Does internal compression initiate the cooling of the expander’s main tower, with the low-pressure heat exchanger handling the cooling load?
Thread Content
This post was last edited by you*n*nyou on 2011-6-16 at 17:03. Does the main tower of the expansion machine operate in a state of subcooling due to internal compression, and does the low-pressure heat exchanger handle the cooling load? What amount is appropriate?
During bare cooling, it is necessary to direct as much of the cooling capacity as possible to the high-pressure plate exchangers, in order to keep the temperature at the inlet of the expander low and thus increase the speed of the cooling tower. However, some of the cooling capacity also needs to be directed to the low-pressure plate exchangers, as the valve allowing air to enter the tower is open; if no cooling capacity is directed to the low-pressure exchangers, the temperature inside the tower will drop very slowly.
Technology is advancing; it’s now possible to start the engine without using direct air cooling!
No matter how much technology advances, it cannot guarantee that there will be no leaks after the pipes are installed, nor that the welding of the internal supports will be perfect and capable of withstanding thermal expansion. The main purpose of cold testing without insulation is to check whether the flange connections of the equipment inside the cryogenic tank move when the system is at low temperature, and whether there is any leakage. It also serves to determine whether the internal pipe supports deform at low temperatures and could cause damage to the pipes. . . . And whether the device prevents leaks at low temperatures. . If you don’t allow for cooling before driving, the brackets will deform due to the sudden drop in temperature, causing the pipes to come loose and leak fluid – which would be a real nightmare. . . . Dredging sand. . . .
For internal compression expanders with gas entering at the bottom of the tower, it is recommended that the temperatures of the high and low heat exchangers decrease evenly, with a temperature difference not exceeding 10 degrees; I have seen cases where cracks in the heat exchangers occurred due to excessive temperature differences...
During natural cooling, the temperatures of various parts inside the tower should be cooled as synchronously as possible to reduce thermal stress; the lower plates certainly also need to be cooled
Bro, I suggest you study the \"New Questions and Answers on Oxygen Workers\" carefully. Currently, the full cooling method is used during the cooling phase; that is, the temperatures of the equipment and pipelines inside the cold box need to drop evenly in order to reduce stress. Also, the expander operates under high temperature and high enthalpy drop conditions, thereby avoiding the use of high-quality cooling capacity to cool devices with high temperatures.
The fluid in our expander is cooled during low-load operation, so heat must be removed; it’s not about finding ways to lower the inlet temperature. During cooling, all the equipment inside the cold box must be cooled evenly, and it is also necessary to prevent the formation of dead zones; otherwise, it will cause problems once operation begins. In some devices, in order to accelerate the cooling process, during the initial stage of cooling, the gas exiting the expander is directly introduced into the heat exchanger to lower the temperature at the inlet of the expander, thereby increasing the cooling capacity; later on, this gas is introduced into the tower to cool the distillation tower.
Learn from **. . . . . . . . . . . . . . . . . . . .
Indeed, there are many air separation units these days that don’t use direct cooling, but this requires good design and installation; in addition, it’s essential to check for leaks carefully. We have a Hangyang 33600 air separation unit that didn’t use direct cooling due to problems with the imported expansion machine – in fact, even after using domestic expansion machines for two days, the temperature didn’t drop, and there was basically no frosting in the upper column or the argon system – so we started operating it with sand instead. Now, more than three years later, everything is working normally. But it also takes courage to resolve not to stay cold naked. In fact, based on the operating conditions of many air separation units, there are quite a number of such units that, despite meeting the requirements for natural cooling, require sand removal within just half a year of operation.
Reply to 4#: It’s me, Jiu Tian. It seems that in one factory, there’s no need for pre-cooling; the machine can be started right away, and it’s still working well until now.