Results

The simulator provides multiple metrics but this section will focus on the most relevant: average student residence time. Residence time measures how long, on average, it took a student to do their laundry from the time the student enters the room until the time he leaves the room.

Running the base simulation, the average residence time is 97.12 minutes. This is impressive, as it is only 1.12 minutes away from the optimal time. It will be informative to observe how residence time changes as the number of machines change.

I add and subtract washer and dryer pairs to examine how additional machines may affect residence times. It takes subtracting five pairs before residence times start to become substantial. With 11 washers and 11 dryers, residence time rises to 106.49, or 10.49 minutes above the optimal time. Adding five pairs brings residence time closer to optimal - 96.21 minutes. The overall effect of adding pairs is relatively low.

Figure 1: Washers and dryers added and subtracted in equal amounts

What is more interesting is the impact of specific types of machines on the residence times. If we change the number of washers in the room, the residence time is virtually unchanged - with a maximum of 97.31 minutes and a minimum of 97.12 minutes. However, if we remove dryers from the system, the change in residence time closely matches the change in residence time experience when washer/dryer pairs were removed.

Figure 2: Washers added and subtracted, dryers held constant at 16

Figure 3: Dryers added and subtracted, washers held constant at 16

If we assume that the Owen laundry room only has room for 36 machines, then we can adjust the types of machines to find the optimal configuration. Twelve washers and twenty dryers is the optimal configuration - with 96.43 minutes of residence time. Thirteen washers and nineteen dryers yields a slightly higher residence time of 96.45 minutes. Eleven washers and twenty-one dryers yields a higher residence time of 96.54 minutes.

Figure 4: Washers and dryers added and subtracted to always total 32