Heat Transfer for a Reboiler?

In summary: The vaporizer is considered to be the "shell" since heat transfer occurs there. To account for phase change, Q = m*Hv is used, where "Hv" is the latent heat of steam and "m" is the flow. However, when using this equation, the calculated duty was significantly lower than expected. Additional information, such as the composition and properties of the streams entering and exiting the reboiler, is needed to accurately calculate the duty.
  • #1
pxp004
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For a general cooler or heater, the calculations for heat transfer are based on the tube side and shell side. So

1) For a reboiler would the vaporizer be the "shell" since that's where the heat transfer occurs?

2) How do you account for the phase change? I used Q = m*cP*dT to calculate duty. Since steam is condensing in the tubes, I was told to use Q = m*Hv instead, where "Hv" is the latent heat of steam and "m" is the flow (kg/s) I have from operating data. I looked up Hv at the given temperature and it was around 1900 kJ/kg. So I calculated the duty to be 200 kW.
I have cP and dT data for my process acid (which is being vaporized). So in order to check myself, I used Q = m*cP*dT for my process acid. I don't have operating data for flow on the process side, so I used the flow specified on the datasheet for the exchanger since they should reasonably be the same. The thing is, when I calculated the duty on the process side, I got 900 W. Thats no where near 200 kW.
So I don't understand where I'm going wrong. If someone can explain what's wrong with my method above and how to make calculations for a reboiler, that would be wonderful.
 
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  • #2
You need to provide more information. Is this a reboiler for a distillation column? If so, there is one stream entering the reboiler, and two streams exiting. Do you know the properties of any of these streams, like composition? Do you know how to calculate the enthalpy of any of these streams, given its composition, and the temperature and pressure of the reboiler? What is the identification (e.g., liquid from tray above) of the one stream entering and the two streams exiting?

Chet
 

What is heat transfer for a reboiler?

Heat transfer for a reboiler is the process of transferring heat from one medium to another in order to maintain the desired temperature for a reboiler. It is an essential process in distillation and other industrial processes that require heating.

What are the different types of heat transfer for a reboiler?

The three main types of heat transfer for a reboiler are conduction, convection, and radiation. Conduction is the transfer of heat through a solid material, convection is the transfer of heat through a fluid, and radiation is the transfer of heat through electromagnetic waves.

How does heat transfer affect the efficiency of a reboiler?

Heat transfer greatly affects the efficiency of a reboiler. If the heat transfer rate is too low, the reboiler may not be able to maintain the desired temperature, leading to decreased efficiency. On the other hand, if the heat transfer rate is too high, it can cause excessive energy consumption and potential damage to the reboiler.

What factors influence the heat transfer rate for a reboiler?

The heat transfer rate for a reboiler is influenced by factors such as the type and design of the reboiler, the properties of the heating and cooling mediums, the temperature difference between the mediums, and the flow rate of the mediums. Other factors such as fouling and corrosion can also affect the heat transfer rate.

How can the heat transfer rate for a reboiler be improved?

The heat transfer rate for a reboiler can be improved by optimizing the design and operation of the reboiler, using efficient heat transfer surfaces, maintaining proper flow rates and temperature differences, and addressing any issues such as fouling or corrosion. It is also important to regularly monitor and maintain the reboiler to ensure efficient heat transfer.

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