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One experimental method of measuring an insulating material’s thermal
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- A hollow pure aluminum sphere with an electrical heater in the center is used in tests at steady-state conditions to determine the thermal conductivity of insulating materials. The inner diameter of the sphere is 0.350m; the outer diameter is 0.400m. For this test, the inner surface temperature of the pure aluminum sphere is held at a constant temperature of 250.0°C. The pure aluminum sphere is uniformly covered with an insulating material, 0.0900m thick. The outside surface of the insulating material is exposed to convection; T_inf = 22.0°C, h_inf = 25.0 W/(m2-K). The power required to keep the inner surface of the sphere at 250.0°C is 85.0W (this is assumed to be equal to the heat transfer rate, q). Ignoring contact resistance, determine the thermal conductivity of the insulating material, k.arrow_forwardSamples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 4.96 kg; sample B has a mass of 1.35 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.80 °C. What is the specific heat of sample A? 100 AT, 60 20 10 20 8. 16 t (min) Q/m (kJ/kg) (a) (b)arrow_forwardSamples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 5.37 kg; sample B has a mass of 1.64 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.10 °C. What is the specific heat of sample A? 100 AT A 60 20 10 20 8. 16 t (min) Q/m (kJ/kg) (a) (b) Number i Units T (°C) AT (C°)arrow_forward
- While swimming, conduction can play a big role in heat loss from the body. The body of one swimmer has a total surface area of 1.80 m2 and an average thickness of 1.60 mm. The skin's thermal conductivity is 0.370 W/m-K. If the water's temperature is 20.0°C, and the blood reaching the inner surface of the skin is at 37.0°C, what is the rate of energy loss for that person through conduction?arrow_forwardSamples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 4.79 kg; sample B has a mass of 1.50 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.50 °C. What is the specific heat of sample A? Number i T (°C) 100 60 20 0 A Units 10 t (min) (a) 20 AT (Cº) AT, 0 8 Q/m (kJ/kg) (b) 16arrow_forwardA closed box is filled with dry ice at a temperature of -83.9 °C, while the outside temperature is 26.9 °C. The box is cubical, measuring 0.350 m on a side, and the thickness of the walls is 3.80 x 10-2 m. In one day, 3.35 x 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made. Number 30251.3 Unitsarrow_forward
- A copper bar is welded end to end to a bar of an unknown metal. The two bars have the same lengths and cross-sectional areas. The free end of the copper bar is maintained at a temperature TH that can be varied. The free end of the unknown metal is kept at 0.0∘C. To measure the thermal conductivity of the unknown metal, you measure the temperature T at the junction between the two bars for several values of TH. You plot your data as T versus TH both in kelvins, and find that your data are well fit by a straight line that has slope 0.460. What do your measurements give for the value of the thermal conductivity of the unknown metal? Use kCu = 385 W/(m⋅K) .arrow_forwardA 880 cm X 1680 cm house is built on a 15.6 cm thick concrete slab of thermal conductivity 0.62 W/m.K.. If the ground temperature of the slab is 7.6ºC while the interior of the house is 21ºC. Calculate the following: a) The temperature difference in kelvin Answer for part 1 . b) The temperature gradient (ΔT/Δx) in kelvin/metre Answer for part 2 . c) The heat loss rate through the concrete slab in kilowatt Answer for part 3 .arrow_forwardA box with a total surface area of 1.20 m2 and a wall thickness of 4.00 cm is made of an insulting material. A 10.0 -W electric heater inside the box maintains the inside temperature at 15.0 °C above the outside temperature. Find the thermal conductivity k of the insulating material.arrow_forward
- You are insulating a metal pipe carrying a hot fluid. The outside Diameter of the pipe is 3.5 cm, and the pipe has a length of 7.7 meters. Due to the fluid inside the pipe, the outside surface of the metal fluid pipe is kept at a constant temperature of 85.0°C. The metal pipe is inserted inside of a thin-wall circular tube, which has an inside diameter of 11.2 cm (ignore the resistance of the thin-wall circular tube). The space between the outside of the hot metal pipe and the inside of the thin-wall circular tube is filled with foam insulation, k = 0.036 W/m-K. The outside of the thin-walled circular tube is kept at a constant temperature of 28.0°C. Due to a manufacturing error, the metal pipe was not centered inside the thin-wall tube when the foam insulation was added, but was instead installed with an eccentricity of 2.0 cm (i.e. the center of the metal pipe is 2.0 cm distance from the center of the thin-walled circular tube). Calculate the increase in the heat transfer rate due to…arrow_forwardA 900 g copper rod at 20 degrees celcius has a length of 1.0000 m. The thermal expansion coefficient of copper is 17 x 10^-6 degrees celcius -1. The specific heat capacity is 0.385 kJ/kg degrees celcius. Question A: The copper is heated to 400 degrees celcius. What is the new length? Give the answer in meters and with 4 digits of precision after the decimal. Question B: The hot copper is then quenched by dunking the entire rod in a bucket with 10 kg of water at 20 degrees celcius. The specific heat capaciy of water is 4.18 kJ/kg degrees celcius. If none of the water turns to steam what is the equilibrium temp of the copper rod and water? Please give the answer in degrees celcius Question C: You measure the equilbrium temp and find that it is 24 degrees celcius. If the latent heat of vaporization of water is 2,260 kJ/kg, what mass of water turned to steam? Answer in gramsarrow_forwardIn an experiment to determine the specific heat of copper, a piece of copper weighing 50.06 is first heated to 100°C in steam. It is then immersed into water at 27.06°C.The water in the calorimeter weighs 100.08 g and the inner aluminum cap weighs 50.07 g. If the final temperature is 30.01°C, what is the specific heat of copper in CGS units given that the specific heat of aluminum is 0.22 cal/g- C? (Put only the value in three significant figures without the unit.) hanges to this answer Question 14 of 20arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning