HFO-1234yf Retrofit Composition for PAG Miscibility in MAC Systems
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Solution Overview
Problem
There is a need for a cost-effective method to replace R-134a refrigerant in existing heat transfer systems with HFO-1234yf, particularly in mobile air conditioning (MAC) systems, while addressing the miscibility issues of base-line PAG lubricants that do not form a single phase fluid with HFO-1234yf over a wide temperature range.
Innovation Solution
A liquid heat transfer composition comprising at least 50% HFO-1234yf, 0.01% to 10% PAG lubricant, and 1% to 5% dispersant, which forms a single phase fluid over -10°C to 55°C, and a retrofitting method to introduce this composition into MAC systems without removing existing PAG lubricant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If R-134a is replaced with HFO-1234yf in existing heat transfer systems, then environmental performance is improved (lower GWP), but miscibility with base-line PAG lubricants deteriorates (does not form single phase fluid over wide temperature range)
Solution Approach 1:
The patent introduces a miscibility enhancer as an intermediary substance that mediates between HFO-1234yf and base-line PAG lubricant. The enhancer has high miscibility with both components, acting as a bridge to achieve homogeneous mixing. The composition includes HFO-1234yf (50-99 wt%), base-line PAG lubricant (1-49 wt%), and miscibility enhancer (0.1-10 wt%), where the enhancer enables single-phase fluid formation across wide temperature ranges despite the inherent incompatibility between refrigerant and lubricant
Solution Approach 2:
The patent modifies the chemical composition parameters by adding the miscibility enhancer component, which changes the phase behavior parameters of the system. This addition transforms the system from a two-phase immiscible system to a single-phase miscible system across the operating temperature range of -10°C to 55°C, while maintaining the environmental benefits of HFO-1234yf
2Stability of the object's composition
If existing PAG lubricant is removed via flushing to achieve proper miscibility, then miscibility is improved, but time and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-formulating a miscibility enhancer that can be introduced into the system along with or alongside HFO-1234yf. This enhancer proactively addresses the miscibility issue before it causes operational problems, eliminating the need for subsequent lubricant removal operations. The enhancer is included in the retrofit composition at 0.1-10 wt%, ensuring immediate miscibility upon refrigerant replacement
Solution Approach 2:
The patent extracts the miscibility enhancement function from the refrigerant replacement process itself. Rather than requiring separate lubricant removal and replacement operations, the miscibility enhancer is extracted as a distinct functional component that is added to the HFO-1234yf charge, enabling the refrigerant to carry its own lubricant compatibility solution throughout the system
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 solution ensures high miscibility and efficiency of HFO-1234yf with PAG lubricants, maintaining system performance and reducing environmental impact by avoiding costly lubricant removal processes.
Implementation Method 1
said dispersant is present in an amount of from about 1% by weight to about 5% by weight based on the weight of said PAG lubricant and said dispersant; and said heat transfer composition is a single phase fluid over the temperature range of from about −10° C. to about 55° C.
Data Source
AI summary
The present invention relates to heat transfer compositions comprising 1234yf refrigerant, PAG lubricant and dispersant and to methods of retrofitting R134a MAC systems with using such compositions.