Quiz #1 Closed Book, Open Appendices, Closed Notes, CLOSED CALCULATORS An astronaut has a mass of 161 lbm on the surface of the earth. Calculate his weight (in lbf) on planet Rigel 4 where g = 20.0 ft/s 2? Work only in English units AND SHOW YOUR WORK. ANSWER: 100.0 lbf
Quiz #2 A vacuum gauge connected to a tank reads 5 psi where the local barometric reading is 394.4 inches H 2 O. Determine the absolute pressure in the tank. Take ρ H2O = 62.4 lbm/ft 3. Work only in English units AND SHOW YOUR WORK. Answer in units of psia. ANSWER: 9.24 psia
Quiz #3 Closed Book, Open Appendices, Closed Notes A 90-hp (shaft output) electric car is powered by an electric motor mounted in the engine compartment. If the motor has an average efficiency of 91%, determine the rate of heat supply by the motor to the engine compartment at full load. ANSWER: 6.29 BTU/s or 6.64 kw
Quiz #4 Ten kilograms of R-134a fill a 1.348-m 3 rigid container at an initial temperature of -40 ºC. The container is then heated until the pressure is 200 kpa. a) Draw this process on a T-v diagram with respect to saturation lines, and b) Find the initial pressure (if saturated, show me why), and c) Determine the final temperature. ANSWERS: 51.25 kpa, 66.3 ºC
Quiz #5 A piston-cylinder device contains 0.8 kg of water at 300 ºC and 1 MPa. The water is cooled at constant pressure until one-half of the mass condenses. a) Show this process on a T-v diagram with respect to saturation lines, b) Find the final temperature, c) Determine the initial volume occupied by the water, and d) the volume occupied by the liquid at the final state. ANSWERS: 179.88 ºC, 0.2064 m 3, 4.5E-4 m 3
Quiz #6 A rigid 3.5 ft 3 vessel contains a mixture of liquid water and vapor at 200 ºF with 12.3 % quality. The mixture is then heated until its temperature is 300 ºF. Calculate the heat transfer required for this process. Also, draw this process on a T-v diagram with respect to saturation lines. ANSWER: 440.3 BTU
Quiz #7 A piston-cylinder device contains 3 lbm of oxygen. The gas is heated from 120 to 240 ºF. The initial pressure inside the container is 50 psia. Determine: a) the initial volume of the container (in ft 3 ), and b) the amount of heat that must be added. Include your Super Bowl prediction ANSWERS: 11.7 ft 3, 78.8 BTU
Quiz #8 Helium is to be compressed from 120 kpa and 310 K to 700 kpa and 430 K. A heat loss of 20 kj/kg occurs during the compression process. Neglecting kinetic energy changes, determine the power input required for a mass flow rate of 90 kg/min. ANSWER: 965 kw
Quiz #9 Closed Book, Open Appendices, Closed Notes A residential heat pump has a coefficient of performance of 2.4. How much heating effect, in BTU/h, will result when 5 hp is supplied to this heat pump? Also: What Technical Elective would you prefer next semester? a) Compressible Flow b) Adv. c) Vibrations ANSWER: 30,530 BTU/h
Quiz #10 A refrigerator needs to absorb heat from a space at 15 ºC at a rate of 16,000 kj/h and reject heat to a reservoir at 36 ºC. Determine the minimum power required for this refrigerator (in kw). Also find the rate of heat rejected to the high temperature reservoir, in kj/h. ANSWERS: 0.324 kw & 17,170 kj/h
Quiz #11 A heavily insulated piston-cylinder device contains 1 ft 3 of steam at 60 psia and 400 ºF. The steam is now compressed in a reversible manner to a pressure of 180 psia. Determine the work done on the steam during this process, in BTU. ANSWER: 10.76 BTU
Quiz #12 Air is expanded in an adiabatic, reversible turbine from 200 psia and 900 ºF to a pressure of 20 psia. Assuming variable specific heats for air, compute: a) the outlet temperature of the air, and b) the work produced by this turbine, in BTU/lbm. ANSWERS: 721.8 R, 159.7 BTU/lbm
Quiz #13 Closed Book, Open Appendices, Closed Notes A refrigeration unit compresses saturated R- 134a vapor at 20 ºC to 1000 kpa. How much power is required to compress 0.7 kg/s of R- 134a with a compressor efficiency of 87 percent? ANSWER: 9.28 kw
Quiz #14 Closed Book, Closed Appendices, Open Notes Humid air at 1 atm, 20 ºC and 80% relative humidity is heated in a pipe at constant pressure to 40 ºC. The mass volumetric flow rate at the inlet is 355 m 3 /min. Find the relative humidity of the air at the pipe exit and the rate of heat transfer (in kw). Plot the process on the Psychrometric Chart on back. ANSWERS: about 25% and 140 kw