Date on Master's Thesis/Doctoral Dissertation

8-2014

Document Type

Master's Thesis

Degree Name

M.S.

Department

Mechanical Engineering

Committee Chair

Williams, Stuart J., 1981-

Committee Member

Kelecy, Andrea

Committee Member

Yang, Li

Subject

Dishwashing machines

Abstract

A dishwasher works by using water pressure to operate the Spray Arms. There are different types of wash systems with the most common being two spray arms, a lower and middle arm. These two spray arms operate independently from each other and can be powered individually. In this particular wash system, the subsystem of interest is the Mid Spray Arm which is connected with the Bottle Blaster where both operate simultaneously. The Mid Spray Arm is used to clean the upper dishwasher rack while the Bottle Blaster is used to clean bottles, also in the upper rack. In order to have proper cleaning performance in the dishwasher, the Mid Spray Arm needs to rotate with at least 20 revolutions per minute (RPM). Since the Mid Spray Arm and Bottle Blaster are connected together, the flow rate requirement is 12 gallons per minute (GPM); which is higher than a system that doesn’t include a Bottle Blaster (approximately 8.5 GPM). In order to reduce the amount of water usage and flow rate, a new system was configured that will independently operate the Mid Spray Arm and Bottle Blaster. For that, three different designs were created and a Pugh Matrix was used to select the appropriate design. The selected design will operate using water pressure to block the Mid Spray Arm port or the Bottle Blaster port and is attached to the Main Conduit before the Mid Spray Arm. This new system reduced the water consumption of the entire dishwasher due to the fact that is able to operate with a smaller pump. The new system provides 8.53 GPM to the Mid Spray Arm and 6.48 GPM to the Bottle Blaster compared to 9.88 GPM and 7.32 GPM respectively with the current system. This new system has a better cleaning performance due to the increased in RPM’s, now 25 RPM, on the Mid Spray Arm. Also, since a smaller pump can be used the new pump price will be $12.38, which is approximately 17% less expensive than the current pump. Another advantage is the reduction in noise by approximately 11% from an initial 21.3 dBa pump output.

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