Chapter 4, Problem 4.2P

****I hope that the solution is written on the computer and not written so that I can transfer it and understand it more quickly A composite wall of a refrigerator consists of three different materials; A, B, and C. Two of the used materials have known thermal conductivity, kA = 30 W/m. K and kC=45 W/m. K, and known thickness, LA=0.20 m and LC = 0.15 m. The third material, B, which is sandwiched between materials A and C, is of known thickness, LB = 0.15 m, but unknown thermal conductivity kB. Under steady-state operating conditions, measurements reveal an outer surface temperature of Ts,o = 20°C, an inner surface temperature of Ts,i = 600°C, and a refrigerator air temperature of T∞ = 800°C. The inside convection coefficient h is known to be 25 W/m2.K. (a) First, draw the thermal circuit for this wall. (b) What is the value of thermal conductivity for material B?

A small sphere (emissivity = 0.745, radius = r1) is located at the center of a spherical asbestos shell (thickness = 1.72 cm, outer radius = r2; thermal conductivity of asbestos is 0.090 J/(s m Co)). The thickness of the shell is small compared to the inner and outer radii of the shell. The temperature of the small sphere is 727 °C, while the temperature of the inner surface of the shell is 406 °C, both temperatures remaining constant. Assuming that r2/r1 = 6.54 and ignoring any air inside the shell, find the temperature in degrees Celsius of the outer surface of the shell.

Steam is being transported in a pipe at a chemical production facility in Gebze, Kocaeli. Theouter diameter of the pipe is 8 cm, and the surrounding air temperature is 20 °C. On the surface of thepipe, the combined heat transfer coefficient is 35 W/m2*K. The surface temperature of the pipe is 150 °C.Steady-state conditions exist.(a) What is the rate of heat loss from the pipe to the surroundings?(b) The power used to generate the steam is obtained from natural gas. Perform an online search forapproximate values of the calorific value of natural gas, as well as the cost of natural gas per cubicmeter, and estimate the financial loss due to heat loss from this steam pipe within a period of oneyear. Indicate your sources clearly in your answer.

The composite wall of an oven consists of three materials, two of which are of knownthermal conductivity, kA = 20 W/m – K and kC = 50 W/m – K, and known thickness, LA =0.30 m and LC = 0.15 m. The third material, B, which is sandwiched between materialsA and C, is of known thickness, LB = 0.15 m, but unknown thermal conductivity kB.Under steady – state operating conditions, measurements reveal an outer surfacetemperature of 600 oC, and an oven air temperature of 800 oC. The inside convectioncoefficient h is known to be 25 W/m2 – K. total rate of heat transfer = 550 W/m2.What is the value of kB?

How long should it take to boil an egg? Model the egg as a sphere with radius of 2.3 cm that has properties similar to water with a density of = 1000 kg/m3 and thermal conductivity of k = 0.606 Watts/(mC) and specific heat of c = 4182 J/(kg C). Suppose that an egg is fully cooked when the temperature at the center reaches 70 C. Initially the egg is taken out of the fridge at 4 C and placed in the boiling water at 100 C. Since the egg shell is very thin assume that it quickly reaches a temperature of 100 C. The protein in the egg effectively immobilizes the water so the heat conduction is purely conduction (no convection). Plot the temperature of the egg over time and use the data tooltip in MATLAB to make your conclusion on the time it takes to cook the egg in minutes.

A new 1 ft thick insulating material was recently tested for heat resistant properties. The data recorded temperatures of 70 deg. F and 210 deg. F on the cold and hot sides, respectively. If the thermal conductivity of the insulating material is 0.026 Btu/ft . h .⁰ F, calculate the rate of the heat flux,Q/A, through the wall in Btu/ft^2 . h. Resolve the problem in SI units.

After the sinking of RMS Titanic, US operated the International Ice patrol with the purpose of monitoring the presence and movements of icebergs in the Atlantic and Arctic oceans. Once, they observed a unique tabular iceberg in a form of a rectangle (250 km x 50 km x 300 m). How many years would it take to melt the iceberg solely by heat from the sun if the ice absorbs a mean of 98 J/m2 -s, 12.5 hrs per day? Note: the exposed area for heating is 250 km x 50 km and the density is 920 kg/m3 .   This is my solution.

Model the following heat transfer situations. Specify heat flows and storages. Try to write down the mathematical expressions. (i) Solar heating of the road surface (ii) A steam pipe passing through an open space between two buildings (iii) Heat transfer from a person in a warm room in the cold season (iv) Pressure cooker-warming up-cooling down (v) Pressure cooker-steady conditions (vi) A rod with one end in a furnace and the remaining surface in atmosphere (vii) A wire carrying current, exposed to air (viii) A water heater (electrical) with hot water being drawn out with cold water admission. (ix) Cake being baked in an oven or a fruit placed in a refrigeration (x) A frying pan placed on a stove. 1.2 Choose the correct statement in each question. (i) A pipe carrying steam at about 300°C traverses a room, the air being still at 30°C. The major fraction of the heat loss will be by (a) conduction to the still air (b) convection to the air (c) radiation to the surroundings…

Two plane disks each 1.25 m in diameter are parallel and directly opposed to each other. They are separated by a distance of 0.5 m. Disk 1 is heated by electrical resistance to 833.3 K. Both disks are insulated on all faces except the two faces directly opposed to each other. Assume that the surroundings emit no radiation and that the disks are in space. Calculate the temperature of disk 2 at steady state and also the electrical energy input to disk 1. Hint: The fraction of heat lost from area 1 to space is (1 – F12)