Calculations for Flex Heater

[jayman350]

I am working on integrating a flexible heater into a design that currently houses Pyrex test tubes. The idea is to pre-heat the samples before they enter the measurement chamber.

I have carried out the Overall Heat Transfer Coefficient calcs to determine what that would be. Now I am kind of stuck. What do I need to do to be able to determine what the correct sizing would be for the heater (they are being rated as X W/in^s) and how long it will take to raise the sample from room temp to 70 deg C?

thanks for any help

Jay

 

[IRstuff]

You need to know the amount of Joule heat required, i.e., thermal_mass * delta_temp, and the actual heat flow, which you claimed to have done.

TTFN

FAQ731-376

 

[jayman350]

thanks, I now have the Joule heat required and the heat flow of the system.

I'm sure there is a calculation relating heat required and heat flow I just can't seem to remember/find it.

Can I just multiply the heat flow by time and have the output be how much heat has been transferred to the system in that time frame? I could then set Q = (heat flow)*(time) to determine how long it will take to get up to temp.

 

[IRstuff]

Joule_heat/heat_flow = time

This gives you the absolute minimum possible time to achieve the end result. However, for any bulk process, there are thermal conductivities not accounted for here.

TTFN

FAQ731-376