EES 0837 Lecture Notes - Lecture 21: Calorie, Seasonal Energy Efficiency Ratio, Thermodynamics

• School: Temple University
• Department: Earth & Environmental Science
• Course: EES 0837
• Professor: Ralph

Document Summary

Lecture - 21: quantifying heat energy, we"ve already seen many examples of quantifying heat. 1 kilocalorie is the heat energy associated with raising 1 kg (1 liter) of water 1 c. In general, q = cpmt, where cp is the heat capacity: we need to also point out that a change in heat energy accompanies a change in entropy: Q = ts (t expressed in (cid:1)k, assumed constant: adding heat increases entropy. The gain in entropy in the sink must at least balance the loss of entropy in goes up (heat added): remember that q = ts total entropy must never decrease the source. Stot = sh + sc = qh/th + qc/tc (cid:2) 0. Qc (cid:2) (tc/th)qh sets a minimum on qc: what does this entropy limit mean, w = qh qc, so w can only be as big as the minimum qc will allow, so the maximum efficiency is: Max efficiency is (825 300)/825 = 525/825 = 64%