Undergrad Flow rate calculation of coating application

Thread starter bertcoen
Start date Sep 6, 2022
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Application Calculation Cfd Coating Flow Flow rate Rate

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SUMMARY

The forum discussion centers on calculating the flow rate of a coating application using a pressure tank set at 15 psi and a 1/8" flexible hose. The user seeks to apply the Hagen-Poiseuille equation for pressure drop calculations but questions its applicability due to the variable opening of the dispensing valve. The conversation highlights the importance of the Energy Equation for incompressible, steady flow and discusses the relationships between flow rate, pressure, valve radius, and viscosity, concluding that viscosity fluctuations may significantly impact flow rate stability.

PREREQUISITES

Understanding of the Hagen-Poiseuille equation for laminar flow calculations
Familiarity with the Energy Equation for fluid dynamics
Knowledge of Newtonian fluid behavior and viscosity concepts
Experience with pressure measurement techniques in fluid systems

NEXT STEPS

Research the Energy Equation and its application in fluid dynamics
Explore the Bernoulli equation and its relevance to flow rate calculations
Investigate the effects of viscosity on flow rate in Newtonian fluids
Conduct experiments with fluids of known viscosity to compare results

USEFUL FOR

Engineers, coating application specialists, and fluid dynamics researchers looking to optimize flow rate calculations and understand the impact of viscosity in coating processes.

Sep 8, 2022

Tom.G

Science Advisor

Gold Member

bertcoen said:

curing mechanism of the coating is a humidity reactive system.

Two possible ways I see this could cause your variations:

1) The spray nozzle is not being cleaned at end-of-shift and the residual compound is curing in it during the night.
2) Air used to pressureize the tank is moist causing partial curing. Air right out of a compressor is notoriously wet.

#1 has an obvious solution.
#2 As a test, get a tank of Dry Nitrogen with appropriate pressure regulator. Purge the reservoir,hose, nozzle, etc. and try that for a few days/weeks.

If #2 solves the problem, consider a dryer for the air line (expensive), perhaps a dessicant canister (periodic maintenance required) in the air line, or continue with the Dry Nitrogen tank.

Cheers,
Tom

p.s. As a last resort, farm out the coating process to someone else with a well-written/comprehensive quality requirement.

The downside (beyond cost) is the incoming quality-control inspections needed.