-
Hydrogen has the simplest formula of all the elements. Jupiterimages/Photos.com/Getty Images Thermodynamics involves the study of energy conversion, such as heat, within an open or closed system. Although the science was first applied to increase the efficiency of steam engines, today's scientists are looking to produce more sustainable vehicles that can rely on hydrogen as a fuel source. To this end, the study of the thermodynamic properties of hydrogen is an important one. The hydrogen atom is relatively simple, having only one proton and a single orbiting electron.
Higher Heating Value
-
The heating value of a substance refers to the amount of heat produced when a certain amount of it is combusted. It is usually expressed in units of energy--joules--per unit of molecular weight--moles. The higher heating value can be calculated by returning the resulting products of combustion back to their temperature before combustion, in particular making sure to condense any water vapor that has been produced. Hydrogen's higher heating value is -286 kJ/mol.
Lower Heating Value
-
The lower heating value is a quantity that can be calculated by subtracting the water vapor's heat of vaporization from the higher heating value. Hydrogen's lower heating value is -242 kJ/mol. Engineers use hydrogen's lower heating value in systems where any vapor produced will be lost through an exhaust.
Content
-
The energy content of one kilogram of hydrogen is 141.9 million joules at its higher heating value. This is equivalent to 39.4 kilowatt-hours of energy. At its lower heating value, one kilogram contains 120.1 million joules or 33.3 kilowatt-hours of energy.
No comments:
Post a Comment