Reversible Cooling Loop Using HFO-1234yf for Low-Temperature HVAC
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Solution Overview
Problem
The use of HFC-134a as a coolant in automobile air conditioning systems leads to air infiltration and corrosion when outside temperatures drop below -15°C, causing pressure drops and degradation of components like the compressor and evaporator.
Innovation Solution
A reversible cooling loop using 2,3,3-tetrafluoropropene as the coolant, with a four-way valve for reversing flow direction, and optionally including saturated or unsaturated hydrofluorocarbons, thermally coupled to the engine cooling circuit, and featuring air/coolant or liquid/coolant heat exchangers to manage heat exchange effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HFC-134a is used as coolant in the evaporator, then the cooling function is provided, but air infiltration occurs and corrosion develops when outside temperature is approximately -15°C or lower
Solution Approach 1:
The patent changes the chemical parameter of the coolant from HFC-134a to HFO-1234yf (2,3,3,3-tetrafluoropropene). This parameter change fundamentally alters the physical and chemical properties of the coolant, specifically its vapor pressure characteristics at low temperatures. HFO-1234yf maintains higher vapor pressure at -15°C and below, preventing the pressure drop that causes air infiltration and subsequent corrosion in the evaporator and compressor.
2Temperature
If the outside temperature drops to approximately -15°C or lower, then the cooling demand increases, but pressure drop develops in the evaporator leading to air infiltration
Solution Approach 1:
The patent changes the thermal parameter of the coolant by substituting HFC-134a with HFO-1234yf. This substitution modifies the vapor pressure-temperature relationship of the coolant. HFO-1234yf exhibits higher vapor pressure at sub-ambient temperatures compared to HFC-134a, thereby maintaining positive pressure in the evaporator even when outside temperature drops to -15°C or lower, preventing air infiltration.
3Quantity of substance
If HFC-134a is used as coolant, then the existing cooling system operates, but compressor performance degrades and components corrode at low temperatures
Solution Approach 1:
The patent changes the chemical composition parameter of the coolant from HFC-134a to HFO-1234yf. This parameter change improves compressor performance at low temperatures by maintaining higher vapor pressure, ensuring proper refrigerant circulation and preventing air infiltration that causes corrosion. The new coolant maintains system reliability while preserving the required quantity for effective cooling.
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 prevents air infiltration and improves the efficiency of the cooling loop, maintaining higher evaporator pressure and reducing corrosion, especially at low temperatures, while offering better compressor performance and energy management in both heating and cooling modes.
Implementation Method 1
the thermal engine has a circuit in which flows a heat transfer fluid which is used for cooling the engine and also for heating the passenger compartment
Implementation Method 2
an air heater which recovers the heat stored by the heat transfer fluid in order to heat the passenger compartment
Implementation Method 3
The evaporator is a heat exchanger which draws heat from the air which is to be blown into the passenger compartment
Implementation Method 4
The condenser is provided with forced ventilation, causing the condensation of the gas which arrives in the gaseous state at high pressure and temperature
Implementation Method 5
The expansion valve can be used to regulate the inflow of the gas into the loop by a modification of the passage cross section depending on the temperature and pressure at the evaporator
Data Source
AI summary
A method for the heating and/or air conditioning of the passenger compartment of an automobile using a reversible cooling loop in which flows a coolant containing 2,3,3,3-tetrafluoropropene. The method is particularly useful when outdoor temperature is lower than −15° C. The method can be used for hybrid automobiles designed for operating alternatively with a thermal engine and an electric motor.