Thermodynamics ENERGY, WORK, AND HEATWork is defined for mechanical systems as the action of a force on an object through a distance.It equals the product of the force (F) times the displacement (d).W = Fd (1-15)where:W = work (ft-lbf)F = force (lbf)d = displacement (ft)Example:Determine the amount of work done if a force of 150 lbf is applied to an object until ithas moved a distance of 30 feet.Solution:Using Equation 1-15W = FdW = (150 lbf)(30 ft)W = 4500 ft-lbfIn dealing with work in relation to energy transfer systems, it is important to distinguish betweenwork done by the system on its surroundings and work done on the system by its surroundings.Work is done by the system when it is used to turn a turbine and thereby generate electricity ina turbine-generator. Work is done on the system when a pump is used to move the working fluidfrom one location to another. A positive value for work indicates that work is done by thesystem on its surroundings; a negative value indicates that work is done on the system by itssurroundings.HeatHeat, like work, is energy in transit. The transfer of energy as heat, however, occurs at themolecular level as a result of a temperature difference. The symbol Q is used to denote heat.In engineering applications, the unit of heat is the British thermal unit (Btu). Specifically, thisis called the 60 degree Btu because it is measured by a one degree temperature change from 59.5to 60.5°F.Rev. 0 Page 19 HT-01