Lesson 23 1. (10 pt) Write the equation for the thermal efficiency of a Carnot heat engine below: T η = T 1 L H 2. (10 pt) Can the thermal efficiency of an actual engine ever exceed that of an equivalent Carnot engine? Yes/no 3. (10 pt) Write the equation for the COP of Carnot refrigerator below: CO P r TL = T T H L 4. (10 pt) Write the equation for the COP of a Carnot heat pump below. COP hp TH = T T H L 5. (20pt) List the completely reversible processes of a Carnot cycle below: (A) Isothermal expansion (B) Adiabatic expansion (C) Isothermal compression (D) Adiabatic compression 6. (10 pt) Write the inequality of Clausius below: δq T 0 7. (5 pt) The inequality of Clausius is consistent with the Kelvin-Planck statement of the Second Law. 8. (15 pt) Write the inequality of Clausius for an internally reversible cycle below. δq T = 0 9. The δq of an actual heat engine must be positive/zero/negative. T
Lesson 22 1. (10 pt) What is the upper limit on the thermal efficiency of a reversible heat engine whose energy reservoirs are at 427 o C and 27 o C? 57% 2. (15 pt) The problem with many alternative energy proposals is with the quality of the energy. 3. (15 pt) Write the equation for the thermal efficiency of a reversible heat engine in terms of the reservoir temperatures below. h = 1 T L T H 4. (10pt) The coefficient of performance of an actual heat pump must be less than or equal to that of an equivalent Carnot heat pump. 5. (20 pt) You wish to use a heat pump to heat a house (T = 72 o F) using ground water (T = 50 o F) as a thermal reservoir. What is the maximum COP you can achieve? 24.2 6. (10 pt) The actual heat pump COP of question 5 less than/greater than/equal to the number you calculated. 7. (10 pt) Irreversibilities cause the performance index of cyclic devices to be less than that of equivalent reversible devices. 8. (10 pt) It is possible to create a cyclic device which receives heat from a thermal reservoir and only produces work. True/false
Lesson 21 1. (10) The thermal efficiency of a heat engine can never exceed 100%. 2. (15 pt) Write the relationship between heat transfers and thermodynamic temperature for a reversible heat engine below. 3. (5 pt) The International Temperature scale agrees/disagrees with the thermodynamic temperature scale. 4. (20 pt) Write the second law corollaries for heat pumps below: (A) The COP is always less than that of an equivalent reversible heat pump (B) All reversible heat pumps operating between the same two thermal reservoirs have the same COP 5. (10 pt) A reversible heat engine uses two thermal reservoirs at 500 K and 300 K. Heat is added to this engine at a rate of 100 kw. What is the rate at which this engine rejects heat? 60 kw 6. (10 pt) A reversible heat pump uses two thermal reservoirs at 500 K and 300 K. Heat is added to this engine at a rate of 100 kw. What is the rate at which this engine rejects heat? 167 kw 7. (5 pt) There is no upper limit on the COP of a heat pump? True/false 8. (5 pt) There is no upper limit on the COP of a heat engine? True/false 9. (5 pt) All heat engines that use the same thermal reservoirs have the same thermal efficiency? True/false 10. (5 pt) All heat pumps that use the same thermal reservoirs have the same thermal efficiency? True/false 11. (10 pt) Heat is added to a reversible heat engine at a rate of 1 MW from a thermal reservoir whose temperature is 900 K. If this engine rejects heat at a rate of 300 kw, what is the temperature of the thermal sink? 300 K
Lesson 19 1. (10 pt) A thermal energy reservoir can transfer heat without changing its temperature. 2. (5 pt) A thermal energy reservoir from which heat is removed is called a source reservoir. 3. (5 pt) A thermal energy reservoir to which heat is added is called a sink reservoir. 4. (5 pt) The second law is a consequence of the fact that processes only occur in certain directions. 5. (5 pt) Is it possible to operate a heat engine without any heat rejection? No 6. (15 pt) Write the Kelvin-Planck statement of the second law below: It is impossible for any device that operates in a cycle to receive heat from a single reservoir and produce a net amount of work. 7. (15 pt) Write the Clausius statement of the second law below: It is impossible for any system to operate such a way that the sole result would be an energy transfe by heat from a cooler to a hotter body 8. (5 pt) The Kelvin-Planck statement limits the thermal efficiency to less than 100%. 9. (5 pt) A refrigerator or heat pump rejects heat to a high-temperature energy reservoir. 10. (5 pt) The desired output of a refrigerator is Q l while that of a heat pump is Q h. 11. (10 pt) Write the definition of a reversible process below. a process that can be reversed without leaving any trace in the surroundings 12. (15 pt) List 3 things that make a process irreversible below. Friction Unrestrained expansion Heat transfer over a finite temperature difference
Lesson 18 1. (10 pt) What working fluid property remains constant throughout a throttling device? ENTHALPY 2. (10 pt) What working fluid property decreases as it passes through a throttle device? pressure 3. (10 pt) What property remains constant in a mixing device? pressure 4. (10 pt) The pressure of each stream in heat exchanger does not change? True/False 5. (10 pt) Heat exchangers can be modeled as either a multi -stream device or as two single -stream devices. 6. (5 pt) The two streams of a heat exchanger do not intermix? True/False. 7. (5 pt) The two streams of a heat exchanger must be the same fluid? True/False 8. (10 pt) The process experienced by the streams passing though a heat exchanger is a constant pressure process. 9. (10 pt) Both the energy and mass balance must be satisfied for all thermodynamic systems. 10. (10 pt) When an initially empty rigid tank is filled from a constant fluid property source, the final specific internal energy of the fluid in the tank must equal the specific enthalpy of the source. 11. (10 pt) In order to maintain the temperature constant while empting a rigid container, you must add work and/or heat.
Lesson 17 1. (10 pt) The process experienced by the stream passing though a pipe or duct is a constant pressure process. 2. (10 pt) The first law for a multi-stream mixing chamber must be written on a per unit mass/rate basis. 3. (10 pt) The first law for a pipe or duct can be written on either a rate or per unit mass basis. 4. (20 pt) Write the general first law equation below. Q W + m(h + ke + pe) m(h + ke + pe) = (me) 2 (me) 1 in 5. (5 pt) Per unit mass (i.e., specific) quantities can be converted to rate quantities in open iout systems by multiplying them by the mass flow rate. 6. (10 pt) According to the first law, nozzles increase kinetic energy while decreasing enthalpy of a fluid. 7. (10 pt) Diffusers do not transfer heat or work. 8. (15 pt) Turbines are adiabatic machines that produce work by decreasing the enthalpy of the working fluid as it passes through the turbine. 9. (5 pt) The kinetic and potential energies of a turbine can typically be neglected. 10. (10 pt) Compressors decrease/increase the specific volume of the working fluid by applying work to it. 11. (5 pt) What working fluid property remains constant throughout a throttling device? enthalpy 12. (5 pt) What working fluid property decrease as it passes through a throttle device? pressure 13. (5 pt) What property remains constant in a mixing device? pressure 14. (5 pt) The pressure of each stream in heat exchanger does not change? True/False 15. (10 pt) Heat exchangers can be modeled as either a multi-stream device or as two single-stream devices. 16. (5 pt) The two streams of a heat exchanger do not intermix? True/False. 17. (5 pt) The two streams of a heat exchanger must be the same fluid? True/False 18. (10 pt) The process experienced by the streams passing though a heat exchanger is a constant pressure process.
19. (10 pt) Write the general energy balance equation below. m in m out = m 2 m 1 20. (10 pt) Both the energy and mass balance must be satisfied for all thermodynamic systems. 21. (10 pt) When an initially empty rigid tank is filled from a constant fluid property source, the final specific internal energy of the fluid in the tank must equal the specific enthalpy of the source. 22. (10 pt) In order to maintain the temperature constant while empting a rigid container, you must add work and/or heat.
ME 2322 Thermodynamics I Lesson 16 1. (15 pt) Flow work represents the work required to move fluid across an open-system boundary. 2. (5 pt) The equation for the flow work is: w flow = Pv 3. (10 pt) Enthalpy is the sum of the internal energy and flow work. 4. (15 pt) The rate at which energy is transported through an opening in a uniform-flow opensystem is given by: E = m (h + V2 2 + gz) 5. (15 pt) Energy can be transferred into (out of) a steady-flow system by heat, work, and mass. 6. (15 pt) The first law for a steady-flow system can be written in rate form as: 7. (15) The first law reduces to: Q W = m (h + ke + pe) m (h + ke + pe) out ın q w = h 2 h 1 For a steady-state, single-stream system on a per unit mass basis and negligible kinetic and potential energies. 8. (5 pt) The symbol W represents power. 9. (5 pt) the symbol Q represents rate of heat transfer.f
ME 2322 Thermodynamics I Lesson 15 1. (5pt) Fluid properties in a steady-state system can change with location, but not with time. 2. (5 pt) Uniform (one-dimensional) flow implies that fluid properties are the same/different across any inlets or outlets for a steady-flow system. 3. (10pt) The mass balance for a uniform-flow, single-stream steady-state system can be written as A 1 V 1 /v 1 = A 2 V 2 /v 2? True/false 4. (10 pt) In a steady-state system, all changes with time are zero. 5. (15 pt)incompressible oil enters a nozzle with velocity V 1 and area A 1. It leaves through an area that is ½ the size of A 1. The oil velocity at the exit is double that at the entrance. 6. (15 pt)incompressible oil enters a nozzle with velocity V 1 and area A 1. It leaves through an area that is three times the size of A 1. The oil velocity at the exit is 1/3 that at the entrance. 7. (15 pt) A commercial salad dressing mixer mixes 2000 kg/hr of water with 800 kg/hr of canola oil. What is the rate of salad dressing production in kg/min? 46.7 kg/min 8. (15 pt) The mass balance for a steady-state system with multiple inlets and outlets is written as: m = m i 9. (10 pt) Subcooled liquid water (v = 0.001 m 3 /kg) enters a system with a volume flow rate of 25 m 3 /s. What is the mass flow rate at this entrance? 25,000 kg/s o
ME 2322 Thermodynamics I Lesson 14 1. (10pt) Volume flow rates can be converted to mass flow rates by multiplying/dividing the volume flow rate by the substances specific volume. 2. (10 pt) When using a fluid velocity to calculate flow rates, you must use the velocity component perpendicular to the flow area. 3. (10pt) When the fluid area-average specific volume and velocity are used, the mass flow rate is given by: m = AV /v 4. (15 pt) The conservation of mass equation for an open system with multiple inlets and outlets is written as: dm sys dt = m m 5. (15 pt) The general equation for the mass flow rate is: m = ρv n da A 6. (15 pt) The integral form of the conservation of mass is written as: 7. (10 pt) The term d dt V ρdv system. in out d dt ρdv = ρv nda ρv n da V i A o physically represents the rate at which mass is accumulated in the 8. (10 pt) The term i ρv n da physically represents the rate at which mass enters the system. A 9. (5 pt) When mass flows into a system and not out, the mass contained in the system must increase with time. A