Estimating power required to get heat exchanger up to temperature

[pcarrollg]

Hi,

I am working on a fuel delivery system with multiple heat exchangers, piping, etc. I am trying to determine how much power I will need to heat up the gas in the system at the inlet so that all of the components of my system will reach the operating temperatures. For example, I am looking at using a heater near a pipe to warm and incoming airflow that will then be sent to the rest of the system. What I need to figure out is what the q value of that air will need to be to get the rest of the system up to temperature.

I started with a lumped transient conduction model and used the weights of each heat exchanger, howeever we are looking for something more accurate. I'm thinking something like a transient heat exchanger analysis but am having trouble figuring out exactly how to do this.

I know what the design temperature and flows are at each point in the system and have calculated the Q value of the hot and cold streams at each point. How do I get from having the air Q values to determining how much time it will take for a certain mass of heat exchanger to reach it's operating temperature, and then tie that into a total power needed to heat the initial air stream.

Any suggestions are greatly appreciated.

 

[Achy47]

Hello,

Thank you for your post. It seems like you are on the right track with your approach of using a transient heat exchanger analysis. This type of analysis takes into account the changing temperatures and flows in your system over time, which will give you a more accurate estimate of the power needed to heat up the gas in your system.

To determine the time it will take for a certain mass of heat exchanger to reach its operating temperature, you will need to consider the heat capacity and thermal conductivity of the material, as well as the temperature difference between the hot and cold streams. From there, you can use equations such as the heat transfer rate equation (Q = mCpΔT) to calculate the amount of time needed.

Once you have determined the time needed for each component to reach its operating temperature, you can then calculate the total power needed by summing up the heat transfer rates for each component. This will give you a more accurate estimate of the total power needed to heat the initial air stream.

I would also recommend consulting with a heat transfer expert or using a computer simulation program to assist with your analysis. These tools can help you accurately model the heat transfer processes in your system and provide you with more precise results.

I hope this helps. Good luck with your research!