Variable-Volume Exhaust Nozzle Control for Minimum Discharge Velocity
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Solution Overview
Problem
Existing exhaust systems face challenges in varying exhaust volume while maintaining minimum discharge velocity, leading to increased energy consumption and potential re-entrainment of exhaust effluent, as they typically operate at constant fan speeds and flow rates.
Innovation Solution
A variable cross-sectional outlet area nozzle system is integrated with a variable speed exhaust fan, a non-invasive flow monitoring system, a controller, and a bypass air damper, allowing for modulation of fan speed and nozzle area based on static pressure and airflow conditions to control discharge velocity and volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fan speed is reduced to lower energy consumption, then energy consumption decreases, but discharge velocity drops below minimum requirements
Solution Approach 1:
The patent changes the geometric parameter of the nozzle (cross-sectional area) rather than relying solely on fan speed adjustment. By varying the nozzle area dynamically, the system maintains discharge velocity requirements while allowing fan speed to be reduced for energy savings.
Solution Approach 2:
The system transitions from static nozzle geometry to dynamic adjustment of nozzle cross-sectional area. The variable area nozzle can be modified in real-time to match varying exhaust requirements, enabling both energy efficiency and velocity maintenance.
2Speed
If constant volume exhaust system is used to maintain minimum discharge velocity, then discharge velocity is maintained, but energy consumption increases
Solution Approach 1:
The system replaces constant volume operation with dynamic volume adjustment. The variable area nozzle allows the exhaust system to adapt its volume to actual demands, eliminating the need to maintain constant high fan speeds for energy consumption.
Solution Approach 2:
The patent implements dynamic changes in nozzle cross-sectional area parameter to match varying exhaust requirements. This allows the system to operate at lower energies when full exhaust capacity is not needed, while still maintaining minimum velocity requirements.
3Quantity of substance
If variable volume system with bypass air damper is used to reduce exhaust flow, then exhaust volume decreases, but fan energy savings are not realized
Solution Approach 1:
The patent extracts the bypass damper component from the system and replaces it with a variable area nozzle. This removes the need for unconditioned air mixing while still achieving variable volume exhaust, enabling actual fan energy savings.
Solution Approach 2:
Instead of using bypass air to reduce exhaust volume, the system changes the nozzle area parameter to directly control the exhaust flow. This allows the fan to operate at lower speeds and consume less energy while still meeting exhaust requirements.
4Use of energy by moving object
If fixed area outlet nozzle is used with reduced fan flow, then energy consumption decreases, but re-entrainment of exhaust effluent occurs
Solution Approach 1:
The patent dynamically adjusts the nozzle area parameter to maintain optimal discharge velocity. By keeping velocity above minimum requirements even at reduced fan flows, the system prevents re-entrainment while still achieving energy savings.
Solution Approach 2:
The system transitions from fixed nozzle geometry to dynamic adjustment. The variable area nozzle can be optimized in real-time to maintain discharge velocity and prevent re-entrainment, even when fan flow is reduced for energy efficiency.
Data Source
AI summary
An exhaust system for exhausting air from a space includes a variable-volume exhaust air moving system having at least one fan having an inlet and an outlet. A duct is connected to the inlet and an outlet nozzle defining a variable cross-sectional outlet area is fluidly connected to the outlet. A selectively operable bypass damper is fluidly connected to the inlet. A sensor is located in the exhaust system for detecting at least one of a pressure condition and a flow condition therein. A control system controls the at least one fan, the outlet nozzle, and the bypass damper, based on a signal sent from the sensor.