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One experimental method of measuring an insulating material’s thermal
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An Introduction to Thermal Physics
- The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?arrow_forward500 g of Ice at 0 °C is kept in an insulated cubic box. The length of the box is 30 cm and the thickness of the wall is 0.5 cm. The thermal conductivity of the wall is 0.04 W/mK. If the environment temperature outside the box is 25 °C, Determine (a) the rate of heat loss due to the heat conduction.arrow_forwardThe walls of the storage room are 3 m high, 16 m wide, and 25 cm thick. The thermal conductivity is k = 0.85 W / (m ° C). During the day, the inner wall surface temperature is 22 ° C and the outer surface temperature is 4 ° C: a. Using the Thermal Resistance Concept, calculate the heat transfer resistance for the wall. = Answer ° C / watt. b. Calculate the rate of heat transfer through the wall at steady-state conditions. = Answerwattarrow_forward
- What is the rate of heat transfer in J/s through the body's skin and the fat layer just beneath its surface? Treat the skin and fat as a single layer that is 1.20 cm thick. Assume the temperature of the inner surface of the layer corresponds to internal body temperature, or 36.7 °C, and the temperature of the outer surface of the layer corresponds to skin temperature, or 34.0 °C. Take the total surface area of the layer to be 1.50 m² and use a value of 0.413 W/(m-C°) for the average thermal conductivity of the layer. Number Unitsarrow_forwardA 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_forwardA closed box is filled with dry ice at a temperature of -86.0 °C, while the outside temperature is 21.0 °C. The box is cubical, measuring 0.394 m on a side, and the thickness of the walls is 4.49 × 102 m. In one day, 3.76 × 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made. Number Unitsarrow_forward
- Samples 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_forwardWhile 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_forward
- Samples 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_forwardA 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_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning