Flaw of Jarzynski's equality when applied to systems with several   degrees of freedom
  Simple example: During the sudden expansion of an isolated ideal gas from a small volume V_0 into a larger one V_1, the entropy changes by Delta S= N ln(V_1/V_0)=-beta Delta F>0 but no work W is produced nor absorbed. Consequently, Jarzynski's identity <exp(-beta W)>= exp(-beta Delta F) is wrong. 
D.H.E.Gross