Request for guidance on the sequence in which hot and cold fluids should be introduced into a shell-and-tube heat exchanger
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The medium in the tube side is steam, while the medium in the shell side is propylene. The purpose is to evaporate the propylene. But our procedures indeed state that steam should be introduced first, before propylene is fed in. Is this approach correct? My intention is to let propylene pass first, and then introduce steam.
This post was last edited by xlxuiin on 2015-6-9 19:01. The rules are correct. The heat absorption during the vaporization of liquid hydrocarbon media leads to low temperatures, and introducing them directly into the shell side can cause damage to the equipment due to these low temperatures. First, introduce steam slowly, making sure to supply water in a timely manner to raise the temperature in the tube side before introducing propylene.
If propylene is added first. Propylene cannot evaporate, causing the equipment to run idly uselessly and leading to energy waste.
Borrowing the owner’s valuable forum to ask as well: The fluid in the tube side is aromatic hydrocarbons, while the fluid in the shell side is heat transfer oil. During operation: 1. Should the aromatic hydrocarbons be added after the heat transfer oil has been heated to the desired temperature? 2. First add the aromatic hydrocarbons, then add the heat transfer oil, until the desired temperature is reached?
Sorry, it’s a fixed tube sheet type. :lol
To reduce temperature difference stress, I think one should first start the cold fluid when starting the machine, and gradually introduce the hot fluid; when stopping, one should first turn off the hot fluid and then the cold fluid. @haiyangqh, please ask a local to take a look, thanks.
Select the flow path according to the following principles: ① Unpure and scale-prone fluids should be routed in the tube side, as cleaning inside the tubes is more convenient； ②Corrosive fluids should be routed in the tube side to prevent both the tube bundle and the shell from being corroded simultaneously ； ③Fluids with high pressure should flow in the tube side to prevent the shell from being subjected to pressure ； ④Saturated steam should flow in the shell side, as the heat transfer coefficient for steam condensation is independent of flow velocity, and the condensed liquid can be easily removed ； So, generally, the management layer is implemented first
Generally, the coolant is turned on first and then the heating fluid. If the order is reversed and the equipment that has been heated is suddenly cooled, the different expansion coefficients of various components may lead to leaks, similar to the principle behind quenching.
Just the day before yesterday, after removing the blockage, we had to put into use a gas-to-gas heat exchanger with fixed tube sheets; this exchanger uses flue gas from a 500-degree furnace to heat process gas at 160 degrees, and its material is stainless steel. Naturally, I should first put the flue gas into use, but a worker asked me, “Shouldn’t we use the cold medium first?” ” My answer is: 1. Before introducing the cold medium into the heat exchanger, I lower the furnace temperature; at that time, the furnace temperature (the temperature of the furnace chamber) was less than 400 degrees. 2. The cold medium must not be allowed to proceed to the next processing step without being heated first. ——This is the key to the problem!