2) Urethane (k = 0.026 W/m-K) is used to insulate the sidewall and the top and bottom of a cylindrical hot water tank. The insulation is 40 mm thick and is sandwiched between sheet metal of thin-wall construction. The height and inside diameter of the tank are 2 m and 0.8 m, respectively. The tank is in ambient air with T = 10 °C and h = 10 W/m²-K. If the hot water maintains the inner surface at 55 °C, and energy costs amount to $0.15 per kWh, what is the daily cost to maintain the water in storage? Argue that the thermal resistance of the tank wall is negligible. What does this say about the temperature drop across the tank wall?

2) Urethane (k = 0.026 W/m-K) is used to insulate the sidewall and the top and bottom of a cylindrical hot water tank. The insulation is 40 mm thick and is sandwiched between sheet metal of thin-wall construction. The height and inside diameter of the tank are 2 m and 0.8 m, respectively. The tank is in ambient air with T = 10 °C and h = 10 W/m²-K. If the hot water maintains the inner surface at 55 °C, and energy costs amount to $0.15 per kWh, what is the daily cost to maintain the water in storage? Argue that the thermal resistance of the tank wall is negligible. What does this say about the temperature drop across the tank wall?

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

Thermodynamics problem. A membrane type electrical heater of 20,000 w/m? capacity is sandwiched between an Insulation of 25 mm thickness with thermal conductivity of 0.029 W/m-K and a metal plate with k = 12.6 W/m-K of thickness 15 mm. The convection coefficient is 150 W/m2-K. The surroundings are at 5°C. Determine the surface temperature of the heater and the flow on either side.
A 1,155 ft², 4 in. thick concrete wall has inside and outside surface temperatures of 24°C and 4°C. A 2 in. insulation batt with a thermal conductivity of k= 0.03 Btu/(h. ft. °F) is added to the wall. Determine the reduction in heat transfer rate. What is the thickness of the insulation in meters? 0.0508 x Your response differs from the correct answer by more than 10%. Double check your calculations. m What is the thermal conductivity value of the insulation batt in W/(m. K)? 0.05188 W/(mK) What is the R-value of the concrete wall (in m². K/W)? 0.022578 X Your response differs from the correct answer by more than 10%. Double check your calculations. m². K/W What is the R-value of the insulation batt (in m² K/W)? 1.9584 X Your response differs from the correct answer by more than 100%. m² K/W What is the heat transfer rate (in W) when the insulation is added? X W What is the percent reduction in the heat transfer rate? 96 x %
It is intended to reduce heat losses of a glass window (k = 1.4 W/m.K) with 6 mm thick, covering it with a polystyrene insulation (k = 0.027 W/(m.K) with 25 mm thickness. The contact resistance between the glass and the insulation is estimated at 0.002 m². K/W, while the heat transfer coefficient by convection of the outer surface of the window is worth he = 20 W/(m². K). With insulation, the convection heat transfer coefficient in the inner wall is hi = 2 W/m². K; no insulation is hi = 5 W/m². K. If the total surface area of the window is A = 12 m², what are the heat losses associated with insulated and non-insulated window for indoor and outdoor air temperatures Ti= 20 ºC and Te = – 12 ºC?
A 1-in Sch 40 stainless steel pipe with a thermal conductivity of 45 W/m-K can move 1,000 kg of saturated steam per hour at 150 °C. Refractory material 0.25 inches thick with a thermal conductivity of 0.025 W/m-K insulates the pipe. At a temperature of 25 °C, the pipe is exposed to the outside air. There is a 1135 W/m2 internal heat transfer coefficient.40 W/m2-K is the outside heat transfer coefficient, whereas -K. Suppose that only the radial direction is involved in steady-state heat transfer and that radiation effects are negligible. ✓ Determine how much heat is being lost through these pipes to the environment.a. 399.1 W/mb. 1525.0 W/mc. 618.4 W/md. 1128.7 W/me. none of the above √ How about the insulated pipe's surface temperature?a. 118.5 °Cb. None of the abovec. 101.5 °Cd. 216.3 °Ce. 292.2 °C
Troom = 25°C Problem-4: An 8-m-internal-diameter spherical tank made of 1.5-cm-thick stainless steel (k = 15 W/m-K) is used to store iced water at 0°C. The tank is located in a room whose temperature is 25°C. The walls of the room are also at 25°C. The outer surface of the tank is black (emissivity = 1), and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m²-K and 10 W/m².K, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a 24-h period. The heat of the fusion of water at atmospheric pressure is hf5 333.7 kJ/kg. Iced water D D₁= 8 m Tin = 0°C 1.5 cm
Hot-surface temperature of a 12-mm thick fire brick wall is maintained at 913 K. If the average thermal conductivity of the wall material is 0.123 W/m.K. Determine the maximum heat loss through the wall to ensure its cold-surface temperature does not exceed 364 K. For an ambient air temperature of 292 K, what is the surface coefficient of the wall material?
A thick-walled tube of stainless steel (L = 0.50 m; k = 21.63 W/m-K) with an inside diameter of 0.0254 m and outside diameter of 0.0508 m, is covered with an insulation (∆x =0.0254 m) with k = 0.2423 W/m-K. If the inside wall temperature of the pipe is at 400 oC, calculate the temperature at the interface between the metal and the insulation (in oC) if the outside surface of the insulation is at 29.8 oC. 99 K in Pa.
A thick-walled cylindrical tubing of hard rubber (k=0.151 W/m*K) having an inside radius of 5 mm and an outside radius of 20 mm is being used as a temporary cooling coil in a bath. Ice water is flowing rapidly inside, and the inside wall temperature is 275 K. The outside surface temperature is 300 K. A total of 20 W must be removed from the bath by the cooling coil. How many meter of tubing are needed?
Thermal jackets are typically put on cryogenicstorage tanks to minimize the heat transfer gainsfrom the surroundings. Consider a cylindercontainer that is 1.5 m long made from steel (k = 750W/m.K) with an inner diameter of 0.5 m and outerdiameter of 0.7 m. If the liquefied natural gas (LNG)inside the cylinder is maintained at 90 K, ambientconditions are Tamb = 20 °C, h = 7 W/m2.K. What isthe required thermal jacket thickness to maintainthe outer temperature of that jacket of 15 °C? (Takea thermal conductivity of the insulation to be kins =0.015 W/m.K). Image credit: Okorder. Image forillustrative purposes only.
An industrial cold room has four 200 mm thick walls made of concrete. The walls are insulated on the outside with a layer of foam 60 mm thick. Cladding with a thickness of 15 mm protects the foam on the outside from the elements. The composite wall surface temperatures are –3 °C on the inside and 18 °C on the outside of the room respectively. The thermal conductivities of concrete, foam and cladding are 0.75, 0.35 and 0.5 W/m K respectively. Assuming perfect thermal contact between the layers of the composite walls, draw the typical temperature distribution across the layers and determine the heat energy gained per hour through all 4 walls of the room with a total surface area of 20 m2. What does this heat energy represent in terms of the refrigeration system of the cold room?
A 0.5-ampere current is flowing through a long electrically conducting cylindrical rod. The diameter of the rod is 6 mm, the electrical resistance of the rod is R = 2000 /m, and k =0.9 W/m K for the rod. The rod is encased in a 2-mm thick Pyrex tube and a 20°C liquid is flowing over the outer surface of the Pyrex tube. The convection heat transfer coefficient for the liquid h= 800 W/m2 . K. The interfacial conductance (contact resistance) at the interface between the rod and the Pyrex tube is h = 1200 W/m² - K. a) Compute the rate of heat generation in the rod and use it compute the volumetric rate of heat generation. b) Find the temperature drop across the interface between the outer surface of the rod and the inner surface of the Pyrex tube. c) Find the temperature at the center of the rod.
A large spherical storage tank, 2 m in diameter, is buried in the earth at a location where the thermal conductivity is 1.5 W/m.°C. The tank is used for the storage of an ice mixture at 0°C, and the ambient temperature of the earth is 20°C. Calculate the heat loss from the tank.