MEC E230 Lecture 3: September 12, Mass and Energy Balance

• School: University of Alberta
• Department: Mechanical Engineering
• Course: MEC E230
• Professor: Marc Secanell

Document Summary

I am interested in balance (money) changes over time a) b) Account for all flows in, e. g. deposits and interests and all flows out c) Assuming that money is neither created nor destroyed, i. e. it is conserved, we can write a. New balance - old balance = deposits +interest - (withdrawals + service fees) Dividing by time, we can find the rate of change. New balance - old balance = (deposits +interest) - (withdrawals + service fees) Draw a control volume around the country"s borders. Keep track of people going in and out of my cv through my cs. Even if borders are closed, the internal population would still change. Since population is not conserved, instead of a conservation law, we write a balance law. In general, we can write a mass and energy balance in any control volume as,