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examI_f2004_soln

# examI_f2004_soln - Name MAE 4800 Exam I November 2 2004...

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Name:_____________________________________ MAE 4800 Exam I November 2, 2004 Open notes Open book Closed neighbors Open mind Notes: Start exam when instructed – you will be given 75 minutes to complete the exam Write name at top of each page and any additional pages Read each problem carefully – if you still do not understand, ask Clearly state all assumptions Clearly show all your work, commenting on what you are doing – keep in mind that your exam communicates to those who are grading what you know To maximize points, plug in numbers at the end – solve algebraically first Reference table you are using for properties Good luck! Gary L. Solbrekken MAE 4800, Fall 2004 11/02/04

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Name:_____________________________________ Problem 1 (50 points) A type k thermocouple is used to measure the temperature of a heat sink and the temperature of the ambient air (see sketch below). A third thermocouple is placed in an ice bath. The measured voltages from the Keithly 2701 meter are shown in the table below. The input heat, q, is 70W. DVM Ice bath Airflow Input heat - q Sketch of Heat Sink Measurement Configuration Thermocouple EMF [mV] Ice bath -0.919 Airflow 0.447 Heat sink 3.26 Table of Thermocouple Voltage Measurements Part 1 (25 points) – What is the heat sink-to-ambient thermal resistance ( Ψ sa )? Solution: The heat sink thermal resistance is: q T T a s sa - = ψ The heat sink temperature is found by algebraically adding the voltage of the heat sink thermocouple and the ice bath thermocouple. The result is: 3.26 –(-0.919) = 4.179 mV.
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examI_f2004_soln - Name MAE 4800 Exam I November 2 2004...

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