4. An orange 102 mm in diameter having a surface temperature of 21.1°C is placed on...
3. A spherical ball having a diameter of 5 mm and at a temperature of 90°C is covered by a 3 mm thick plastic insulation. The ball is exposed to air at 24°C, with a combined convection and radiation heat transfer coefficient of 35 W/m² °C. Determine if the plastic insulation on the ball will help or hurt heat transfer from the ball.
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched in a large bath having a constant temperature of 320 K with a convection heat transfer of 75 W/m2.K. The thermophysical properties of the sphere material are: p=400 kg/mº, c=1600 J/kg-K, and k=1.7 W/mK. (Use characteristic length Lc=VIA to determine applicability of lumped method; Use radius of the sphere for one term approximation) a) Calculate the time required for the surface of the sphere...
A long wire with circular cross section and diameter D = 1 mm is submerged in an oil bath with temperature To 20。C. The wire is initially at temperature T = 20。C, the same temperature as the oil. A current is passed through the wire, resulting in a volumetric heat generation of q - 1.5 x 108 W/m3. The convection coefficient is h - 500 W/m2 - K, and the properties of the wire are ρ-8000 kg/m3, Cp-500 J/kg-K, and...
Homework 7 heat transfer 2018-20 1) A horizontal tube of 12.5-mm dimeter with an outer srface temperature of 240°C is placed in a room with an air temperature of 20°C. Estimate the heat transfer rate per unit length of the tube due to free convection. 2) Air at -10°C flows at 10 m/s over the roof plate of two 5m length rooms whose air is at Too-200C. The roof plate is 0.20-m thick concrete (k = 0.6 w/ m. K)....
summatize the following info and break them into differeng key points. write them in yojr own words
apartus
6.1 Introduction—The design of a successful hot box appa- ratus is influenced by many factors. Before beginning the design of an apparatus meeting this standard, the designer shall review the discussion on the limitations and accuracy, Section 13, discussions of the energy flows in a hot box, Annex A2, the metering box wall loss flow, Annex A3, and flanking loss, Annex...
summarizr the followung info and write them in your own words and break them into different key points. 6.5 Metering Chamber: 6.5.1 The minimum size of the metering box is governed by the metering area required to obtain a representative test area for the specimen (see 7.2) and for maintenance of reasonable test accuracy. For example, for specimens incorporating air spaces or stud spaces, the metering area shall span an integral number of spaces (see 5.5). The depth of...