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

2. A Heat Transfer Approach to Sleeping Bag Ratings Modes of heat transfer

3. A Heat Transfer Approach to Sleeping Bag Ratings Factors Rating Heat Generation GenderMetabolism Food Exercise level HydrationWeight Thermal Resistance InsulationClothing FitTent ShapeMoisture

4. A Heat Transfer Approach to Sleeping Bag Ratings 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. A Heat Transfer Approach to Sleeping Bag Ratings Our Project Use heat transfer principles to compare bags All bags are limited by the amount of insulation Approximate as cylinder Body ( q gen. Ti) Air inside,( Rair in) Sleeping bag, ( Rcond) Air out (To, Rair out)

6. A Heat Transfer Approach to Sleeping Bag Ratings Properties and Assumptions Fillings of sleeping bags Feathers k=0.02 mK / W Polyguard Delta k=.041 mK / W h= 5 –Why? R cond < R conv = 1/ h No radiation –Why? Low temperature

7. A Heat Transfer Approach to Sleeping Bag Ratings Thermal Circuit R air in R cond R air out TiTi ToTo 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. A Heat Transfer Approach to Sleeping Bag Ratings Solution and Conclusion qV = ∆T / R total = T i - T o / R total T o = T i - qVR total Currently found online at www.littlegreendesigns.com/Sleepingbags.aspx Model does not give accurate results. However, it does give a good method of comparison.