What is the no-slip condition? What causes it?
> A stationary gas-turbine power plant operates on a simple ideal Brayton cycle with air as the working fluid. The air enters the compressor at 95 kPa and 290 K and the turbine at 760 kPa and 1100 K. Heat is transferred to air at a rate of 35,000 kJ/s. Det
> A simple ideal Brayton cycle with air as the working fluid has a pressure ratio of 10. The air enters the compressor at 520 R and the turbine at 2000 R. Accounting for the variation of specific heats with temperature, determine (a) the air temperature at
> How do the inefficiencies of the turbine and the compressor affect (a) the back work ratio and (b) the thermal efficiency of a gas-turbine engine?
> Why are the back work ratios relatively high in gas-turbine engines?
> What is the back work ratio? What are typical back work ratio values for gas-turbine engines?
> For fixed maximum and minimum temperatures, what is the effect of the pressure ratio on (a) the thermal efficiency and (b) the net work output of a simple ideal Brayton cycle?
> What four processes make up the simple ideal Brayton cycle?
> What does the area enclosed by the cycle represent on a P-v diagram? How about on a T-s diagram?
> How would you define a system to determine the temperature rise created in a lake when a portion of its water is used to cool a nearby electrical power plant?
> Repeat Prob. 9–58E if the compression ratio is reduced to 12. Data from Prob. 9-58: An air-standard dual cycle has a compression ratio of 20 and a cutoff ratio of 1.3. The pressure ratio during the constant volume heat addition process is 1.2. Determine
> An air-standard dual cycle has a compression ratio of 20 and a cutoff ratio of 1.3. The pressure ratio during the constant volume heat addition process is 1.2. Determine the thermal efficiency, amount of heat added, and the maximum gas pressure and tempe
> Repeat Prob. 9–56 using nitrogen as the working fluid. Data from Prob. 9-56: A four-cylinder, two-stroke 2.4-L diesel engine that operates on an ideal Diesel cycle has a compression ratio of 22 and a cutoff ratio of 1.8. Air is at 70°C and 97 kPa at the
> A four-cylinder, two-stroke 2.4-L diesel engine that operates on an ideal Diesel cycle has a compression ratio of 22 and a cutoff ratio of 1.8. Air is at 70°C and 97 kPa at the beginning of the compression process. Using the cold-air-standard assumptions
> Reconsider Prob. 9–54. Using appropriate software, study the effect of varying the compression ratio from 14 to 24. Plot the net work output, mean effective pressure, and thermal efficiency as a function of the compression ratio. Plot the T-s and P-v dia
> Repeat Prob. 9–53, but replace the isentropic expansion process with a polytropic expansion process with the polytropic exponent n = 1.35. Use variable specific heats. Data from Prob. 9-53: An ideal diesel engine has a compression ratio of 20 and uses a
> An ideal diesel engine has a compression ratio of 20 and uses air as the working fluid. The state of air at the beginning of the compression process is 95 kPa and 20°C. If the maximum temperature in the cycle is not to exceed 2200 K, determine (a) the th
> An ideal Diesel cycle has a maximum cycle temperature of 2000°C. The state of the air at the beginning of the compression is P1 = 95 kPa and T1 = 15°C. This cycle is executed in a four-stroke, eight-cylinder engine with a cylinder bore of 10 cm and a pis
> Repeat Prob. 9–50E using constant specific heats at room temperature. Data from Prob. 9-50: An air-standard Diesel cycle has a compression ratio of 18.2. Air is at 120°F and 14.7 psia at the beginning of the compression process and at 3200 R at the end
> An air-standard Diesel cycle has a compression ratio of 18.2. Air is at 120°F and 14.7 psia at the beginning of the compression process and at 3200 R at the end of the heat-addition process. Accounting for the variation of specific heats with temperature
> A pressure gage connected to a tank reads 50 psi at a location where the barometric reading is 29.1 in Hg. Determine the absolute pressure in the tank. Take ρHg = 848.4 lbm/ft3.
> How are the combustion and exhaust processes modeled under the air-standard assumptions?
> Repeat Prob. 9–48 using constant specific heats at room temperature. Data from Prob. 9-48: An air-standard Diesel cycle has a compression ratio of 16 and a cutoff ratio of 2. At the beginning of the compression process, air is at 95 kPa and 27°C. Accoun
> An air-standard Diesel cycle has a compression ratio of 16 and a cutoff ratio of 2. At the beginning of the compression process, air is at 95 kPa and 27°C. Accounting for the variation of specific heats with temperature, determine (a) the temperature aft
> Rework Prob. 9–46 when the isentropic compression efficiency is 90 percent and the isentropic expansion efficiency is 95 percent. Data from Prob. 9-46: An ideal Diesel cycle has a compression ratio of 18 and a cutoff ratio of 1.5. Determine the maximum
> An ideal Diesel cycle has a compression ratio of 18 and a cutoff ratio of 1.5. Determine the maximum air temperature and the rate of heat addition to this cycle when it produces 200 hp of power; the cycle is repeated 1200 times per minute; and the state
> Do diesel or gasoline engines operate at higher compression ratios? Why?
> If the pressure of a substance is increased during a boiling process, will the temperature also increase or will it remain constant? Why?
> For a specified compression ratio, is a diesel or gasoline engine more efficient?
> Does water boil at higher temperatures at higher pressures? Explain.
> What is the cutoff ratio? How does it affect the thermal efficiency of a Diesel cycle?
> The maximum safe air pressure of a tire is typically written on the tire itself. The label on a tire indicates that the maximum pressure is 35 psi (gage). Express this maximum pressure in kPa.
> What is the net force acting on a car cruising at a constant velocity of 70 km/h (a) on a level road and (b) on an uphill road?
> What is vapor pressure? How is it related to saturation pressure?
> How does the ideal Diesel cycle differ from the ideal Otto cycle?
> What is a boundary layer? What causes a boundary layer to develop?
> How does a diesel engine differ from a gasoline engine?
> Even though steel is about 7 to 8 times denser than water, a steel paper clip or razor blade can be made to float on water! Explain and discuss. Predict what would happen if you mix some soap with the water.
> When we double the compression ratio of an ideal Otto cycle, what happens to the maximum gas temperature and pressure when the state of the air at the beginning of the compression and the amount of heat addition remain the same? Use constant specific hea
> A fluid between two very long parallel plates is heated in a way that its viscosity decreases linearly from 0.90 Paâ‹…s at the lower plate to 0.50 Paâ‹…s at the upper plate. The spacing between the two plates is 0.4 mm. Th
> How does the thermal efficiency of an ideal cycle, in general, compare to that of a Carnot cycle operating between the same temperature limits?
> Some rocks or bricks contain small air pockets in them and have a spongy structure. Assuming the air spaces form columns of an average diameter of 0.006 mm, determine how high water can rise in such a material. Take the surface tension of the air–water i
> Repeat Prob. 9–38E using argon as the working fluid. Data from Prob. 9-38: An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 540 and 2400 R. Accounting for the variation
> A vacuum gage connected to a chamber reads 35 kPa at a location where the atmospheric pressure is 92 kPa. Determine the absolute pressure in the chamber.
> A 10-cm-diameter cylindrical shaft rotates inside a 50-cm-long, 10.3-cm-diameter bearing. The space between the shaft and the bearing is completely filled with oil whose viscosity at anticipated operating temperature is 0.300 N⋅s/m2. Determine the power
> An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 540 and 2400 R. Accounting for the variation of specific heats with temperature, determine (a) the amount of heat transf
> Derive a relation for the capillary rise of a liquid between two large parallel plates a distance t apart inserted into the liquid vertically. Take the contact angle to be f.
> A six-cylinder, 4-L spark-ignition engine operating on the ideal Otto cycle takes in air at 90 kPa and 20°C. The minimum enclosed volume is 15 percent of the maximum enclosed volume. When operated at 2500 rpm, this engine produces 90 hp. Determine the ra
> The variation of the dynamic viscosity of water with absolute temperature is given as Using these tabulated data, develop a relation for viscosity in the form of μ = μ(T) = A + BT + CT2 + DT3 + ET4. Using the relation develope
> An ideal Otto cycle has a compression ratio of 7. At the beginning of the compression process, P1 = 90 kPa, T1 = 27°C, and V1 = 0.004 m3. The maximum cycle temperature is 1127°C. For each repetition of the cycle, calculate the heat rejection and the net-
> A spark-ignition engine has a compression ratio of 10, an isentropic compression efficiency of 85 percent, and an isentropic expansion efficiency of 95 percent. At the beginning of the compression, the air in the cylinder is at 13 psia and 60°F. The maxi
> The analysis of a propeller that operates in water at 60°F shows that the pressure at the tips of the propeller drops to 0.1 psia at high speeds. Determine if there is a danger of cavitation for this propeller.
> Repeat Prob. 9–32 using constant specific heats at room temperature. Data from Prob. 9-32: An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 750 kJ/kg of heat is transferred to
> A can of soft drink at room temperature is put into the refrigerator so that it will cool. Would you model the can of soft drink as a closed system or as an open system? Explain.
> The diameter of one arm of a U-tube is 5 mm while the other arm is large. If the U-tube contains some water, and both surfaces are exposed to atmospheric pressure, determine the difference between the water levels in the two arms.
> Reconsider Prob. 9–32. Using appropriate software, study the effect of varying the compression ratio from 5 to 10. Plot the net work output and thermal efficiency as a function of the compression ratio. Plot the T-s and P-v diagrams for the cycle when th
> Consider a 55-cm-long journal bearing that is lubricated with oil whose viscosity is 0.1 kg/m⋅s at 20°C at the beginning of operation and 0.008 kg/m⋅s at the anticipated steady operating temperature of 80°C. The diameter of the shaft is 8 cm, and the ave
> An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 750 kJ/kg of heat is transferred to air during the constant volume heat addition process. Taking into account the variation of s
> Nutrients dissolved in water are carried to upper parts of plants by tiny tubes partly because of the capillary effect. Determine how high the water solution will rise in a tree in a 0.0026-mm diameter tube as a result of the capillary effect. Treat the
> Reconsider Prob. 9–30E. Determine the rate of heat addition and rejection for this ideal Otto cycle when it produces 140 hp. Data from Prob. 9-30: Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid; its state
> Contrary to what you might expect, a solid steel ball can float on water due to the surface tension effect. Determine the maximum diameter of a steel ball that would float on water at 10°C. What would your answer be for an aluminum ball? Take the densiti
> Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid; its state at the beginning of the compression is 14 psia and 60°F; its temperature at the end of the combustion is 1500°F; and its compression ratio is 9. Us
> A capillary tube is immersed vertically in a water container. Knowing that water starts to evaporate when the pressure drops below 2 kPa, determine the maximum capillary rise and tube diameter for this maximum-rise case. Take the contact angle at the inn
> Why is the Carnot cycle not suitable as an ideal cycle for all power-producing cyclic devices?
> A manometer measures a pressure difference as 40 inches of water. What is this pressure difference in pound force per square inch, psi?
> A 0.018-in-diameter glass tube is inserted into mercury, which makes a contact angle of 140° with glass. Determine the capillary drop of mercury in the tube at 68°F.
> What is the difference between fuel-injected gasoline engines and diesel engines?
> A capillary tube of 1.2 mm diameter is immersed vertically in water exposed to the atmosphere. Determine how high water will rise in the tube. Take the contact angle at the inner wall of the tube to be 6° and the surface tension to be 1.00 N/m.
> How is the rpm (revolutions per minute) of an actual four-stroke gasoline engine related to the number of thermodynamic cycles? What would your answer be for a two-stroke engine?
> The surface tension of a liquid is to be measured using a liquid film suspended on a U-shaped wire frame with an 8-cm-long movable side. If the force needed to move the wire is 0.030 N, determine the surface tension of this liquid in air.
> An ideal Otto cycle with a specified compression ratio is executed using (a) air, (b) argon, and (c) ethane as the working fluid. For which case will the thermal efficiency be the highest? Why?
> Consider a 0.15-mm-diameter air bubble in a liquid. Determine the pressure difference between the inside and outside of the air bubble if the surface tension at the air–liquid interface is (a) 0.080 N/m and (b) 0.12 N/m.
> Why are high compression ratios not used in spark-ignition engines?
> What is forced flow? How does it differ from natural flow? Is flow caused by winds forced or natural flow?
> How does the thermal efficiency of an ideal Otto cycle change with the compression ratio of the engine and the specific heat ratio of the working fluid?
> The absolute pressure in a compressed air tank is 200 kPa. What is this pressure in psia?
> A 1.6-mm-diameter tube is inserted into an unknown liquid whose density is 960 kg/m3, and it is observed that the liquid rises 5 mm in the tube, making a contact angle of 15°. Determine the surface tension of the liquid.
> How do the efficiencies of the ideal Otto cycle and the Carnot cycle compare for the same temperature limits? Explain.
> A 2.4-in-diameter soap bubble is to be enlarged by blowing air into it. Taking the surface tension of soap solution to be 0.0027 lbf/ft, determine the work input required to inflate the bubble to a diameter of 2.7 in.
> Are the processes that make up the Otto cycle analyzed as closed-system or steady-flow processes? Why?
> Determine the gage pressure inside a soap bubble of diameter (a) 0.2 cm and (b) 5 cm at 20°C.
> What four processes make up the ideal Otto cycle?
> Is the capillary rise greater in small- or large-diameter tubes?
> Consider a Carnot cycle executed in a closed system with 0.6 kg of air. The temperature limits of the cycle are 300 and 1100 K, and the minimum and maximum pressures that occur during the cycle are 20 and 3000 kPa. Assuming constant specific heats, deter
> Consider a soap bubble. Is the pressure inside the bubble higher or lower than the pressure outside?
> The thermal energy reservoirs of an ideal gas Carnot cycle are at 1240°F and 40°F, and the device executing this cycle rejects 100 Btu of heat each time the cycle is executed. Determine the total heat supplied to and the total work produced by this cycle
> Consider two identical fans, one at sea level and the other on top of a high mountain, running at identical speeds. How would you compare (a) the volume flow rates and (b) the mass flow rates of these two fans?
> A small-diameter tube is inserted into a liquid whose contact angle is 110°. Will the level of liquid in the tube be higher or lower than the level of the rest of the liquid? Explain.
> What is the difference between air-standard assumptions and the cold-air-standard assumptions?
> What is the capillary effect? What is its cause? How is it affected by the contact angle?
> Repeat Prob. 9–18 using helium as the working fluid. Data from Prob. 9-18: An air-standard Carnot cycle is executed in a closed system between the temperature limits of 350 and 1200 K. The pressures before and after the isothermal compression are 150 an
> What is surface tension? What is its cause? Why is the surface tension also called surface energy?
> Reconsider Prob. 9–184. Using appropriate software, investigate the effect of evaporator pressure on the COP and the power input. Let the evaporator pressure vary from 120 to 380 kPa. Plot the COP and the power input as functions of evaporator pressure,
> A rotating viscometer consists of two concentric cylinders—a stationary inner cylinder of radius Ri and an outer cylinder of inside radius Ro rotating at angular velocity (rotation rate) ωo. In the tiny gap between the two cy
> A large refrigeration plant is to be maintained at −15°C, and it requires refrigeration at a rate of 100 kW. The condenser of the plant is to be cooled by liquid water, which experiences a temperature rise of 8°C as it flows over the coils of the condens
> A frustum-shaped body is rotating at a constant angular speed of 200 rad/s in a container filled with SAE 10W oil at 20°C (μ = 0.100 Pa⋅s), as shown in Fig. P10–30. If the thickness of the oil
> A heat pump that operates on the ideal vapor compression cycle with refrigerant-134a is used to heat a house. The mass flow rate of the refrigerant is 0.25 kg/s. The condenser and evaporator pressures are 1400 and 320 kPa, respectively. Show the cycle on
> Someone claims that the absolute pressure in a liquid of constant density doubles when the depth is doubled. Do you agree? Explain.
> Consider the flow of air over the wings of an aircraft. Is this flow internal or external? How about the flow of gases through a jet engine?
> Consider an ice-producing plant that operates on the ideal vapor-compression refrigeration cycle and uses refrigerant 134a as the working fluid. The refrigeration cycle operating conditions require an evaporator pressure of 140 kPa and the condenser pres
> Consider a steady-flow Carnot refrigeration cycle that uses refrigerant-134a as the working fluid. The maximum and minimum temperatures in the cycle are 30 and −20°C, respectively. The quality of the refrigerant is 0.15 at the beginning of the heat absor
