A Heat Transfer Approach to Sleeping Bag Ratings

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A Heat Transfer Approach to Sleeping Bag Ratings

• Moises Alcevedo
• Jordan Ryskamp

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Modes of heat transfer
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Factors
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Different Standards

• Ratings are given as a temperature
• Manufacturers pick their ratings
• Many are optimistic
• No recognized standards
• Make different assumptions
• Young male in a tent wearing thermals
• Older larger female sleeping under the stars

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Our Project

• Use heat transfer principles to compare bags
• All bags are limited by the amount of insulation
• Approximate as cylinder

Air out (To, Rair out)
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Properties and Assumptions

• Fillings of sleeping bags
• Feathers
• k0.02 mK / W
• Polyguard Delta
• k .041 mK / W
• h 5
• Why? Rcond lt Rconv 1/ h
• No radiation
• Why? Low temperature

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Thermal Circuit
Ti
To
Rair in Rcond Rair out
Rtotal Rair in Rcond Rair out Rair in
1/hA 1/h2?RbodyL Rcond Ln(Rout s.b./Rin
s.b.) / 2?kL Rair out 1/hA 1/h2?Rout s.b.L
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Solution and Conclusion

• qV ?T / Rtotal
• Ti - To / Rtotal
• To Ti - qVRtotal

Model does not give accurate results. However, it
does give a good method of comparison.
Currently found online at www.littlegreendesigns.c
om/Sleepingbags.aspx