-----Original Message----- From: Abd ul-Rahman Lomax > Yes, I understood that. The heat, though, doesn't come from expansion of hydrogen.
Wrong. Some of the heat does come from expansion of hydrogen. Of course much more comes from combustion. >When air initially at a moderate temperature is expanded through a valve, >its temperature decrease because it starts out below the inversion >temperature of the constituent gases, and the expansion will cause a >temperature reduction as the result of the Joule-Thomson effect. Any gas >expanded at constant enthalpy will experience a temperature decrease ONLY if >is below the inversion temperature, however, and if above it will usually >experience a temperature increase. > I was not assuming endothermy from expansion, but from evaporation (more like sublimation in this case). There is no difference. > It's simply the reversal of the heat released from absorption. If hydride/deuteride formation is exothermic, and it is, then de-formation is endothermic. Wrong. You are missing the balance point. The balance is between the energy used to pressurize the gas before loading and the net energy returned by both hydride formation and hydride release. If the energy needed to compress hydrogen for loading a tank is say 10 W-hrs, then that can be balanced exactly against 5 W-hrs of exotherm for deuteride formation and another 5 W-hrs of exotherm for expansion. Get it? > Note that failure to account for the heat of formation of palladium deuteride could be a possible source of error in the calorimetric analysis of CF experiments. You finally got something right! > But it would not explain heat after death. Partly wrong. It can explain some of it, but usually there is much more heat after death than can be explained by expansion above the inversion temperature. Jones
