Design consideration requires that the surface of a small electronic package be maintained at atemperature not to exceed 82 o C. Noise constraints rule out the use of fans. The power dissipated inthe package is 35 watts and the surface area is 520 cm2 . The ambient temperature and surroundingwalls are assumed to be at 24 o C. The heat transfer coefficient is estimated to be 9.2 W/m2- oC andsurface emissivity is 0.7. Will the package dissipate the required power without violating designconstraints?

Design consideration requires that the surface of a small electronic package be maintained at atemperature not to exceed 82 o C. Noise constraints rule out the use of fans. The power dissipated inthe package is 35 watts and the surface area is 520 cm2 . The ambient temperature and surroundingwalls are assumed to be at 24 o C. The heat transfer coefficient is estimated to be 9.2 W/m2- oC andsurface emissivity is 0.7. Will the package dissipate the required power without violating designconstraints?

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.

Chapter9: Heat Transfer With Phase Change

Section: Chapter Questions

Problem 9.37P

See similar textbooks

Similar questions

1.67 In beauty salons and in homes, a ubiquitous device is the hairdryer. The front end of a typical hairdryer is idealized as a thin-walled cylindrical duct with a 6-cm diameter with a fan at the inlet that blows air over an electric heating coil as schematically shown in the figure. The design of this appliance requires two power settings, with which the air blown over the electric heating coil is heated from the ambient temperature of to an outlet temperature of and with exit air velocities of 1.0 m/s and 1.5 m/s. Estimate the electric power required for the heating coil to meet these conditions, assuming that heat loss from the outside of the dryer duct is neglected.
1.29 A spherical interplanetary probe with a 30-cm diameter contains electronic equipment that dissipates 100 W. If the probe surface has an emissivity of 0.8, what is its surface temperature in outer space? State your assumptions in the calculations.
A pipe carrying superheated steam in a basement at 10C has a surface temperature of 150C. Heat loss from the pipe occurs by radiation (=0.6) and natural convection (hc=25W/m2K). Determine the percentage of the total heat loss by these two mechanisms.
A cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.
8.15 A mercury bath at is to be heated by immersing cylindrical electric heating rods, each 20 cm tall and 2 cm in diameter. Calculate the maximum electric power rating of a typical rod if its maximum surface temperature is .
Heat is transferred at a rate of 0.1 kW through glass wool insulation (density=100kg/m3) with a 5-cm thickness and 2-m2 area. If the hot surface is at 70C, determine the temperature of the cooler surface.
1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.
The heat transfer rate from hot air by convection at 100C flowing over one side of a flat plate with dimensions 0.1m0.5m is determined to be 125 W when the surface of the plate is kept at 30C. What is the average convection heat transfer coefficient between the plate and the air?
The heat transfer coefficient between a surface and a liquid is 57 W/(m2K). How many watts per square meter will be transferred in this system if the temperature difference is 10C?
A spherical communications satellite, 2 m in diameter, is placed in orbit around the earth. The satellite generates 1000 W of internal power from a small nuclear generator. If the surface of the satellite has an emittance of 0.3, and is shaded from solar radiation by the earth, estimate its surface temperature.
1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.
Question:- A cylindrical steel tank with a diameter of 3 m and height of 4.4 m is used to store chilled water (at 9.3 °C) as part of an air conditioning system for a building. The heat transfer (convection) co-efficient for the surface of the tank in contact with the water in this application is 15 W/(m2.K). Given the surface temperature of the metal tank is 40 °C. At what rate must heat energy be removed from the water just to maintain its temperature constant at 9.3 °C ? Assume the tank is an enclosed cylinder and that the tank is always full. Note - the thickness of the tank is not relevant to this problem. Work in base SI units.