Chapter 7, Problem 7.25CU

An isolated system is at rest. There is no change in the system potential energy. What is the change in the system internal energy? Use the energy balance equation to explain.

One kilogram of Air contained in a piston-cylinder assembly undergoes the power cycle consisting of the following processes: Process 1-2: Isothermal (T1=T2= 300 K) compression from state 1 at p1= 1 bar and T1=300 K to P2= 3 bar and T2= 300 K. Process 2-3: Constant (specific) volume (υ3 = υ2) heating from P2= 3 bar and T2= 300 K to T3= 1200 K and υ3 = υ2 (to be determined). Process 3-4: Polytropic expansion with exponent n (to be determined) from state 3 at T3= 1200 K and υ3 = υ2 (to be determined) to state 4 at T4= 820 K and υ4 = υ1 (to be determined). Process 4-1: Constant (specific) volume (υ4 = υ1, to be determined) cooling from state 4 at T4= 820 K and υ4 = υ1 (to be determined) to state 1 at p1= 1 bar and T1=300 K. . Complete the following tasks under the assumption of ideal gas behavior for air and negligible changes in kinetic and potential energy in all processes. Find all the properties of the four states: T, p, υ, u, and h; Sketch the thermodynamic cycle in the p-υ  and T-υ…

QUIZ 4 Steam enters a converging-diverging nozzle (as shown in Figure 1) operating at steady state with p1 = 40 bar, T1 = 400° C, and a velocity of 10 m/s. The steam flows through the nozzle with negligible heat transfer and no significant change in potential energy. At the exit, p2 = 15 bar, and the velocity is 665 m/s. The mass flow rate is 2 kg/s. Determine the exit area of the nozzle, in m?. m = 2 kg/s Insulation P2 = 15 bar V2 = 665 m/s P1 = 40 bar T = 400°C V = 10 m/s Control volume 1 boundary Figure 1

Which of the following statements best describes the 2nd law of thermodynamics? The total entropy of a a reservoir must stay the same or increase. The change in internal energy for an ideal gas is given as A U=mc _▲T. V Heat energy will always be transferred from a hotter object to a colder object. Around a complete cycle, the net heat and net work additions must sum to zero. O A reversible cyclic engine can convert all the heat input it receives into useful work output.

Based on thermodynamics of a process, explain intermediary energy. Mention the three characteristic features of this intermediary energy

⦁    Which of the following statements does not correctly represent the second law of thermodynamics?⦁    Perpetual motion machines do not exist.⦁    Heat flows spontaneously from high temperature regions to low temperature regions.⦁    The entropy of the universe tends to decrease.⦁    Heat cannot be converted to work with 100% efficiency.⦁    Transporting heat from low temperature regions to high temperature regions requires the application of external work.

Three sub steps of a thermodynamic cycle are employed in order to change the state of a gas from 1 bar, 1.5 cubic meter and internal energy of 512 kJ. The processes are: 1st step: Compression at constant PV to a pressure of 2 bar and internal energy of 690 kJ. 2nd step: A process where work transferred is zero and heat transferred is - 150 kJ. 3rd step: A process where work transferred is -50 kJ. without KE and PE changes, determine: a. heat transferred during 1st step (kJ) b. heat transferred during 3rd step (kJ)

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An internal combustion engine is a commonly-analyzed thermodynamic system. In a few sentences, describe the flows of energy and matter across the boundaries of a typical engine.