Water vapor endothermic conversion

The enthalpy change for a reaction depends on the states of the reactants and products. If the product in Equation 5.18 were H20(g) instead of H20(/), AH would be —802 kJ instead of —890 kJ. Less heat would be available for transfer to the surroundings because the enthalpy of H20(g) is greater than that of H20(Z). One way to see this is to imagine that the product is initially liquid water. The liquid water must be converted to water vapor, and the conversion of 2 mol H20(() to 2 mol H20(g) is an endothermic process that absorbs 88 kJ ... 

Warm clothing decreases convective heat loss in cold weather. Evaporative cooling occurs when perspiration is generated at the skin surface by the sweat glands (T Figure 5.19). Heat is removed from the body as the perspiration evaporates. Perspiration is predominantly water, so the process is the endothermic conversion of liquid water into water vapor ... 

The reaction will be carried out in an adiabatic packed bed. The reaction is endothermic, and cofeeding of hot water vapor into the bed is therefore applied. The conversion level tie = 0.45 is required. Determine the necessary bed length and the temperature of the outlet gas. 

Description A heated mixture of ethanol vapor and steam is fed to an adiabatic dehydration reactor (1). The steam provides heat for the endothermic reaction and pushes the reaction to 99-"% conversion of ethanol with 99-"% selectivity to ethylene. Recovered H O is stripped of light ends (2) and recycled as process steam. Product ethylene is compressed and put through a water wash (3) before passing to the ethylene oxide reactor section. 

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