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Chapter 1 Solutions
Introduction to Heat Transfer
- A thermocouple shielded by a layer of aluminum foil and copper with an emissivity of 0.05 and 0.02 is used to measure the temperature of hot gases flowing in a duct whose walls are maintained at T= 380K. The thermometer shows a temperature of Tth= 540 K. Assuming emissivity of the thermocouple junction is 0.7 and convection heat transfer coefficient to be h= 130 W/m2.C, determine the actual temperature of the gas.arrow_forwardThe furnace wall shown in the figure is made of a material with a thermal conductivity of 5 W / m ° C, the radiant emission coefficient of the outer surface of the wall is 0.95, Stefan Boltzman constant is 5.67x104 W / m ^ 2 (K ^ 4), ambient temperature and air temperature 297 K is. The heat transfer coefficient between the outer surface of the wall and the air is h = 20 W / m (K ^ 2). Wall inner surface temperature 573 K, outer surface temperature 308 K Since the value is kept constant a) Find the layer thickness of the wall? b) Find the layer thickness of the wall if the moving fluid medium on the outer surface of the wall is corroded?arrow_forwardThe temperature of a cylindrical tank containing liquid nitrogen is -10 ° C. Tank diameter is 16 cm. The amount of heat lost by convection and radiation from the tank to the environment is 65.5 W / m. Calculate the temperature of the environment where the tank is located: h = 4.35 W / m2K, ∈ = 1.arrow_forward
- In a textile unit, hot fluid flows through a long steel pipe (k=15 W/m°C) with inner and outer diameters of 70 mm and 75 mm, respectively. The convection coefficient between the hot fluid and the inner surface of the pipe is 100 W/m²K, the convection coefficient between the outer surface of the pipe and the ambient air is 10 W/m²K, and the emissivity (emission) coefficient of the pipe is 0,75. Under steady regime conditions; Since the pipe outer surface temperature is 80°C, the outside air and ambient temperature is 20°C,a) The total amount of heat lost to the environment per unit length of the pipe,b) Calculate the hot fluid temperature and the pipe inner surface temperature.arrow_forward3. A food-processing plant requires that two large process areas A and B be kept at constant temperature TA 12°C. The refrigeration load of area A is 175 kW. The heating load of area B is 210 kW. Conditioning of the two spaces is achieved by an (cyclic) electrical air-conditioning and heating unit (CM) that also interacts with the environment at To = 5°C, as shown in the В., 12°С 8°C and TB Work R 5°C figure. А, —8°С a. What is the least amount of electrical power required to operate the air- conditioning and heating unit? b. Determine the rate of energy exchange between the unit (CM) and the environment in case a.arrow_forwardA thermocouple shielded by a layer of aluminum foil and copper with an emissivity of 0.05 and 0.02 is used to measure the temperature of hot gases flowing in a duct whose walls are maintained at T= 380K. Assuming emissivity of the thermocouple junction is 0.7 and convection heat transfer coefficient to be h= 130 W/m2.C, determine the radiation heat transfer from thermocouple junction to duct wall.arrow_forward
- A spherical pellet (ρ =1000 kg/m3 , c = 1000 J/(kg⋅K)) with a radius ro = 1 cm is cooled from an initial temperature of 200°C by immersion in water bath at 10°C with a convection coefficient h = 100 W/(m2 K). Evaluate the temperature in the center and on the surface of the pellet after 10 s of immersion for two cases: (a) Thermal conductivity of the pellet k = 0.1 W/(m⋅K) (b) Thermal conductivity of the pellet k = 5 W/(m⋅K)arrow_forwardi need the answer quicklyarrow_forwardA thermometric well is placed in a pipe having diameter of 55 mm. Pipe wall temperature is 100°C and heat transfer coefficient inside the pipe is 300 W/m² K. Thickness of thermowell is 1.2 mm and its length is 50 mm. Thermal conductivity of thermowell material. Is 30 W/mK. If the temperature of the gas flowing through the pipe is recorded by thermometer as 200°C, determine the true temperature of gas. If the error in gas temperature is to be reduced by 80% by increasing the length of thermowell, determine the new length of thermowell. Draw a sketch of this thermowell. Take perimeter to area ratio for thermowell as 1/T (T= thickness).arrow_forward
- Please solve asap.arrow_forwardThe heat generated in the circuitry on the surface of a silicon chip (k =130 W/m.C) is conducted to the ceramic substrate to which it is attached. The chip is 6 mm X 6 mm in size and 0.5 mm thick and dissipates 3 W of power for 24 hours. Disregarding any heat transfer through the 0.5 mm high side surfaces, determine the amount of heat dissipates during the 24-hour period. Silicon chip 0.5 mm 3 W CeramicC substrate Select one a. None of the above b. 0.072KWh c. 0.72KWh d. 0.027KWharrow_forwardA thin board of 0.5 cm thickness is exposed to a fluid of T, = 22°C and h = 30 W/m².K from one side with an emissivity of 0.7 where it faces a surrounding whose temperature is Tsur = 30°C. A heat flux of q" = 3500 W/m? is applied to the other side. Each side has an area of 12cm×12cm. Tsur (a) If the board has the following properties: k = 15.1 W/m.K, c, = 480 J/kg.K and p = 8055 kg/m², express an equation for the variation of temperature with respect to time. (b) Find the initial time rate of change of the board temperature if the initial board temperature is q" h 50°C.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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