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Heat energy of phosphoric acid evaporation
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Leopoldo Mauro Collaoni
Heat energy of phosphoric acid evaporation
As it turns out, I was just confused on the question being asked. You actually can use Q=mC p ΔT to answer the question. However, instead of using it for Phosphoric acid, you use it based on the water, as you know the mass of water being evaporated out, the specific heat capacity of water at this temperature, and the change in temperature of the water. This Q required by the water will be equal to that added to the phosphoric acid by the heat exchanger.
As a side note, I was incorrect in stating that Q=mC p ΔT is not applicable to phosphoric acid. It is applicable, however not reccomended for this problem as you do not know the mass flow rate of the phosphoric acid through the recycle stream, nor is it easy to find the heat capacity of dilute phosphoric acid at the very high temperatures at which this evaporation would take place.
As it turns out, I was just confused on the question being asked. You actually can use Q=mC p ΔT to answer the question. However, instead of using it for Phosphoric acid, you use it based on the water, as you know the mass of water being evaporated out, the specific heat capacity of water at this temperature, and the change in temperature of the water. This Q required by the water will be equal to that added to the phosphoric acid by the heat exchanger.
As a side note, I was incorrect in stating that Q=mC p ΔT is not applicable to phosphoric acid. It is applicable, however not reccomended for this problem as you do not know the mass flow rate of the phosphoric acid through the recycle stream, nor is it easy to find the heat capacity of dilute phosphoric acid at the very high temperatures at which this evaporation would take place.
You need to know the latent heat of vaporization of the solution, which would be the same as that of water when phosphoric acid concentration is low.
See Fig. 10 of this bulletin for latent heat of vaporization as a function of phosphoric acid concentration, but keep in mind this is only strictly valid at the stated temperature.
If you are varying phosphoric acid concentration (concentrating phosphoric acid) you would need to integrate heat of vaporization as a function of phosphoric acid concentration over the appropriate concentration range.
Also, as phosphoric acid concentration gets very high, it is no longer valid to consider the evaporating solution to be only water, it will increasingly contain phosphoric acid as well.
You need to know the latent heat of vaporization of the solution, which would be the same as that of water when phosphoric acid concentration is low.
See Fig. 10 of this bulletin for latent heat of vaporization as a function of phosphoric acid concentration, but keep in mind this is only strictly valid at the stated temperature.
If you are varying phosphoric acid concentration (concentrating phosphoric acid) you would need to integrate heat of vaporization as a function of phosphoric acid concentration over the appropriate concentration range.
Also, as phosphoric acid concentration gets very high, it is no longer valid to consider the evaporating solution to be only water, it will increasingly contain phosphoric acid as well.
Hello, I am given latent heat and it is assumed that the concentration within the evaporator as well as the concentration in the recycle stream are the same concentration as the exit stream. Can you help with what I should do in this case?More
As it turns out, I was just confused on the question being asked. You actually can use Q=mC p ΔT to answer the question. However, instead of using it for Phosphoric acid, you use it based on the water, as you know the mass of water being evaporated out, the specific heat capacity of water at this temperature, and the change in temperature of the water. This Q required by the water will be equal to that added to the phosphoric acid by the heat exchanger.
As a side note, I was incorrect in stating that Q=mC p ΔT is not applicable to phosphoric acid. It is applicable, however not reccomended for this problem as you do not know the mass flow rate of the phosphoric acid through the recycle stream, nor is it easy to find the heat capacity of dilute phosphoric acid at the very high temperatures at which this evaporation would take place.
As it turns out, I was just confused on the question being asked. You actually can use Q=mC p ΔT to answer the question. However, instead of using it for Phosphoric acid, you use it based on the water, as you know the mass of water being evaporated out, the specific heat capacity of water at this temperature, and the change in temperature of the water. This Q required by the water will be equal to that added to the phosphoric acid by the heat exchanger.
As a side note, I was incorrect in stating that Q=mC p ΔT is not applicable to phosphoric acid. It is applicable, however not reccomended for this problem as you do not know the mass flow rate of the phosphoric acid through the recycle stream, nor is it easy to find the heat capacity of dilute phosphoric acid at the very high temperatures at which this evaporation would take place.
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You need to know the latent heat of vaporization of the solution, which would be the same as that of water when phosphoric acid concentration is low.
See Fig. 10 of this bulletin for latent heat of vaporization as a function of phosphoric acid concentration, but keep in mind this is only strictly valid at the stated temperature.
If you are varying phosphoric acid concentration (concentrating phosphoric acid) you would need to integrate heat of vaporization as a function of phosphoric acid concentration over the appropriate concentration range.
Also, as phosphoric acid concentration gets very high, it is no longer valid to consider the evaporating solution to be only water, it will increasingly contain phosphoric acid as well.
You need to know the latent heat of vaporization of the solution, which would be the same as that of water when phosphoric acid concentration is low.
See Fig. 10 of this bulletin for latent heat of vaporization as a function of phosphoric acid concentration, but keep in mind this is only strictly valid at the stated temperature.
If you are varying phosphoric acid concentration (concentrating phosphoric acid) you would need to integrate heat of vaporization as a function of phosphoric acid concentration over the appropriate concentration range.
Also, as phosphoric acid concentration gets very high, it is no longer valid to consider the evaporating solution to be only water, it will increasingly contain phosphoric acid as well.
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