Combustion Convection Oven Venting With Variable Exhaust Damper
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Solution Overview
Problem
Commercial combustion convection ovens are not energy efficient due to unnecessary airflow and heat loss when burners are off, as they continue to exhaust heated air and use multi-speed fans that result in excessive airflow under all conditions.
Innovation Solution
A moveable exhaust damper that selectively closes the exhaust plenum when burners are off, and a variable speed fan system with controlled dampers to manage airflow based on operating modes, reducing airflow and heat loss during non-heating cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exhaust plenum remains open to allow airflow through the oven during heating, then sufficient fresh air is supplied to the burners for safe operation, but heated air escapes unnecessarily through the exhaust when burners are off, reducing energy efficiency
Solution Approach 1:
The exhaust damper is made movable between open and closed positions, allowing the system to dynamically adapt its airflow characteristics based on operational requirements. During heating, the damper opens to allow exhaust flow; during holding temperature, it closes to prevent heat loss.
Solution Approach 2:
The system changes the airflow parameter by moving the exhaust damper from an open state (during heating) to a closed state (during holding temperature), thereby controlling the amount of air flowing through the exhaust plenum based on the operational phase.
2Reliability
If multi-speed fans are used to provide sufficient airflow under worst case conditions, then adequate air circulation is achieved during heating, but excessively large amounts of airflow occur under better conditions, removing heat unnecessarily from the cooking cavity
Solution Approach 1:
The fan speed is made variable rather than fixed, allowing the system to adjust airflow magnitude based on thermal conditions. The controller reduces fan speed during holding temperature phase, thereby reducing unnecessary heat removal while maintaining adequate circulation.
Solution Approach 2:
Instead of providing full airflow capacity at all times, the system applies partial airflow (reduced fan speed) during holding temperature when full circulation is not needed, thereby avoiding excessive heat removal while still maintaining adequate air movement.
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
Significantly reduces energy consumption by minimizing airflow and heat loss when burners are off, improving overall energy efficiency by retaining heated air in the cooking cavity.
Implementation Method 1
a moveable exhaust damper that selectively closes off the exhaust plenum so as to inhibit the escape of heated air from the oven's cooking cavity
Implementation Method 2
Such ovens also employ fans to forcibly circulate the air in the cooking cavity so as to improve thermal transfer to the food
Implementation Method 3
Commercial combustion convection ovens utilize combustion of a gas to supply the heat to the cooking cavity to heat the food therein
Data Source
AI summary
A combustion convection oven has improved energy efficiency. The oven includes a moveable exhaust damper that selectively closes off the exhaust plenum so as to inhibit the escape of heated air from the oven's cooking cavity. The exhaust damper is open when the oven is in a heating mode with the burners on, but closed when the oven is in a heated mode where the burners are off. Thus, airflow through the oven is significantly reduced or eliminated when the burners are off. The damper may have a degree of openness that is controlled to be inverse to the speed of the oven's fan.