What preheating temperature can be achieved in the reactor using 1.0 MPa medium-pressure superheated steam (200°C)?
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This post was last edited by Xuege Juanjuan on 2022-11-29 at 10:48. I recently encountered a problem: we are using medium-pressure superheated steam at 1.0 MPa (200°C) to preheat the air inside the tube side of a shell-and-tube reactor to 130°C. The steam flows through the shell side, and since the design pressure for that side is 0.1 MPa, the steam enters from the upper part of the shell side, with all outlets at the lower part kept open to prevent excessive pressure. As a result, the temperature of the air in the tube side rises to 99°C and doesn’t go any higher; no change occurs even after heating throughout the night. Theoretically, this reactor can be considered a vacuum device, and the steam exiting the heat exchanger should be superheated, so the temperature in the tube side should reach 130°C. Does anyone know what the reason for this is? Could it be an issue related to the dimensions of the equipment?
Everyone, please share some suggestions: handshake
Using 1.0 MPa steam to heat equipment designed for a pressure of 0.1 MPa is not appropriate, right? Feeding high-pressure fluid into low-pressure equipment is equivalent to flashing, which causes the steam temperature to drop.
In special cases, for temporary heating and flashing, I understand that. What’s important to me is to consider the aspect of heat – where does it go? Temperature reducers and pressure regulators also work in this way, but they require the addition of water to cool down
Is the outlet of the shell side of your heat exchanger still in a vapor state? Steam heating relies on the latent heat generated during its condensation process; you can control the outlet so that the steam condenses inside the heat exchanger, without causing overpressure in the equipment
It cannot be allowed to condense; the temperature cannot rise due to the high latent heat of vaporization. The state of the material will be that of low-pressure saturated steam, and at normal pressure the temperature is only 100°C. The air in the pipe circuit certainly cannot be heated any further, as it cannot exceed 100°C； Imagine adiabatic expansion of steam: the initial state is medium-pressure steam at 200°C and 1.0 MPa, while the final state is steam at atmospheric pressure at 150°C. Theoretically, there should be a temperature difference of 50°C to heat the air; however, once condensation occurs, the excess heat is stored in the water in the form of latent heat, so this latent heat cannot be utilized during the heating process
Think of the back part as a pot being heated under standard atmospheric pressure, so it can only reach around 99
When there is water present, it can be considered as heating at atmospheric pressure; however, this is not the case when there is no water. Can’t atmospheric-pressure steam also be superheated steam? If it is superheated steam, why can’t it be heated above 100°C?
Measure the temperature at the steam outlet.
It’s definitely not high; if it were high, the temperature would rise. Now that we have the results, let’s consider what the cause is What problem?
This post was last edited by kingwang81 on 2022-11-30 14:05 – stored in water in the form of latent heat? I really can’t understand your theory. Check the enthalpy value of steam; the conditions you described for the steam at the inlet and outlet do not exist