In a manufacturing process, long aluminum rods of square cross section with
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Fundamentals of Heat and Mass Transfer
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- 5.43 A refrigeration truck is traveling at 130 km/h on a desert highway where the air temperature is . The body of the truck is idealized as a rectangular box 3 m wide, 2.1 m high, and 6 m long, at a surface temperature . Assume that (1) the heat transfer from the front and back of the truck is neglected, (2) the stream does not separate from the surface, and (3) the boundary layer is turbulent over the whole surface. Calculate the required cooling rate of the refrigeration unit.arrow_forwardAtmospheric boundary layers can be estimated using turbulent flow approximations over a flat-plate and the velocity profile given for the ‘Turbulent Core’ applies across the entire boundary layer. Assume the wind is blowing at 10 m/s at a height of 80 m above a smooth and flat beach. Air temperature can be assumed to be 20oC. (a) Estimate the shear stress produced by the wind on the beach surface in Pa if the air is at standard sea-level conditions. (b) Determine the wind velocity striking your nose if you are standing and your nose is 170 cm off the ground. (c) Determine the wind velocity striking your nose if you are lying on the beach and your nose is 17 cm off the ground?arrow_forwardAn 8-mm-diameter plastic sphere whose density is 1150 kg/m3 is dropped into water at 20°C. Determine the terminal velocity of the sphere in water.arrow_forward
- What are the turbulence intensity differences on offshore and onshore?arrow_forwardA series of 10 chips are placed on an insulating substrate as shown in the figure. Each chip has a length (Lc) of 15 mm, it is 20 mm wide and 10 mm thick. Upstream of the chips there is an input length (Le) of 15 mm. Whether each chip should dissipate 0.5 W and stay at a maximum temperature of 80 °C, what should be the speed uꝏ that the ambient air at 25 °C should be blown so that this condition is met? The emissivity of the chips is 0.8. consider that the chips do not exchange heat with each other and there is a turbulence generator upstream of the plate.arrow_forwardAir at atmospheric pressure and a temperature of 25°C is in parallel flow at a velocity of 5 m/s over a 1‐m‐long flat plate that is heated from below with a uniform heat flux of 1,250 W/m^2. Assume the flow is fully turbulent over the length of the plate. (a) Calculate the plate surface temperature, Ts(L), and the local convection coefficient, hx(L), at the trailing edge, x = L. (b) Calculate the average temperature of the plate surface, T¯s. (c) Plot the variation of the surface temperature, Ts(x), and the convection coefficient, hx(x), with distance on the same graph. Explain the key features of these distributionsarrow_forward
- Dry air at 25◦C and atmospheric pressure blows over a 30-cm-square surface of ice at a velocity of 1.5m/s. Estimate the amount of moisture evaporated per hour, assuming that the block of ice is perfectly insulated except for the surface exposed to the airstream.arrow_forwardConsider a constant updraft in the central core of a warm cloud (T>0∘C) isolated from entrainment. Why does the average cloud droplet radius increase with height in this updraft core? a.The adiabatic liquid water content increases with height above cloud base. b.The average cloud droplet radius only increases if new CCN are activated. c.The cloud droplet growth rate depends on the inverse of the average cloud droplet radius.arrow_forwardWhich parameter does not affect an earlier occurrence of the transition of Laminar flow to turbulent flow in the boundary layer of the flat plate?arrow_forward
- For the steady flat plate boundary layer flow, determine the wall shear stress assuming the following velocity profile. Where, δ is the boundary layer thickness and U is the outer flow velocity (constant).arrow_forwardAirflows over two thin flat plates are shown. The velocity profiles and boundary thickness are to scale. Case I Case II Compared to case II, the Reynolds Number for Case I isarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning