Furnace Heat Exchanger Layout With Air Bypass Recombination
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Solution Overview
Problem
Inefficiencies in heat transfer between hot gases and air flow in furnaces due to air bypassing the heat exchangers, exacerbated by the need to maintain safe external temperatures, leading to increased furnace size and potential corrosion from condensation.
Innovation Solution
A furnace design incorporating a primary and secondary heat exchanger with a collection/discharge box and an air bypass channel, where a portion of the air is diverted through the bypass channel to receive heat from the collection/discharge box, and the recombined air is passed over the heat exchangers, enhancing heat transfer efficiency without requiring large physical separation or additional baffles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air baffles are added to direct air flow through the heat exchanger, then heat transfer efficiency is improved, but the furnace enclosure size increases to accommodate the baffles
Solution Approach 1:
The heat exchanger is divided into multiple sections (primary heat exchanger, collection/discharge box, secondary heat exchanger) arranged in series. This segmentation allows the air flow to be directed through each section sequentially, improving heat transfer efficiency without requiring additional baffles that would increase the overall furnace size.
Solution Approach 2:
The patent utilizes the vertical dimension by stacking the primary heat exchanger, collection/discharge box, and secondary heat exchanger one above the other. This vertical arrangement allows efficient heat transfer through multiple heat exchanger sections while maintaining a compact horizontal footprint, avoiding the need for larger furnace enclosure dimensions.
2Temperature
If the heat exchanger is spaced away from the furnace enclosure wall to maintain safe external temperatures, then safety is improved, but air bypass increases reducing heat transfer efficiency
Solution Approach 1:
The heat exchanger system is segmented into multiple sections (primary heat exchanger, collection/discharge box, secondary heat exchanger) that can be spaced from the enclosure wall. This segmentation allows the creation of a bypass channel that directs air flow through all heat exchanger sections in series, maintaining safety clearance while preventing air bypass and preserving heat transfer efficiency.
Solution Approach 2:
A bypass channel is introduced as an intermediary flow path that directs air through the collection/discharge box and all heat exchanger sections. This intermediary channel ensures that even when the heat exchanger is spaced from the enclosure wall for safety, the air flow is properly directed through all heating sections, maintaining heat transfer efficiency.
3Productivity
If a bypass channel is created to divert air, then heat transfer efficiency is improved by reducing bypass, but the device complexity increases
Solution Approach 1:
The collection/discharge box serves multiple functions: it collects hot gases from the primary heat exchanger, acts as a heating surface for air in the bypass channel, and distributes gases to the secondary heat exchanger. By merging these functions into a single component, the bypass channel design achieves improved heat transfer efficiency without significantly increasing device complexity.
Solution Approach 2:
The collection/discharge box performs multiple functions within the bypass channel system: gas collection, air heating, and gas distribution. This multi-functionality allows the bypass channel to improve heat transfer efficiency while minimizing the addition of separate components, thereby limiting the increase in device complexity.
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 design improves heat transfer efficiency by recombining heated air, reduces the risk of corrosion, and allows for a more compact furnace structure while maintaining safe external temperatures.
Implementation Method 1
The hot gases are routed through the internal channels of the heat exchangers, so that the desired transfer of heat from the hot gases to the air flow is achieved
Implementation Method 2
The diverted air is passed over the collection/discharge box to receive heat from the hot gases within the collection/discharge box
Implementation Method 3
the un-diverted air is passed over the primary and secondary heat exchanger to receive heat form the hot gases flowing through the heat exchangers
Data Source
AI summary
A furnace for heating air includes a primary heat exchanger and a secondary heat exchanger to transfer heat from a flow of hot gases, the secondary heat exchanger being arranged downstream from the primary heat exchanger. A collection/discharge box fluidly couples an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger. An enclosure houses the primary heat exchanger, the collection/discharge box, and the secondary heat exchanger, and includes an air inlet and an air outlet. A main air flow path extends through the enclosure from the air inlet to the air outlet, and the primary and secondary heat exchangers are arranged along the main air flow path. An air bypass channel is arranged to be fluidly parallel to a section of the main air flow path, and the collection/discharge box is arranged along the bypass channel.