Write the appropriate Nusselt value for the each set of conditions provided below. Write your answer in 4 decimal places. DO NOT round off intermediate values. 1. Forced convection over a flat plate at constant qs. Calculated Re at mean temperature is 3500 and Pr=0.7154. Nu = 2. Natural convection in a small holding tank with a heating element at the bottom. The calculated Ra number is 2.37 x 10°. Nu = 3. Forced convection through an elliptical duct at constant Ts, where a/b=8. The temperature of the fluid at the inlet is higher than at the exit. Flow is fully developed with Re = 33,370 and Pr = 0.693. Nu = 4. Natural convection over a sphere with Ra = 5 x 10° and Pr = 0.7362. Nu = %3D

Write the appropriate Nusselt value for the each set of conditions provided below. Write your answer in 4 decimal places. DO NOT round off intermediate values. 1. Forced convection over a flat plate at constant qs. Calculated Re at mean temperature is 3500 and Pr=0.7154. Nu = 2. Natural convection in a small holding tank with a heating element at the bottom. The calculated Ra number is 2.37 x 10°. Nu = 3. Forced convection through an elliptical duct at constant Ts, where a/b=8. The temperature of the fluid at the inlet is higher than at the exit. Flow is fully developed with Re = 33,370 and Pr = 0.693. Nu = 4. Natural convection over a sphere with Ra = 5 x 10° and Pr = 0.7362. Nu = %3D

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.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.13P

See similar textbooks

Similar questions

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.
1.15 A thermocouple (0.8-mm-diameter wire) used to measure the temperature of the quiescent gas in a furnace gives a reading of . It is known, however, that the rate of radiant heat flow per meter length from the hotter furnace walls to the thermocouple wire is 1.1 W/m and the convection heat transfer coefficient between the wire and the gas is K. With this information, estimate the true gas temperature. State your assumptions and indicate the equations used.
An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.
Solution on all other sites including this site are wrong Only attempt if previously not attempted. Answer part a and b A) Among the nondimensional numbers, in free convection, average Nusselt number depends on only Grashof and Prandtl numbers. only Grashof number. Rayleigh number. Reynolds number. B) For ideal gases, the specific heat capacity at constant pressure, thermal conductivity, dynamic viscosity, and Prandtl number are independent of pressure. How will the ratio of thicknesses of velocity boundary layer and thermal boundary layer change if pressure is increased from 1 atm to 5 atm for the flow of an ideal gas over a flat plate? We need to know the actual fluid properties to tell It will remain the same. It will decrease by a factor of 5. It will increase by a factor of 5.
Write the appropriate Nusselt value for the each set of conditions provided below.1. Forced convection over a flat plate at constant qs. Calculated Re at mean temperature is 3500 and Pr= 0.7154. 2. Natural convection in a small holding tank with a heating element at the bottom. The calculated Ra number is 2.37 x10^93. Forced convection through an elliptical duct at constant Ts, where a/b=8. The temperature of the fluid at the inlet is higher than at the exit. Flow is fully developed with Re = 33370 and Pr= 0.693. 4. Natural convection over a sphere with Ra = 5 x 10^9 and Pr = 0.7362 PS. Do not round off intermediate values
A house located in the south of the country was built using windowsdoubles to reduce heat loss to the outside environment on very cold days. Consider that the house has 6 windows 80 cm high and 1.2 m wide, each consisting of 2 layers of glass (kv=1.4 W/(m.oC) 4 mm thick, separated from each other for a spacing of 10 mm filled with stagnant air (ka=0.024 W/(mK), we disregard natural convection effects) On a day when the interior of the house is kept at 22oC, with h=10 W/(m2. K) while the external environment is at 5oC with h=50 W/(m2.K), it is requested:(a) What is the rate of heat dissipation through the windows?(b) What are the temperatures on the glass surfaces inside and in theexterior of the house?(c) Which of the resistances is the limiting in the dissipation process ofheat?(d) Estimate the increase in dissipation rate if we consider that the natural air convection in the space between the windows is characterizedby a convective coefficient h=5 W/(m.K).(e) How the value obtained…
A thermocouple junction, which may be approximated as a sphere, is to be used for temperature measurement in a gas stream. The convection coefficient between the junction surface and the gas is h=400W/m².K, and the junction thermophysical properties are ĸ= 20W/m.°K, c= 400J/kg.°K and ρ=8500kg/m³. Determine the junction diameter needed for the thermocouple to have a time constant of 1s. If the junction is at 25°C and is placed in a gas stream that is at 200°C, how long will it take for the junction to reach 199°C?
A school classroom is 6 m long, 6 m wide and 3 m high. There is a 2.5 m x 4 m window in the east wall. Only the east wall/window is exterior. Assume the thermal conditions in adjacent spaces (west, south, north, above and below) are the same as those of the classroom. Determine the cooling load at 9:00 am, 12:00 noon on July 21. Other known conditions include: Latitude = 40o N Ground reflectance = 0.2 Clear sky with a clearness number = 1.0 Overall window heat transmission coefficient = 7.0 W/m2.K Room dry-bulb temperature = 25.5°C Permissible temperature exceeded = 2.5% Schedule of occupancy: 20 people enter at 8:00 am and stay for 8 hours Lighting schedule: 300 W on at 8:00 AM for 8 hours Exterior wall structure: • Outside surface, A0 • Face brick (100 mm), A2 • Insulation (50 mm), B3 • Concrete block (100 mm), C3 • Inside surface, E0 Exterior window: • Single glazing, 3 mm • No exterior shading, SC = 1.0
Differentiate between free and forced convection with examples.
In presence of an external flow when will the convective heat transfer be dominated by free convection and not by the forced convection due to the external flow? Gr ≫ Re². Gr ≪ Re. Gr ≫ Re. Gr ≪ Re For ideal gases, the specific heat capacity at constant pressure, thermal conductivity, dynamic viscosity, and Prandtl number are independent of pressure. How will the ratio of thicknesses of velocity boundary layer and thermal boundary layer change if pressure is increased from 1 atm to 5 atm for the flow of an ideal gas over a flat plate? It will decrease by a factor of 5. It will remain the same. It will increase by a factor of 5. We need to know the actual fluid properties to tell.
Experiment No. (5) Heat Transfer, Power Input and Surface temperature 4. In what functions does Nusselt number in natural convection differ from forced convection, Discuss.
A 10 cm * 10 cm plate has a constant surface temperature of 150°C. Determine the Grashof number if the chip is placed in the following fluids: air (1 atm, 30°C), liquid water (30°C), and engine oil (10°C). Discuss how the Grashof number affects the natural convection flow.