# High Altitude Balloon Payload Heat Transfer

1. Apr 10, 2013

I would like eventually compute the battery duty cycle required to keep a high altitude balloon payload somewhat temperature controlled. On my last flight I failed the GPS tracker due to unknown cause (maybe CTE). At any rate the cold temperatures are not good for components, accelerometer biases, GPS receivers...
Link to the post flight report shows altitude and temperature vs. time. http://busadriver.com/NTNS-3%20130316/NTNS-3%20Postflight%20Analyses%20130329.pdf
Temperature trends are that the payload heats up, gradually cools well above what would be isentropic expansion until apogee. Then there is a steep drop in temperature as the plane initially descends at 20k ft/min. This is typical of HAB payloads and what I'm concerned about.
I need help in setting up a heat transfer model so that the ascent or decent can be modeled. I simple heat exchanger can be incorporated to heat the air as it comes back in on decent if I can determine if it's feasible to do any good within a reasonable power budget.
The problem appears to the H2 tank expansion thread on this forum, but not quite. I'm assuming that I have internal heat generation, a significant thermal mass in both electronics and wiring and walls, isentropic expansion, cold air that enters on descent and the heat exchanger operating on that air. The heat exchanger could be as simple as a heated aluminum vent tube of adequate length.
I think this can be solved numerically if I had the governing equation(s). Any help would be appreciated.
BTW, the video is linked to the summary page.
Of course the other option is to just put in the heat exchanger, turn it on on descent and see what happends. I'd like to model it 1st.
Regards,
Larry G