A long, highly polished aluminum rod of diameter
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Introduction to Heat Transfer
- An electric heater producing 260 W of heat is used to warm up a room containing 7 m3 of air. If we assume the room is perfectly sealed and there is no heat loss through the room boundaries, such that all of the heater output goes into increasing the air temperature, how long will it take to heat up the air in the room from 5.0 °C to 24.1 °C? Give your answer to the nearest minute and assume that the specific volume (v = 0.85 m3/kg) and specific heat capacity at constant volume (cv = 1.005 kJ/(kg K)) remain constant throughout the heating process.arrow_forward5 Problem = 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 ρ 1000 kg/m³ and thermal conductivity of k = 0.606 Watts/(m.°C) 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. Figure 1: Image source: [Link]arrow_forwardThe temperature of an experimental heated enclosure is being ramped up from 80 to 450°F at the rate of 19°F/min. A thermocouple, embedded in a Thermowell for protection, is being used to monitor the oven temperature. The thermocouple has a time constant of 84 s. At t = 10 min, what is the difference between the actual temperature and the temperature indicated by the thermocouple? Final answer in whole number. Please show your complete solution and write readable.arrow_forward
- The temperature of an experimental heated enclosure is being ramped up from 80 to 450°F at the rate of 19°F/min. A thermocouple, embedded in a Thermowell for protection, is being used to monitor the oven temperature. The thermocouple has a time constant of 84 s. At t = 10 min, what is the difference between the actual temperature and the temperature indicated by the thermocouple? Final answer in whole number. Please show your complete solution and write readable.arrow_forwardEXPERIMENT PROBLEM: A certain mechanical device with a mechanism similar to a piston contains a certain amount of gas. Upon compression from 55 L to 15 L, the gas released 350 J of heat. Experiment shows that the external pressure of the mechanical device is given by: Pext = AsinV + BcosV + CsinhV + DcoshV Where: A = 100 B = 80 C = 1x10⁻²⁵ D = 5x10⁻³⁰ sin = sine function cos = cosine function sinh = hyperbolic sine function cosh = hyperbolic cosine function V = in liters Pext = in atm Determine the change in internal energy of the system in kilojoules. TIP: usually, expressions involving trigonometric functions are in radians.arrow_forwardThe pin-connected structure shown in Fig. P5-68 consists of a rigid bar ABCD, a steel [E = 210 GPa, and α = 11.9(10−6)/°C] bar BF, and an aluminum alloy [E = 73 Gpa and α = 22.5(10−6)/°C] bar CE. The cross-sectional areas are 1200 mm2 for bar BF and 900 mm2 for bar CE. The bars are unstressed when the structure is assembled at 40°C. Determine a. The normal stresses in the bars after the temperature is reduced to − 20° C. b. The shearing stresses in the 30-mm-diameter pins at A, B, and C. Pin B is in double shear, and pins A and C are in single shear. c. The vertical component of the displacement of pin D from it original position. Figure P5-68arrow_forward
- A mass less spring having a spring content k=185 N/m, is inside a horizontal barrel. It's left end is rigidly fixed at position z= 0.0 cm, and it's right end is at X=L, where L=19.7 cm. The spring is then squeezed so that the right end of the spring is at the X=s, where S=13 cm. A ball of mass 50g is put in front of the spring and the spring is released. Calculate the speed of the ball in m/s. as it comes out of the barrel. Ignore friction Inside the barrel.arrow_forwardDamian’s car weighs 2000kg. The spring has a natural unstretched length of 2m and a spring constant of k = 80000N/m. Hooke's law can be written as T = kd. Where T is the tension force in newtons, k is the spring constant and d is the length in metres. Let x(t) be the position of the front of Damian’s car and let y(t) be the position of the back of Eva’s 4WD. We will assume that the position of Eva’s car is a known function of time. Q1 a) Create a sketch of the positions of the vehicles similar to the one given and add the positions x and y. b) What is the extension of the spring in terms of x(t) and y(t)? Be careful to take into account that the unstretched length of the spring is 2m.arrow_forwardThe temperature of a experimental heated enclosure is being ramped up from 80 to 450°F at the rate of 20°F/min. A thermocouple, embedded in a Thermowell for protection, is being used to monitor the oven temperature. The thermocouple has a time constant of 6 s. ( a ) At t = 10 min, what is the difference between the actual temperature and the temperature indicated by the thermocouple? What is it at 60 min? ( b ) When the thermocouple indicates 450°F, the heater will begin to modulate and maintain the temperature at the desired 450°F. What is the actual oven temperature when the thermocouple first indicates 450°F?arrow_forward
- Initially, the temperature of an object is 70 degrees celsius, it is taken outside. The temperature of the surrounding is 20 degrees celsius at 3:03 Pm, the temperature of the body becomes 42 degrees celsius. Later, the object is then taken back inside where the temperature is 80 degrees celsius. At 3:10 PM, the temoerature of the object is 71 degrees celsius. Determine the time when the object is brought inside.arrow_forwardThe inner and outer radii of a hollow cylinder are 15 mm (r, ) and 25 mm (r, ), respectively. The temperatures of the inner and outer walls are 400°C (T,) and 350°C (T,), respectively. The thermal conductivity of the cylinder material obeys the relationship K = (400-0.05T) W/mK where T is in degrees Celsius. Find the heat transferred from the hollow cylinder per unit length. The thermal conductivity,arrow_forwardAccording to the Stefan-Boltzmann Law, the thermal radiation energy emitted (per unit time) by a hot object is proportional to the fourth power of the absolute temperature: E = kT, where k is a proportionality constant and T is measured in kelvin. Find the relationship between the measured error in temperature T and the resulting error in energy E.arrow_forward
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