Heat And Mechanical Work In Engine. . . Victor.F. Mavika.
1067 WordsMar 20, 20175 Pages
Heat and Mechanical work in Engine
Dr. Elena Gregg
The first law of thermodynamics is a state for principle of conservation of energy. In most cases, any process that does not obey it never happens. However, there different processes that do not violet it but never occur in nature. First law of thermodynamics fails to answer some important questions.
i. It is known that first law cannot indicate direction of heat transfer. Heat flows from hot body to a cold body and never the reverse. If the reverse process occurs energy would still be conserved, yet first law does not explain this phenomenon. ii. First law does not tell why heat energy cannot be converted…show more content…
A simple engine consists of a cylinder containing gas which is fitted with frictionless movable piston. Since heat engine operates in cycle (Returns to original state after series of processes) there is always work done which also implies continuous conversion of heat into work. To understand the way heat engine works one need to understand the whole idea of Carnot cycle.
The cycle was first discussed by French scientist in 1824. His work explains that work could only be done when heat flowed from higher temperature to a lower one. He proposed ideal engine that operates cyclically and reversibly. This is the practical arrangement to convert heat into mechanical work. Sade Carnot designed this ideal engine free from imperfectness of the actual heat engines. Carnot engine consists of the cylinder, sink, working substance and insulating pad.
Cylinder is the main part of the Carnot engine with insulating walls and the conducting base; it is fitted with frictionless piston which increases the efficiency of the engine. Source is the hot body maintained at a very high temperature with infinite thermal capacity meaning any amount of heat can be taken out without changing temperature of the source. Sink is the opposite of the source. It is he body at a very low temperature which also has infinite thermal capacity. Working substance in the cylinder is normally ideal gas that absorbs heat from the source, as heat is absorbed