MEN 310 Exam 2, Fall 2001

Notre Dame University Faculty of Engineering Mechanical Engineering Dep. TEST— MEN310 (eat Transfer) January 03, 2002 ste ‘1. ‘On a tropical island, a a large qeftigerated shed (20:20) has been operating at. - + 5°C for a numberof years so that thé underground i is ‘also at 5°C for an”. “$ appreciabte’ distance below the surface. Jt is thei put out of 'sérvice! a Wood © ™ floor is removed and ambient air at 27°C is allowed to circulate through the «:, shed at a velocity of 5 km/h. How long will it take for the ground 1m below LE the surface to reach 15°C. The soil is assumed to be wet with a conductivity of on ; 2.6 WimK and a diffusivity of 4.5x107%m’ss. | at’ eet APs = 10 2, An § om-thick square slab (40x40cm) of resin (9=2600 ko/m*, I=1 wink, and c=800 J/kg.) is to be cured under an array of air jets at 100°C flowing with a heat transfer coefficient of 40W/m™C, as shown in fig P2, If the initial temperature of the resin is 20°C, detennine the temperature of the back face after,10 minutes using an explicit technique and the grid given. Assume that the back face of the slab i is insulated and the edge losses are negligible. . eee Points: 1 (40%), and 2 (60%).