Dual Cycle Engine Coolant Heat Recovery

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Solution Overview

Problem

Internal combustion engines lose a significant portion of fuel heating value through radiation and engine coolant, leading to inefficient waste heat recovery, and existing solutions like the Rankine cycle are impractical for vehicles due to inefficiencies and cooling issues such as transition film boiling.

Innovation Solution

A dual cycle internal combustion steam engine design where the coolant is maintained at an elevated temperature above the boiling point of water, using a non-aqueous liquid coolant with controlled flow and residence time to enhance heat transfer, and a cooling jacket with a circuitous pathway to maximize heat recovery through a steam expander.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the coolant temperature is increased to improve waste heat recovery, then the fraction of waste heat recovered increases, but transition film boiling occurs leading to uncontrolled heating and potential engine damage

Engineering Contradiction:

Improvewaste heat recovery fractionVSAvoidengine operation reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent changes the chemical composition parameter of the coolant by using non-aqueous liquids (such as glycols, esters, or synthetic oils) instead of conventional water-based coolants. This parameter change raises the boiling point of the coolant to above 212°F, preventing transition film boiling and allowing the coolant temperature to be maintained at elevated levels (240°F-300°F or more) for improved waste heat recovery without causing runaway heating conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of high coolant temperatures (which normally cause transition film boiling and engine damage) into a beneficial effect by using non-aqueous coolants that can withstand these temperatures. The elevated temperature coolant becomes a useful thermal interface that efficiently transfers heat to the feed water in the Rankine cycle system, improving overall energy recovery while the non-aqueous coolant prevents the harmful boiling transition.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Use of energy by moving object

If conventional water-based coolant is used, then heat transfer to feed water is effective, but the coolant boils at low temperature causing transition film boiling and uncontrolled heating

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidcoolant boiling point

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent fundamentally changes the thermal parameter of the coolant by selecting non-aqueous liquids with boiling points above 212°F (such as glycols with boiling points around 290°F, esters around 300°F, or synthetic oils above 400°F). This parameter change allows the coolant to be heated to elevated temperatures without boiling, maintaining effective heat transfer to the feed water while preventing the harmful transition film boiling that occurs with conventional water-based coolants.

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 design significantly increases the fraction of waste heat recovered, preventing transition film boiling and ensuring reliable operation by maintaining high coolant temperatures and efficient heat transfer, thus improving fuel efficiency and reducing the risk of engine damage.

Implementation Method 1

The non-aqueous liquid coolant...serves as a thermal interface between two thermodynamic cycles of energy conversion...enables a much greater amount of the coolant heat to be transferred to a steam expander

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

a vaporizable working fluid...transferred to a steam expander that is provided as a part of an internal combustion piston engine

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

a cooling jacket with a circuitous pathway to maximize heat recovery through a steam expander

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS8661817B2High efficiency dual cycle internal combustion steam engine and method

Publication Date: 2014.03.04 THERMAL POWER RECOVERY LLC

AI summary

The coolant in the cooling jacket of a dual cycle internal combustion steam engine is intentionally maintained at an elevated temperature that may typically range from about 225° F.-300° F. or more. A non-aqueous liquid coolant is used to cool the combustion chamber together with a provision for controlling the flow rate and residence time of the coolant within the cooling jacket to maintain the temperature of the coolant at a selected elevated temperature that is substantially above the boiling point of water but below the boiling point of the coolant. The coolant is passed from the jacket through a heat exchanger in a first circuit to transfer heat to a vaporizable working fluid such as water and is then returned. An optional second circuit is an intrajacket perturbation circuit within the engine can be used to disrupt and disperse pockets of vapor that may tend to form before damaging hot spots can develop around the combustion chamber. A cooling jacket design is tailored to extract heat at the highest possible temperature from each heat transfer zone as by having the coolant follow a circuitous helical pathway to achieve more efficient and improved heat transfer from the combustion chamber to the cooling medium.