Piston cylinder thermodynamics calculator12/15/2023 ![]() As a result the efficiency cannot be 100%.Chapter 2: The second law of thermodynamics Homework2 For losing some heat in the lower temperature reservoir, the equivalency of heat and work is not possible. The high temperature reservoir will supply heat to system and the low temperature one will take heat out of the system and maintain the cyclic process. Here for the system to complete the cycle two reservoir is needed. Which States that, it is impossible to construct a system which will operate in a cycle, extract heat from a reservoir, and do an equivalent amount of work on the surrounding. But this statement cannot be true if we consider the second law. This conception of the First law leads us to the statement that "Thermal efficiency of an engine could be 100%". So as long as the heat and work are equivalent it satisfies the first law. According to the first law, when any closed system is taken through a cycle, the net work done by the system is proportional to the net heat taken by the system from the surrounding. (b) "The thermal efficiency of an engine could be 100% if the first law were our only guide"- justify this statement in context of t he second law. Mathematically, when work is converted into heat, we always have: While when heat is converted to work in a complete closed cycle process, we have: Therefore whenever any machine will absorb heat to produce work, it will lose/radiate some energy to the surrounding (also called a sink). While work is being a high-grade form o f energy can be completely converted into heat. Basically it means that heat being a low-grade energy can never be converted into work with 100% efficiency. Produces work in a complete cycle, while dealing with a single body at a fixed temperature. What is the "perpetual motion machine of the second kind?" Q.4 (a) Write down the Kelvin-Planck statement of the second law of thermodynamics. Determine the power output of the turbine and the fraction of the power from the turbine used to operate compressor of a plant whose net output is 40,000 kW. The maximum and minimum temperature and pressure are 1200K, 0.38MPa, and 290K, 0.095MPa. ![]() (c) A gas power generation plant operates on a Brayton, cycle. (b) Derive an expression for the air standard efficiency of the diesel cycle. Q.3 (a) What are the assumptions for air standard cycles? Make a list for five air standard cycles. If a heat pump is to work on this cycle consuming the same power, and extracting the same amount of heat, calculate the reciprocal thermal efficiency of the pump. Find out the heat rejected to the surroundings and the power required to run the compressor. It extracts 8350 KJ/min from a chamber which is to be maintained at a temperature lower than that of surroundings. (b) For a certain refrigerator working on reversed carnot cycle, the COP is 5. (c) What is the difference between characteristic gas constant and universal gas constant? Q.2 (a) Discuss, giving diagrammatic sketch, the application of reversed cycle for refrigeration. Derive an expression for the approximate heat absorbed by a gas when heated from an absolute temperature T1 to T2 and initial entropy of S1 to S2. Q.1 (a) What is Clausius inequality theorem? What is the significance of Clausius-Clapeyron equation? (b) Explain clearly what is meant by entropy of a gas.
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