Heat transfer from a transistor may be enhanced by inserting it in an aluminum sleeve (k 200 W/m K) having 12 integrally machined longitudinal fins on its outer surface. The transistor radius and height are r1 2.5 mm and H 4 mm, respectively, while the fins are of length L r3 r2 8 mm and uniform thickness t 0.8 mm. The thickness of the sleeve base is r2 r1 1 mm, and the contact resistance of the sleeve-transistor interface is Rt,c 0.6 103 m2 K/W. Air at T 20 C flows over the fin surface, providing an approximately uniform convection coeffficient of h 30 W/m2 K. (a) When the transistor case temperature is 80 C, what is the rate of heat transfer from the sleeve? (b) Identify all of the measures that could be taken to improve design and/or operating conditions, such that heat dissipation may be increased while still maintaining a case temperature of 80 C. In words, assess the relative merits of each measure. Choose t what you believe to be the three most promising measures, and numerically assess the effect of corresponding changes in design and/or operating conditions on thermal performance.
IT 100 Week 12 11/8 Digital Safety and Security Exam 3 A. Security Tools a. Personal Firewall security tool that detects and protects personal computers from unauthorized intrusions. b. Antivirus Program protects a computer against viruses by identifying and removing computer viruses found in memory, on storage media, or on incoming files. c. Spyware remover program that detects and deletes spyware and similar programs. d. Adware remover program that detects and deletes adware. e. Antivirus keeps older viruses from attacking computers. f. Antimalware keeps up on newer viruses that could attack. g. Other secur