In: Mechanical Engineering
4. Given a system of five (5) 3500-lb, 700 feet per minute (fpm) elevator cars. Gearless traction motors are being used for this system. Each car operates approximately 65% of the time and while in operation, each car draws 96% of the full load. Calculate
a. Heat generated in the machine room during peak periods. Assume solid-state control is used. (5 points)
b. Assume the following operation profile during a 24-hour day
5 hours peak use
3 hours of 70% peak
4 hours of 50% peak
12 hours of 10% peak
Calculate the approximate monthly energy cost using the electricity rate of $0.10/kWh assuming 25 days of operation per calendar month (10 points)
Given that,
E = 3500 x 700 = 24500000 ft lb/min = 56350 W
Heat generated = W / V
V = 0.96
Heat generation = 56350 / 0.96 = 58697.9 W/m3
b) Given that,
The working hours daily = 12 hrs
Energy consumption daily = 5365
rate = $0.1 / Kwh
25 days per month
Then the cost calculation = $2.02 / month
= $24.68 / year.