Questions and Answers of Fundamentals Thermal Fluid

Water is flowing through a Venturi meter whose diameter is 7 cm at the entrance part and 4 cm at the throat. The pressure is measured to be 380 kPa at the entrance and 150 kPa at the throat.
Water flows at a rate of 0.011 m3/s in a horizontal pipe whose diameter increases from 6 to 11 cm by an enlargement section. If the head loss across the enlargement section is 0.65 m and the kinetic
A 3-m-high large tank is initially filled with water. The tank water surface is open to the atmosphere, and a sharp-edged 10-cm-diameter orifice at the bottom drains to the atmosphere through a
Reconsider Prob. 12??71. Using an appropriate software, investigate the effect of the tank height on the initial discharge velocity of water from the completely filled tank. Let the tank height vary
Reconsider Prob. 12??71. In order to drain the tank faster, a pump is installed near the tank exit. Determine the pump head input necessary to establish an average water velocity of 6.5 m/s when the
A wind tunnel draws atmospheric air at 20°C and 101.3 kPa by a large fan located near the exit of the tunnel. If the air velocity in the tunnel is 80 m/s, determine the pressure in the tunnel.
The power generated by a wind turbine is proportional to the cube of the wind velocity. Inspired by the acceleration of a fluid in a nozzle, someone proposes to install a reducer casing to capture
The water in a 25-m-deep reservoir is kept inside by a 150-m-wide wall whose cross section is an equilateral triangle, as shown in Fig. P11??49. Determine (a) The total force (hydrostatic +
A 30-ton, 4-m-diameter hemispherical dome on a level surface is filled with water, as shown in Fig. P11??48. Someone claims that he can lift this dome by making use of Pascal??s law by attaching a
A semicircular 40-ft-diameter tunnel is to be built under a 150-ft-deep, 800-ft-long lake, as shown in Fig. P11??47E. Determine the total hydrostatic force acting on the roof of the tunnel. Water
Repeat Prob. 11??45 for a total water height of 2 m. 2 m Water A Gate 3 m B
A 3-m-high, 6-m-wide rectangular gate is hinged at the top edge at A and is restrained by a fixed ridge at B. Determine the hydrostatic force exerted on the gate by the 5-m-high water and the
Reconsider Prob. 11??43. Using an appropriate software, investigate the effect of air pressure above water on the cable force. Let this pressure vary from 0.5 MPa to 15 MPa. Plot the cable force
An elastic air balloon having a diameter of 30 cm is attached to the base of a container partially filled with water at + 4°C, as shown in Fig. P11??43. If the pressure of the air above the water is
The 0.5-m-radius semi-circular gate shown in the figure is hinged through the top edge AB. Find the required force to be applied at the center of gravity to keep the gate closed. = 80 kPa (abs) alr
An air-conditioning system requires a 34-m-long section of 12-cm-diameter ductwork to be laid underwater. Determine the upward force the water will exert on the duct. Take the densities of air and
The hull of a boat has a volume of 180 m3, and the total mass of the boat when empty is 8560 kg. Determine how much load this boat can carry without sinking(a) In a lake(b) In seawater with a
It is said that Archimedes discovered his principle during a bath while thinking about how he could determine if King Hiero’s crown was actually made of pure gold. While in the bathtub, he
A 170-kg granite rock (ρ = 2700 kg/m3) is dropped into a lake. A man dives in and tries to lift the rock. Determine how much force the man needs to apply to lift it from the bottom of the lake. Do
The weight of a body is usually measured by disregarding buoyancy force applied by the air. Consider a 20-cm-diameter spherical body of density 7800 kg/m3. What is the percentage error associated
An inverted cone is placed in a water tank as shown. If the weight of the cone is 16.5 N, what is the tensile force in the cord connecting the cone to the bottom of the tank? 40 cm 10 cm 20 cm Water
A spherical shell made of a material with a density of 1600 kg/m3 is placed in water. If the inner and outer radii of the shell are R1 = 5 cm, R2 = 6 cm, determine the percentage of the shell’s
Consider a large cubic ice block floating in seawater. The specific gravities of ice and seawater are 0.92 and 1.025, respectively. If a 25-cm-high portion of the ice block extends above the surface
A 10-cm-diameter cylindrical shaft rotates inside a 40-cm-long 10.3-cm diameter bearing. The space between the shaft and the bearing is completely filled with oil whose viscosity at anticipated
Consider laminar flow of a Newtonian fluid of viscosity Î¼ between two parallel plates. The flow is one-dimensional, and the velocity profile is given as u(y) = 4umax[y/h - (y/h)2],
The variation of the dynamic viscosity of water with absolute temperature is given asT, K
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
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
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 ϕ.
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
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 20°C. What
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
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 0.024 N, determine the
A 0.03-in-diameter glass tube is inserted into kerosene at 68°F. The contact angle of kerosene with a glass surface is 26°. Determine the capillary rise of kerosene in the tube. -0.03 in
Determine the gage pressure inside a soap bubble of diameter(a) 0.2 cm(b) 5 cm at 20°C.
A 1.2-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
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
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
Is the capillary rise greater in small- or large-diameter tubes?
Consider a soap bubble. Is the pressure inside the bubble higher or lower than the pressure outside?
What is the capillary effect? What is its cause? How is it affected by the contact angle?
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 surface tension? What is its cause? Why is the surface tension also called surface energy?
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 (Î¼ = 0.100 Paˆ™s), as shown in Fig.
Repeat Prob. 10€“30 for umax= 7 m/s.In ProblemIn regions far from the entrance, fluid flow through a circular pipe is one dimensional, and the velocity profile for laminar flow is given by
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 - r2/R2), where R is the radius of the
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
The dynamic viscosities 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 Sutherland correlation for carbon
Reconsider Prob. 10€“25. Using an 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
The clutch system shown in Fig. P10€“25 is used to transmit torque through a 2-mm-thick oil film with Î¼ = 0.38 Nˆ™s/m2between two identical 30-cm-diameter disks.
A rotating viscometer consists of two concentric cylinders€”an inner cylinder of radius Rirotating at angular velocity (rotation rate) Ï‰i, and a stationary outer cylinder of
A thin 30-cm Ã— 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
Consider the flow of a fluid with viscosity Î¼ through a circular pipe. The velocity profile in the pipe is given as u(r) = umax(1 - rn/Rn), where umaxis the maximum flow velocity, which
A 50-cm Ã— 30-cm Ã— 20-cm block weighing 150 N is to be moved at a constant velocity of 0.80 m/s on an inclined surface with a friction coefficient of 0.27.(a) Determine the
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
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?
How does the dynamic viscosity of(a) Liquids and(b) Gases vary with temperature?
How does the kinematic viscosity of(a) Liquids(b) Gases vary with temperature?
What is a Newtonian fluid? Is water a Newtonian fluid?
What is viscosity? What is the cause of it in liquids and in gases? Do liquids or gases have higher dynamic viscosities?
The analysis of a propeller that operates in water at 20°C shows that the pressure at the tips of the propeller drops to 2 kPa at high speeds. Determine if there is a danger of cavitation for this
In a piping system, the water temperature remains under 30°C. Determine the minimum pressure allowed in the system to avoid cavitation.
A pump is used to transport water to a higher reservoir. If the water temperature is 20°C, determine the lowest pressure that can exist in the pump without cavitation.
The analysis of a propeller that operates in water at 70°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
Does water boil at higher temperatures at higher pressures? Explain.
What is cavitation? What causes it?
What is a boundary layer? What causes a boundary layer to develop?
What is forced flow? How does it differ from natural flow? Is flow caused by winds forced or natural flow?
What is the no-slip condition? What causes it?
Define internal, external, and open-channel flows.
Define incompressible flow and incompressible fluid. Must the flow of a compressible fluid necessarily be treated as compressible?
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?
A solar collector system delivers heat to a power plant. It is well known that the thermal collection efficiency ηsc of a solar collector diminishes with increasing solar collection output
How do the following quantities change when a simple ideal Rankine cycle is modified with reheating? Assume the mass flow rate is maintained the same. (a) increases, (b) decreases, (c) remains the
Consider a simple ideal Rankine cycle with fixed boiler and condenser pressures. What is the effect of superheating the steam to a higher temperature on (a) increases, (b) decreases, (c) remains the
Consider a simple ideal Rankine cycle with fixed turbine inlet temperature and condenser pressure. What is the effect of increasing the boiler pressure on Pump work input: (a) increases, (b)
Consider a simple ideal Rankine cycle with fixed turbine inlet conditions. What is the effect of lowering the condenser pressure on Pump work input: (a) increases, (b) decreases, (c) remains the same
For a specified compression ratio, is a diesel or gasoline engine more efficient?
Repeat Prob. 9–29 for a compression ratio of 8.5.In ProblemAn ideal Otto cycle has a compression ratio of 10.5, takes in air at 90 kPa and 408C, and is repeated 2500 times per minute. Using
Can the mean effective pressure of an automobile engine in operation be less than the atmospheric pressure?
What are the air-standard assumptions?
Helium gas is throttled steadily from 400 kPa and 60°C. Heat is lost from the helium in the amount of 1.75 kJ/kg to the surroundings at 25°C and 100 kPa. If the entropy of the helium increases by
A mass of 25 lbm of helium undergoes a process from an initial state of 50 ft3/lbm and 60°F to a final state of 10 ft3/lbm and 240°F. Determine the entropy change of helium during this process,
Air enters a nozzle steadily at 280 kPa and 77°C with a velocity of 50 m/s and exits at 85 kPa and 320 m/s. The heat losses from the nozzle to the surrounding medium at 20°C are estimated to be 3.2
Some properties of ideal gases such as internal energy and enthalpy vary with temperature only [i.e., u = u(T) and h = h(T)]. Is this also the case for entropy?
Steam enters a steady-flow adiabatic nozzle with a low inlet velocity as a saturated vapor at 6 MPa and expands to 1.2 MPa.(a) Under the conditions that the exit velocity is to be the maximum
Steam is accelerated as it flows through an actual adiabatic nozzle. The entropy of the steam at the nozzle exit will be (greater than, equal to, less than) the entropy at the nozzle inlet.
The entropy of the working fluid of the ideal Carnot cycle (increases, decreases, remains the same) during the isothermal heat rejection process.
The entropy of the working fluid of the ideal Carnot cycle (increases, decreases, remains the same) during the isothermal heat addition process.
The entropy of steam will (increase, decrease, remain the same) as it flows through an actual adiabatic turbine.
A piston–cylinder device contains superheated steam. During an actual adiabatic process, the entropy of the steam will (never, sometimes, always) increase.
A piston–cylinder device contains nitrogen gas. During a reversible, adiabatic process, the entropy of the nitrogen will (never, sometimes, always) increase.
A piston–cylinder device contains helium gas. During a reversible, isothermal process, the entropy of the helium will (never, sometimes, always) increase.
Is a quantity whose cyclic integral is zero necessarily a property?
Is there any way to increase the efficiency of a Carnot heat engine other than by increasing TH or decreasing TL?
During a throttling process, the temperature of a fluid drops from 30 to - 20°C. Can this process occur adiabatically?
Steam flows steadily into a turbine with a mass flow rate of 26 kg/s and a negligible velocity at 6 MPa and 600°C. The steam leaves the turbine at 0.5 MPa and 200°C with a velocity of 180 m/s. The
Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold
Repeat Prob. 4€“109 for isobutane.Liquid propane is commonly used as a fuel for heating homes, powering vehicles such as forklifts, and filling portable picnic tanks. Consider a propane
Complete this table for refrigerant-134a: Phase description P, psia h, Btu/lbm T, °F 78 80 15 10 0.6 70 129.46 180 110 1.0

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