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A Heat Transfer Approach to Sleeping Bag Ratings

Explore how heat transfer principles can be used to compare sleeping bags, considering factors like insulation, fillings, and different assumptions. Our project aims to apply a heat transfer approach to evaluate sleeping bag ratings and provide a method of comparison. Visit www.littlegreendesigns.com/Sleepingbags.aspx for more information.

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A Heat Transfer Approach to Sleeping Bag Ratings

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  1. A Heat Transfer Approach to Sleeping Bag Ratings Moises Alcevedo Jordan Ryskamp

  2. Modes of heat transfer

  3. Factors

  4. 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

  5. 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)

  6. Properties and Assumptions Fillings of sleeping bags • Feathers k=0.02 mK / W • Polyguard Delta k= .041 mK / W • h= 5 • Why? Rcond < Rconv = 1/ h • No radiation • Why? Low temperature

  7. 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

  8. 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.com/Sleepingbags.aspx

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