A glass window 1m x 2m and .005m thick has thermal conductivity of 1.4W/m K. Inner surface temp of 15C and outside of -20C, what is the heat loss through the glass. double paned construction two panes separated by .01m, if glass surfaces are 10C and -15C, with air thermal conductivity of .024W/m K q''= -k dT/L q’’= 1.4W/m•K((288K-253K)/(.005m)), q’’=9800W/m2, q=9800W/m2 • 2m2 = 19600W Double Paned: Rtot = L/kg+L/ka+L/kg, Rtot = (.005m)/(1.4W/(m•K))+(.010m)/(.024W/(m•K))+(.005m)/(1.4W/m•K) Rtot=0.424K/W, q=ΔT/Rtot, q=(283K-253K)/(.0424K/W), q=70.75W It just seemed like too big of a difference to be the correct answer. Just one more I wasn't sure of. The 5mm thick bottom of a 200mm diameter pan may be copper(k = 390W/m K) or aluminum (240W/m K). When used to boil water the surface of the bottom exposed to the water is nominally 110C. IF the heat transferred from the stove to the pot is 600W, what is the temperature of the surface in contact with the stove for the two materials A=0.031416m2, q''=19100W q=k(Tbottom-Tin)/L (q•L)/k+Tin=Tbottom,alum Tbottom,alum=(19100W/m^2(.005m))/(240W/m•K)+383K = 383.398K Tbottom,copper=(19100W/m^2(.005m))/(390W/m•K)+383K = 383.245K Again, just wasn't sure, it seemed the numbers were too close.