Is the amount of steam produced the same under different pressures?
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There is such a question: A certain waste heat boiler generates steam; given the same amount of heat supplied, is the quantity of steam produced at 1.0 Mpa equal to the quantity produced at 1.5 Mpa? Does the amount of steam produced vary depending on the pressure? Thank you, looking forward to your participation
Not that many. According to the law of conservation of energy, ignoring heat loss, the same amount of energy input should result in the same amount of energy output. The calorific value of high-pressure steam is greater than that of low-pressure steam (in kj/kg); for the same amount of kj, the lower the calorific value, the less mass there is
It’s definitely different; without taking into account the reduced heat transfer efficiency due to the lower temperature, the flue gas temperature will increase, which in turn leads to a decrease in the amount of heat absorbed. The gas production volume also decreases significantly. Additionally, the enthalpy values at 1.0 Mpa and 1.5 Mpa are lower, which further contributes to this reduction.
The amount of steam generated is related to the heat supplied and the boiler efficiency. Under the same heat supply, the amounts of steam generated at 1.0 Mpa and 1.5 Mpa will not be exactly the same. This is because the density and enthalpy of steam vary at different pressures. According to the steam equation of state, the density of steam is proportional to pressure; therefore, steam at 1.5 Mpa has a higher density than steam at 1.0 Mpa. At the same heat input, steam with a higher density occupies a smaller volume; therefore, the amount of steam generated at 1.5 Mpa will be relatively small. Furthermore, the enthalpy of steam also changes with pressure. Enthalpy represents the energy contained in a unit mass of steam, and it is related to the temperature of the steam. At the same heat supply, the enthalpy of steam at 1.5 Mpa is relatively high, indicating that a unit mass of 1.5 Mpa steam contains more energy. In short, the amount of steam generated under different pressures varies. .
At the same heat supply, the amount of saturated steam produced at 1.0 Mpa is greater than that at 1.5 Mpa.
No. The latent heat of saturated steam at 1.0 MPa is greater than that of saturated steam at 1.5 MPa. Therefore, the amount of steam generated at 1 MPa should be less than that at 1.5 MPa.
The calorific value of steam varies with different pressure levels; therefore, steam generated from the same amount of energy should also differ
You have only considered the latent heat, without taking into account the difference in saturation temperatures between the two; you can simulate it to find out. Putting it another way, according to your view, the amount of steam that generates a relatively high pressure with the same amount of heat is greater than the amount of steam that generates a relatively low pressure – do you think that’s correct?
Agree with the opinion above; otherwise, the devices would all be used to produce high-quality high-pressure steam