Experiments to determine the local convection heat transfer coefficient for uniform flow normal to a heated circular disk have yielded a radial Nusselt number distribution of the form
where both n and a are positive. The Nusselt number at the stagnation point is correlated in terms of the Reynolds
Obtain an expression for the average Nusselt number,
Want to see the full answer?
Check out a sample textbook solutionChapter 6 Solutions
Fundamentals of Heat and Mass Transfer
Additional Engineering Textbook Solutions
Manufacturing Engineering & Technology
Applied Statics and Strength of Materials (6th Edition)
Thinking Like an Engineer: An Active Learning Approach (3rd Edition)
Introduction to Heat Transfer
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
Mechanics of Materials (10th Edition)
- 6.1 Determine the heat transfer coefficient at the stagnation point and the average value of the heat transfer coefficient for a single 5-cm-OD, 60-cm-long tube in cross-flow. The temperature of the tube surface is , the velocity of the fluid flowing perpendicular to the tube axis is 6 m/s, and the temperature of the fluid is . Consider the following fluids: (a) air, (b) hydrogen, and (c) water.arrow_forwardEstimate the mass-transfer coefficient for moist air flowing normal to a 25 mm diameter tube (Nu = 0.615 Re0.47). The air velocity is 0.5 m/s. Assume standard air.arrow_forwardConsider an air solar collector that is 1 m wide and 4 m long and has a constant spacing of 3 cm between the glass cover and the collector plate. Air flows at an average temperature of 45°C at a rate of 0.12 m3/s through the 1-m-wide edge of the collector along the 4-m-long passageway. Disregarding the entrance and roughness effects and the 90° bend, determine the pressure drop in the collector.arrow_forward
- a rectangular duct made of commercial steel is used to channel air at 1 atm and 35°C at an avergae velocity of 7m/s. The duct is 15 cm by 20 cm and 12m long. Disregarding the entrance effects, determine the fan power needed to overcome the pressure losses in this section of the duct.arrow_forwardAgas at 0°C and avelocity of 2.5 m/s, flows over a 1.2 m long, 2 m wide plate that is maintained at 80°C. If the gas properties are: density= 1.142 kg/m3, cp= 1.04 kJ/kg.K, ν= 15.63×10–6m2/s, k = 0.0262 W/m.K,and Pr= 0.708,determine:(a)The critical length of the flow[m](b)The average heat transfer coefficient[W/m2.K](c)Total rate of heat transfer from the plate[W]arrow_forwardThe 100-mmmm-diameter pipe is connected by a nozzle to a large reservoir of air that is at a temperature of 60 ∘C∘C and absolute pressure of 550 kPakPa . The backpressure causes M1>1M1>1, and the flow is choked at the exit, section 2, when L� = 5 mm. Assume a constant friction factor of 0.0085 throughout the pipe. Gas constant for air is R� = 286.9 J/[kg⋅K]J/[kg⋅K] and its specific heat ratio is k� = 1.40. (Figure 1) Determine the mass flow through the pipe. Express your answer using three significant figures.arrow_forward
- Answer completely Show how the Darcy-Weisbach equation can be derived from the Hagen-Poiseuille equation through the introduction of the Reynolds number. What is the friction factor, f, equal to for flow at a laminar condition? What is it equal to in other regimes of flow?arrow_forward1) Atmospheric air at 25oC and with a speed of 50 m/s is pumped by a fan over a flat plate. a)What is the minimum plate length in order to achieve a Reynolds number of 108 ? b)At what distance from the leading edge would transition occur if critical Re #= 5x105 ? 2) Local Nusselt number is given as Nux=0.04Rex0.9 Pr 1/3. Obtain an expression for, a) average heat transfer coefficient, x b) local heat transfer coefficient, hx c) What is the ratio of the average to local coefficient, x / hx 3) Air is in parallel flow over a flat heater surface which is to be maintained at 140oC. Airflow induces a drag force of 0.25 N on the heater. What is the electrical power needed to maintain the prescribed surface temperature? 4) Air at 1 atm with a velocity of 4 m/s and a temperature of 50oC flows over a flat plate that is at a uniform temperature of 100oC. The plate has a length of 0.20 m and a width of 0.1 m. a) What is the average heat…arrow_forwardWhat is the physical significant of prandtl number? Question does the value of the prandtl number depend on the type of flow, or the flow geometry? Does the prandtl number of air change with pressure? does it change your temperature?arrow_forward
- Air at 20°C, 1 atm flows with a velocity of 4.5 m/s over a flat plate having a sharp leading edge. The plate surface isisothermal at 60°C.(a)Find out the distance from leading edge at which the flow in the boundary layer changes from laminar to turbulent.(b)Using exact solution,determinethe following parameters at the location established at part (a):(i)Thickness of the hydrodynamic boundary layer(ii)Thickness of the thermalboundary layer(iii)Local convective heat transfer coefficient(iv)Average convective heat transfer coefficient(v)Heat transfer rate from both sides per unit width of the plate(vi)Mass entrainment in the boundary layer(vii)The skin friction coefficientarrow_forwardWhat is turbulent viscosity? What causes it?arrow_forwardDetermine the stagnation temperature and stagnation pressure of air that is flowing at 36 kPa, 238 K, and 325 m/s.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning