Linear Counter-Flow Heat Exchanger for Convection Oven Efficiency

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Solution Overview

Problem

Convection ovens face inefficiencies in heat transfer due to the need for oxygen in combustion processes, where ambient air is used, leading to energy loss in heating air from ambient to cooking temperatures, and previous solutions have not fully optimized space and cost within conventional oven sizes.

Innovation Solution

The implementation of a linear counter-flow heat exchanger design in convection ovens, where heated fluid flows parallel to and opposite the direction of process air, maximizing heat transfer efficiency and reducing structural stresses by using a single heat element per heat exchange duct, which follows the path of process air flow without crossing it.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If crossflow or cross counter-flow heat exchanger designs are used, then heat transfer efficiency is improved, but device complexity and construction difficulty increase

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidconstruction difficulty

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent inverts the conventional crossflow arrangement by using longitudinal flow paths where combustion gases and process air flow parallel to each other in the same direction rather than crossing perpendicular to each other. This inversion simplifies the heat exchanger geometry while maintaining effective heat transfer from the combustion process to the process air.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The heat exchanger is divided into multiple longitudinal ducts, with separate ducts for combustion gases and process air. This segmentation allows independent flow paths while maintaining thermal coupling through the duct walls, simplifying the overall structure compared to complex crossflow arrangements.

Inventive Principle:

Principle #1Segmentation

2Loss of energy

If conventional heat exchanger designs are used, then heat transfer occurs, but space utilization within the oven is suboptimal

Engineering Contradiction:

Improveheat transfer effectivenessVSAvoidspace utilization

Core Design Contradiction:

Loss of energyVSVolume of moving object

Solution Approach 1:

The heat exchanger utilizes the vertical dimension by arranging ducts in multiple levels and incorporating upward and downward flow paths. This three-dimensional arrangement maximizes heat transfer surface area within the limited horizontal footprint of the oven, improving space utilization.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The heat exchanger ducts are arranged to nest within the oven structure, with combustion gas ducts and process air ducts positioned in nested or adjacent configurations. This nesting allows compact integration of the heat transfer system within the oven's existing volume.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Power

If multiple heating elements are used per heat exchange duct, then heat transfer capacity increases, but structural stresses increase

Engineering Contradiction:

Improveheat transfer capacityVSAvoidstructural stresses

Core Design Contradiction:

PowerVSStress or pressure

Solution Approach 1:

Instead of concentrating multiple heating elements in one duct, the system segments the heating capacity across multiple ducts, each with a single heating element. This distribution reduces the thermal and structural stress on any single duct while maintaining the overall heat transfer capacity of the system.

Inventive Principle:

Principle #1Segmentation

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 enhances heat transfer efficiency, reduces energy consumption, and optimizes space within the oven, achieving improved cooking performance while minimizing structural stresses and costs.

Implementation Method 1

a heat exchanger for heating the process air circulating in the cooking chamber

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

linear counter-flow, a method not previously employed in convection ovens. In the linear counter-flow method, the flow of heat (e.g., heated fluid F, products of combustion in the heat exchange ducts) is parallel to the flow of process air A (linear), but the flow of heat is in an opposite direction (counter-flow) to the direction in which the process air A flows

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS10314315B2Convection oven with linear counter-flow heat exchanger

Publication Date: 2019.06.11 LBC BAKERY EQUIP

AI summary

A convection oven includes a cooking chamber for cooking a food product, an air circulator that circulates process air in a first direction through the cooking chamber and along a circulation path in a circulation passage. A heat exchanger includes one or more heat transfer ducts longitudinally arranged along the circulation path. One or more heating elements heat a fluid that is circulated in a second direction through the one or more heat transfer ducts which is opposite to the first direction. The process air absorbs heat from the heated fluid as the process air travels along the circulation path back to the cooking chamber. A partition wall may separate first and second parallel portions of the one or more heat transfer ducts. A heat exchanger may preheat fluid entering the one or more heat transfer ducts using heated fluid leaving the heat transfer ducts.