Dual-Circuit Air Conditioning Using Non-Flammable HFO Refrigerants
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Solution Overview
Problem
Current air conditioning systems face challenges in being both efficient and safe, particularly in stationary heating and cooling, due to the high global warming potential and flammability of refrigerant fluids like R-410A, and the increased costs and dimensions associated with single-phase water-based systems.
Innovation Solution
A vapor compression circuit using a first refrigerant fluid coupled with a secondary nonflammable refrigerant fluid, comprising hydrofluoroolefins and hydrochlorofluoroolefins, which allows for efficient heat exchange and safe circulation, reducing energy costs and facility dimensions by using a nonflammable refrigerant fluid with a low boiling point in the secondary circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If R-410A refrigerant fluid is used in vapor compression circuits, then high energy efficiency is achieved, but high global warming potential (GWP 2100) and flammability issues arise
Solution Approach 1:
The system is divided into two separate circuits: a primary vapor compression circuit using R-410A for efficient heat transfer, and a secondary circuit using non-flammable refrigerant (R-1234yf or R-1234ze) for safe distribution. This segmentation allows each circuit to use the optimal refrigerant for its specific function, resolving the contradiction between energy efficiency and safety.
Solution Approach 2:
A heat exchanger serves as an intermediary component between the primary and secondary circuits, enabling thermal energy transfer without direct refrigerant mixing. This allows the system to maintain the high efficiency of R-410A while using safer refrigerants in the secondary circuit that interfaces with building spaces.
2Object-affected harmful factors
If single-phase water-based heat transfer fluid is used in secondary circuits, then nonflammability is achieved, but pipework dimensions and pumping energy increase considerably
Solution Approach 1:
The system changes the physical parameters of the secondary circuit refrigerant by selecting compounds with lower boiling points (R-1234yf: -29.6°C, R-1234ze: -62.6°C) compared to water-based fluids. This allows the refrigerant to remain in liquid or vapor-liquid equilibrium state at operating conditions, enabling compact heat exchangers and reduced pipework dimensions while maintaining non-flammability.
Solution Approach 2:
The secondary circuit utilizes phase transitions of the low-boiling-point refrigerants to enhance heat transfer efficiency. The refrigerants evaporate and condense within the heat exchangers, providing high heat transfer coefficients that reduce the required heat exchanger surface area and pipework dimensions compared to single-phase water-based systems.
3Object-affected harmful factors
If maximum load per circuit is reduced to limit flammable fluid circulation, then safety is improved, but system performance decreases
Solution Approach 1:
By segmenting the system into primary and secondary circuits with different refrigerants, the secondary circuit can be designed to handle the full building load using non-flammable refrigerants. This eliminates the need to reduce maximum circuit load for safety reasons, as the secondary circuit refrigerants (R-1234yf, R-1234ze) are non-flammable yet maintain efficient heat transfer 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 solution enables efficient and safe air conditioning with reduced energy consumption and facility size, allowing for the safe circulation of nonflammable refrigerants in sensitive zones without load limitations, while maintaining high heat transfer efficiency.
Implementation Method 1
heat exchange between the environment and the first refrigerant fluid
Implementation Method 2
heat exchange between the first and the second refrigerant fluid
Implementation Method 3
heat exchange between the second refrigerant fluid and the air to be conditioned
Data Source
AI summary
A process for conditioning air, by means of a main circuit, the main circuit being a vapor compression circuit, wherein a first refrigerant circulates, and a secondary circuit with no compressor, wherein a non-flammable second refrigerant including a hydrofluoroolefin and/or a hydrochlorofluoroolefin circulates, the main circuit and the secondary circuit being coupled to one another; the process including a heat exchange between the surroundings and the first refrigerant, a heat exchange between the first and second refrigerants, and a heat exchange between the second refrigerant and the air to be conditioned. Also, an air conditioning plant for implementing the process.