Scraped surface heat exchanger and method for preparing food

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Solution Overview

Problem

Conventional scraped surface heat exchangers face issues with product fouling and inefficient heat transfer due to pivoting scraper blades that move radially and tangentially, leading to inconsistent heating and cooling, especially when processing viscous materials like chocolate, which results in abrasive damage and increased downtime for maintenance.

Innovation Solution

A scraped surface heat exchanger design featuring a non-pivotal connection for the sweeping element, with a T-shaped projection and apertures that maintain the blade's position relative to the shaft, ensuring minimal contact with the inner surface and preventing radial and tangential movements, thereby reducing fouling and enhancing heat transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If pivoting scraper blades are used to continuously scrape the inner surface, then heat transfer efficiency is improved, but product fouling increases and blade wear accelerates

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidproduct fouling

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

Instead of using blades that continuously scrape and contact the inner surface (conventional approach), the invention uses blades that periodically contact and lift off the surface. This inverted approach reduces fouling accumulation while maintaining effective heat transfer during contact periods, solving the contradiction between heat transfer efficiency and fouling prevention

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The blade is designed to periodically contact and lift off the inner surface during rotation, creating a rhythmic scraping action. This periodic contact maintains heat transfer effectiveness when the blade is in contact while reducing overall fouling accumulation compared to continuous scraping, directly addressing the technical contradiction

Inventive Principle:

Principle #19Periodic action

2Temperature

If pivoting scraper blades are used to scrape viscous materials, then heat exchange is enhanced, but radial and tangential blade movement occurs reducing scraping efficiency

Engineering Contradiction:

Improveheat exchange efficiencyVSAvoidscraping efficiency

Core Design Contradiction:

TemperatureVSEase of operation

Solution Approach 1:

The invention inverts the conventional pivoting blade design by using a non-pivoting blade that maintains fixed radial and tangential positions. The blade is secured to the shaft with set screws that prevent movement, eliminating the radial and tangential drift that occurs with pivoting blades while maintaining effective heat exchange through periodic contact

Inventive Principle:

Principle #13The other way round (Inversion)

3Temperature

If continuous scraping action is applied to viscous products like chocolate, then heat transfer is improved, but abrasive damage to the heat exchanger surface increases

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidabrasive damage

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The blade periodically contacts and lifts off the inner surface during rotation, creating intermittent rather than continuous scraping. This periodic action maintains heat transfer effectiveness during contact periods while significantly reducing cumulative abrasive damage to the heat exchanger surface compared to continuous scraping

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Instead of continuous contact scraping that causes abrasive damage, the invention uses periodic contact where the blade lifts off the surface after each scraping action. This inverted approach from continuous to intermittent contact reduces abrasive wear while maintaining heat transfer efficiency

Inventive Principle:

Principle #13The other way round (Inversion)

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 significantly reduces product fouling, maintains consistent temperature changes, and extends blade life by minimizing direct contact with the inner surface, resulting in improved heat transfer efficiency and reduced maintenance needs.

Implementation Method 1

A cooling or heating medium such as ammonia, glycerol, hot water or steam is circulated through the jacketed cylindrical chamber and provides heat exchange by the usual heat exchange process

Methodology Applied

Scientific EffectHeat exchange: Conduction (thermal)

Implementation Method 2

A cooling or heating medium such as ammonia, glycerol, hot water or steam is circulated through the jacketed cylindrical chamber and provides heat exchange by the usual heat exchange process

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentEP3191786B1Scraped surface heat exchanger and method for preparing food

Publication Date: 2021.03.31 SOCIETE DES PRODUITS NESTLE SA

Figure 1~2
Figure 3~4a
Figure 4b~5

AI summary

A scraped surface heat exchanger comprising a heat exchange surface, a rotatable shaft, said shaft having at least one mounting means, and a sweeping element wherein said sweeping element comprises,a blade having at least one aperture for engaging with the mounting means such that the sweeping element is connected to the mounting means and characterised in that when the rotatable shaft is rotating relative to the heat exchange surface the sweeping element has substantially no movement relative to the rotating shaft and said sweeping element has substantially no contact with the inner surface of the heat exchanger.