Refrigerant Composition for Vehicle HVAC Low-Temperature Pressure
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Solution Overview
Problem
The existing refrigerant HFC-134a in motor vehicle air conditioning systems experiences negative pressure at low external temperatures, leading to air infiltration and corrosion issues, particularly when the external temperature is around −10° C.
Innovation Solution
A refrigerant composition comprising 4% to 6% difluoromethane (HFC-32), 2.5% to 3.5% pentafluoroethane (HFC-125), and 91% to 93.5% tetrafluoropropene is used, which maintains a higher pressure at the evaporator, preventing air infiltration and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If HFC-134a refrigerant is used in the air conditioning system, then the system can operate at low temperatures, but negative pressure forms in the evaporator causing air infiltration and corrosion
Solution Approach 1:
The patent changes the physical-chemical parameters of the refrigerant by replacing HFC-134a with a mixture containing HFO-1234yf, HFC-125, and HFC-32. This composition change modifies the pressure-temperature characteristics of the refrigerant, ensuring positive pressure in the evaporator at low temperatures while maintaining appropriate operating conditions across the temperature range.
Solution Approach 2:
The patent uses a composite refrigerant mixture combining multiple components (HFO-1234yf, HFC-125, and HFC-32) in specific proportions. This composite approach allows the refrigerant to exhibit optimized properties that neither component alone could provide, specifically maintaining positive pressure at low temperatures while preserving cooling efficiency.
2Quantity of substance
If HFC-134a refrigerant is used, then the air conditioning system can cool the passenger compartment, but air infiltration occurs at low temperatures leading to corrosion
Solution Approach 1:
The refrigerant composition is changed to achieve positive pressure in the evaporator at low temperatures, which prevents air infiltration. The specific mixture of HFO-1234yf, HFC-125, and HFC-32 maintains the cooling capability while eliminating the harmful pressure drop that causes air ingress and subsequent corrosion of system components.
Solution Approach 2:
The patent converts the potential harm of low-temperature operation into a benefit by selecting a refrigerant composition that naturally maintains positive pressure at these temperatures. What was previously a problematic condition (low temperature operation) becomes advantageous as it now prevents corrosion without sacrificing cooling performance.
3Reliability
If the refrigerant pressure is increased to prevent air infiltration, then system reliability improves, but compressor efficiency may be affected
Solution Approach 1:
The patent optimizes the pressure parameters by selecting a refrigerant composition that achieves positive pressure at the evaporator outlet without excessive pressure increases throughout the system. The HFO-1234yf-based mixture provides just enough pressure elevation to prevent air infiltration while maintaining pressure differential ratios that preserve compressor efficiency and overall system performance.
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 proposed refrigerant composition effectively prevents air infiltration and enhances the efficiency of the refrigerating loop, maintaining system performance even at low temperatures, with improved compressor efficiency and COP compared to HFC-134a.
Implementation Method 1
a circuit for circulation of a heat-exchange fluid which is used for the cooling of the engine and also for the heating of the passenger compartment
Implementation Method 2
The evaporator is a heat exchanger which removes heat from the air which will be blown into the passenger compartment
Implementation Method 3
The condenser, by virtue of forced ventilation, brings about the condensation of the gas which arrives in the gaseous state at high pressure and high temperature
Implementation Method 4
The compressor, directly driven by the engine of the vehicle using a belt and a pulley, compresses the refrigerant, forcing it back under high pressure and high temperature toward the condenser
Implementation Method 5
The expansion valve makes it possible to regulate the flow rate for entry of the gas into the loop via a modification of passage section depending on the temperature and on the pressure in the evaporator
Data Source
AI summary
A method for heating and/or air-conditioning in a motor vehicle interior by means of a reversible refrigeration loop in which a refrigerant fluid circulates, said fluid including: between 4 and 6 wt. % of difluoromethane (HFC-32); between 2.5 and 3.5 wt. % of pentafluoroethane (HFC-125); and between 91 and 93.5 wt. % of tetrafluoropropene, preferably 2,3,3,3-tetrafluoropropene.