Solution-422home1-2009_1_

Solution-422home1-2009_1_ - 155: 422 PROCESS SIMULATION AND...

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155: 422 PROCESS SIMULATION AND CONTROL Spring 2008 Homework 1 (Solutions) Assigned: 01/28/09 Due date: 02/04/09 Problem 1: Exercise 1.4 textbook page 13 No, a microwave oven typically uses only a timer to operate the oven for a set (desired) period of time and a power level setting that turns the power on at its maximum level for a fixed fraction of the so-called duty cycle, generally several seconds. Thus setting the Power Level at 6 (60% of full power) and the Cook Time to 1:30 would result in the oven running for a total of one and one-half minutes with the power proportioned at 60% (i.e., turned on 100% for 6 seconds and off for 4 seconds, if the fixed duty cycle is 10 seconds long). This type of control is sometimes referred to as programmed control, as it utilizes only time as the reference variable. The big disadvantage of such an approach is that the operator (here the cook) has to estimate what settings will achieve the desired food temperature or will cook the food to the desired state. This can be dangerous, as many people can attest who have left a bag of popcorn in the oven too
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Solution-422home1-2009_1_ - 155: 422 PROCESS SIMULATION AND...

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