Stone mix concrete slabs are used to absorb thermal energy from flowing air that is carried from a large concentrating solar collector. The slabs are heated during the day and release their heat to cooler air at night. If the daytime airflow is characterized by a temperature and convection heat transfer coefficient of
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Fundamentals of Heat and Mass Transfer
- 2.34 Show that the temperature distribution in a sphere of radius . made of a homogeneous material in which energy is released at a uniform rate per unit volume , isarrow_forwardA refrigerator has a coefficient of performance of 2.50, requires 150 W of electrical power to operate, and maintains a temperature of -4.00 °C within its interior compartment. How long would it take to cool a dozen 1.00 L of water in a plastic wrapper from 33.0 °C to -4.00 °C in this refrigerator? Any heat escaping the plastic should be ignored. Remember that 1.00 g/cm3 is the density of water.arrow_forwardQuestion 2 Water flows through a pipe at an average temperature of T = 50°C. The inner and outer radii of the pipe are ri = 6 cm and r2 = 6.5 cm, respectively. The outer surface of the pipe is wrapped with a thin electric heater that consumes 300 W per m length of the pipe. The exposed surface of the heater is heavily insulated so that the entire heat generated in the heater is transferred to the pipe. Heat is transferred from the inner surface of the pipe to the water by convection with a heat transfer coefficient of h = 55 W/m2 . °C. Assuming constant thermal conductivity and one-dimensional heat transfer, express the mathematical formulation (the differential equation and the boundary conditions) of the heat conduction in the pipe during steady operation and obtain temperature distribution in pipe.arrow_forward
- Example 1: Single-pane window, the window have: Height = 0.8 m Width 1.5 m Thickness = 4 mm k (glass) = 0.78 W/m.K Temperature of air at inner surface = 20°C Temperature of air at outer surface = -10°C Convection heat transfer coefficient on the inner surface h1= 10 W/m2·°C Convection heat transfer coefficient on the outer surface h2= 40 W/m2·°C Determine the heat transfer through the window?arrow_forwardtemperature at every interface. Q4: A thin metal plate is insulated on the back and exposed to solar radiation on the front surface. The exposed surface of the plate has an absorptivity of 0.7 for solar radiation. If solar radiation is incident on the plate at a rate of 700 W/m2 and the surrounding air temperature is 10°C, determine the surface temperature of the plate when the heat loss by convection equals the solar energy absorbed by the plate. Take the convection heat transfer coefficient to be 30 W/m2 °C, and disregard any heat loss by radiation.arrow_forwardQ1/ Consider a large plane wall of thickness L=0.03 m. The wall surface at x =0 is insulated, while the surface at x =L is maintained at a temperature of 30°C. The thermal conductivity of the wall is k=25 W/m °C, and heat is generated in the wall at a rate of g = 9oe0.5x/L W/m³ Where g, = 8 x 10 W /m². Assuming steady one-dimensional heat transfer, (a) express the differential equation and the boundary conditions for heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and (c) determine the temperature of the insulated surface of the wall.arrow_forward
- A wall of length "L" m and height "H" m is made from a thick bricklayer of 20 cm with thermal conductivity of 0.59 W/mK is subjected to heat transfer due to the outside temperature as 38 oC and inside temperature 24 oC. If the energy loss is 12867 kJ in 9 hours. Determine the Heat transfer rate, Surface Area and Length and Height of the wall, if L = 2 H. Solution: Heat Transfer Rate (in Joule/Sec) = Surface Area of the Wall (in m2) = Height of the Wall (H in m) = Length of the Wall (L in m) =arrow_forwardDetermine the conduction heat transfer INSULATOR rate through the wall. T$2 Tst k H Ts2 M L H INSULATOR W Н %3D 0,6 т L = 0,5 m М 3D 2 ст k = 0,15- mK Ts2 = 10°C Ts1 = 30°C,arrow_forwardIn a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 0.6 cm enters into the boiler that has the thermal conductivity as 0.33 W/mK. The boiler is maintained at 105C and temperature of the water that flows inside the pipe is at 28C. If the energy transfer (Q) is 118922 kJ in 6 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.016 L. Change in Temperature (in K) = Heat Transfer Rate (in W) = Surface Area of the Pipe (m2) =arrow_forward
- Steam at T1 = 320°C and h1 = 60 W/m2·°C flows in a cast iron pipe (k = 80 W/m·°C). The inner and outer diameters are D1 = 5 cm and D2 = 5.5 cm, respectively. The insulation thickness is 3-cm-glass wool insulation with k= 0.05 W/m · °C. The temp. of the surroundings at T2 = 5°C and heat transfer coefficient of h2=18 W/m2·°C. Determine 1. Heat loss from the steam per unit length of the pipe. 2. Determine the temperature at the surfaces of the pipe and the insulation.arrow_forwardIn a thermal power plant, a vertical copper pipe of "D" diameter, "H" height and thickness 1 cm enters into the boiler that has the thermal conductivity as 0.35 W/mK. The boiler is maintained at 102C and temperature of the water that flows inside the pipe is at 25C. If the energy transfer (Q) is 119031 kJ in 7 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Height of the pipe, if H = 27 D.arrow_forwardConsider a pipe with an inner radius of 15 cm, an outer radius of 20 cm, and k = 15 W / m ∙ oC.The heat transfer coefficient of the fluid in the pipe is 40 W / m2 ∙ oC, and the fluid is 500oC on average.flows with heat. The convection coefficient between the outer surface of the pipe and the surrounding air is 12 W / m2 ∙ oCand the air temperature is 20 oC. Assume that the heat conduction in the pipe is unidimensional and continuous.by,a) The main differential equation and boundary conditions for heat conduction through the pipe material.Determine.b) By solving this differential equation, the special equation that gives the temperature change in the pipe material.obtain.c) Find the pipe outer surface temperature.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning