# Estimating power required to get heat exchanger up to temperature

1. Oct 15, 2015

### 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.

2. Oct 20, 2015