Choked-Flow Mass Flow Verification Across Wide MFC Ranges
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Solution Overview
Problem
Current methods for verifying mass flow rates in electronic device manufacturing are inefficient, inaccurate, and require bulky equipment, often limited to low mass flow rate ranges, resulting in significant process downtime and uncertainty due to reliance on pressure rate of rise principles.
Innovation Solution
A mass flow verification system utilizing choked flow principles with a plurality of differently-sized flow restrictors and isolation valves, coupled with pressure and temperature sensors, to determine mass flow rates through equations that account for flow restrictor coefficients and gas correction factors, allowing for precise and efficient verification across a wider range of flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional verification equipment is used, then mass flow verification can be performed, but the equipment is bulky and expensive, increasing device complexity and cost
Solution Approach 1:
The patent replaces traditional mechanical verification equipment with a computational approach using choked flow equations. The system uses pressure and temperature measurements combined with mathematical models (equations of state and choked flow relationships) to determine mass flow rates, eliminating the need for bulky mechanical verification devices while maintaining or improving accuracy
Solution Approach 2:
The patent creates a virtual model of the flow system using mathematical equations that replicate the physical flow behavior. By using equations of state and choked flow relationships, the system copies the physical verification process in the computational domain, allowing accurate mass flow determination without physical verification equipment
2Measurement precision
If traditional verification methods are used, then mass flow can be verified, but verification time is long, resulting in significant process downtime
Solution Approach 1:
The patent replaces time-consuming mechanical verification procedures with instantaneous computational calculations. By using choked flow equations that relate pressure, temperature, and mass flow rate, the system provides immediate verification results without the prolonged measurement and analysis required by traditional methods
Solution Approach 2:
The patent establishes predetermined choked flow coefficients and equations of state in advance, allowing the verification system to perform rapid calculations during actual verification. The mathematical models are prepared beforehand with all necessary constants and relationships, enabling instant computation of mass flow rates from simple pressure and temperature measurements
3Adaptability or versatility
If traditional verification equipment is used, then verification can be performed, but it is limited to low mass flow rate ranges
Solution Approach 1:
The patent uses different choked flow coefficients corresponding to different mass flow rate ranges. By selecting appropriate coefficients based on the expected flow range and using equations that account for varying flow conditions, the system maintains high accuracy across a broad spectrum of mass flow rates, from low to high flows
Solution Approach 2:
The patent creates a universal verification system that can handle multiple mass flow rate ranges using the same choked flow equations and pressure/temperature measurement approach. By incorporating multiple choked flow coefficients and gas correction factors, the single system adapts to verify mass flow across diverse operating conditions without requiring separate equipment for different flow ranges
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces equipment footprint, increases accuracy, and significantly reduces verification time, enabling precise mass flow control with minimal downtime, even at higher mass flow rates, by using only two measurements—pressure and temperature—under choked flow conditions.
Implementation Method 1
determine a mass flow rate in response to a temperature measured by the temperature sensor under a choked flow condition and a first pressure measured by the first pressure sensor under the choked flow condition
Data Source
AI summary
Mass flow verification systems and apparatus may verify mass flow rates of mass flow controllers (MFCs) based on choked flow principles. These systems and apparatus may include a plurality of differently-sized flow restrictors coupled in parallel. A wide range of flow rates may be verified via selection of a flow path through one of the flow restrictors based on an MFC's set point. Mass flow rates may be determined via pressure and temperature measurements upstream of the flow restrictors under choked flow conditions. Methods of verifying a mass flow rate based on choked flow principles are also provided, as are other aspects.