A long rectangular plate of AISI 304 stainless steel is initially at 1200 K and is cooled by an array of slot jets (see Figure 7.17). The nozzle width and pitch are
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Fundamentals of Heat and Mass Transfer
- Air (pressure 1 atm) enters a circular pipe 5 cm in diameter at 20 °C with an average speed of 5 m/s. The tube wall is maintained at a constant surface temperature of 160°C, and the mean outlet temperature is 80°C. Estimate the length of the tube. Mainly, I also need the solution from concepts of how the heat flow behaves in the system, it can be with a diagram.arrow_forwardA 20 °C water flows to 50cmx60cm flat plate with velocity of 6m/s . The flat plate surface temperature is maintained at 40 °C . The air flows parallel to the 50cm side of the plate. If the kinematic viscosity of water is 78x10-8 m2/s, at what length the flow become turbulent? If the average laminar heat transfer coefficient of water is 7740W/m2 °C , what is the overall heat transfer at the laminar section?arrow_forwardYou are designing an IC heatsink which uses round pins in cross-flow. The heatsink must dissipate 3000W. The heatsink has 10 rows of 8 columns of round pins with a diameter of 1mm. The pins have longitudinal and transverse pitch of 6mm. The incoming air is at 25oC with a velocity of 3 m/s. Assume fluid properties are constant. If the pins are arranged in-line: a) Find the Reynold’s Number b) Find the Nusselt Number c) If the pins are 30mm tall, how hot must the pin surface be (average) to dissipate the proper amount of heat?arrow_forward
- The exact expression for the local Nusselt number for laminar flow along a flat plate is given by: Nux=h(x)x/k=0.332Pr1/3Rex1/2. Atmospheric air at Tinf=400K with a velocity uinf=1.5m/s flows over a flat plate L=2m long maintained at a uniform temperature Tw=300K. Calculate the heat transfer rate from the airstream to the plate from x=0 to x=L=2m for w=0.5m. A. 234 W B. 334 W C. 434 W D. 134 Warrow_forward3.0 Consider two cases involving parallel flow of dry air at V=V= 1.5 m/s, T∞=T∞=45°C, and atmospheric pressure over an isothermal plate at Ts=Ts=20°C. In the first case, Rex,c=Rex,c=5 × 105, while in the second case the flow is tripped to a turbulent state at x=x=0 m. At what xx‐location, in m, are the thermal boundary layer thicknesses of the two cases equal? What are the local heat fluxes, in W/m2, at this location for the two cases?arrow_forwardAir is flowing at a speed of 30 m/sec over a flat plate. The air temperature is 20o C and its pressure is 1 atm. The plate is kept at a constant temperature of 65o C. What is the heat transfer rate per unit length between 7.5 cm to 30 cm, from the edge of the plate?arrow_forward
- A thermocouple junction is in the form of 8 mm diameter sphere. Properties of materialare: Cp = 420 J/kg-K; ρ = 8000 kg/m3 ; k = 40 W/m-K; h = 40 W/m2 -K. This junction isinitially at 40 oC and inserted in a stream of hot air at 300 oC. Find the following:a. Time constant of the thermocouple.b. The thermocouple is taken out from the hot air after 10 seconds and kept in still airat 30 oC. Assuming the heat transfer coefficient in air is 10 W/m2-oC, find thetemperature attained by the junction 20 seconds after removal from hot air.arrow_forwardA 20degC water flows to 50cmx60cm flat plate with velocity of 6m/s . The flat plate surface temperature is maintained at 40deg C. The air flows parallel to the 50cm side of the plate. If the kinematic viscosity of water is 78x10-8 m2/s, at what length the flow become turbulent? If the average laminar heat transfer coefficient of water is 7740W/m2 degC, what is the overall heat transfer at the laminar section?arrow_forwardLaminar flow occurs when the Reynolds number (Re*) is below 2000; turbulent flow occurs when the Reynolds number is above 2000. For the following species, determine the maximum value of the average 1D speed for which laminar flow will occur: a) Ne at 293 K where ?η is 313 ?μP and ?ρ = (PM)/(RT) through a 2.00 mm (id) pipe b) Liquid water at 293 K where ?η is 0.891 cP and ?ρ = 0.998 g/mL through a 2.00 mm (id) pipe *Re = (?ρ **d)/?η, where d is the diameter of the tube through which the fluid is flowing.arrow_forward
- Water at a flow rate of 0.215 kg/s is cooled from 70°C to 30°C by passing it through a thin-walled tube of diameter of 50 mm and maintaining a coolant at 15°C in cross flow over the tube. What is the required tube length if the coolant is air and its velocity is V = 20 m/s?Water : cp = 4181 J/kg⋅K, μ = 548 × 10-6 N⋅s/m2, k = 0.643 W/m⋅K, Pr = 3.56.Air : ν = 15.89 × 10-6 m2/s, k = 0.0263 W/m⋅K, Pr = 0.707.(Hint: For external flow use Churchill/Bernstein correlation.)arrow_forward8. A coal fired steam boiler uses 3000 kg of coal per hour. Air required for combustion is 15.5 kg ofcoal at barometric pressure of 98.2 KPa. The flue gas has temperature of 285 degree Celsiusand an average molecular weight of 30. Assuming an ash loss of 11% and allowable gas velocityof 7.5 meters per second. Find the diameter of the chimney 9. The gas density is 0.75 kg per cubic meters and air density is of 1.15 kg per cubic meter. If thedriving pressure is 0.25 KPA. Determine the height of the chimney. 10. A powerplant situated at an altitude having an ambient air of 96.53 KPa and 23.88 degreeCelsius. Flue gases at a rate of 5.0 kg per second enter the stack at 200 degree Celsius andleaves at 160 degree Celsius. The flue gases gravimetric analysis are 18% CO2, 7% O2 and 75%N2. Calculate the height of the stack necessary for a driving pressure of 0.20 KPaKindly answer all please. Thank youarrow_forwardIn low-speed incompressible flow, the peak pressure coefficient (at theminimum pressure point) on an airfoil is −0.41. Estimate the criticalMach number for this airfoil, using the Prandtl-Glauert rule.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning