Consider a cylindrical copper rod in whích there is a unifom volumetric heating q = 12 kW/m³. The rod is in a cross flow of air at velocity and temperature which are v, = 10 m/s and T. = 350 K respectively. The rod surface temperature is Ts = 400K. The rod outer diameter and length are D = 5 cm and L = 50 cm respectively. Assume natural convection and radiation to be negligible and you can neglect heat transfer from the tips of the cylinder. I. Estimate the drag experienced by the rod. II. Find the average convection heat transfer coefficient which characterises convection from the outer surface using the appropriate correlation. III. Find the time rate of change of temperature of the full rod at the initial time when the rod is first placed in the air flow. Air Properties: At T, = 350 K: v = 20.92 x 10-6 m2 /s, p 1 kg/m³ k = 30 x 10-3 W /m. K, Pr = 0.70 At T, = 400 K: p = 0.871 kg/m3, u= 230 x 10-7 N.s/m², Pr, = 0.69 Copper Properties: At T, = 400 K: p = 8900 kg/m³ , c = 385 J/kg K, k = 400 W /m K

Consider a cylindrical copper rod in whích there is a unifom volumetric heating q = 12 kW/m³. The rod is in a cross flow of air at velocity and temperature which are v, = 10 m/s and T. = 350 K respectively. The rod surface temperature is Ts = 400K. The rod outer diameter and length are D = 5 cm and L = 50 cm respectively. Assume natural convection and radiation to be negligible and you can neglect heat transfer from the tips of the cylinder. I. Estimate the drag experienced by the rod. II. Find the average convection heat transfer coefficient which characterises convection from the outer surface using the appropriate correlation. III. Find the time rate of change of temperature of the full rod at the initial time when the rod is first placed in the air flow. Air Properties: At T, = 350 K: v = 20.92 x 10-6 m2 /s, p 1 kg/m³ k = 30 x 10-3 W /m. K, Pr = 0.70 At T, = 400 K: p = 0.871 kg/m3, u= 230 x 10-7 N.s/m², Pr, = 0.69 Copper Properties: At T, = 400 K: p = 8900 kg/m³ , c = 385 J/kg K, k = 400 W /m K

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.54P

See similar textbooks

Similar questions

Consider two cases involving parallel flow of dry air at V=V= 2.5 m/s, T∞=45°C, and atmospheric pressure over an isothermal plate at Ts=20°C. In the first case, Rex,c=R⁢ex,c=5 × 105, while in the second case the flow is tripped to a turbulent state at x=0 m. a. At what x‐location, in m, are the thermal boundary layer thicknesses of the two cases equal? in m b. what is the q'' lam at W / m^2 c. what is the q'' turb at W / m^2
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 coefficient
Consider two cases involving the parallel flow of dry air at V= 1.5 m/s, T∞=45°C, and atmospheric pressure over an isothermal plate at Ts=20°C. In the first case, Rex,c=R5 × 105, while in the second case the flow is tripped to a turbulent state at x=0 m. At what x‐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?
A power plant continuously releases from a 70-m stack a plume into the ambient atmosphere of temperature 298 k. The stack has a diameter 5m, the exit velocity is 25 m s^-1, and the exit temperature is 398 K. For neutral conditions and a 20 km h^-1 wind, how high above the stack is the plume 200 m downwind? (If you could please explain for you steps when you do it, that would be awesome. :) )
Q2: Air at standard conditions of I atm and 27°C flows over a flat plate at 20 m/s. The plate is 60 cm square and is maintained at 97°C. Calculate the heat transfer from the plate. Answers: Q= 681 W,
Q3: Air flows across a 20-cm-square plate with a velocity of $ m/s. Free-stream conditions are 10-C and 0.2 atm. A heater in the plate surface furnishes a constant heat-flux condition at the wall so that the average wall temperature is 100-C. Calculate the surface heat flux and the value of h at an x position of 10 cm. Answers: Q= 1414 W, b= 13.3 Wm?.C
Convection H.T. Q3: In an industrial facility, air is to be preheated before entering a furnace by geothermal water at 120°C flowing through the tubes of a tube bank located in a duct. Air enters the duct at 20°C and 1 atm with a mean velocity of 4.5 m/s, and flows over the tubes in normal direction. The outer diameter of the tubes is 1.5 cm, and the tubes are arranged in-line with longitudinal and transverse pitches of SL = Sr = 5 cm. There are 6 rows in the flow direction with 10 tubes in each row. Determine the rate of heat transfer per unit length of the tubes, and the pressure drop across the tube bank. For this square in-line tube bank, if the friction coefficient is 0.16. Also, the correction factor 1 for the square arrangements. Properties: (p = 1.06 kg/m', k =0.02808 W/m °C, u = 2.008x10-5 kg/m.s, Pr = 0.7202 and Cp= 1007 J/kg.K). Take C, = 0.286, C2 = 0.95 and m = 0.608. Ans. q = 23.12 kW, AP = 21 Pa]
Hot water, k=48 W/m. It flows along the cast iron pipe, which is oC, at a speed of 1.4 m/s. The inner and outer diameter of the pipe are 3.0 and 3.5 cm, respectively. The pipe is located in a 15 m section of a basement floor with a temperature of 15 oC. If the water temperature drops from 70 OC to 67 OC when passing through the basement, and the film heat transfer coefficient on the inner surface of the pipe is 400 W/m2. If oC is, calculate the convective heat transfer coefficient on the outer surface of the pipe and the heat that will be transferred.
Air at 400C flows with a velocity of 7 m/s over a 5m long and 4m wilde surface of a flat plate whose surface temperature is 800C. Find the rate of heat transfer from the laminar flow region of the surface. (For air at 400C , V = 1.702 × 10-5 , pr = 0.7255, K = 0.02662 w/m . K). (a) 1.796 KW (b) 2.543 KW (c) 0.796 KW (d) 2.321 KW
Oil at 350 K is flowing over a flat plate maintained at 425 K. Tha plate is 0.75 m long and 200 mm wide. The velocity of flow is 0.25 m/s. The properties are evaluated at the mean temperature of 350 deg C. Properties of the oil are v = 50 x 10^-6 m^2/s, k = 0.14 W/m-K, Pr = 600, p = 853 kg/m^3. The Nusselt number is most nearly:
Oil at 350 K is flowing over a flat plate maintained at 425 K. Tha plate is 0.75 m long and 200 mm wide. The velocity of flow is 0.25 m/s. The properties are evaluated at the mean temperature of 350 deg C. Properties of the oil are v = 50×10^-6 m^2 / s , k = 0.14 W / m - K Pr = 600 , p = 853 kg /m^3. The Nusselt number is most nearly:
For internal flow with fully developed flow condition The velocity profile .................... change and the thermal profile .............................. change in the direction of flow Please fill the blank Blank 1 ( Does or does not) Blank 2 ( Does or does not )