ME 311-004 Question of these 2 devices using a sketch b) What is irreversibility
ID: 2087811 • Letter: M
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ME 311-004 Question of these 2 devices using a sketch b) What is irreversibility? List and explain some causes of irreversibility c) Draw a Carnot cycle in a T-s diagram and name the processes in the cycle. Explain what makes ich the Carnot cycle the most efficient cycle A Carnot heat engine is operating where the source is at 150 C and supplies 100 KW of heat to the heat engine. The engine produces 30 kW of net work. What is the sink temperature in "C ) re Fr.g? cf he, 8 ha. Purp @re olpos.ic. nk ) to ink 1 (S net work.nc 1ey&veuycls; les cho toro 50order 30 K TL?21.1K-73 //Explanation / Answer
Heat pump and refrigerator are similar in operation. Both transfer heat from a lower temperature to a higher temperature by doing the work on the system. The difference is that in refrigerator the higher temperature is the ambient temperature and the lower is below ambient. But in heat pump, the higher temperature is above ambient and the lower temperature is ambient.
Irreversibility is the impossibility of restoring back the surroundings of a system to its initial state in a thermodynamic process. During an irreversible process some heat dissipation happens due to intermolecular friction and collisions when system changes its state. This causes irreversibility. The causes of irreversibility can include friction, mixing of two systems, chemical reactions etc.
The T-s diagram of Carnot cycle can be found on the following link:
https://www.quora.com/Why-Carnot-engine-is-called-reversible
Carnot cycle is the most efficient because it is completely reversible with no increase in entropy. If there were a cycle more efficient than Carnot cycle, then it would have resulted in net generation of work as we could have used a Carnot refrigerator (which would use less energy than the energy produced by the more efficient cycle) to return the objects back to their original temperatures.
Carnot efficiency = 1 - Tlow / Thigh = 1 - Work output / Heat input
1 - Tlow / (273 + 150) = 1 - 30 / 100
Tlow = 126.9 K = -146.1 deg C
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