Redesign of a Liquid Nitrogen Re-circulation System for

Photo of Brian Hyde, Sumedh Joshi, Stephen Wiese Students: Brian Hyde, Sumedh Joshi, Stephen Wiese

Sponsor: Air Liquide

Date: Fall 2008

Requirements:
In order to minimize changes to the current system, the redesign must: generate 2 feet of pressure head, maintain 140 gallons per minute flow rate, and minimize interruptions in flow. In accordance with the current patent, the system must deliver turbulent flow of liquid nitrogen. The redesign must adhere to Food and Drug Administration strict cleaning regulations. For example, the system must disassemble with ease (for cleaning), have no internal lubrication, and withstand temperatures in the range of -320°

Problem:
Due to the reliability issues that Air Liquide has observed with their pelletizer machine, the senior design team has been tasked with redesigning the liquid nitrogen delivery system. The team must analyze and model the current and alternative methods used to lift the liquid nitrogen from the sump to the pelletizing channel and make recommendations to Air Liquide based on the analysis.

Solution:
The team concluded that the main causes of the problem were cavitation and fluid recirculation. To avoid these problems, the impeller design was changed to have angled blades at an optimized angle of 40°. In addition, the impeller was raised out of the duct to change the system from a centrifugal impeller to an axial-flow impeller. The changes were modeled in FloWorks and determined to be sufficient in improving the reliability of the system.

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