Chapter 6, Problem 6.5DOEP

A closed system undergoes a thermodynamic cycle with three steps: process 1-2 (from state 1 to state 2), process 2-3 (from state 2 to state 3), process 3-1 (from state 3 to state 1). During process 1-2, the system internal energy increases by 20J, during process 3-1, the system internal energy decreases by 15J. What is the change of system internal energy in process 2-3? Enter the answer with the sign: + or - , but without units. For example, +27. Enter zero with no sign: 0.

1. A gas within a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes: Process 1-2: Compression with PV = constant, from P₁ = 1 bar, V₁ = 2 m³ to V₂ = 0.2 m³, U₂ − U₁ = 100 kJ; 2 Process 2-3: Constant volume to P3 = P₁; Process 3-1: Constant-pressure and adiabatic process. Neglect the changes of kinetic and potential energy in all three processes. (a) Sketch the cycle on a P-V diagram; (b) Determine the net work (i.e., W12 + W23 + W31) of the cycle, in kJ; (c) Determine the heat transfer for process 2-3, in kJ. Hint: System's state variables remain unchanged after a cycle, i.e. (U₂ − U₁) + (U3 − U₂) + (U₁ − U3) = 0

Thermodynamics  explain the application of the first law of thermodynamics to appropriate systems.

With the aid of illustrations, describe the four types of thermodynamic process.

The molar heat capacities of substances varies with temperature. The general function for determining the molar heat capacity is given below; Cp m = (a + bT + cT 2 )R . In case of a gas where a = 3.245, b = 7.108 x10^ -4 K ^-1 , and c = -4.06 x10 ^-8 K^ -2 for temperatures in the range of 800 Kelvins to 1,500 Kelvins. What is the change in the enthalpy (in KiloJoules per Kelvin per mole) for two moles of this gas at 1,500 kelvins? NOTE: Express answer in THREE SIGNIFICANT FIGURES.

Steam in a piston-cylinder assembly undergoes a polytropic process, with n = 2, from an initial state where V1 = 2.63160 ft³, p1 = 400 Ib;/in?, and u1 = 1322.4 Btu/lb to a final state where u2 = 1036.0 Btu/lb and v2 = 3.393 ft/lb. The mass of the steam is 1.5 lb. Changes in kinetic and potential energy can be neglected. Determine the change in volume, in ft3, the energy transfer by work, in Btu, and the energy transfer by heat, in Btu.

Macroscopic and Microscopic Point of View in Thermodynamics

1. Define thermodynamic system, surrounding, boundary and universe. Show different types of boundaries. Give examples with sketches for open, close, and isolated systems.

Steam in a piston-cylinder assembly undergoes a polytropic process, with n = 2, from an initial state where V₁ = 3.50880 ft³, p₁ = 400 Ibr/in2, and u₁ = 1322.4 Btu/lb to a final state where u₂ = 1036.0 Btu/lb and v₂ = 3.393 ft³/lb. The mass of the steam is 2.0 lb. Changes in kinetic and potential energy can be neglected. Determine the change in volume, in ft3, the energy transfer by work, in Btu, and the energy transfer by heat, in Btu. Step 1 Determine the change in volume, in ft³. ΔV= i ft3