In the effort to find the best way to cool a smooth thin-walled copper tube, an engineer decided to flow air either through the tube or across the outer tube surface. The tube has a diameter of 5 cm, and the surface temperature is maintained constant. Determine (a) the convection heat transfer coefficient when air is flowing through its inside at 25 m/s with bulk mean temperature of 50°C and (b) the convection heat transfer coefficient when air is flowing across its outer surface at 25 m/s with film temperature of 50°C.

In the effort to find the best way to cool a smooth thin-walled copper tube, an engineer decided to flow air either through the tube or across the outer tube surface. The tube has a diameter of 5 cm, and the surface temperature is maintained constant. Determine (a) the convection heat transfer coefficient when air is flowing through its inside at 25 m/s with bulk mean temperature of 50°C and (b) the convection heat transfer coefficient when air is flowing across its outer surface at 25 m/s with film temperature of 50°C.

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.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.4P

See similar textbooks

Similar questions

7.43 Liquid sodium is to be heated from 500 K to 600 K by passing it at a flow rate of 5.0 kg/s through a 5-cmID tube whose surface is maintained at 620 K. What length of tube is required?
Consider turbulent forced convection in a circular tube. Will the heat flux be higher near the inlet of the tube or near the exit? Why?
Air enters a 25-cm-diameter 12-m-long underwater duct at 50°C and 1 atm at a mean velocity of 7 m/s, and is cooled by the water outside. If the average heat transfer coefficient is 85 W/m2?K and the tube temperature is nearly equal to the water temperature of 10°C, determine the exit temperature of air and the rate of heat transfer. Evaluate air properties at a bulk mean temperature of 30°C. Is this a good assumption?
Air enters a 20-cm-diameter 12-m-long underwater duct at 50°C and 1 atm at a mean velocity of 7 m/s, and is cooled by the water outside. If the average heat transfer coefficient is 85 W/m2 °C and the tube temperature is nearly equal to the water temperature of 5°C, determine the exit temperature of air and the rate of heat transfer
Combustion gases passing through a 5-cm-internal-diameter circular tube are used to vaporize waste water at atmospheric pressure. Hot gases enter the tube at 225 kPa and 250oC at a mean velocity of 2.5 m/s, and leave at 150o If the average heat transfer coefficient is 150 W/m2K and the inner surface temperature of the tube is 110oC, determine (a) the tube length and (b) the rate of evaporation of water.
In the effort to find the best way to cool a smooth thin-walled copper tube, an engineer decided to flow air either through the tube or across the outer tube surface. The tube has a diameter of 6 cm, and the surface temperature is maintained constant. Determine the convection heat transfer coefficient when air is flowing through a thin-walled tube at 25 m/s with bulk mean temperature of 50°C. _____ w/m^2k
Consider an air solar collector that is 1 m wide and 5 m longand has a constant spacing of 3 cm between the glass cover andthe collector plate. Air enters the collector at 30°C at a rate of0.15 m3/s through the 1-m-wide edge and flows along the 5-mlong passage way. If the average temperatures of the glasscover and the collector plate are 20°C and 60°C, respectively,determine (a) the net rate of heat transfer to the air in thecollector and (b) the temperature rise of air as it flows throughthe collector.
Air at 60°C leaves a furnace and passes through a 12-m long, 20-cm × 20-cm square duct at an average velocity of 4 m/s. If the duct has a constant surface temperature of 33°C, determine the exit temperature of the air and the rate of heat transfer.
Air at 10oC enters a 10-cm-diameter and 4-m-long pipe at a rate of 0.035 kg/s. The inner surface of the pipe has a roughness of 0.22 mm, and the pipe is nearly isothermal at 60o Determine the rate of heat transfer to air using the Nusselt number relation given by (a) Eq. 8–66 and (b) Eq. 8–71. Evaluate air properties at a bulk mean temperature of 20oC. Is this a good assumption?
Hot carbon dioxide exhaust gas at 1 atm is being cooled by flat plates. The gas at 220oC flows in parallel over the upper and lower surfaces of a 1.5-m-long flat plate at a velocity of 3m/s. if the flat plate surface temperature is maintained at 80oC, determine (a) the local convection heat transfer coefficient at 1 m from the leading edge, (b) the average convection heat transfer coefficient over the entire plate, and (c) the total heat flux transfer to the plate.
A computer cooled by a fan contains eight printed circuit boards (PCBs), each dissipating 10 W of power. The height of the PCBs is 12 cm and the length is 18 cm. The clearance between the tips of the components on the PCB and the back surface of the adjacent PCB is 0.3 cm. The cooling air is supplied by a 10-W fan mounted at the inlet. If the temperature rise of air as it flows through the case of the computer is not to exceed 10°C, determine (a) the flow rate of the air that the fan needs to deliver, (b) the fraction of the temperature rise of air that is due to the heat generated by the fan and its motor, and (c) the highest allowable inlet air temperature if the surface temperature of the components is not to exceed 70°C anywhere in the system. As a first approximation, assume flow is fully developed in the channel. Evaluate properties of air at a bulk mean temperature of 25°C. Is this a good assumption?
What does the logarithmic mean temperature difference represent for flow in a tube whose surface temperature is constant? Why do we use the logarithmic mean temperature instead of the arithmetic mean temperature?