Dual-Loop Air Conditioning with Low-GWP Indoor Refrigerant for Safety
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Solution Overview
Problem
Conventional air conditioning and refrigeration systems face challenges in achieving high efficiency and low global warming potential (GWP) while ensuring safety, as many refrigerants that meet these criteria are flammable or toxic, posing risks to occupants when leaked into living spaces.
Innovation Solution
The system employs a dual refrigerant circuit design with a first heat transfer fluid in an outdoor loop and a second, safer heat transfer fluid in an indoor loop, utilizing trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)) or trans-1,3,3-tetrafluoropropene (HFO-1234ze(E)) as the indoor refrigerant, which has low flammability and toxicity, and a more hazardous refrigerant in the outdoor loop, ensuring safety and environmental friendliness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If low GWP refrigerants are used to achieve high efficiency and low environmental impact, then global warming potential is reduced, but flammability and toxicity increase posing safety risks
Solution Approach 1:
The system divides the refrigeration cycle into two separate loops: an outdoor loop containing the compressor and condenser that can tolerate higher GWP refrigerants, and an indoor loop containing the evaporator that uses low-GWP, safe refrigerants. This segmentation allows each loop to be optimized independently for its specific requirements.
Solution Approach 2:
An intermediate heat exchanger serves as a mediator between the outdoor loop and indoor loop, enabling heat transfer between the two refrigerant circuits without direct mixing of the refrigerants. This allows the system to benefit from both high-GWP and low-GWP refrigerant properties while maintaining safety.
2Productivity
If hazardous refrigerants are used to achieve high capacity and efficiency, then cooling performance is improved, but safety risks to occupants increase when leaked
Solution Approach 1:
The refrigeration system is segmented into outdoor and indoor loops with different refrigerant selections. The outdoor loop can use hazardous refrigerants for high capacity, while the indoor loop uses safe refrigerants, eliminating the safety risk indoors while maintaining overall system capacity.
Solution Approach 2:
Different refrigerant quality requirements are applied to different locations: the outdoor loop allows hazardous refrigerants where leakage risk to occupants is minimal, while the indoor loop mandates safe refrigerants where occupancy occurs. This local differentiation optimizes both capacity and safety.
3Object-affected harmful factors
If safe refrigerants with low flammability and toxicity are used in the indoor loop, then safety is improved, but system complexity increases due to dual circuit design
Solution Approach 1:
The system merges two separate refrigeration loops (outdoor and indoor) into a single integrated air conditioning system that shares common components like the compressor and intermediate heat exchanger. This combining approach achieves safety through dual-circuit refrigerant selection while minimizing overall system complexity.
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 configuration provides air conditioning systems with high capacity, efficiency, and low GWP, while significantly reducing the risk of flammability and toxicity hazards, achieving a GWP reduction of approximately 10 times compared to traditional systems like R-410A, with efficiencies matching or exceeding those of prior systems.
Implementation Method 1
a compressor is used to compress a heat transfer vapor from a lower to a higher pressure, which in turn adds heat to the vapor
Implementation Method 2
This added heat is typically rejected in a heat exchanger, commonly referred to as a condenser. In the condenser the vapor, at least in major proportion, is condensed to produce a liquid heat transfer fluid
Implementation Method 3
In the condenser the vapor, at least in major proportion, is condensed to produce a liquid heat transfer fluid
Implementation Method 4
Once it has been condensed, the high-pressure heat transfer fluid undergoes a substantially isoenthalpic expansion, such as in by passing through an expansion device or valve, where it is expanded to a lower pressure, which in turn results in the fluid undergoing a decrease in temperature
Implementation Method 5
The lower pressure, lower temperature heat transfer fluid from the expansion operation then is typically routed to an evaporator, where it absorbs heat and in so doing evaporates
Implementation Method 6
where it absorbs heat and in so doing evaporates
Data Source
AI summary
Refrigerant systems for conditioning air and/or items located within a dwelling including a high temperature refrigerant circulation loop located substantially outside of the dwelling and a low temperature transfer circuit, which contains HCFO-1233zd(E) substantially inside of the dwelling and at least one intermediate heat exchanger which permits exchange of heat between the high temperature circuit and the HFCO-1233zd(E) in the low temperature heat transfer circuit.