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 absorption process and 0.80 at the end. Show the cycle on a T-s diagram relative to saturation lines, and determine (a) the coefficient of performance, (b) the condenser and evaporator pressures, and (c) the net work input.
> 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
> Repeat Prob. 10–28 for umax = 6 m/s. Data from Prob. 10-28: In regions far from the entrance, fluid flow through a circular pipe is one dimensional, and the velocity profile for laminar flow is given by u(r) = umax(1 −
> Rooms with floor areas of up to 15 m2 are cooled adequately by window air conditioners whose cooling capacity is 5000 Btu/h. Assuming the COP of the air conditioner to be 3.5, determine the rate of heat gain of the room, in Btu/h, when the air conditione
> In regions far from the entrance, fluid flow through a circular pipe is one dimensional, and the velocity profile for laminar flow is given by u(r) = umax(1 − r 2/R2), where R is the radius of the pipe, r is the radial distance from the
> 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 and 300 kPa, respectively. If the net work output per cycle is 0.5 kJ, determi
> For flow over a plate, the variation of velocity with vertical distance y from the plate is given as u(y) = ay − by2 where a and b are constants. Obtain a relation for the wall shear stress in terms of a, b, and μ.
> A steam power plant operates on an ideal Rankine cycle with two stages of reheat and has a net power output of 75 MW. Steam enters all three stages of the turbine at 550°C. The maximum pressure in the cycle is 10 MPa, and the minimum pressure is 30 kPa.
> A 50-cm × 30-cm × 20-cm block weighing 150 N is to be moved at a constant velocity of 1.10 m/s on an inclined surface with a friction coefficient of 0.27. (a) Determine the force F that needs to be applied in the horizontal dire
> A health magazine reported that physicians measured 100 adults’ blood pressure using two different arm positions: parallel to the body (along the side) and perpendicular to the body (straight out). Readings in the parallel position were up to 10 percent
> Consider a steam power plant operating on the ideal Rankine cycle with reheat between the pressure limits of 30 MPa and 10 kPa with a maximum cycle temperature of 700°C and a moisture content of 5 percent at the turbine exit. For a reheat temperature of
> Reconsider Prob. 10–24. Using appropriate software, investigate the effect of oil film thickness on the torque transmitted. Let the film thickness vary from 0.1 mm to 10 mm. Plot your results, and state your conclusions. Data from Prob
> Steam enters the turbine of a steam power plant that operates on a simple ideal Rankine cycle at a pressure of 6 MPa, and it leaves as a saturated vapor at 7.5 kPa. Heat is transferred to the steam in the boiler at a rate of 40,000 kJ/s. Steam is cooled
> The clutch system shown in Fig. P10–24 is used to transmit torque through a 2-mm-thick oil film with μ = 0.38 N⋅s/m2 between two identical 30-cm-diameter disks. When the driving shaft rotates at a speed o
> Feedwater at 4000 kPa is heated at a rate of 6 kg/s from 200°C to 245°C in a closed feedwater heater of a regenerative Rankine cycle. Bleed steam enters this unit at 3000 kPa with a quality of 90 percent and leaves as a saturated liquid. Calculate the ra
> Helium is used as the working fluid in a Brayton cycle with regeneration. The pressure ratio of the cycle is 8, the compressor inlet temperature is 300 K, and the turbine inlet temperature is 1800 K. The effectiveness of the regenerator is 75 percent. De
> A rotating viscometer consists of two concentric cylinders—an inner cylinder of radius Ri rotating at angular velocity (rotation rate) ωi, and a stationary outer cylinder of inside radius Ro. In the tiny gap between the two c
> Consider a simple ideal Brayton cycle operating between the temperature limits of 300 and 1250 K. Using constant specific heats at room temperature, determine the pressure ratio for which the compressor and the turbine exit temperatures of air are equal.
> A thin 30-cm × 30-cm flat plate is pulled at 3 m/s horizontally through a 3.6-mm-thick oil layer sandwiched between two plates, one stationary and the other moving at a constant velocity of 0.3 m/s, as shown in Fig. P10–22.
> An ideal dual cycle has a compression ratio of 14 and uses air as the working fluid. At the beginning of the compression process, air is at 14.7 psia and 120°F, and it occupies a volume of 98 in3. During the heat-addition process, 0.6 Btu of heat is tran
> Explain why some people experience nose bleeding and some others experience shortness of breath at high elevations.
> The viscosity of a fluid is to be measured by a viscometer constructed of two 75-cm-long concentric cylinders. The outer diameter of the inner cylinder is 15 cm, and the gap between the two cylinders is 1 mm. The inner cylinder is rotated at 300 rpm, and
> A typical hydrocarbon fuel produces 43,000 kJ/kg of heat when used in a spark-ignition engine. Determine the compression ratio required for an ideal Otto cycle to use 0.039 g of fuel to produce 1 kJ of work. Use constant specific heats at room temperatur
> Consider the flow of a fluid with viscosity μ through a circular pipe. The velocity profile in the pipe is given as u(r) = umax(1 − rn/Rn), where umax is the maximum flow velocity, which occurs at the centerline; r is the
> A four-cylinder, four-stroke, spark-ignition engine operates on the ideal Otto cycle with a compression ratio of 11 and a total displacement volume of 1.8 L. The air is at 90 kPa and 50°C at the beginning of the compression process. The heat input is 0.
> Define incompressible flow and incompressible fluid. Must the flow of a compressible fluid necessarily be treated as compressible?
> Repeat Prob. 9–169 using argon as the working fluid. Data from Prob. 9-169: Consider an engine operating on the ideal Diesel cycle with air as the working fluid. The volume of the cylinder is 1200 cm3 at the beginning of the compression process, 75 cm3
> The dynamic viscosity of carbon dioxide at 50°C and 200°C are 1.612 × 10–5 Pa·s and 2.276 ×10–5 Pa·s, respectively. Determine the constants a and b of the Sutherland correlation for carbon dioxide at atmospheric pressure. Then predict the viscosity of ca
> Repeat Prob. 9–16E using constant specific heats at room temperature. Data from Prob. 9-16: An air-standard cycle with variable specific heats is executed in a closed system and is composed of the following four processes: 1-2 v = constant heat addition
> The viscosity of a fluid is to be measured by a viscometer constructed of two 5-ft-long concentric cylinders. The inner diameter of the outer cylinder is 6 in, and the gap between the two cylinders is 0.035 in. The outer cylinder is rotated at 250 rpm, a
> Consider an engine operating on the ideal Diesel cycle with air as the working fluid. The volume of the cylinder is 1200 cm3 at the beginning of the compression process, 75 cm3 at the end, and 150 cm3 after the heat-addition process. Air is at 17°C and 1
> What is the difference between gage pressure and absolute pressure?
> A Diesel cycle has a compression ratio of 22 and begins its compression at 85 kPa and 15°C. The maximum cycle temperature is 1200°C. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using (a) constant specific heats at r
> Consider two identical small glass balls dropped into two identical containers, one filled with water and the other with oil. Which ball will reach the bottom of the container first? Why?
> An Otto cycle with a compression ratio of 8 begins its compression at 94 kPa and 10°C. The maximum cycle temperature is 900°C. Utilizing air standard assumptions, determine the thermal efficiency of this cycle using (a) constant specific heats at room te
> How does the kinematic viscosity of (a) liquids and (b) gases vary with temperature?
> A Carnot cycle is executed in a closed system and uses 0.0025 kg of air as the working fluid. The cycle efficiency is 60 percent, and the lowest temperature in the cycle is 300 K. The pressure at the beginning of the isentropic expansion is 700 kPa, and
> What is viscosity? What is the cause of it in liquids and in gases? Do liquids or gases have higher dynamic viscosities?
> Repeat Prob. 9–164 using constant specific heats at room temperature. Data from Prob. 9-164: An air-standard cycle with variable specific heats is executed in a closed system with 0.003 kg of air, and it consists of the following three processes: 1-2 Is
> What is a Newtonian fluid? Is water a Newtonian fluid?
> An air-standard cycle with variable specific heats is executed in a closed system with 0.003 kg of air, and it consists of the following three processes: 1-2 Isentropic compression from 100 kPa and 27°C to 700 kPa 2-3 P = constant heat addition to initia
> In a piping system, the water temperature remains under 30°C. Determine the minimum pressure allowed in the system to avoid cavitation.
> Heated air is at 150°C. What is the temperature of this air in °F?
> What is the difference between pound-mass and pound-force?
> Why does a bicyclist pick up speed on a downhill road even when he is not pedaling? Does this violate the conservation of energy principle?
> The president of Circle H assigned you to perform a complete investigation to determine the causes of certain quality problems and to recommend appropriate corrective action. You have authority to talk to any other person within the company. The early st
> The Cincinnati Water Works (CWW) serves approximately 1 million customers.59 Its billing system allows customer service representatives (CSRs) to retrieve information from customer accounts quickly using almost any piece of data such as customer name, ad
> Legal Sea Foods operates several restaurants and fish markets in the Boston area and other East Coast locations. The company’s standards of excellence mandate that it serves only the freshest, highest quality seafood. It guarantees the quality by buying
> How can a manager effectively balance the three key components of a service system design?
> Refer to Example 5.1 and Figure 5.3: Example 5.1: Suppose that a hospital wants to design a process for administering medication to a patient. Clearly, the last subprocess is “patient receives medicine.” The input to
> List some of the common processes that your college or university has, and with which you interact. How might these processes be improved?
> Provide some examples of processes that are repeat able and measurable and some that are not.
> Identify some of the key processes associated with the following business activities for a typical company: sales and marketing, supply chain management, managing information technology, and managing human resources.
