Liquefied natural gas (LNG) is transported in very large tankers, stored as liquid in
equilibrium with its vapor at approximately atmospheric pressure. If LNG is essentially pure methane, the storage temperature then is about 111.4 K, the normal boiling
point of methane. The enormous amount of cold liquid can in principle serve as a heat
sink for an onboard heat engine. Energy discarded to the LNG serves for its vaporization. If the heat source is ambient air at 300 K, and if the efficiency of a heat engine
is 60% of its Carnot value, estimate the vaporization rate in moles vaporized per kJ of
power output. For methane, ΔHn
lv = 8.206 kJ⋅mol−1.