Consider a spherical shell satellite with outer diameter of 4 m and shell thickness of 10 mm that is reentering the atmosphere. The shell satellite is made of stainless steel with properties of
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Heat and Mass Transfer: Fundamentals and Applications
- Q2/ A 4-m-internal-diameter spherical tank made of 1.75-cm-thick stainless steel (k 15 W/m °C) is used to store iced water at 0°C. The tank is located in a room whose temperature is 35°C. The walls of the room are also at 35°C. The outer surface of the tank is black, and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m2 °C and 10 W/m2· °C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a l-h period. The heat of fusion of water at atmospheric pressure is hif 334 kJ/kg.arrow_forwardA 6 cm diameter cylinder is initially at a temperature of 10 °C. Later, this cylinder was thrown into water at 80°C. Calculate how long it will take for the center temperature of the cylinder to reach 50 °C by taking the convection heat transfer coefficient as 80W //m?K. Thermal properties of the cylinder material k=0,587 W/m°C a = 0,13x10-m² /sarrow_forwardA plate heated with a heat flux of 5 kW/m^2 and has an emissivity of 0.3. the air is over the plate has a temperature of 313 K and the heat transfer coefficient is 15 W/m^2K. the surrounding temperature is also the same as the air temperature. *Determine the surface temperature of the plate.arrow_forward
- The top surface of the passenger car of a train moving at a velocity of 70 km/h is 2.8 m wide and 8 m long. The top surface is absorbing solar radiation at a rate of 200 W/m?, and the temperature of the ambient air is 30°C. Assuming the roof of the car to be perfectly insulated and the radiation heat ex- change with the surroundings to be small relative to convec- tion, determine the equilibrium temperature of the top surface of the car. Answer: 35.1°C 200 W/m2 Air 30°C 70 km/harrow_forwardConsider a thin suspended hotplate that measures 0.4 mx 0.4 m. The isothermal plate has a mass of 3.75 kg, a specific heat of 2770 J/kg-K, and a temperature of 200°C. The ambient air temperature is 25°C and the surroundings temperature is 25°C. If the convection coefficient is 6.4 W/m²-K and the emissivity of the plate is = 0.42, determine the time rate of change of the plate temperature, dT/dt, when the plate temperature is 200°C. Evaluate the magnitude of the heat losses by convection and by radiation. dT/dt = i 19radl = i 19conv = i K/s W Warrow_forwardA 6 cm diameter sphere is initially at a temperature of 100C. Later, this sphere was thrown into water at 800C. Calculate how long it will take for the center temperature of the sphere to reach 500C by taking the convection heat transfer coefficient as 80W / m2K. Thermal properties of sphere material: k=0,627 W/moC a=0,151x10-6 m2/sarrow_forward
- Convection. A thin 100 cm long and 10 cm wide horizontal plate is placed in a large tank full of water at 60°C. At what uniform temperature, in °C, should be maintained in the plate if the rate of heat supplied to the plate is 2 kW as heat is dissipated from either side? The convection heat transfer coefficient at the lower side is h, = 384.5 W/m²K and h,= 3215.5 W/m²K at the upper side.arrow_forwardConvection 2. For a boiling process such as shown in Figure below, the ambient temperature Tin Newton's law of cooling is replaced by the saturation temperature of the fluid Tsat. Consider a situation where the heat flux from the hot plate is q=20 x 105 W/m². If the fluid is water at atmospheric pressure and the convection heat transfer coefficient is hw=20 x 103 W/m2 K, determine the upper surface temperature of the plate, Ts, w. In an effort to minimize the surface temperature, a technician proposes replacing the water with a dielectric fluid whose saturation temperature is Teat, d=52 °C. If the heat transfer coefficient associated with the dielectric fluid is h = 3 x 103 W/m2 K, will the technician's plan work?arrow_forwardHi, can you help me to answer this question using the first law of thermodynamics formula to explain this event? On a hot summer day, a student turns his fan on when he leaves his room in themorning. When he returns in the evening will the room be warmer or cooler than theneighborouing rooms ? Explain your answer using the first law of thermodynamics.Assume ALL doors and windows are kept closed.arrow_forward
- A pipe 30 m long with an outer diameter of 75 mm is used to carry steam at a rate of 1000 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe. a. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam coming out = Answer kJ / kg. c. Determine the vapor heat change / loss along the flow = Answer watt. d. Specify the minimum required insulation thickness = Answer cm.arrow_forwardSilver shafts of 0.1 m diameter are heat treated in a gas-fired furnace whose gases are at 1200 K and provide a convection coefficient of 50 W/m².K. The shafts enter the furnace at 400 K and they remain in the furnace for 1000 s. Determine the centerline temperature of the shaft when it comes out of the furnace?arrow_forwardA 5.0-cm-diameter cylinder is heated to a temperature of 200 oC, and air at 30 oC forced across it at a velocity of 50 m/s (h = 180 W/m2K). If the surface emissivity is 0.7, calculate the total heat loss per unit length if the walls of the enclosing room are at 10 oC. Comment on your calculation. COMPLETE SOLUTIONarrow_forward
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