AME 230-Midterm Exam 1-Fall 2023-Answers

1 Fall 2023 AME 230 -Thermodynamics Midterm Exam # 1 Answers September 18, 2023 • You will have about 50 Minutes for this exam. • This is a closed-note and closed-book exam. • Useful formulas, constants and tables are provided. • Answers to problems 8 and 9 should use Use thermodynamics problem-solving method. • Neatness is very important. If I cannot follow the solution, that problem will not be graded. I, ______________________________ (Print Name), with ID #___________________, Understand that I should NOT receive any unauthorized help from or give any unauthorized help to anyone else during this exam; otherwise, I will get an automatic “F” in this exam. < signature >____________________ Score

2 Midterm #1, AME 230, Fall 2023 Print Name (clearly) 1. Indicate whether the following statements are true or false (each 3 point) a) The specific volume is not the reciprocal of the density. A: True B: False b) Work is energy transfer for which the sole effect on everything external to the system could have been the raising of a weight. A: True B: False c) A system may contain energy in the form of heat. A: True B: False d) A change in the total energy of a system is described by the change in its internal, kinetic and potential energy. A: True B: False e) The temperature of a system can be changed by a heat transfer only. A: True B: False f) If a closed system undergoes a thermodynamic cycle, there can be no net work or heat transfer. A: True B: False g) Water in a glass with ice cubes consists of several phases. A: True B: False h) The work done by a system is taken as negative ( W < 0). A: True B: False i) Heat transfer from a system is taken as positive (Q > 0). A: True B: False j) Specific heat is the energy required to raise the temperature of the unit mass of a substance by one degree keeping volume or pressure constant A: True B: False

3 Midterm #1, AME 230, Fall 2023 Print Name (clearly) 2. Through a Venturi meter shown in picture below a steady flow of kerosene is established. As the kerosene flows from point a to point b does the pressure increase or decrease as the pipe diameter decreases? (4 point) Answer (one word, no explanation needed): decreases 3. What is The First Law of Thermodynamics (definition in your own words if understandable and the standard definition are both acceptable). (4 point) Answer: (a) energy is conserved or (a) energy can be neither created nor destroyed during a process; it can only change forms 4. For any particular application, energy transfer by heat can occur by one or more of three modes. List the three modes of energy transfer by heat and name the laws associated with each. (6 point) Answer: a. Conduction (Fourier’s law) b. Convection (Newton’s law of cooling) c. Radiation (Stefan-Boltzmann law) 5. What is the quality of the liquid-vapor mixture of H 2 O if its specific volume, υ = 1 m³/kg at 100°C, with v f = 1.0435 × 10 -3 m³/kg and v g = 1.673 m³/kg. (You do not need to Use thermodynamics problem-solving method, but you need to clearly show all relevant equations and calculations). (6 point) Since v = (1 – x ) v f + x v g ࠵? = ࠵? − ࠵? ! ࠵? " − ࠵? ! = 1 ࠵? # ࠵?࠵? − 1.0425 ×10 $# ࠵? # ࠵?࠵? 1.673 ࠵? # ࠵?࠵? − 1.0425 ×10 $# ࠵? # ࠵?࠵? = 0.597