Solid objects, such as your desk or a rod of aluminum, can conduct heat. The magnitude of the thermal diffusivity of the material determines how quickly the heat moves through a given amount of material. The equation for thermal diffusivity (a) is given by:
Experiments are conducted to change the specific heat (Cp) of the material while holding the thermal conductivity (k) and the density (ρ) constant. The results are shown graphically.
- a. What are the units of the constant 0.088? Simplify your answer.
- b. If the thermal conductivity of the material is 237 watts per meter kelvin, what is the density of the material?
- c. If the material has a density of 4500 kilograms per cubic meter, what is the thermal conductivity of the material in units of watts per meter kelvin?
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- The following graph shows the thermal behavior of 2 kg of a material called Uniandesato undergoing a solid-liquid phase transition. In a container, thermally insulated from the outside, 20 kg of liquid water at a temperature of 80°C are placed. In addition to this, an unknown amount of Uniandesato in a 100% solid state at its melting temperature (10°C) is added. The specific heat of water is 4186 J/kg°C. a) If the system reaches an equilibrium temperature of 60°C, calculate the initial amount of Uniandesato added to the container. b) Calculate the change in entropy during this process and show that it is consistent with the Second Law of Thermodynamics. Hint: Extract the necessary information to solve this problem from the graph.arrow_forwardA temperature difference of 85 •C is impressed across a fiberglass layer of 13 cm thickness. The thermal conductivity of the fiberglass is 0.035 W/m • -C. Compute the heat transferred through the material in kcal per hour per unit square meter area.arrow_forwardB7arrow_forward
- Determine k, thermal conductivity of a wall if q = 1000 kcal/m2 -hr at thickness, k = 33 mm and ∆t = 30°C.arrow_forwardA solid steel cube is stored in a freezer, where the temperature is −20.0 ̊C. While the cube is in the freezer, you measure its side length (L) to be 1.75050 meters. The cube is then placed outside for a long time, so that the temperature of the cube reaches the temperature of the air outside. As a result, the side length increases to 1.75170 meters due to thermal expansion. The coefficient of linear expansion for steel is 12.0×10−6 ̊C−1. (a) What is the temperature of the air outside? Give your answer in degrees Celsius ( ̊C). (b) What is the volume of the cube when its temperature is 20.0 ̊C? Give your answer in cubic meters (m3).arrow_forward1arrow_forward
- . A thermocouple is a temperature-measurement device that consists of two dissimilar metal wires joined at one end. An oversimplified diagram follows. Metal 1 ΡOTENTIOMΕΤER V(mV) Metal 2 A voltage generated at the metal junction is read on a potentiometer or millivoltmeter. When certain metals are used, the voltage varies linearly with the temperature at the junction of the two metals: V(mV) = aT(°C) +b An iron-constantan thermocouple (constantan is an alloy of copper and nickel) is calibrated by inserting its junction in boiling water and measuring a voltage V = 5.27 mV, and then inserting the junction in silver chloride at its melting point and measuring V = 24.88 mV. (a) Derive the linearequation for V(mV) in terms of T(°C). Then convert it to an equation for T in terms of V. (b) If the thermocouple is mounted in a chemical reactor and the voltage is observed to go from 10.0 mV to 13.6 mV in 20 s, what is the average value of the rate of change of temperature, dTldt, during the…arrow_forwardNumber 16.arrow_forwardHello. Can you please help answer the question shown in the photo? It is a 3-part question which I have attempted many times. I was able to calculate the correct answer for part 2, but part 1 and part 3 still says I am incorrect. Please show how to properly solve the problem. The topic is heat transfer. Thank you.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning