Q7)The components of an electronic system are located in a 1.5-m-long horizontal ductwhose cross section is 20 cm x 20 cm. The components in the duct are not allowed tocome into direct contact with cooling air, and thus are cooled by air at 30°C flowing(1)SOFwierza-11-22over the duct with a velocity of 200 m/min. If the surfacetemperature of the duct is not to exceed 65°C, determine thetotal power rating of the electronic devices that can bemounted into the duct.DammeLore

Answered: Image /qna-images/answer/cdef815c-76d4-4b62-98e1-b72195c9cc5b.jpg

Q7) The components of an electronic system are located in a 1.5-m-long horizontal duct whose cross section is 20 cm x 20 cm. The components in the duct are not allowed to come into direct contact with cooling air, and thus are cooled by air at 30°C flowing (1)

Q7) The components of an electronic system are located in a 1.5-m-long horizontal duct whose cross section is 20 cm x 20 cm. The components in the duct are not allowed to come into direct contact with cooling air, and thus are cooled by air at 30°C flowing (1)

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 5.37P

See similar textbooks

Similar questions

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.
Water at 15°C is to be heated to 65°C by passing it over a bank of resistance heating rods 4 m long and 1 cm in diameter which are maintained at 90°C. The water is approached by the heater rod bank at the normal direction at an average speed of 0.8 m/s. The rods are arranged in line with longitudinal and transverse steps of SL = 4 cm and ST = 3 cm.Determine the number of rows of NL tubes in the direction of flow needed to achieve the indicated temperature rise. I need the solution from fundamental concepts of how the heat flow behaves in the system
Air at 1atm, 35 degree celcius (ρ = 1.145 kg/m3 and μ = 1.895 x 10-5 kg/m.s) and average velocity of 7 m/s, enters a 10m section of a circular pipe with diameter of 20cm. Neglecting the entrance effects, determine the fan power needed to overcome the pressure losses in the duct. Use friction factor f= 0.020336
A desktop computer is to be cooled by a fan. The electronic components of the computerconsume 60 W of power under full load conditions. The computer is to operate inenvironments at temp. up to 45° C and at elevations up to 3400 m where the averageatmospheric pressure is 66.63 KPa, air density at this condition 0.73 kg/m³. The exit temp. ofair is not to exceed 60° C, air density of 0.7 kg/m³, to meet reliability requirements. Also theaverage velocity of the air is not to exceed 110 m/min at the exit of the computer case wherethe fan is installed to keep the noise level down. Assume that there is an increase in internalenergy of 10.779 kj/kg. Determine the flow rate of the fan that needs to be installed and thediameter of the casing of the fan.
How does the wall shear stress ?w vary along the flow direction in the fully developed region in (a) laminar flow and (b) turbulent flow?
What are the two mechanisms theoretically considered in turbulent flow?
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]
1) 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…
Air enters a 7-m-long section of a rectangular duct of cross section 15 cm X 20 cm at 50°C at an average velocity of 7 m/s. If the walls of the duct are maintained at 10°C, determine: (a) the outlet temperature of the air, (b) the rate of heat transfer from the air, and (c) the fan power needed to overcome the pressure losses in this section of the duct.
Air enters a 10-m-long section of a rectangular duct of cross section 15 cm * 20 cm made of commercial steel at 1 atm and 358C at an average velocity of 7 m/s. Disregarding the entrance effects, determine the fan power needed to overcome the pressure losses in this section of the duct.
The 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.
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.