Heat transfer sheet assembly with an intermediate spacing feature

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Solution Overview

Problem

Conventional heat transfer sheets in rotary regenerative air preheaters face a trade-off between structural rigidity and operational efficiency, with high soot blowing pressures causing mechanical damage and reduced efficiency due to increased pressure drop and fouling, especially at the cold-end elements.

Innovation Solution

A heat transfer sheet assembly with a first sheet element and a second sheet element of complementary profiles, featuring parallel sheet spacing features and lobular undulations, along with an intermediate sheet spacing feature that enhances structural rigidity and facilitates turbulent flow, maintaining thermal performance and withstanding higher soot blowing pressures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional sheet spacing features are used to maintain structural rigidity, then structural integrity is improved, but pressure drop increases and heat transfer efficiency decreases

Engineering Contradiction:

Improvestructural rigidityVSAvoidpressure drop

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The sheet is divided into multiple functional zones: wide gauged spacing features for structural support, lobular undulations for heat transfer enhancement, and intermediate spacing features for flow management. This segmentation allows each zone to optimize its function without compromising the others.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the sheet have different properties: the wide gauged spacing features provide structural rigidity where needed, the lobular undulations create turbulence for heat transfer enhancement in flow regions, and intermediate spacing features maintain channel integrity. Each local region is optimized for its specific function.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If high soot blowing pressures are applied to clean fouling, then cleaning effectiveness is improved, but mechanical damage to sheets increases

Engineering Contradiction:

Improvefouling removalVSAvoidmechanical damage

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The sheet combines multiple material features with different properties: the base sheet material provides structural strength, while the lobular undulations and intermediate spacing features create a composite structure that is both mechanically robust and resistant to fouling accumulation, allowing effective cleaning at lower pressures.

Inventive Principle:

Principle #40Composite materials

3Productivity

If turbulent flow is induced through undulations to increase heat transfer, then heat transfer efficiency is improved, but pressure drop increases

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidpressure drop

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The lobular undulations are positioned specifically in the flow channels where they can induce turbulence for heat transfer enhancement, while the wide gauged spacing features maintain overall structural rigidity. This localized application of turbulence-inducing features maximizes heat transfer benefit while minimizing pressure drop penalty.

Inventive Principle:

Principle #3Local quality

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

The solution improves structural rigidity and thermal performance while maintaining operational efficiency, reducing mechanical damage and fouling, and achieving up to an 8% improvement in heat transfer efficiency without negatively impacting pressure drop.

Implementation Method 1

The heat transfer sheets absorb heat from the flue gas stream and transfer this heat to the combustion air stream

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

Some heat transfer sheets include undulation patterns between the sheet spacing features to impede flow in a portion of the channel and thereby causing turbulent flow which increases heat transfer efficiency

Methodology Applied

Scientific EffectTurbulent flow: Turbulence

Data Source

PatentUS11236949B2Heat transfer sheet assembly with an intermediate spacing feature

Publication Date: 2022.02.01 ARVOS LJUNGSTROM LLC

AI summary

A heat transfer sheet assembly for a rotary regenerative heat exchanger has first and second heat transfer sheet elements stacked one against the other with a first repeat of a first profile on one sheet element opposing a second repeat of a second profile on the other sheet element. The sheet elements are spaced apart by a plurality of wide-gauged parallel sheet spacing features of the first profile repeat RI of the second profile repeat to form a generally close sided elongate channel for gaseous flow therethrough. The second profile of repeat includes an elongate fifth sheet spacing feature in the form of a lobe contacting undulations of the adjacent first profile of repeat.