Consider a hot automotive engine, which can be ap-proximated as a 0.5-m-high, 0.40-m-wide, and 0.8-m-long rec-tangular block. The bottom surface of the block is at atemperature of 80°C and has an emissivity of 0.95. The ambi-ent air is at 20°C, and the road surface is at 25°C. Determinethe rate of heat transfer from the bottom surface of the engineblock by convection and radiation as the car travels at a veloc-ity of 80 km/h. Assume the flow to be turbulent over the entiresurface because of the constant agitation of the engine block.

Given: The width of the rectangular block, w = 0.4 m The length of the rectangular block, L = 0.8 m…

Answered: Consider a hot automotive engine, which…

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

A heater plate measures 40 cm x 40 cm in the tank and is kept at a constant temperature of 70 °C. Show with calculations in which case the oil at the temperature of 30 °C in the tank can be heated the most.
Consider a hot baked potato. Will the potato cool faster or slower when we blow the warm air com ing from our lungs on it instead of letting it cool naturally in the cooler room air? Briefly explain your answer.
7-115 Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.8-m-long tubes inside which the refrigerant is evaporating at –20°C. Air approaches the tube bank in the normal direction at 0°C and 1 atm with a mean velocity of 5 m/s. The tubes are arranged in-line with longitudinal and transverse pitches of SL = ST = 1.5 cm. There are 25 rows in the %D flow direction with 15 tubes in each row. Determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. Evaluate the air properties at an assumed mean temperature of -5°C and 1 atm. Is this a good assumption? 0.8 m Air 0°C 1 atm ST = 1.5 cm 5 m/s 0.8 cm 1.5 cm/ S, = Refrigerant, –20°C FIGURE P7–115
How is volume flow rate different than velocity? What happens to volume flow rate in areas where fluid pressure is high?
Consider steady, laminar, two-dimensional flow over a hot plate. Does the convective heat transfer coefficient (h) increase, decrease, or remain constant with distance from the leading edge? Explain.
Liquid mercury is flowing at 0.9kg/s through a 5-cm diameter tube with inlet and outlet mean temperatures of 100°C and 200°C, respectively. The tube surface temperature is maintained constant at 250°C. Determine the tube length using the Dittus-Boelter equation, in m. ______ m
Determine the convection heat transfer coefficient (in W/m2-K) for air flowing at a velocity of 3 m/s in a 10-cm diameter and 10-m long tube. Air enters the tube at 10°C and leaves at 20°C, i.e. air is heated. Take the property of air at 1 atm and assume flow to be fully developed. For air at 1 atm: Temperature k, W/m-K v, m?/s Pr 15°C 0.02476 1.470x10-5 0.7323 20°C 0.02514 1.516×10-5 0.7309 25°C 0.02551 1.562x105 0.7296
Thick fluids such as asphalt and waxes and the pipes in which they flow are often heated in order to reduce the viscosity of the fluids and thus to reduce the pumping costs. Consider the flow of such a fluid through a 100-m-long pipe of outer diameter 30 cm in calm ambient air at 0oC. The pipe is heated electrically, and a thermostat keeps the outer surface temperature of the pipe constant at 250C. The emissivity of the outer surface of the pipe is 0.8, and the effective sky temperature is-300C. Determine the power rating of the electric resistance heater, in kW, that needs to be used. Also, determine the cost of electricity associated with heating the pipe during a 10-h period under the above conditions if the price of electricity is $0.09/kWh. Properties The properties of air at 1 atm and the film temperature of (Ts+To)/2 = (25+0)/2 = 12.5°C are: k = 0.02458 W/m.oC, v = 1.448x10-5 m2/s, Pr = 0.7330 D=m
Fruit is impeded from ripening when it reaches high temperatures (>32°C). Farmer Joe isworried that Deleware's summer heat wave will affect the ripening of his ground cherries.The spherical fruit (1 cm in diameter) is surrounded by a spherical papery husk (λhusk = 0.3W/m K) with an inner diameter of 2 cm and an outer diameter of 2.1 cm. The air in betweenthe fruit and the husk is stagnant (λair = 0.03 W/m K). On a calm day in July, the delewareair (outside of the husk) is very warm, with a temperature of ~38°C and a heat transfercoefficient of h deleware,calm = 10 W/m 2K. (a) Sketch the system, labeling all temperatures, dimensions, and proportionality constants. (b) sketch the electrical analogy tothis system, labeling all temperatures, resistances, and heat flows (c) what is the overall resistance to heat transfer from the air in Deleware to the fruit?
Fluid with a density of 602 kg/m³ flows inside a 3.3 cm diameter tube at a velocity of 1.7 m/s. The fluid enters the tube at 85°C and exits at 33°C. At the average bulk temperature, the thermal conductivity is 0.50 W/m K, the absolute viscosity is 6.26 x 104 kg/m s and the Prandtl number is 6.65. Using the Dittus-Boelter correlation Nu-0.023Re0.8p where n = 0.4 for heating: n = 0.3 for cooling What is the convection heat transfer coefficient? Express your answer in W/m² K?
A horizontal pipe with a diameter of 18 cm and a length of 10 m, which contains hot oil and has a surface temperature of 383.8 ° C, has an atmospheric pressure of 760 mm Hg. It is located in an environment (open air) where the temperature is 25 °C. Determine the rate of heat transfer from the pipe to the air (the heat transferred by radiation will be neglected).
Solar radiation is incident on the glass cover of a solar collector at a rate of 700W/m². The glass of collector absorbs 88 percent of the incident radiation on it and has an emissivity of 0.9. The entire hot water needs of a family can be provided by a single collector of 1.2m height and 2m width. The temperature of the glass cover of the collector is measured to be 35C° on a day when the surrounding air temperature is 25C° and the wind is blowing at 30km/h. The effective sky temperature for radiation exchange between the glass cover and the open sky is -40C°. Water enters the tubes which attached to the absorber plate at a rate of 1kg/min. Assuming the back surface of the absorber plate to be heavily insulated and the only heat loss to occur through the glass cover, determine (a) the total rate of heat loss from the collector, (b) the collector efficiency, which is the ratio of the amount of heat transferred to the water to the solar energy incident on the collector, and (c) the…

SEE MORE QUESTIONS

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