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, Chapter: 10- BOILING AND CONDENSATION -Problem: 104 >> During a heat treatment process, a 20-mm diameter cylindrical steel rod with a length of 200 mm was removed from a furnace when it reached a uniform temperature of 500°C and was suddenly submerged horizontally in a water bath at atmospheric pressure. If the steel rod has an emissivity of 0.9, determine the boiling heat transfer coefficient and the total heat transfer coefficient when it was initia
Answer Preview: To determine the boiling heat transfer coefficient and the total heat transfer coefficient when the steel rod was initially submerged in the water bat…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 106 >> Water is boiled at 100°C by a spherical platinum heating element of diameter 15 cm and emissivity 0.10 immersed in the water. If the surface temperature of the heating element is 350°C, determine the convective boiling heat transfer coefficient.
Answer Preview: To determine the convective boiling heat transfer coefficient you can use the equation for convective heat transfer during boiling which is described …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 115 >> Saturated isobutane vapor in a binary geothermal power plant is to be condensed outside an array of eight horizontal tubes. Determine the ratio of the condensation rate for the cases of the tubes being arranged in a horizontal tier versus in a vertical tier of horizontal tubes.
Answer Preview: The rate of condensation for saturated isobutane vapor can be determined using the Nusselt number Nu and the heat transfer coefficient h for the given …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 125 >> Saturated water vapor is condensing on a 0.5 m2 vertical flat plate in a continuous film with an average heat transfer coefficient of 7 kW/m2 · K. The temperature of the water is 80°C (hfg = 2309 kJ/kg) and the temperature of the plate is 60°C. The rate at which condensate is being formed is (a) 0.0303 kg/s(b) 0.07 kg/s(c) 0.15 kg/s(d) 0.24 kg/s(e) 0.28 kg/s
Answer Preview: To calculate the rate at which condensate is being formed on the vertical flat plate …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 60 >> A vertical 0.2 m × 0.2 m square plate is exposed to saturated water vapor at atmospheric pressure. If the surface temperature is 80°C and the flow is laminar, estimate the local heat transfer coefficients at the middle and at the bottom of the plate.
Answer Preview: To estimate the local heat transfer coefficients at the middle and at the bottom of the square plate …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 79 >> Saturated steam at 95°F is condensed on the outer surfaces of an array of horizontal pipes through which cooling water circulates. The outer diameter of the pipes is 1 in and the outer surfaces of the pipes are maintained at 65°F. Determine (a) The rate of heat transfer to the cooling water circulating in the pipes(b) The rate of condensation of steam per unit length of a single horizontal pipe.
Answer Preview: To determine the rate of heat transfer to the cooling water and the rate of condensation of steam per unit length of a single horizontal pipe we ll us…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 53 >> What is the difference between film and dropwise condensation? Which is a more effective mechanism of heat transfer?
Answer Preview: Film condensation and dropwise condensation are two different mechanisms of condensation that occur when a vapor transitions into a liquid state on a …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 52 >> For steady two-dimensional flow over an isothermal flat plate in the x-direction, express the boundary conditions for the velocity components u and v, and the temperature T at the plate surface and at the edge of the boundary layer.
Answer Preview: In the context of steady two dimensional flow over an isothermal flat plate in the x direction commo…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 123 >> At a distance x down a vertical, isothermal flat plate on which a saturated vapor is condensing in a continuous film, the thickness of the liquid condensate layer is d. The heat transfer coefficient at this location on the plate is given by (a) kl/?(b) ?hf(c) ?hfg(d) ?hg(e) None of them
Answer Preview: The heat transfer coefficient at a location on a condensing surface is typically related to the prop…

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 38 >> Consider fluid flow over a surface with a velocity profile given asDetermine the shear stress at the wall surface, if the fluid is(a) Air at 1 atm(b) Liquid water, both at 20°C. Also calculate the wall shear stress ratio for the two fluids and interpret the result. Transcribed Image Text: u(y) 100(y
Answer Preview: To determine the wall shear stress at the surface for the given velocity profile we can use the Newtonian fluid shear stress formula w du dy Where w i…

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 44 >> When the variation of spectral radiation quantity with wavelength is known, how is the corresponding total quantity determined?
Answer Preview: To determine the total quantity of spectral radiation from a source when you have the variation of spectral radiation quantity with wavelength you nee…

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 10 >> A cordless telephone is designed to operate at a frequency of 8.5 × 108 Hz. Determine the wavelength of these telephone waves.
Answer Preview: The wavelength of a wave can be calculated using the following equati…

, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 34 >> A 1-m-long and 0.1-m-thick steel plate of thermal conductivity 35 W/m · K is well insulated on its both sides, while the top surface is exposed to a uniform heat flux of 5500 W/m2. The bottom surface is convectively cooled by a fluid at 10°C having a convective heat transfer coefficient of 150 W/m2 · K. Assuming one dimensional heat conduction in the lateral direction, find the temperature at the
Answer Preview: To find the temperature at the midpoint of the steel plate you can use the one dimensional heat cond…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 120 >> Saturated steam at 270.1 kPa condenses inside a horizontal, 10-m-long, 2.5-cm-internal-diameter pipe whose surface is maintained at 110°C. Assuming low vapor velocity, determine the average heat transfer coefficient and the rate of condensation of the steam inside the pipe.
Answer Preview: To determine the average heat transfer coefficient and the rate of condensation of the steam inside …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 55 >> Consider steady, laminar, two-dimensional flow over an isothermal plate. Does the wall shear stress increase, decrease, or remain constant with distance from the leading edge?
Answer Preview: In steady laminar two dimensional flow over an isothermal plate the wall shear stress typically incr…

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 21 >> Consider two identical bodies, one at 1000 K and the other at 1500 K. Which body emits more radiation in the shorter-wavelength region? Which body emits more radiation at a wavelength of 20 ?m?
Answer Preview: The body at 1500 K emits more radiation in the shorter wavelength region and …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 99 >> Water is boiled at 120°C in a mechanically polished stainless-steel pressure cooker placed on top of a heating unit. The inner surface of the bottom of the cooker is maintained at 130°C. The cooker that has a diameter of 20 cm and a height of 30 cm is half filled with water. Determine the time it will take for the tank to empty.
Answer Preview: To determine the time it will take for the pressure cooker to empty we need to consider the heat transfer and the boiling process We can use the princ…

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, Chapter: 11- HEAT EXCHANGERS -Problem: 127 >> There are two heat exchangers that can meet the heat transfer requirements of a facility. Both have the same pumping power requirements, the same useful life, and the same price tag. But one is heavier and larger in size. Under what conditions would you choose the smaller one?
Answer Preview: Choosing between two heat exchangers with the same pumping power requirements useful life and price tag but different sizes one smaller and one larger …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 50 >> To understand the burnout phenomenon, boiling experiments are conducted in water at atmospheric pressure using an electrically heated 30-cm-long, 3-mm-diameter nickel-plated horizontal wire. Determine(a) The critical heat flux(b) The increase in the temperature of the wire as the operating point jumps from the nucleate boiling to the film boiling regime at the critical heat flux. Take the emissivi
Answer Preview: To determine the critical heat flux and the increase in the temperature of the wire as it transitions from nucleate boiling to film boiling at the cri…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 63 >> Saturated steam at 1 atm condenses on a 3-m-high and 8-m-wide vertical plate that is maintained at 90°C by circulating cooling water through the other side. Determine(a) The rate of heat transfer by condensation to the plate,(b) The rate at which the condensate drips off the plate at the bottom. Assume wavy-laminar flow. Is this a good assumption?
Answer Preview: 1 a The rate of heat transfer by condensation to the plate To determine the rate of heat transfer by condensation to the plate we can use the followin…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 55 >> What is the modified latent heat of vaporization? For what is it used? How does it differ from the ordinary latent heat of vaporization?
Answer Preview: The modified latent heat of vaporization also known as the effective latent heat of vaporization is a concept used in the field of thermodynamics and …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 70 >> Repeat Prob. 10–69 for a horizontal tube.Data from problem 69Saturated steam at 55°C is to be condensed at a rate of 10 kg/h on the outside of a 3-cm-outer-diameter vertical tube whose surface is maintained at 45°C by the cooling water. Determine the required tube length. Assume wavy laminar flow, and that the tube diameter is large, relative to the thickness of the liquid film at the bottom of th
Answer Preview: To repeat Prob 10 69 for a horizontal tube we can use the following steps Calculate the heat transfer coefficient The heat transfer coefficient for co…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 56 >> Consider film condensation on a vertical plate. Will the heat flux be higher at the top or at the bottom of the plate? Why?
Answer Preview: In film condensation on a vertical plate the heat flux is typically higher at the top of the plate compared to the bottom This is due to several facto…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 127 >> An air conditioner condenser in an automobile consists of 2 m2 of tubular heat exchange area whose surface temperature is 30°C. Saturated refrigerant-134a vapor at 50°C (hfg = 152 kJ/kg) condenses on these tubes. What heat transfer coefficent must exist between the tube surface and condensing vapor to produce 1.5 kg/min of condensate? (a) 95 W/m2 · K(b) 640 W/m2 · K(c) 727 W/m2 · K(d) 799 W/m2 · K
Answer Preview: To calculate the heat transfer coefficient needed to produce 1 5 kg min of condensate on a 2 m 2 sur…

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, Chapter: 11- HEAT EXCHANGERS -Problem: 129 >> A heat exchanger is to be selected to cool a hot liquid chemical at a specified rate to a specified temperature. Explain the steps involved in the selection process.
Answer Preview: Selecting a heat exchanger for cooling a hot liquid chemical to a specified temperature and at a specified rate involves several steps to ensure that the process is efficient safe and cost effective H…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 59 >> The Reynolds number for condensate flow is defined as Re = 4m?/p?l, where p is the wetted perimeter. Obtain simplified relations for the Reynolds number by expressing p and m? by their equivalence for the following geometries:(a) A vertical plate of height L and width w,(b) A tilted plate of height L and width W inclined at an angle u from the vertical,(c) A vertical cylinder of length L and diame
Answer Preview: To obtain simplified relations for the Reynolds number Re by expressing the wetted perimeter p and mass flow rate m for different geometries we ll con…

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, Chapter: 11- HEAT EXCHANGERS -Problem: 130 >> A heat exchanger is to cool oil (cp = 2200 J/kg · K) at a rate of 13 kg/s from 120°C to 50°C by air. Determine the heat transfer rating of the heat exchanger and propose a suitable type.
Answer Preview: To determine the heat transfer rating of the heat exchanger we can use the basic equation for heat transfer Q m cp T Where Q is the heat transfer rate …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 42 >> Repeat Prob. 10–41E for a heating element temperature of 988°F.Data from problem 41Water is boiled at atmospheric pressure by a horizontal polished copper heating element of diameter D = 0.5 in and emissivity ? = 0.05 immersed in water. If the surface temperature of the heating element is 788°F, determine the rate of heat transfer to the water per unit length of the heating element.
Answer Preview: To repeat the problem for a heating element temperature of 988F we will use the same principles of h…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 46 >> Cylindrical stainless steel rods are heated to a uniform temperature of 700°C and then quenched in water at 1 atm. The rods are 25 cm in length, 25 mm in diameter, and their surface have an emissivity of 0.3. Determine the convection heat transfer coefficient and the total rate of heat removed from a rod at the instant it is submerged in the water during quenching.
Answer Preview: To determine the convection heat transfer coefficient and the total rate of heat removed from a rod during quenching you can use Newton s Law of Cooli…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 100 >> Water is to be boiled at sea level in a 30-cm-diameter mechanically polished AISI 304 stainless steel pan placed on top of a 3-kW electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the temperature of the inner surface of the bottom of the pan. Also, determine the temperature difference between the inner and outer surfaces of the
Answer Preview: To determine the temperature of the inner surface of the bottom of the pan and the temperature diffe…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 83 >> Saturated water vapor at a pressure of 12.4 kPa is condensed over an array of 100 horizontal tubes, each with a diameter of 8 mm and a length of 1 m. The tube surfaces are maintained with a uniform temperature of 30°C. Determine the condensation rates of the tubes for(a) A rectangular array of 5 tubes high and 20 tubes wide(b) A square array of 10 tubes high and 10 tubes wide. Compare and discuss
Answer Preview: To determine the condensation rates of the tubes we need to calculate the heat transfer rate from the saturated water vapor to the tube surfaces The h…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 66 >> Reconsider Prob. 10–65. Using EES (or other) software, investigate the effects of plate temperature and the angle of the plate from the vertical on the average heat transfer coefficient and the rate at which the condensate drips off. Let the plate temperature vary from 40°C to 90°C and the plate angle from 0° to 60°. Plot the heat transfer coefficient and the rate at which the condensate drips off
Answer Preview: To investigate the effects of plate temperature and the angle of the plate from the vertical on the average heat transfer coefficient and the rate at …

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 41 >> What does a solid angle represent, and how does it differ from a plane angle? What is the value of a solid angle associated with a sphere?
Answer Preview: A solid angle is a geometric concept that measures the amount of space or solid content subtended by …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 48 >> Express continuity equation for steady two-dimensional flow with constant properties, and explain what each term represents.
Answer Preview: The continuity equation for steady two dimensional flow with constant properties in fluid dynamics i…

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 91 >> Air at 1 atm is flowing over a flat plate with a free stream velocity of 70 m/s. If the convection heat transfer coefficient can be correlated by Nux = 0.03 Rex0.8  Pr1/3, determine the friction coefficient and wall shear stress at a location 2 m from the leading edge. Evaluate fluid properties at 20°C.
Answer Preview: To determine the friction coefficient Cf and wall shear stress at a location 2 m from the leading ed…

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 148 >> Starting with an energy balance on the volume element, obtain the two-dimensional transient explicit finite difference equation for a general interior node in rectangular coordinates for T(x, y, t) for the case of constant thermal conductivity and uniform heat generation.
Answer Preview: To derive the two dimensional transient explicit finite difference equation for temperature T x y t …

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 141 >> Repeat Prob. 4–140 for a copper wire (? = 8950 kg/m3, cp = 0.383 kJ/kg · K, k = 386 W/m · K, and ? = 1.13 × 10-4 m2/s).Data from problem 140Long aluminum wires of diameter 3 mm (? = 2702 kg/m3, cp = 0.896 kJ/kg · K, k = 236 W/m · K, and ? = 9.75 × 10-5 m2/s) are extruded at a temperature of 350°C and exposed to atmospheric air at 30°C with a heat transfer coefficient of 35 W/m2 · K.(a) Determine h
Answer Preview: To repeat Problem 4 140 for a copper wire we need to substitute the thermal properties of copper into the equations used to solve the problem The ther…

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 156 >> Write a two-page essay on the finite element method, and explain why it is used in most commercial engineering software packages. Also explain how it compares to the finite difference method.
Answer Preview: Title The Finite Element Method A Cornerstone of Engineering Simulation Introduction The Finite Element Method FEM is a powerful numerical technique that has revolutionized the field of engineering an…

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 107 >> The ___________ number is a significant dimensionless parameter for forced convection and the ___________ number is a significant dimensionless parameter for natural convection. (a) Reynolds, Grashof(b) Reynolds, Mach(c) Reynolds, Eckert(d) Reynolds, Schmidt(e) Grashof, Sherwood
Answer Preview: The correct choices are a Reynolds Grashof The Reynolds numb…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 74 >> A 3-m spherical tank storing cold fluid has a uniform surface temperature of 5°C. The lower temperature of the tank surface is causing condensation of moisture in the air at 25°C. The tank is situated in the vicinity of high voltage devices, and water from the condensation on the tank surface can cause electrical hazard. To prevent such incident, a system is to be implemented to remove 0.5 kg/s of
Answer Preview: To determine whether the preventive system is capable of handling the rate of condensation from the tank surface we need to calculate the rate of cond…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 80 >> Repeat Prob. 10–79E for the case of 32 horizontal pipes arranged in a rectangular array of 4 pipes high and 8 pipes wide.Data from problem 79Saturated steam at 95°F is condensed on the outer surfaces of an array of horizontal pipes through which cooling water circulates. The outer diameter of the pipes is 1 in and the outer surfaces of the pipes are maintained at 65°F. Determine (a) The rate of he
Answer Preview: To solve this problem we ll follow the same principles as in problem 10 79E but for an array of 32 horizontal pipes arranged in a rectangular array of …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 54 >> What is an irregular boundary? What is a practical way of handling irregular boundary surfaces with the finite difference method?
Answer Preview: An irregular boundary in the context of numerical methods like the finite difference method FDM refers to a boundary of a computational domain that do…

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, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 26 >> A transformer that is 10 cm long, 6.2 cm wide, and 5 cm high is to be cooled by attaching a 10-cm × 6.2-cm-wide polished aluminum heat sink (emissivity = 0.03) to its top surface. The heat sink has seven fins, which are 5 mm high, 2 mm thick, and 10 cm long. A fan blows air at 258C parallel to the passages between the fins. The heat sink is to dissipate 12 W of heat and the base temperature of the
Answer Preview: To determine the minimum free stream velocity the fan needs to supply to avoid overheating we can us…

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, Chapter: 3- Steady Heat Conduction -Problem: 204 >> A 2.5 m-high, 4-m-wide, and 20-cm-thick wall of a house has a thermal resistance of 0.0125°C/W. The thermal conductivity of the wall is (a) 0.72 W/m · K(b) 1.1 W/m · K(c) 1.6 W/m · K(d) 16 W/m · K(e) 32 W/m · K
Answer Preview: To find the thermal conductivity k of the wall we can use the formula for t…

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 114 >> In turbulent flow, one can estimate the Nusselt number using the analogy between heat and momentum transfer (Colburn analogy). This analogy relates the Nusselt number to the coefficient of friction, Cf, as (a) Nu = 0.5 Cf Re Pr1/3(b) Nu = 0.5 Cf Re Pr2/3(c) Nu = Cf Re Pr1/3(d) Nu = Cf Re Pr2/3
Answer Preview: In turbulent flow the Colburn analogy relates t…

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, Chapter: 2- HEAT CONDUCTION EQUATION -Problem: 113 >> The thermal conductivity of stainless steel has been characterized experimentally to vary with temperature as k(T) = 9.14 + 0.021T for 273 < T < 1500 K, where k is in W/m?K and T is in K. Determine the average thermal conductivity between 300 and 1200 K, and express k(T) in the form of k(T) = k0 (1 + ?T ), where k0 is in W/m?K and b is in K?1.
Answer Preview: To determine the average thermal conductivity between 300 K and 1200 K and express k T in the desire…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 49 >> A 3-mm-diameter cylindrical heater is used for boiling water at 100°C. The heater surface is made of mechanically polished stainless steel with an emissivity of 0.3. Determine the boiling convection heat transfer coefficients at the maximum heat flux for(a) Nucleate boiling(b) Film boiling. For film boiling, evaluate the properties of vapor at 1150°C.
Answer Preview: To determine the boiling convection heat transfer coefficients at the maximum heat flux for nucleate boiling and film boiling you can use empirical correlations Let s calculate each one separately a N…

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, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 49 >> The outer surface of an engine is situated in a place where oil leakage can occur. When leaked oil comes in contact with a hot surface that has a temperature above its autoignition temperature, the oil can ignite spontaneously. Consider an engine cover that is made of a stainless steel plate with a thickness of 1 cm and a thermal conductivity of 14 W/m ? K. The inner surface of the engine cover is
Answer Preview: To determine whether a TBC layer with a thickness of 4 mm in conjunction with 7 1 m s air cooling would be sufficient to keep the engine cover surface …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 78 >> Reconsider Prob. 10–77. Using EES (or other) software, investigate the effect of the condenser pressure on the rate of heat transfer and the rate of condensation of the steam. Let the condenser pressure vary from 3 kPa to 15 kPa. Plot the rate of heat transfer and the rate of condensation of the steam as a function of the condenser pressure, and discuss the results.Data from problem 77The condense
Answer Preview: Effect of Condenser Pressure on Rate of Heat Transfer and Condensation To investigate the effect of condenser pressure on the rate of heat transfer an…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 44 >> Air flows over a flat plate at 40 m/s, 25°C and 1 atm pressure.(a) What plate length should be used to achieve a Reynolds number of 1 × 108 at the end of the plate?(b) If the critical Reynolds number is 5 × 105, at what distance from the leading edge of the plate would transition occur?
Answer Preview: a Plate length to achieve a Reynolds number of 1 10 8 at the end of the plate The Reynolds number is …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 153 >> What is the correct steady-state finite-difference heat conduction equation of node 6 of the rectangular solid shown in Fig. P5–153? Transcribed Image Text: (a) T6 = (T?+T3 + T? + ?)/2 (T5+ T?+T? + T10)/2 = (b) T6 (c) T6 = (T?+T3 + T9 + T?1)/4 (d) T6 = (T?+ T5 + T7 + T?0)/4 (e) T6 (T?+ T5 + T7+ T10)
Answer Preview: The correct steady state finite difference heat conduction equation of node 6 of the rectangular sol…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 75 >> Chickens with an average mass of 1.7 kg (k = 0.45 W/m · K and ? = 0.13 × 10-6 m2/s) initially at a uniform temperature of 15°C are to be chilled in agitated brine at 27°C. The average heat transfer coefficient between the chicken and the brine is determined experimentally to be 440 W/m2 · K. Taking the average density of the chicken to be 0.95 g/cm3 and treating the chicken as a spherical lump, de
Answer Preview: Analytical one term approximation method to determine center and surface temperatures of chicken in brine Calculate the Biot number The Biot number Bi …

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 173 >> A small chicken (k = 0.45 W/m · K, ? = 0.15 × 10-6 m2/s) can be approximated as an 11.25-cm-diameter solid sphere. The chicken is initially at a uniform temperature of 8ºC and is to be cooked in an oven maintained at 220ºC with a heat transfer coefficient of 80 W/m2·K. With this idealization, the temperature at the center of the chicken after a 90-min period is (a) 25°C(b) 61°C(c) 89°C(d) 122°C(e)
Answer Preview: The temperature at the center of the chicken after a 90 min period can …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 75 >> Consider film condensation on the outer surfaces of N horizontal tubes arranged in a vertical tier. For what value of N will the average heat transfer coefficient for the entire stack of tubes be equal to half of what it is for a single horizontal tube?
Answer Preview: Substituting the first equation into the second equation we get h single N 1 4 h single 2 Solvi…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 176 >> A large chunk of tissue at 35°C with a thermal diffusivity of 1 × 10-7 m2/s is dropped into iced water. The water is well-stirred so that the surface temperature of the tissue drops to 0 °C at time zero and remains at 0°C at all times. The temperature of the tissue after 4 minutes at a depth of 1 cm is (a) 5°C(b) 30°C(c) 25°C(d) 20°C(e) 10°C
Answer Preview: The correct answer is a 5C The heat equation describes how heat is transferred within …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 30 >> What is the physical significance of the Prandtl number? Does the value of the Prandtl number depend on the type of flow or the flow geometry? Does the Prandtl number of air change with pressure? Does it change with temperature?
Answer Preview: The Prandtl number Pr is a dimensionless parameter that characterizes the relative importance of molecular diffusion of momentum kinematic viscosity t…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 114 >> Repeat Prob. 10–113 for a 3-cm-diameter copper ball.Data from problem 113A 1.2-cm-diameter silver sphere initially at 25°C is suspended in a room filled with saturated steam at 100°C. Using the lumped system analysis, determine how long it will take for the temperature of the ball to rise to 50°C. Also, determine the amount of steam that condenses during this process and verify that the lumped sys
Answer Preview: To solve this problem for a 3 cm diameter copper ball we can follow the same approach as in Problem 10 113 The lumped system analysis assumes that the temperature inside the sphere is uniform and can …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 50 >> For steady two-dimensional flow, what are the boundary layer approximations?
Answer Preview: In the context of steady two dimensional flow boundary layer approximations are used to simplify the analysis of fluid behavior near a solid boundary …

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 131 >> What is the proper storage temperature of frozen poultry? What are the primary methods of freezing for poultry?
Answer Preview: The proper storage temperature for frozen poultry is typically at or below 0 degrees Fahrenheit 18 d…

, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 27 >> Repeat Prob. 7–26 assuming the heat sink to be blackanodized and thus to have an effective emissivity of 0.90. Note that in radiation calculations the base area (10 cm × 6.2 cm) is to be used, not the total surface area.Data from problem 26A transformer that is 10 cm long, 6.2 cm wide, and 5 cm high is to be cooled by attaching a 10-cm × 6.2-cm-wide polished aluminum heat sink (emissivity = 0.03)
Answer Preview: To repeat Problem 7 26 assuming the heat sink to be black anodized and thus to have an effective emi…

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 26 >> The sun can be treated as a blackbody at 5780 K. Using EES (or other) software, calculate and plot the spectral blackbody emissive power Eb? of the sun versus wavelength in the range of 0.01 mm to 1000 mm. Discuss the results.
Answer Preview: To calculate and plot the spectral blackbody emissive power Eb of the sun versus wavelength in the r…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 62 >> Saturated ammonia vapor at 30°C is passed over 30 vertical flat plates, each of which is 10 cm high and 25 cm wide. The average surface temperature of the plates is 10°C. Estimate the average heat transfer coefficient and the rate of ammonia condensation. Assume wavy-laminar flow. Is this a good assumption?
Answer Preview: To estimate the average heat transfer coefficient h and the rate of ammonia condensation we can use the Nusselt number Nu correlation for wavy laminar …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 29 >> What fluid property is responsible for the development of the velocity boundary layer? For what kind of fluids will there be no velocity boundary layer on a flat plate?
Answer Preview: The development of the velocity boundary layer in fluid flow is primarily influenced by the viscosit…

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 46 >> Consider fluid flowing with a free stream velocity of 1 ft/s over a flat plate, where the critical Reynolds number is 5 × 105. Determine the distance from the leading edge at which the transition from laminar to turbulent flow occurs for air (at 1 atm), liquid water, isobutane, and engine oil, and mercury. Evaluate all properties at 50°F.
Answer Preview: To determine the distance from the leading edge at which the transition from laminar to turbulent flow occurs known as the transition point or transit…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 132 >> What are the factors that affect the quality of frozen fish?
Answer Preview: The quality of frozen fish can be affected by various factors both before and after freezing These factors can impact the flavor texture and overall q…

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 17 >> How can a node on an insulated boundary be treated as an interior node in the finite difference formulation of a plane wall? Explain.
Answer Preview: In finite difference formulations of heat conduction problems when you have an insulated boundary within a plane wall it is often necessary to treat n…

, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 13 >> How are the average friction and heat transfer coefficients determined in flow over a flat plate?
Answer Preview: Experimental Measurement a Friction Coefficient Cf To measure the average friction coefficient you t…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 85 >> Saturated ammonia vapor at a pressure of 1003 kPa is condensed as it flows through a 25-mm tube. The tube length is 0.5 m and the wall temperature is maintained uniform at 5°C. If the vapor exits the tube at a flow rate of 0.002 kg/s, determine the flow rate of the vapor at the inlet. Assume the Reynolds number of the vapor at the tube inlet is less than 35,000. Is this a good assumption?
Answer Preview: To determine the flow rate of the vapor at the inlet we can use the mass flow rate equation The mass …

, Chapter: 10- BOILING AND CONDENSATION -Problem: 88 >> Steam is being condensed at 60°C by a 15-m-long horizontal copper tube with a diameter of 25 mm. The tube surface temperature is maintained at 40°C. Determine the condensation rate of the steam during(a) Film condensation,(b) Dropwise condensation. Compare and discuss the results.
Answer Preview: To determine the condensation rate of steam in a copper tube we need to calculate the heat transfer rate for both film condensation and dropwise conde…

, Chapter: 11- HEAT EXCHANGERS -Problem: 140 >> How do heavy clothing and extreme environmental conditions affect the cardiovascular counter-current exchanger?
Answer Preview: The cardiovascular counter current exchanger also known as the rete mirabile is a specialized network of blood vessels found in some animals particularly in fish birds and mammals Its primary function …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 5 >> How do numerical solution methods differ from analytical ones? What are the advantages and disadvantages of numerical and analytical methods?
Answer Preview: Numerical and analytical solution methods are two distinct approaches to solving mathematical and scientific problems and they have their own sets of advantages and disadvantages Analytical Methods Ex…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 112 >> One can expect the heat transfer coefficient for turbulent flow to be ___________ for laminar flow. (a) Less than(b) Same as(c) Greater than
Answer Preview: The heat transfer coefficient for turbulent flow is generall…

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, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 15 >> Repeat Prob. 7–14 for water.Data from problem 14Air at 25°C and 1 atm is flowing over a long flat plate with a velocity of 8 m/s. Determine the distance from the leading edge of the plate where the flow becomes turbulent, and the thickness of the boundary layer at that location.
Answer Preview: To repeat Prob 714 for water we need to calculate the following The Reynolds number Re The critical …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 57 >> Consider film condensation on the outer surfaces of four long tubes. For which orientation of the tubes will the condensation heat transfer coefficient be the highest:(a) Vertical,(b) Horizontal side by side,(c) Horizontal but in a vertical tier (directly on top of each other), (d ) A horizontal stack of two tubes high and two tubes wide?
Answer Preview: The heat transfer coefficient for film condensation depends on various factors including the orientation of the tubes Let s analyze each orientation t…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 43 >> A 20-mm-diameter metal sphere has an emissivity of 0.75. The sphere was removed from a furnace when it reached a uniform temperature of 700°C and was suddenly submerged in a water bath at atmospheric pressure. Estimate the initial heat transfer rate from the submerged metal sphere.
Answer Preview: To estimate the initial heat transfer rate …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 132 >> The refrigerant in a household refrigerator is condensed as it flows through the coil that is typically placed behind the refrigerator. Heat transfer from the outer surface of the coil to the surroundings is by natural convection and radiation. Obtaining information about the operating conditions of the refrigerator, including the pressures and temperatures of the refrigerant at the inlet and the
Answer Preview: To determine if the coil behind a household refrigerator is properly selected you would typically need to gather data about the operating conditions refrigerant properties and system performance Here …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 96 >> If (?T/?y)w = 80 K/m, calculate the Nusselt number for a microchannel of width 1.2 mm if the wall temperature is 50°C and it is surrounded by (a) Ambient air at temperature 30°C,(b) Nitrogen gas at temperature 2100°C.
Answer Preview: To calculate the Nusselt number for a microchannel you can use the formula for the Nusselt number in forced convection which is given by Nu h L k Wher…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 127 >> How does the rate of freezing affect the tenderness, color, and the drip of meat during thawing?
Answer Preview: The rate of freezing can have several effects on meat including its tenderness color and the amount of drip produced during thawing These effects are …

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, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 116 >> A facility is equipped with a wind tunnel, and can measure the friction coefficient for flat surfaces and airfoils. Design an experiment to determine the mean heat transfer coefficient for a surface using friction coefficient data.
Answer Preview: To determine the mean heat transfer coefficient for a surface using friction coefficient data you can conduct an experiment that involves measuring the friction coefficient for various flat surfaces a…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 125 >> The cooling of a beef carcass from 37°C to 5°C with refrigerated air at 0°C in a chilling room takes about 48 h. To reduce the cooling time, it is proposed to cool the carcass with refrigerated air at 210°C. How would you evaluate this proposal?
Answer Preview: Cooling a beef carcass from 37C to 5C is an important step in meat processing to ensure food safety and quality The proposal to use refrigerated air a…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 26 >> What is viscosity? What causes viscosity in liquids and in gases? Is dynamic viscosity typically higher for a liquid or for a gas?
Answer Preview: Viscosity is a measure of a fluid s resistance to flow It is a property that quantifies the internal friction of a fluid as it moves and deforms In si…

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, Chapter: 12- FUNDAMENTALS OF THERMAL RADIATION -Problem: 42 >> For a surface, how is irradiation defined? For diffusely incident radiation, how is irradiation on a surface related to the intensity of incident radiation?
Answer Preview: Irradiation is defined as the total radiant flux incident on a surface per unit area It is typically …

, Chapter: 10- BOILING AND CONDENSATION -Problem: 90 >> Consider a non-boiling gas-liquid two-phase flow in a 102-mm diameter tube, where the superficial gas velocity is one-third that of the liquid. If the densities of the gas and liquid are ?g = 8.5 kg/m3 and ?l = 855 kg/m3, respectively, determine the flow quality and the mass flow rates of the gas and the liquid when the gas superficial velocity is 0.8 m/s.
Answer Preview: To determine the flow quality and the mass flow rates of the gas and the liquid in a non boiling gas …

, Chapter: 11- HEAT EXCHANGERS -Problem: 19 >> Reconsider Prob. 11–18. Using EES (or other) software, plot the overall heat transfer coefficient as a function of the limestone thickness as it varies from 1 mm to 3 mm, and discuss the results.Data from problem 18Repeat Prob. 11–17 by assuming a 2-mm-thick layer of limestone (k = 1.3 W/m · K) forms on the outer surface of the inner tube.Data from problem 117A long thin-walled double-pipe heat ex
Answer Preview: To determine the overall heat transfer coefficient as a function of the limestone thickness we ll fi…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 177 >> The 40-cm-thick roof of a large room made of concrete (k = 0.79 W/m · K, ? = 5.88 × 10-7 m2/s) is initially at a uniform temperature of 15°C. After a heavy snow storm, the outer surface of the roof remains covered with snow at 25°C. The roof temperature at 18.2 cm distance from the outer surface after a period of 2 hours is (a) 14°C(b) 12.5°C(c) 7.8°C(d) 0°C(e) 25°C
Answer Preview: The correct answer is c 7 8C We can use the following equation t…

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, Chapter: 2- HEAT CONDUCTION EQUATION -Problem: 67 >> Consider a chilled-water pipe of length L, inner radius r1, outer radius r2, and thermal conductivity k. Water flows in the pipe at a temperature Tf and the heat transfer coefficient at the inner surface is h. If the pipe is well-insulated on the outer surface,(a) Express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the pipe(b) Obtain a r
Answer Preview: a Differential equation and boundary conditions The differential equation for steady one dimensional …

, Chapter: 11- HEAT EXCHANGERS -Problem: 188 >> Write an essay on the static and dynamic types of regenerative heat exchangers and compile information about the manufacturers of such heat exchangers. Choose a few models by different manufacturers and compare their costs and performance.
Answer Preview: Title Comparative Analysis of Static and Dynamic Types of Regenerative Heat Exchangers Introduction Regenerative heat exchangers are essential components in various industrial processes and energy sys…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 69 >> Saturated steam at 55°C is to be condensed at a rate of 10 kg/h on the outside of a 3-cm-outer-diameter vertical tube whose surface is maintained at 45°C by the cooling water. Determine the required tube length. Assume wavy laminar flow, and that the tube diameter is large, relative to the thickness of the liquid film at the bottom of the tube. Are these good assumptions?
Answer Preview: To determine the required tube length for condensing saturated steam on the outside of a vertical tube we need to apply the principles of heat transfe…

, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 147 >> The thermal conductivity of a solid whose density and specific heat are known can be determined from the relation k = ?/?cp after evaluating the thermal diffusivity a. Consider a 2-cm-diameter cylindrical rod made of a sample material whose density and specific heat are 3700 kg/m3 and 920 J/kg · K, respectively. The sample is initially at a uniform temperature of 25°C. In order to measure the temp
Answer Preview: To determine the thermal diffusivity and the thermal conductivity of the material Calculate the temp…

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 13 >> Explain how the finite difference form of a heat conduction problem is obtained by the energy balance method.
Answer Preview: The finite difference form of a heat conduction problem is obtained by the energy balance method by dividing the spatial domain into discrete segments …

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 39 >> Consider a flow over a surface with the velocity and temperature profiles given aswhere the coefficients C1 and C2 are constants. Determine the expressions for the friction coefficient (Cf) and the convection heat transfer coefficient (h). Transcribed Image Text: u(y) = C?(y + y² - y²) T(y) = C? - e
Answer Preview: To determine the expressions for the friction coefficient Cf and the convection heat transfer coefficient h for the given flow over a surface with vel…

, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 94 >> The implicit method is unconditionally stable and thus any value of time step Dt can be used in the solution of transient heat conduction problems. To minimize the computation time, someone suggests using a very large value of Dt since there is no danger of instability. Do you agree with this suggestion? Explain.
Answer Preview: I do not agree with the suggestion of using a very large value of Dt to minimize the computation time in the implicit method for solving transient hea…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 77 >> The condenser of a steam power plant operates at a pressure of 4.25 kPa. The condenser consists of 100 horizontal tubes arranged in a 10 × 10 square array. The tubes are 8 m long and have an outer diameter of 3 cm. If the tube surfaces are at 20°C, determine(a) The rate of heat transfer from the steam to the cooling water(b) The rate of condensation of steam in the condenser.
Answer Preview: To determine the rate of heat transfer from the steam to the cooling water and the rate of condensation of steam in the condenser we can use principle…

, Chapter: 10- BOILING AND CONDENSATION -Problem: 89 >> Consider a non-boiling gas-liquid two-phase flow in a tube, where the ratio of the mass flow rate is m?l/m?g = 300. Determine the flow quality (x) of this non-boiling two-phase flow.
Answer Preview: The flow quality x in a two phase flow system is a measure of the fraction of th…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 121 >> What are the environmental factors that affect the growth rate of microorganisms in foods?
Answer Preview: The growth rate of microorganisms in foods is influenced by a variety of environmental factors Understanding these factors is essential for food safety and preservation Some of the key environmental f…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 45 >> Water is boiled at 100°C by a spherical platinum heating element of diameter 15 cm and emissivity 0.10 immersed in the water. If the surface temperature of the heating element is 350°C, determine the rate of heat transfer from the heating element to the water.
Answer Preview: To determine the rate of heat transfer from the spherical platinum heating element to the water you …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 9 >> For a one dimensional steady state variable thermal conductivity heat conduction with uniform internal heat generation, develop a generalized finite difference formulation for the interior nodes, with left surface boundary node exposed to constant heat flux and right surface boundary node exposed to convective environment. The variable conductivity is modeled such that the thermal conductivity var
Answer Preview: To develop a generalized finite difference formulation for the one dimensional steady state heat conduction problem with variable thermal conductivity …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 131 >> Starting with an energy balance on the volume element, obtain the steady three-dimensional finite difference equation for a general interior node in rectangular coordinates for T(x, y, z) for the case of constant thermal conductivity and uniform heat generation.
Answer Preview: To obtain the steady three dimensional finite difference equation for temperature T x y z at a gener…

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, Chapter: 3- Steady Heat Conduction -Problem: 197 >> Heat is lost at a rate of 275 W per m2 area of a 15-cm thick wall with a thermal conductivity of k = 1.1 W/m · K. The temperature drop across the wall is (a) 37.5°C(b) 27.5°C(c) 16.0°C(d) 8.0°C(e) 4.0°C
Answer Preview: To find the temperature drop across the wall we can use the formula for heat transfer through a plan…

, Chapter: 10- BOILING AND CONDENSATION -Problem: 86 >> A 10-m-long copper tube with a diameter of 25 mm is used for transporting cold coolant. The coolant flow inside the tube maintains the tube surface temperature at 5°C and causes moist air to condense on the outer surface. Determine the dropwise condensation rate of the moisture in the air, if the saturation temperature is 25°C.
Answer Preview: To determine the dropwise condensation rate of the moisture in the air we can use the followi…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 54 >> Consider steady, laminar, two-dimensional flow over an isothermal plate. Does the thickness of the velocity boundary layer increase or decrease with(a) Distance from the leading edge,(b) Free-stream velocity,(c) Kinematic viscosity?
Answer Preview: In steady laminar two dimensional flow over an isothermal plate the thickness of the velocity boundary layer can be affected by several factors Let s …

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, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 12 >> Consider laminar flow over a flat plate. Will the friction coefficient change with distance from the leading edge? How about the heat transfer coefficient?
Answer Preview: In laminar flow over a flat plate the friction coefficient and the heat transfer coefficient both ch…

, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 89 >> Consider transient one-dimensional heat conduction in a plane wall that is to be solved by the explicit method. If both sides of the wall are subjected to specified heat flux, express the stability criterion for this problem in its simplest form.
Answer Preview: The stability criterion for the explicit …

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, Chapter: 2- HEAT CONDUCTION EQUATION -Problem: 66 >> Consider a solid cylindrical rod of length 0.15 m and diameter 0.05 m. The top and bottom surfaces of the rod are maintained at constant temperatures of 20°C and 95°C, respectively, while the side surface is perfectly insulated. Determine the rate of heat transfer through the rod if it is made of(a) Copper, k = 380 W/m·K,(b) Steel, k = 18 W/m·K,(c) Granite, k = 1.2 W/m·K.
Answer Preview: The rate of heat transfer through a cylindrical rod can be calculated using the following equation q …

, Chapter: 10- BOILING AND CONDENSATION -Problem: 122 >> Heat transfer coefficients for a vapor condensing on a surface can be increased by promoting (a) Film condensation(b) Dropwise condensation(c) Rolling action(d) None of them
Answer Preview: b Dropwise condensation Dropwise condensation is a condensation pr…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 49 >> Is the acceleration of a fluid particle necessarily zero in steady flow? Explain.
Answer Preview: In steady flow the acceleration of a fluid particle can indeed be zero under certain conditions but it is not always zero The concept of steady flow r…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 61 >> A vertical 0.5 m × 0.5 m square plate is used in a process to condensate saturated water vapor. If the desired rate of condensation is 0.016 kg/s, determine the necessary surface temperature of the plate at atmospheric pressure. For this problem, as a first approximation, assume a film temperature of 90°C for the evaluation of the liquid properties and a surface temperature of 80°C for the evaluat
Answer Preview: To determine the necessary surface temperature of the square plate for condensing saturated water va…

, Chapter: 6- FUNDAMENTALS OF CONVECTION -Problem: 86 >> Repeat Prob. 6–85 for an air-flow velocity of 10 m/s.Data from problem 85A metallic airfoil of elliptical cross section has a mass of 50 kg, surface area of 12 m2, and a specific heat of 0.50 kJ/kg · K. The airfoil is subjected to air flow at 1 atm, 25°C, and 5 m/s along its 3-m-long side. The average temperature of the airfoil is observed to drop from 160°C to 150°C within 2 min of cooling. Assum
Answer Preview: To determine the average friction coefficient of the airfoil surface using the momentum heat transfe…

, Chapter: 10- BOILING AND CONDENSATION -Problem: 22 >> Repeat Prob. 10–21E for a platinum-plated heating element.Data from problem 21Water is boiled at 250°F by a 2-ft-long and 0.5-in diameter nickel-plated electric heating element maintained at 280°F. Determine(a) The boiling heat transfer coefficient, (b) The electric power consumed by the heating element, and (c) The rate of evaporation of water.
Answer Preview: To repeat Prob 1021E For a platinum plated heating element we ll need to calculate the boiling heat transfer coefficient the electric power consumed b…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 48 >> A cylindrical rod is used for boiling water at 1 atm. The rod has a diameter of 1 cm and its surface has an emissivity of 0.3. Determine the film boiling convection heat transfer coefficient at the burnout point. Evaluate the properties of vapor at 1150°C. Discuss whether 1150°C is a reasonable film temperature for the vapor properties.
Answer Preview: To determine the film boiling convection heat transfer coefficient at the burnout point we can use the Dittus Boelter equation which relates the Nusse…

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, Chapter: 4- TRANSIENT HEAT CONDUCTION -Problem: 167 >> Carbon steel balls (? = 7830 kg/m3, k = 64 W/m · K, cp = 434 J/kg · K) initially at 150°C are quenched in an oil bath at 20°C for a period of 3 minutes. If the balls have a diameter of 5 cm and the convection heat transfer coefficient is 450 W/m2 · K. The center temperature of the balls after quenching will be.(a) 27.4°C(b) 143°C(c) 12.7°C(d) 48.2°C(e) 76.9°C
Answer Preview: The answer is c 12 7C We can use the following equation to calculate the center temperature of the b…

, Chapter: 7- EXTERNAL FORCED CONVECTION -Problem: 57 >> Air is flowing in parallel over the upper surface of a flat plate with a length of 4 m. The first half of the plate length, from the leading edge, has a constant surface temperature of 50°C. The second half of the plate length is subjected to a uniform heat flux of 86 W/m2. The air has a free stream velocity and temperature of 2 m/s and 10°C, respectively. Determine the local convection heat trans
Answer Preview: To determine the local convection heat transfer coefficients at 1 m and 3 m from the leading edge follow these steps Calculate the Reynolds number at …

, Chapter: 10- BOILING AND CONDENSATION -Problem: 28 >> A 1-mm-diameter nickel wire with electrical resistance of 0.129 V/m is submerged horizontally in water at atmospheric pressure. Determine the electrical current at which the wire would be in danger of burnout in nucleate boiling. Transcribed Image Text: P = 1 atm Nickel wire 0.129 92/m
Answer Preview: To determine the electrical current at which a 1 mm diameter nickel wire with electrical resistance …

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, Chapter: 2- HEAT CONDUCTION EQUATION -Problem: 100 >> A cylindrical fuel rod (k = 30 W/m ? K) of 2 cm in diameter is encased in a concentric tube and cooled by water. The fuel rod generates heat uniformly at a rate of 100 MW/m3, and the average temperature of the cooling water is 75°C with a convection heat transfer coefficient of 2500 W/m2?K. The operating pressure of the cooling water is such that the surface temperature of the fuel rod must be kep
Answer Preview: The variation of temperature in the fuel rod and the temperature of the fuel rod surface can be dete…

, Chapter: 10- BOILING AND CONDENSATION -Problem: 108 >> Saturated steam at 100°F is condensed on a 4-ft-high vertical plate that is maintained at 80°F. Determine the rate of heat transfer from the steam to the plate and the rate of condensation per foot width of the plate. Assume wavy-laminar flow. Is this a good assumption?
Answer Preview: To determine the rate of heat transfer from saturated steam at 100F to a vertical plate maintained at 80F and to find the rate of condensation per foo…

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 14 >> Water is boiled at atmospheric pressure by a horizontal platinum-plated rod with diameter of 10 mm. If the surface temperature of the rod is maintained at 110°C, determine the nucleate pool boiling heat transfer coefficient. Transcribed Image Text: P = 1 atm Water, 100°C T? Platinum-plated rod
Answer Preview: The nucleate pool boiling heat transfer coefficient can be estimated using …

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, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 57 >> Starting with an energy balance on a volume element, obtain the steady two-dimensional finite difference equation for a general interior node in rectangular coordinates for T(x, y) for the case of variable thermal conductivity and uniform heat generation.
Answer Preview: To derive the steady two dimensional finite difference equation for temperature distribution T in a …

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, Chapter: 10- BOILING AND CONDENSATION -Problem: 128 >> Saturated water vapor at 40°C is to be condensed as it flows through a tube at a rate of 0.2 kg/s. The condensate leaves the tube as a saturated liquid at 40°C. The rate of heat transfer from the tube is (a) 34 kJ/s(b) 268 kJ/s(c) 453 kJ/s(d) 481 kJ/s(e) 515 kJ/s
Answer Preview: To find the rate of heat transfer from the tube as saturated water vapor at 40C is condensed you can …

, Chapter: 5- NUMERICAL METHODS IN HEAT CONDUCTION -Problem: 139 >> A fuel element (k = 67 W/m · K) that can be modeled as a plane wall has a thickness of 4 cm. The fuel element generates 5 × 107 W/

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