EML3100 Thermo - Summer 2001 - Notes 5/29/01

• Both are transient
• Both are boundary phenomena
• Both are path functions

This page contains notes on Heat (Q) and derivations for Work (1W2) equations.
Heat (Q)	energy transferred across the system boundary due to a temperature difference. Heat is transferred from the system at higher temperature to the one at lower temperature. Heat is an inexact differential -- it is path dependent. Units SI J, joule English Btu, British Thermal Unit 1 Btu = 778.17 ft-lbf 1 Btu = heat required to raise 1 lb water from 59.5oF to 60.5oF. [ 1 calorie = heat required to raise 1 gm water from 14.5oC to 15.5oC. ] The rate of heat transfer to/from system Q-dot =   Q     dt Specific heat transfer, q = Q m Heat transferred TO a system is POSITIVE. Heat transferred FROM a system is NEGATIVE. Remember, Work done BY a system is POSITIVE. Work done ON a system is NEGATIVE.
Some comments on WORK and HEAT
Links to derivations for Work (1W2) equations.
	W for a process where pV=constant 1W2 = p1V1ln(V1/V2)
	W for a process where pVn=constant 1W2 =   p2V2 - p1V1 --------------------       1 - n
	W for a process expanding against a LINEAR spring 1W2 = (1/2)(p1 + p2)(V2 - V1) = p1(V2 - V1) + (1/2)(p2 - p1)(V2 - V1)
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