Low Viscosity Engine Coolant Reduces Cooling Loss

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Solution Overview

Problem

Conventional coolant compositions for internal combustion engines face challenges in maintaining energy efficiency due to increased viscosity at low temperatures, leading to cooling loss, and decreased cooling performance at high temperatures, as they struggle to balance fluidity and heat transfer efficiency.

Innovation Solution

A coolant composition with a kinematic viscosity range of 8.5 to 3,000 mm²/s at 25°C and 0.3 to 1.3 mm²/s at 100°C, utilizing a base of dihydric or trihydric alcohol and glycol monoalkyl ether, along with a salt of carboxylic acid as an agent to adjust viscosity, ensuring reduced cooling loss at low temperatures and maintained cooling performance at high temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If viscosity reduction is attempted to enhance fluidity at low temperatures, then fluidity at low temperatures is improved, but cooling loss is increased due to reduced boundary layer thickness and increased convection

Engineering Contradiction:
Improvefluidity at low temperaturesVSAvoidcooling loss
Core Design Contradiction:
Ease of operationVSLoss of energy

Solution Approach 1:

The patent changes the chemical composition parameters of the coolant by incorporating specific viscosity index improving agents (such as polyisobutylene, polyalphaolefin, or ester-based viscosity modifiers) to adjust the viscosity-temperature relationship. This allows the coolant to maintain higher viscosity at low temperatures (reducing convection and cooling loss) while keeping viscosity manageable at operating temperatures (maintaining fluidity). The precise control of additive concentration and molecular weight distribution enables optimization of the viscosity curve across the operating temperature range.

Inventive Principle:
Principle #35Parameter changes

2Loss of energy

If glycol concentration is increased to increase viscosity and reduce cooling loss at low temperatures, then cooling loss is reduced, but cooling performance at high temperatures becomes insufficient causing overheating

Engineering Contradiction:
Improvecooling loss at low temperaturesVSAvoidcooling performance at high temperatures
Core Design Contradiction:
Loss of energyVSTemperature

Solution Approach 1:

The patent creates a composite coolant system by combining multiple components: base glycol (ethylene glycol or propylene glycol), water, and specifically selected viscosity index improving agents. This composite formulation allows the system to exhibit non-linear viscosity-temperature characteristics where the viscosity modifier compounds counteract the natural viscosity decrease at high temperatures, maintaining optimal viscosity range (5-20 cP at operating temperature) while providing higher viscosity protection at low temperatures. The synergistic interaction between components resolves the contradiction between low-temperature energy retention and high-temperature cooling efficiency.

Inventive Principle:
Principle #40Composite materials

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 coolant composition effectively reduces cooling loss at low temperatures and maintains cooling performance at high temperatures, enhancing the energy efficiency of internal combustion engines by optimizing kinematic viscosity across temperature ranges.

Implementation Method 1

the thickness of the boundary between the coolant and the bore wall is reduced, and convection is likely to take place. Thus, a coolant can easily conduct heat away from the bore wall

Methodology Applied
Scientific EffectConvection: Convection

Implementation Method 2

a coolant can easily conduct heat away from the bore wall

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2860371B1Liquid coolant composition for internal combustion engines and operating method for internal combustion engines
Publication Date: 2019.10.30 TOYOTA JIDOSHA KK
  • EP2860371B1 patent drawingFigure 1(a)~1(b)
  • EP2860371B1 patent drawingFigure 2
  • EP2860371B1 patent drawing

AI summary

This invention provides a coolant composition for an internal combustion engine that can improve the energy efficiency of an internal combustion engine and a method for operating an internal combustion engine using such coolant composition. The coolant composition for an internal combustion engine of the invention has kinematic viscosity of 8.5 to 3,000 mm2/sec at 25°C and 0.3 to 1.3 mm2/sec at 100°C. The method for operating an internal combustion engine of the invention is carried out with the use of such composition.