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A large plane wall, with a thickness L and a thermal conductivity k, has its left surface
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Heat and Mass Transfer: Fundamentals and Applications
- 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 cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forwardConsider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/m°C, b) free flowing air with h = 7.5 W/m2°C, c) evacuated, d) filled with urethane insulation with k = 0.026 W/m°C, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/m°C PLEASE ANSWER LETTER D AND E, THANK YOUarrow_forward
- 1. A 1000-W iron is left on the iron board with its base exposed to the air at 20°C. The convection heat transfer coefficient between the base surface and the surrounding air is 35 W/m². °C. If the base has an emissivity of 0.6 and a surface area of 0.02 m², determine the temperature of the base of the iron. 2. The inner and outer surfaces of a 5-m x 6-m brick wall of thickness 30 cm and thermal conductivity 0.69 W/m °C are maintained at temperatures of 20°C and 5°C, respectively. Determine the rate of heat transfer through the wall, in W.arrow_forwarda) Coolant flowing through a radiator at the rate of 3 kg/s are cooled from 105 0C to 81 0C. The specific heat capacity of coolant and air are 4.19 kJ/kg K and 1.13 kJ/kJ/K respectively. Th overall heat transfer coefficient from gas to water is 140 W/m2 K. Calculate the surface area required for the radiation if the vehicle speed is 100 km/h. Consider the density of air as 1.225 kg/m3arrow_forwardThe wall of an oven in an industrial plant, made of fire brick (k = 0.71 W/m/K) has thickness of L = 15 cm. The oven is exposed to air at 28oC and the surfaces of the far surroundings are at 20oC. If the temperature of the outer surface of the wall is 92oC and the heat transfer coefficient and emissivity are 20 W/(m^2*K) and 0.8 respectively, determine the temperature of the inner surface of the wall.arrow_forward
- Consider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/moC, b) free flowing air with h = 7.5 W/m2oC, c) evacuated, d) filled with urethane insulation with k = 0.026 W/moC, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/moCarrow_forward2. (a) Consider a 25-cm-diameter spherical ball at 700 K suspended in air and assume the emissivity of the ball to be ε=0.95. Calculate: (i) the total emissive power in kW/m2; (ii) the total amount of radiation emitted by the ball in 3 minutes. (b) The inner and outer surfaces of a 25-cm-thick wall are at 27 oC and 45 oC, respectively. The outer surface of the wall exchanges heat by radiation with surrounding surfaces at 40 oC, and convection with ambient air at 42 oC with convection heat transfer coefficient of 9.0 W/m2 K. Solar radiation incident on the surface is at a rate of 150 W/m2. If the emissivity and the solar absorptivity of the outer surface are 0.75 and 0.85, respectively: (i) write the expression of the energy balance at the outer surface;…arrow_forwardAn electronic box that consumes 200 W of power is cooled by a fan blowing air into the box enclosure. The dimensions of the electronic box are 15 cm * 50 cm * 50 cm, and all surfaces of the box are exposed to the ambient except the base surface. Temperature measurements indicate that the box is at an average temperature of 32°C when the ambient temperature and the temperature of the surrounding walls are 25°C. If the emissivity of the outer surface of the box is 0.75, determine the fraction of the heat lost from the outer surfaces of the electronic box.arrow_forward
- Consider steady heat transfer between two large parallel plates at constant temperatures of T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown in Fig. 1–44. Assuming the surfaces to be black (emissivity ε = 1), determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is (a) filled with still air with k= 0.0219 W/m°C, (b) free flowing air with h= 7.5 W/m^2°C, (c) evacuatedarrow_forwardDoes any of the energy of the sun reach the earth by conduction or convection?arrow_forwardA cylindrical tube has an inner diameter of 2 cm and a wall thickness of 1 cm. The tube is evacuated. In the center, there is a radiation source along its axis that sends 1e^5 W/m^2 to the inner surface of the tube. K for the tube wall is 2 W/m K. If the outer surface of the tube is cooled with water at 298 K with a convective heat transfer coefficient of 100 W/m^2 K, determine the minimum temperature rating for the tube material for safe operation.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning