HW-1: Due by 5:00 pm EDT on Wednesday 13 June 2018 to GradeScope. The solar cell/solar panel shown above depict how a semiconductor can transform solar power into electrical power. Consider the solar panel as the system and sketch all the heat transfer and work interactions associated with it. Be careful that the directions of all arrows are consistent with the actual power flows.
HW-2: Due by 5:00 pm EDT on Wednesday 13 June 2018 to GradeScope. A manual automobile transmission, such as the one shown below, takes torque produced by the engine s crankshaft at a particular revolution rate (input shaft) and either transforms it to a higher torque at a lower rate of revolution or, in the case of overdrive, to a lower torque at an even higher rate of revolution (output shaft). Note that the input shaft is coupled to the output shaft via the counter shaft. Manual transmissions typically transform about 95% of the input shaft power to output shaft power. For a 345 cubic inch (5.7-liter) Chrysler Hemi engine that input shaft power is due to 555 N-m of torque at 3950 rpm. Sketch the power flows considering the transmission as the system. Assume stead state operation and determine where the 5% lost power goes.
HW-3: Due by 5:00 pm EDT on Monday 18 June 2018 to GradeScope. In regions where there is no electricity, hand pumps are used to raise water from below ground level to the surface. In the example shown below, pushing downward on the force rod causes the piston rod to move upward, thereby raising the piston. When the piston begins to move upward the check valve closes and a volume of water equal to the piston cross section area (4 cm diameter) times its vertical rise (16 cm) flows through the outlet. When the piston moves downward, the check valve opens and a fresh charge of water enters. a. Sketch a free body diagram for the piston. b. What is the pressure on the piston surface when it slowly rises? Report your answer in kpa. c. What work is done to lift the water during each stroke? Report your answer in J.
HW-4: Due by 5:00 pm EDT on Monday 18 June 2018 to GradeScope. Roller compaction is a means for making ribbons of material out of loose powders. As shown below, in their simplest form they are a pair of count-rotating cylinders spaced a small distance apart. They operate continuously and steadily. The material entering the compactor is 1.2 cm thick while that exiting is 0.3 cm thick. Both have the same width, 10 cm, and the same density, 700 kg/m 3. If the powder at the roller compactor entrance moves at 0.75 m/s, a. What is the velocity at the exit? Report your answer in m/s. b. What is the mass flow rate of powder passing through the compactor? Report your answer in kg/s.
HW-5: Due by 5:00 pm EDT on Monday 18 June 2018 to GradeScope. Sketch EFDS for HW1 through HW4. Be certain to label all energy/power inflows and outflows, including those that are due to mass flowing into and out of the system. Also, be certain to identify the system, and to draw a system boundary.
HW-6: Due by 5:00 pm EDT on Wednesday 201 June 2018 to GradeScope. A rigid, insulating, and impermeable tank is shown below. It contains a partition, whose characteristics varies from problem to problem. Determine if thermodynamic equilibrium exists in each case. partition a) The left side is filled with O2 and the right side with N2; the partition is rigid and insulating, but not impermeable to mass motion through itself. b) The left side is filled with O2 at 400 K and N2 at 420 K. The partition is impermeable to mass motion through itself, and also rigid. It is not insulated. c) The left side is filled with O2 at 400 K and 3 bar while the right side is filled with N2 at 420 K and 2.4 bar. The partition is impermeable and insulated.
HW-7: Due by 5:00 pm EDT on Wednesday 20 June 2018 to GradeScope. Sketch the following processes on a p-v diagram. a. Constant specific volume of 0.01 m 3 /kg from a pressure of 1 bar to a pressure of 5 bar. b. Constant pressure of 3 bar from a specific volume of 0.01 m 3 /kg to one of 0.0025 m 3 /kg. c. An isothermal compression of air from STP to a pressure of 2.5 bar. Compute the corresponding specific boundary work in each case.
HW-8: Due by 5:00 pm EDT on Monday 25 June 2018 to GradeScope. Use the p-v and p-h charts provided on the WileyPlus site (under the Instructor- Provided heading) to identify the state for water when a. p = 1 bar and = 1000 m 3 /kg b. p = 1 bar and = 500 m 3 /kg c. p = 1 bar and = 1.67 m 3 /kg Now estimate the h and T values for each case.
HW-9: Due by 5:00 pm EDT on Monday 25 June 2018 to GradeScope. Use the water property tables provided on WileyPlus site (under the Instructor- Provided heading) to calculate h and T values for each case below. a. p = 1 bar and = 1000 m 3 /kg b. p = 1 bar and = 500 m 3 /kg c. p = 1 bar and = 1.67 m 3 /kg d. p = 1 bar and = 2.00 m 3 /kg
HW-10: Due by 5:00 pm EDT on Monday 25 June 2018 to GradeScope. Calculate the specific internal energy and specific enthalpy changes for water as it changes from 1 bar and 25 C to 100 bar and 35 C. Report your answers in kj/kg.
HW-11: Due by 5:00 pm EDT on Wednesday 27 June 2018 to GradeScope. Typical residential shower controls mix streams of hot water (140 F, or 60 C) with cold water (60 F, or 15 C) to form a stream of 40 C (104 F) water. The entire system loses energy to the surroundings at a rate of 5 kj/kg of exiting water. What is the ratio of cold water-to-hot water mass flow rates necessary to provide the 40 C water?
HW-12: Due by 5:00 pm EDT on Wednesday 25 June 2018 to GradeScope. The 0.1 kg/s exhaust from a gas turbine combustor can be modeled as air at 10 bar and 1500 K. That air enters a partially insulated turbine, where the heat loss is 15 kw, then exits at 2 bar and 900 K. Calculate the turbine shaft work and report your answer in kw.
HW-13: Due by 5:00 pm EDT on Monday 1 July 2018 to GradeScope. Cooling water enters the condenser in a home air conditioning system before exiting at a temperature 10 K higher (there is no pressure drop). A cross-flow of 0.2 kg/s of R134a enters at 5 bar and 70 C, and then exits as a saturated liquid at 4 bar. Find the water mass flow rate if the condenser is insulated. Report your answer in kg/s.
HW-14: Due by 5:00 pm EDT on Monday 1 July 2018 to GradeScope. One method for storing energy so it can be used at peak hours is by compressing air during off-peak hours and storing it in a cavern. The compressed air is then bled off during peak time and used to drive a turbine/generator set. The processes are clearly transient. The cavern volume is 50,000 m 3 with the initial air pressure and temperature being 1 bar and 27 C. The final air pressure and temperature are 20 bar and 750 K. Calculate the work required to compress atmospheric pressure air (1 bar and 27 C) to its final state in the cavern (20 bar and 750 K). Report your answer in MJ. You may assume the cavern is a good insulator, as well as neglecting kinetic and potential energy changes for the air.
HW-16: Due by 5:00 pm EDT on Monday 81 July 2018 to GradeScope. Example 5.9 from the LectureBook.
HW-17: Due by 5:00 pm EDT on Monday 8 July 2018 to GradeScope. The turbojet engine shown below has air inlet conditions of 0.b bar and 250 K at a velocity of 265 m/s. The air decelerates through the intake section until its velocity is essentially zero. What is the temperature at the end of the intake section? The compressor has a pressure ratio (poutlet/pinlet) = 20 and an exit temperature of 600 K. What is the compressor exit pressure and temperature? The combustor exit temperature is 1750 K. All the turbine haft power goes to driving the compressor. What is the turbine exit temperature? Finally, the nozzle exit pressure and temperature are 0.3 bar and 850 K, respectively. What is the nozzle exit velocity?
HW-18: Due by 5:00 pm EDT on Monday 9 July 2018 to GradeScope. A 5 kg block of Fe is dropped into a very large vat of water. The Fe and water initial temperatures are 95 and 25 C, respectively. The Fe final temperature is 25 C and the water can be treated as a thermal reservoir. Take the water to be the system and determine the entropy generation. Report your answer in kj/k.
HW-19: Due by 5:00 pm EDT on Monday 9 July 2018 to GradeScope. There is no HW 19. Enjoy!
HW-20: Due by 5:00 pm EDT on Wednesday 11 July 2018 to GradeScope. A 5 kg block of Fe is dropped into a 100 kg vat of water. The Fe and water initial temperatures are 95 and 25 C, respectively. Find the final water-fe temperature. Compute the entropy changes for the Fe block and for the water.
HW-21: Due by 5:00 pm EDT on Wednesday 11 July 2018 to GradeScope. Calculate the entropy changes for each of the components in the gas turbine engine problem (HW 17).
HW-25: Due by 5:00 pm EDT on Monday 23 July 2018 to GradeScope. Return to HW 17 and calculate the nozzle isentropic efficiency and specific entropy generation.
HW-27: Due by 5:00 pm EDT on Monday 23 July 2018 to GradeScope. Return to HW 17 and change the turbine exit T to 700 K. Then calculate the specific isentropic efficiency and entropy generation for the compressor and turbine. Recall that all the turbine work goes into the compressor. In addition, you may assume adiabatic flow through the compressor and turbine.
HW-28: Due by 5:00 pm EDT on Monday 23 July 2018 to GradeScope. Calculate isentropic efficiencies for the rotating machinery devices given in Example 7.2 from the LectureBook
HW-29: Due by 5:00 pm EDT on Monday 23 July 2018 to GradeScope. Example 7.5 from the LectureBook
HW-30: Due by 5:00 pm EDT on Wednesday 25 July 2018 to GradeScope. The example on page 10 of LectureBook Chapter 9. Water flows out of the condenser as Saturated Liquid.
HW-31: Due by 5:00 pm EDT on Wednesday 15 July 2018 to GradeScope. The example on page 12 of LectureBook Chapter 9. The pressure in the reheat section is 1.57 MPa.