A spherical object that is made of a material with specific heat=383 J/kg.K, and density = 8954 kg/m³. The diameter of the sphere is 5-cm and it is initially at a uniform temperature of 150•C. It is suddenly exposed to an environment at 20 C having a heat-transfer coefficient h=28W/m2 •C. Using the lumped-capacity method of analysis, calculate the time necessary for the sphere emperature to reach 90 C.

A spherical object that is made of a material with specific heat=383 J/kg.K, and density = 8954 kg/m³. The diameter of the sphere is 5-cm and it is initially at a uniform temperature of 150•C. It is suddenly exposed to an environment at 20 C having a heat-transfer coefficient h=28W/m2 •C. Using the lumped-capacity method of analysis, calculate the time necessary for the sphere emperature to reach 90 C.

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

In the system given in the figure below, a glass is heated under winter conditions. Since there are convection conditions on both surfaces of this glass, how much should the heat flow of the film heater be, considering that the t∞2 temperature is between 0-30?
A food product with 73% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 970 kg / m³, the thermal conductivity is 1.2 W / (m K), and the initial freezing temperature is -2 ° C. After 11 hours in the freezing medium -30 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = W / (m² K).
Pr
A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe. a. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam coming out = Answer kJ / kg. c. Determine the vapor heat change / loss along the flow = Answer watt. d. Specify the minimum required insulation thickness = Answer cm.
A mectal cylinder of 5 cm in diameter and initially at a temperature about 150 °C. the eylinder is suddenly immersed in liquid with temperature at 50 °C and heat transfer coeflicient about 2000 W/m.°C. Under typical operation conditions the center temperature and surface temperature are measured to be 110 °C and 90 °C after 1 minute, respectivielly. Calculate the thermal conductivity for this material.
A food product with 80% moisture content in a 10 cm diameter can wants to be frozen. The density of the product is 1000 kg / m³, the thermal conductivity is 1.0 W / (m K), and the initial freezing temperature is -2 ° C. After 14 hours in the freezing medium -30 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder.
based on a large 4 cm thick plate that is initially at a uniform temperature of 20°C that is heated by passing it through a space maintained at 500°C. The plate remains in the space for a period of 7 min. Take the heat transfer coefficient to be 120-W/m2°C. Example 4-4 [k = 110-W/m°C, r = 8530-kg/m³, C, = 0.380-kJ/kg°C, a = 33.9 x 10-6 m²/s] The dimensionless distance from center to a point 0.4-cm below the outer surface is 0.5 0.8 none of the above 0.2
Steel cubes 10 mm in width are annealed by heating to 1,377 K and then slowly cooling to 469 K in an air environment for which T∞ = 301 K and h = 24 W/m2-K. Assuming the properties of the steel to be k = 24 W/m · K, ρ = 7,047 kg/m3, and c = 916 J/kg · K, estimate the time required for the cooling process.
. A hollow sphere with an outer diameter (d,) of 4 cm and outer diameter of 12 cm is kept at an inner surface temperature (T,) of 383 K and outer surface temperature (T,) of 323 K. Calculate the heat transfer and temperature at d = 8 cm. The thermal conductivity of the sphere is 150 W/m°C.
The thermal conductivity of a solid material can be determined using asetup similar to the one shown in the accompanying figure. The thermocouples are placed at 2.5 cm intervals in the known material (copper alloy, k - 52 w/m.k) and the unknown sample, as shown. The known material is heated on the top by a heating element, and the bottom surface of the sample is cooled by running water through the heat sink shown. Determine the thermal conductivity of the unknown sample for the set of data given in the accompanying table. Assume no heat loss to the surroundings and perfect thermal contact at the common interface of the sample and the copper.
One vessel having a carbon-steel wall of thickness 5 mm carrying saturated steam and water at 423K. The vessel is insulated with magnesia of thickness 50 mm. If the ambient air temperature is 321 K, determine the heat loss from the vessel. Given: i. thermal conductivity of carbon steel is 52 W/m.K ii. thermal conductivity of magnesia is 0.5 W/m.K iii. surface coefficient of insulation surface is 3 W/m2.K