Segmented Evaporator Fins for Practical Inductive Defrost Heating

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Solution Overview

Problem

Conventional fins-on-tubes evaporator and heat exchanger systems have low electrical resistance, making it difficult to implement energy-saving inductive heating techniques like Pulse Electro-Thermal Deicing/Defrosting (PETD), as they require high electric currents and are not easily compatible with existing power supplies, and this limits their fin density and efficiency.

Innovation Solution

The system increases the electrical resistance by partitioning fins into sequential sections with longitudinal excisions, allowing for energy-saving inductive heating by matching the system's reactance to its electrical resistance, enabling the use of PETD or equivalent techniques while maintaining the same form factor and interface as conventional systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional fins-on-tubes evaporators are used with low electrical resistance, then manufacturing is simple and cost is low, but inductive heating requires extremely high currents that are difficult and expensive to provide

Engineering Contradiction:

Improveenergy efficiency of inductive heatingVSAvoidcomplexity of power supply system

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The evaporator is divided into multiple electrically isolated sections using non-conductive spacers positioned at intervals along the tube. This segmentation increases the overall electrical resistance of the evaporator, allowing inductive heating to be performed at practical current levels while maintaining the same heating capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Non-conductive spacers are introduced as intermediary elements between conductive sections of the evaporator. These spacers serve as electrical insulators that increase resistance while allowing the evaporator to maintain its structural integrity and heat transfer functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If conventional evaporators use low fin density to allow airflow, then airflow is sufficient, but evaporator performance and efficiency are reduced

Engineering Contradiction:

Improveevaporator cooling performanceVSAvoidenergy loss during defrost cycles

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The evaporator incorporates rapid periodic defrost cycles using inductive heating. The high-resistance design enables short-duration, high-intensity heating pulses that quickly remove frost buildup, allowing the evaporator to maintain high fin density while performing efficient periodic defrosting that minimizes energy loss and prevents airflow restriction.

Inventive Principle:

Principle #19Periodic action

3Speed

If PETD is applied to conventional evaporators with low resistance, then rapid defrosting is achieved, but extremely high currents of 10,000 A are required

Engineering Contradiction:

Improvedefrosting speedVSAvoidelectric current magnitude

Core Design Contradiction:

SpeedVSQuantity of substance

Solution Approach 1:

By segmenting the evaporator into multiple electrically isolated sections using non-conductive spacers, the overall electrical resistance increases. This allows PETD to achieve rapid defrosting speeds while operating at practical current levels rather than requiring extreme currents of 10,000 A.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrical resistance parameter of the evaporator is fundamentally changed by introducing non-conductive spacers. This parameter change transforms the evaporator from a low-resistance component requiring extreme currents to a high-resistance component suitable for practical PETD implementation at achievable current levels.

Inventive Principle:

Principle #35Parameter changes

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 reduces the current required for high-power heating by several orders of magnitude, increases efficiency, and allows for more frequent and energy-saving defrosting cycles, enabling higher fin density and reduced volume without increasing manufacturing complexity or cost.

Implementation Method 1

system and method for energy-saving inductive heating of evaporators

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

inductive heating by matching the system's reactance to its electrical resistance

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Implementation Method 3

PETD utilizes rapid resistive heating of particular element for fast and efficient defrosting

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS8931296B2System and method for energy-saving inductive heating of evaporators and other heat-exchangers

Publication Date: 2015.01.13 TRUSTEES OF DARTMOUTH COLLEGE THE

AI summary

A novel fins-on-tubes type evaporator/heat exchanger system that is optimized for energy-saving inductive heating thereof by configuring it to increasing its resistance to a value at which the system's reactance at its working frequency is comparable to its electrical resistance. The system includes a set of tubes configured for flow of cooling material therethrough, and also includes a set of fins positioned and disposed perpendicular to, and along, the tubes, in such a way that at least a portion of the fins comprises longitudinal excisions therein.