A sphere which is 12.7 mm in diameter, is at 66 °C before it is inserted into an airstream havinga temperature of 27 °C. The surface temperature of the sphere is 55 °C after 69 seconds measuredby a thermocouple. This sphere has density 8933 kg/m³, cp = 389 J/kg∙K, k=398 W/m KAssume this sphere can be treated as a lumped system. Find the convective heat transfer coefficientand then calculate Bi number to justify the assumption that this sphere can be treated as a lumpedsystem.

The Biot number (Bi) is approximately 0.0671Explanation:Given:Diameter of the sphere (d) = 12.7 mm =…

Answered: A sphere which is 12.7 mm in diameter,…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

You are designing a small heatsink to cool a high-powered IC on a control unit PCB. The IC puts out 40,000 W/m2 and has a size of 40mm x 20mm. A fan blows 40 degrees C air across the IC at a speed of 4 m/s. The IC is well insulated on its back face. If the convection coefficient is 62 W/m2K, what is the surface temperature of the IC?
A hot steel ball of 5 mm in diameter initially at 100 oC is left to cool down in air at 20 oC. Assume a constant convective heat transfer coefficient h = 15 W/m2K through the course of the cooling process. Cp, steel = 0.49 kJ / kg K , k,steel = 45.0 W / m K , rho, steel = 7800 kg/m^3 Cp,air = 1.00 kJ/kg K ; k_air = 0.025 W / m K; rho,air = 1.2 kg/m^3 a) Calculate the rate of convective heat transfer when the steel ball is uniformly at 100 oC. b) Assuming the steel as a lumped system, find the temperature of the steel ball after 0.5 s.
Problem: A solid copper cube of 10-cm edge length(p =8954 kg/m³, c = 383 J/kg.K, k= 386 W/m.K) initially at a uniform temperature T;= 250°C is suddenly immersed in a well-stirred fluid which is maintained at a uniform temperature T = 50 °C. The heat transfer coefficient between cube and the fluid h=20O W/m²K. A. Check whether the lumped system analysis is suitable. B. Determine the temperature of the copper block at t= 5 min after the immersion. TE 250°C 10 cm Tm= 50 °C, h=200 w/mk
A vertical pipe 90 mm diameter and 2.5 m height is maintained at a constant temperature of 125 o The pipe is surrounded by still atmospheric air at 25 oC. Find heat loss by natural convection. Properties of water at 75 oC: Density = 1.0145 kg/m3 Kinematic viscosity = 20.55 x10-6 m2/s Prandtl number (Pr) = 0.693 Thermal conductivity (k) = 30.06 x 10–3 W/m K
KNOWN: Expression for face-averaged Nusselt numbers on a cylinder of rectangular cross section. Dimensions of the cylinder. FIND: Average heat transfer coefficient over the entire cylinder. Plausible explanation for variations in the face-averaged heat transfer coefficients. SCHEMATIC: Air V = 10 m/s T = 300 K c = 40 mm ASSUMPTIONS: (1) Steady-state conditions, (2) Constant properties. d = 30 mm
Thermal jackets are typically put on cryogenicstorage tanks to minimize the heat transfer gainsfrom the surroundings. Consider a cylindercontainer that is 1.5 m long made from steel (k = 750W/m.K) with an inner diameter of 0.5 m and outerdiameter of 0.7 m. If the liquefied natural gas (LNG)inside the cylinder is maintained at 90 K, ambientconditions are Tamb = 20 °C, h = 7 W/m2.K. What isthe required thermal jacket thickness to maintainthe outer temperature of that jacket of 15 °C? (Takea thermal conductivity of the insulation to be kins =0.015 W/m.K). Image credit: Okorder. Image forillustrative purposes only.
A 300 mm thick wall (k= 1.5 W/mK, p = 2600 kg/m³, cp = 1000 J/kg⚫K) has a uniform original temperature of 900 °C. At the time t = 0, its both surfaces are suddenly exposed to air (T∞ = 25 °C, h = 30 W/m²K). (a) Calculate the Biot number of the wall. Does it have a uniform temperature? (b) After 3 hours, what is the temperature at the middle plane (@x = 0)? Symme try ½ L= 300 mm h = 30 W/m² K wall T∞ = 25°C h = 30 W/m² K To=25°C 9. Ah (T-To G=ept Hot air x p = 2600 kg/m³ k=1.5 W/m K 900c Hot air Tr= 96w arrume te Now.
A car's rear window is defogged by the passage of hot air over its inner surface. If the hot air is at T∞, i = 40 °C and the corresponding convection heat transfer coefficient is hi = 30 W/(m²K), what are the temperatures of the inner and outer surfaces of the glass, which has 4 mm thick, if the outdoor ambient air temperature for T∞, e = −10 °C and the associated convective coefficient for he = 65 W/(m²K)?

Recommended textbooks for you

Elements Of Electromagnetics

Mechanical Engineering

ISBN:

9780190698614

Author:

Sadiku, Matthew N. O.

Publisher:

Oxford University Press

Mechanics of Materials (10th Edition)

Mechanical Engineering

ISBN:

9780134319650

Author:

Russell C. Hibbeler

Publisher:

PEARSON

Thermodynamics: An Engineering Approach

Mechanical Engineering

ISBN:

9781259822674

Author:

Yunus A. Cengel Dr., Michael A. Boles

Publisher:

McGraw-Hill Education

Elements Of Electromagnetics

Mechanical Engineering

ISBN:

9780190698614

Author:

Sadiku, Matthew N. O.

Publisher:

Oxford University Press

Mechanics of Materials (10th Edition)

Mechanical Engineering

ISBN:

9780134319650

Author:

Russell C. Hibbeler

Publisher:

PEARSON

Thermodynamics: An Engineering Approach

Mechanical Engineering

ISBN:

9781259822674

Author:

Yunus A. Cengel Dr., Michael A. Boles

Publisher:

McGraw-Hill Education

Control Systems Engineering

Mechanical Engineering

ISBN:

9781118170519

Author:

Norman S. Nise

Publisher:

WILEY

Mechanics of Materials (MindTap Course List)

Mechanical Engineering

ISBN:

9781337093347

Author:

Barry J. Goodno, James M. Gere

Publisher:

Cengage Learning

Engineering Mechanics: Statics

Mechanical Engineering

ISBN:

9781118807330

Author:

James L. Meriam, L. G. Kraige, J. N. Bolton

Publisher:

WILEY

SEE MORE TEXTBOOKS