Heat Transfer Fluid Solubility for Heat Pump Safety

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Solution Overview

Problem

Existing heat transfer fluid circuits in heat pump systems face challenges with flammable refrigerants leaking into the brine circuit due to leaks, leading to inefficiencies and safety risks from undissolved gas outgassing and flammable mixtures, which conventional double-walled exchangers cannot fully prevent.

Innovation Solution

A mixing station with additives and a mixing process is introduced, using water-soluble hydrocarbon compounds and coated nanoparticles to enhance solubility, combined with a circulation system and non-return valves to ensure safe dissolution of leaked refrigerants in the heat transfer fluid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If double-walled heat exchangers are used to prevent refrigerant leakage, then safety is improved, but heat transfer efficiency deteriorates due to poor thermal conductivity of materials and air gap insulation

Engineering Contradiction:
ImprovesafetyVSAvoidheat transfer efficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces a heat transfer fluid as an intermediary substance that fills the space between the refrigerant and the outer wall, enabling efficient heat transfer while maintaining the safety benefits of the double-walled structure. The heat transfer fluid has high thermal conductivity and fills gaps that would otherwise act as insulators.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the physical state and properties of the heat transfer fluid under different operating conditions (temperature, pressure) to optimize heat transfer efficiency while maintaining safety. The fluid is selected to remain in liquid phase under normal operating conditions, ensuring high thermal conductivity.

Inventive Principle:
Principle #35Parameter changes

2Loss of energy

If conventional heat exchangers are used without double-walled design, then heat transfer efficiency is maintained, but refrigerant leakage into heat transfer fluid causes flammable mixtures and safety risks

Engineering Contradiction:
Improveheat transfer efficiencyVSAvoidflammable mixtures
Core Design Contradiction:
Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The heat transfer fluid acts as a protective intermediary between the refrigerant and the environment, designed to be non-flammable and chemically stable. Even if refrigerant leaks into the heat transfer fluid, the mixture remains safe due to the non-flammable properties of the heat transfer fluid.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potential harm of refrigerant leakage into a beneficial situation by selecting heat transfer fluids that are non-flammable and have high solubility for refrigerants. The leaked refrigerant dissolves in the heat transfer fluid, preventing the formation of flammable gas pockets and actually improving heat transfer efficiency.

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

3Stability of the object's composition

If refrigerant solubility in heat transfer fluid is low, then phase separation occurs and gas pockets form during temperature changes, but increasing solubility may require adding substances that could affect system compatibility

Engineering Contradiction:
Improvehomogeneous mixtureVSAvoidsystem compatibility
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent selects heat transfer fluids with specific physical and chemical parameters (high refrigerant solubility, non-flammability, chemical stability) that naturally achieve homogeneous mixing without requiring additional solubility-enhancing additives. The fluid properties are optimized to maintain solubility across the operating temperature range.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses composite heat transfer fluids that combine multiple components to achieve both high refrigerant solubility and system compatibility. The composite formulation ensures non-flammability, chemical stability, and high solubility while being compatible with existing system materials and components.

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

Ensures safe and continuous operation of the heat pump system by preventing gas pockets and maintaining efficient heat transfer, even in the event of leaks, by ensuring complete dissolution of refrigerants in the heat transfer fluid.

Implementation Method 1

additives are added to the heat transfer fluid circuit... Propylene glycol is the preferred antifreeze for aqueous heat transfer fluid circuits. This has the advantage of being completely miscible with water and non-toxic to humans and the environment in the event of an accident. One advantage of this antifreeze is that it significantly increases the solubility of R290 and other alkanes.

Methodology Applied
Scientific EffectSolubility enhancement: Solvation

Implementation Method 2

A mixing station with additives and a mixing process is introduced, using water-soluble hydrocarbon compounds and coated nanoparticles to enhance solubility, combined with a circulation system and non-return valves to ensure safe dissolution of leaked refrigerants in the heat transfer fluid.

Methodology Applied
Scientific EffectFluid circulation: Convection

Data Source

PatentEP4166854B1Solubility enhancement of alkanes
Publication Date: 2025.10.08 VAILLANT GMBH(DE)
  • EP4166854B1 patent drawingFigure 1

AI summary

The invention ensures that gaseous alkane-containing components of the working fluid can dissolve safely in the heat transfer fluid and remain dissolved therein. This problem is solved by means of additives to increase the solubility of alkanes dissolved in the heat transfer fluid, wherein the heat transfer fluid is a mixture of water, antifreeze, and corrosion inhibitors, and wherein the additive is at least one water-soluble hydrocarbon compound, in conjunction with a mixing process and a mixing station.