Author: haroonkhan

Entropy Defining entropy in an exact word or line is impossible. It can be viewed as a measure of molecular disorder or molecular randomness. As a system becomes more disordered, the positions of the molecules become less predictable and the entropy increases. Thus, the entropy of a substance is lowest in the solid phase and…

The Clausius inequality is given by the equation where δQ represents the heat transfer at a part of the system boundary during a portion of the cycle, and T is the absolute temperature at that part of the boundary. The symbol δ is used to distinguish the differentials of non-properties, such as heat and work, from the differentials of properties, written…

The two corollaries of the second law known as Carnot corollaries:

The efficiency of a heat engine cycle greatly depends on how the individual processes are executed. The net work can be maximized by using reversible processes. The best known reversible cycle is the Carnot cycle. Note that the reversible cycles cannot be achieved in practice because of irreversibilities associated with real processes. But, the reversible…

In reversible process things happen very slowly, without any resisting force, without any space limitation, everything happens in a highly organized way (it is not physically possible; it is an idealization). Internally reversible process—a system undergoes through a series of equilibrium states, and when the process is reversed, the system passes through exactly the same…

From Figure 1.14 (a), let us assume that a heat engine receives heat QH from high temperature reservoir and converts it into work rejecting no heat to sink, thus violating Kelvin–Plank’s statement. Refrigerator receives heat QL from low temperature reservoir and supplies an amount (QH + QL) to high temperature reservoir when W = QH work is supplied to it. Thus, it operates to conform Clausius statement.…

Violation of Kelvin–Plank Statement by Violating Clausius Statement From Figure 1.13 (a) let us assume that a heat pump receives heat QL from low temperature reservoir at TL and supplies it to high temperature sink at TH without any external work, thus violating the Clausius statement. A larger quantity of heat (QH + QL) is supplied to heat engine (by high temperature source at TH) which…

It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body. In other words, a refrigerator cannot be operated without external work supplied to refrigeration system. Heat flows from high temperature to low temperature reservoir.…

The Kelvin–Plank statement of the second law of thermodynamics refers to a thermal reservoir. A thermal reservoir is a system of infinite heat capacity that remains at a constant temperature even though energy is added or removed by heat transfer. A reservoir is an idealization, of course, but such a system can be approximated in…

Second law of thermodynamics overcomes the limitations of first law of thermodynamics. First law of thermodynamics does not tell how much of heat is changed into work. Second law of thermodynamics shows that the total heat supplied to a system cannot be transferred solely into the work using single reservoir, i.e., some part of heat…