Low-Profile Exhaust Hood Layout for Thermal Plume Capture
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Solution Overview
Problem
Conventional exhaust hoods face challenges in capturing thermal plumes efficiently due to external environmental disruptions and the need for higher exhaust rates to manage transient loads, leading to fumes being injected into occupied spaces.
Innovation Solution
The design of an eyebrow-type exhaust hood with a baffle plate and sloping rear planar boundary creates a remote suction zone, guiding thermal plumes into a slot positioned away from oven walls, enhancing capture efficiency and reducing energy waste by minimizing oversupply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exhaust rate is increased to manage transient loads and capture thermal plumes, then capture efficiency is improved, but energy consumption increases due to oversupply
Solution Approach 1:
The hood temporarily captures bursts of effluent in a buffer zone before they escape into the occupied space. This preliminary capture action allows the moderate average exhaust rate to catch up, avoiding the need for continuous high exhaust rates and reducing energy waste
2Productivity
If exhaust rate is increased to achieve full capture and containment, then capture efficiency is improved, but energy waste increases due to oversupply
Solution Approach 1:
The buffer zone temporarily holds effluent bursts, allowing the exhaust system to operate at a moderate average rate rather than requiring continuous high-rate operation, thus minimizing energy waste while maintaining capture efficiency
3Productivity
If buffer zone is implemented to capture transient effluent bursts, then capture efficiency is improved, but external environment may displace fumes adding excess ambient air
Solution Approach 1:
The suction inlet is positioned at a specific location (displaced from the back end) with specific geometric features (shallow angle sloping portion) to create localized flow patterns that capture thermal plumes while minimizing the harmful effect of external environment displacing fumes
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 configuration increases the effective capture zone and reduces energy consumption by efficiently capturing thermal plumes and minimizing the escape of fumes into occupied spaces, while allowing for a more compact and efficient exhaust system.
Implementation Method 1
bursts of effluent, which rise into the hood due by thermal convection
Implementation Method 2
giving the moderate average exhaust rate time to catch up
Data Source
AI summary
A low profile exhaust hood has a high inlet and a high aspect ratio of horizontal to vertical. A sloping wall of the recess guides hot plumes upwardly to the inlet. The inlet is sized to provide an exhaust face velocity that is at least as high as a highest possible plume velocity for a 400 F oven. The inlet is located high and forwardly to cause a suction zone to be generated near the forward edge of the hood to aid in capturing plumes tending to escape which are remote from the sloping wall.