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physics
principles of heat transfer

Questions and Answers of Principles Of Heat Transfer

Consider the Design Problem 10.2 (stated in Chapter 10), and the cooling water and steam inlet conditions specified. Design this steam condenser by calculating both the condensing heat transfer
A long, heated, cylindrical steel rod is removed from a heat treatment furnace and has to be cooled to complete the process. If the surface temperature of the rod is at 150°C and the cooling fluid
An 20-cm-diameter horizontal steam pipe carries 1.66 kg/min of dry, pressurized, saturated steam at 120°C. If the ambient air temperature is 20°C, determine the rate of condensate flow at the end
The electronic controls of a medical imaging device are housed in a compartment such that it heat dissipates heat to the ambient from a flat vertical plate surface, 15 cm wide and 20 cm high, to
Liquid nitrogen is typically delivered in large dewars by suppliers to a jobsite. In many applications nitrogen vapor is required, so it is necessary to provide a means for evaporating the liquid
In Chapters 2, 4, and 6 you determined the required heat transfer coefficients for water flowing over the outside surface of a heating element. Those solutions required an assumption that by limiting
You are to design an electrically powered steam generator for use in a laboratory experiment. The boiler is to provide 1 g/s of dry saturated steam at 150 kPa. The primary design considerations are
In a metal alloy manufacturing and heat treatment plant and in its immersion quenching process, steel plates are first heated in a furnace and then quenched (or cooled) in a coolant bath to obtain
For establishing an experimental station that carries out mineral prospecting on the Moon and also houses periodic human visits for space-based explorations, a cooling (or thermal management) system
Calculate the peak heat flux for nucleate pool boiling of water at 300 kPa pressure and 110ºC on clean copper.
In space-based systems, such as the International Space Station, for example, highly efficient cooling systems are deployed that involve force convection boiling. In a laboratory experiment to
A vertical, rectangular water duct 1 m high and 0.10 m deep shown in the sketch is placed in an environment of saturated steam at atmospheric pressure. If the outer surface of the duct is about
Saturated methyl chloride at 430 kPa (abs) condenses on a horizontal 10 × 10 bank of tubes. The 5-cm- OD tubes are equally spaced and are 10 cm apart center-to- center on rows and columns. If the
The one-pass condenser, heat exchanger shown in the sketch has 64 tubes arranged in a square array with 8 tubes per line. The tubes are 1.22 m long and are made of copper with an outside diameter of
Analyze the effectiveness of a heat exchanger intended to heat water with the flue gas from a combustion chamber as shown in the schematic diagram. The water is flowing through a finned tube, having
Saturated steam vapor leaves a steam turbine at a massflow rate of 2 kg/s and a pressure of 0.5 atm, as shown in the following diagram. Design a heat exchanger to condense the vapor to the saturated
Estimate the cross-sectional area required for a 30-cm-long methanol-nickel heat pipe to transport 30 W at atmospheric pressure.
In the manufacture of can ice, cans having inside dimensions of 27.5 × 55 × 125 cm with 2.5 cm inside taper are filled with water and immersed in brine at a temperature of –12ºC. For the purpose
Benzene flowing at 12.5 kg/s is to be cooled continuously from 82°C to 54°C by 10 kg/s of water available at 15.5°C. Using Table 10.6, estimate the surface area required for (a) Cross-flow
Hot water is used to heat air in a double-pipe heat exchanger as shown in the following sketch. If theheat transfer coefficients on the water side and on the air side are 550 W/m2 K and 55 W/m2 K
The temperature of a 100-m-diameter cooling pond is 7ºC on a winter day. If the air temperature suddenly drops to – 7°C, calculate the thickness of ice formed after three hours.
It is common practice in industry to recover thermal energy from the flue gas of a furnace. One method of using this thermal energy is to preheat the furnace combustion air with a heat exchanger that
In the shell of a shell-and-tube heat exchanger with two shell passes and eight tube passes, 12.6 kg/s of water is heated from 80°C to 150°C. Hot exhaust gases having roughly the same physical
A steam-heated, single-pass tubular preheater is designed to raise 5.6 kg/s of air from 20°C to 75°C, using saturated steam at 2.6 MPa (abs). It is proposed to double the flow rate of air, and in
In a single-pass counter flow heat exchanger, 1.25 kg/s of water enters at 15°C and cools 2.5 kg/s of an oil having a specific heat of 2093 J/kg K from 95°C to 65°C. If the overall heat transfer
A small space heater is constructed of 1.25 cm, 18-gauge brass tubes that are 60 cm. The tubes are arranged in equilateral, staggered triangles on 3.6 cm centers with four rows of 15 tubes each. A
Water at a rate of 0.32 L/s and a temperature of 27°C enters a No. 18 BWG 1.6 cm condenser tube made of nickel chromium steel (k = 26 W/m K). The tube is 3 m long, and its outside is heated by steam
A shell-and-tube counter flow heat exchanger is to be designed for heating an oil from 27°C to 82°C. The heat exchanger has two tube passes and one shell pass. The oil is to pass through 3.8 cm
Determine the appropriate size of a shell-and-tube heat exchanger with two tube passes and one shell pass to heat 8.82 kg/s of pure ethanol from 15.6°C to 60°C. The heating medium is saturated
Calculate the overall heat transfer coefficient and the rate of heat flow from the hot gases to the cold air in the cross-flow tube bank of the heat exchanger shown in the accompanying illustration
As a designer working for a major electric appliance manufacturer, you are required to estimate the amount of fiberglass insulation packing (k = 0.035 W/m K) that is needed for a kitchen oven shown
A small gray sphere having an emissivity of 0.5 and a surface temperature of 537°C is located in a blackbody enclosure having a temperature of 37°C. Calculate for this system (a) The net rate
A simple solar heater consists of a flat plate of glass below which is located a shallow pan filled with water, so that the water is in contact with the glass plate above it. Solar radiation passes
A long wire 0.7 mm in diameter with an emissivity of 0.9 is placed in a large quiescent air space at 270 K. If the wire is at 800 K, calculate the net rate of heat loss. Discuss your assumptions.
Wearing layers of clothing in cold weather is often recommended because dead-air spaces between the layers keep the body warm. The explanation for this is that the heat loss from the body is less.
On a cold winter day, the outside wall of a home is exposed to an air temperature of – 2°C when the inside temperature of the room is at 22°C. As a result of this temperature gradient, there is
The inner wall of a rocket motor combustion chamber receives 160 kW/m2 by radiation from a gas at 2760°C. The convection heat transfer coefficient between the gas and the wall is 110 W/ (m2 K). If
A heat exchanger wall consists of a copper plate 2 cm thick. The heat transfer coefficients on the two sides of the plate are 2700 and 7000 W/ (m2 K), corresponding to fluid temperatures of 92 and
A composite refrigerator wall is composed of 5 cm of corkboard sandwiched between a 1.2-cm-thick layer of oak and a 0.8-mm-thick layer of aluminum lining on the inner surface. The average convection
A small oven with a surface area of 0.28 m2 is located in a room in which the walls and the air are at a temperature of 27°C. The exterior surface of the oven is at 150°C, and the next heat
The walls of a typical industrial furnace used for the heat treating of metals are usually a composite structure made up of layers of firebrick, high- temperature insulation, steel plates, and outer
The ceiling of a tract house is constructed of wooden studs with fiberglass insulation between them. On the interior of the ceiling is plaster and on the exterior is a thin layer of sheet metal. A
Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the
In beauty salons and in homes, a ubiquitous device is the hairdryer. The front end of a typical hairdryer is idealized as a thin-walled cylindrical duct with a 6-cm diameter with a fan at the inlet
The interior wall of a large, commercial walk-in type meat freezer is covered under normal operating conditions with a 2-cm thick layer of ice. One day, a power outage cuts electricity to the
Many specialized applications (ranging from advanced gas-turbine blades to medical devices and implants) require metal components that are coated with a protective material layer. In a manufacturing
Estimate the R-values for a 5-cm-thick fiberglass board and a 2.5-cm-thick polyurethane foam layer. Then, compare their respective conductivity times- density products if the density for fiberglass
Design a pressure vessel that can hold 45 kg of saturated steam at 2.75 MPa (abs) for a chemical process. The shape of the vessel is to be a cylinder with hemispherical ends. The vessel is to have
An inventor wants to increase the efficiency of wood-burning stoves by reducing the energy lost through the exhaust stack. He proposes to accomplish this by attaching fins to the outer surface of the
The heat transfer coefficient between a surface and a liquid is 57 W/ (m2 K). How many watts per square meter will be transferred in this system if the temperature difference is 10°C?
Suppose that waste heat from a refinery is available for a chemical plant located 1.6 km away. The waste stream from the refinery consists of 1 standard cubic meter per second of corrosive gas at
Electrical resistance heaters are usually made from coils of nichrome wire. The coiled wire can be supported between insulators and backed with a reflector, for example, as in a supplemental room
The shield of a nuclear reactor is idealized by a large 25-cm-thick flat plate having a thermal conductivity of 3.5 W/(m K). Radiation from the interior of the reactor penetrates the shield and there
Calculate the rate of heat loss per foot and the thermal resistance for a 15-cm schedule 40 steel pipe covered with a 7.5-cm-thick layer of 85% magnesia. Superheated steam at 150ºC flows inside the
A very thin silicon chip is bonded to a 6-mm thick aluminum substrate by a 0.02-mm thick epoxy glue. Both surfaces of this chip-aluminum system are cooled by air at 25ºC, where the convective heat
A cylindrical liquid oxygen (LOX) tank has a diameter of 1.22 m, a length of 6.1 m, and hemispherical ends. The boiling point of LOX is –179.4ºC. An insulation is sought that will reduce the
For the design of a novel type of nuclear power plant, it is necessary to determine the temperature distribution in a large slab-type nuclear fuel element. Volumetric heat is generated uniformly in
Nomads in the desert make ice by exposing a thin water layer to cold air during the night. This icing or freezing of thin layers of water is often also referred to as ice making by nocturnal (or
A solution with a boiling point of 82ºC boils on the outside of a 2.5-cm tube with a No. 14 BWG gauge wall. On the inside of the tube flows saturated steam at 420 kPa (abs). The convection heat
Estimate the rate of heat loss per unit length from a 5-cm ID, 6-cm OD steel pipe covered with high temperature insulation having a thermal conductivity of 0.11 W/(m K) and a thickness of 1.2 cm.
A long, hollow cylinder is constructed from a material whose thermal conductivity is a function of temperature according to k = 0.15 + 0.0018T, where T is in ºC and k is in W/(m K). The inner and
A spherical vessel, 0.3 m in diameter, is located in a large room whose walls are at 27°C (see sketch). If the vessel is used to store liquid oxygen at –183°C and both the surface of the storage
A spherical interplanetary probe with a 30-cm diameter contains electronic equipment that dissipates 100 W. If the probe surface has an emissivity of 0.8, what is its surface temperature in outer
The heat transfer coefficient for a gas flowing over a thin flat plate 3-m long and 0.3-m wide varies with distance from the leading edge according toIf the plate temperature is 170°C and the gas
A wall with a thickness L is made of a material with a thermal conductivity that varies with its thickness x according to the equation, k = (ax + b) W/mK, where a and b are constants. If the heat
In an experimental set up in a laboratory, a long cylinder with a 5-cm diameter, and an electrical resistance heater inside its entire length is cooled with water flowing crosswise over the cylinder
Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 816°C and 260°C, respectively. Determine the rate of heat transfer by radiation between the
A cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2
To determine the thermal conductivity of a structural material, a large 15-cm-thick slab of the material is subjected to a uniform heat flux of 2500 W/m2 while thermocouples embedded in the wall at
A furnace wall is to be constructed of brick having standard dimensions of 22.5 cm × 11 cm × 7.5 cm Two kinds of material are available. One has a maximum usable temperature of 1040°C and a
On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to a temperature of – 5°C, while the inner surface is kept at 20°C. The thermal conductivity of
To insulate high-temperature surfaces it is economical to use two layers of insulation. The first layer is placed next to the hot surface and is suitable for high temperature. It is costly and is
Design a heating system for a small factory in Denver, Colorado. This is a multistep problem that is continued in subsequent chapters. In the first step, you are to determine the heating load on the
Design a thermocouple installation to measure the temperature of air flowing at a velocity of 15 m/s in a 1-m-diameter duct. The air is at approximately 1000°C and the duct walls are at 200°C.
In a cylindrical fuel rod of a nuclear reactor, heat is generated internally according to the equationCalculate the temperature drop from the centerline to the surface for a 2.5-cm-diameter rod
Liquid oxygen is to be stored on the service module of NASA’s new Orion Spacecraft (NASA, “Orion Quick Facts,” FS-2014-08-004-JSC, Lyndon B. Johnson Space Center, Houston, TX)* in a spherical
The development of contact lenses has transformed the solutions that are available today for vision impairments. However, wearing them also poses several problems that includes the condition of dry
In cryogenic surgery, a small spherical probe is bought into contact with the diseased tissue which is frozen and thereby destroyed. One such probe can be modeled as a 3-mm diameter sphere whose
The top of a 30-cm I-beam is maintained at a temperature of 260ºC, while the bottom is at 93ºC. The thickness of the web is 1.25 cm. Air at 260ºC is blowing along the side of the beam so that h̅
Determine by means of a flux plot the temperatures and heat flow per unit depth in the ribbed insulation shown in the accompanying sketch. Insulated boundary 100°C k = 0.5 W/m K 30°C 30°C -24
Determine the rate of heat flow per meter length from the inner to the outer surface of the molded insulation in the sketch. Use k = 0.17 W (m K). 15 cm 7.5 cm Insulation Temperature of this
A large number of 3.8-cm-OD pipes carrying hot and cold liquids are embedded in concrete in an equilateral staggered arrangement with centerlines 11.2 cm apart as shown in the sketch. If the pipes in
A long, 1-cm-diameter electric cable is embedded in a concrete wall (k = 0.13 W/m K) that is 1 m × 1 m, as shown in the sketch. If the lower surface is insulated, the surface of the cable is 100ºC,
A 15-cm-OD pipe is buried with its centerline 1.25 m below the surface of the ground (k of soil is 0.35 W/(m K)). An oil having a density of 800 kg/m3 and a specific heat of 2.1 kJ/(kg K) flows in

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