plates may be different from those originally used, or the gap between the baffle plates and the cylinder might be too large, or there could be a deviation in the position of the upper and lower baffle plates.
The new heat exchanger was designed based on the schematic drawings of the old equipment.
The temperature of the process gas is 30 degrees, while the outlet temperature is 10 degrees. Currently, the temperature of the process gas is 23 degrees, but the outlet temperature remains between 9 and 10 degrees. The inlet temperature of ethylene glycol remains constant at 1-2 degrees. Ethylene glycol is already at full capacity
Some water vapor from the process gas will condense