Dual Expansion Valve Refrigerant Circuit for Suction Wetting Control
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Solution Overview
Problem
Air conditioning apparatuses with refrigerant circuits featuring expansion valves on both sides of a receiver face challenges in controlling suction wetting, leading to potential compressor reliability issues due to temperature increases and liquid compression risks when using R32 as refrigerant, especially without an accumulator on the suction side.
Innovation Solution
Incorporating a receiver gas vent pipe with a controllable valve to direct gas refrigerant to the compressor, combined with upstream expansion valve subcooling control and downstream expansion valve suction wetting control, to stabilize refrigerant flow and maintain a liquid state, ensuring high controllability and preventing excessive temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas refrigerant is injected from the receiver into the compressor, then the compressor reliability is improved, but the suction wetting control becomes difficult
Solution Approach 1:
The patent divides the single expansion valve function into two separate expansion valves (first expansion valve on upstream side, second expansion valve on downstream side of receiver). This segmentation allows independent control of refrigerant flow before and after the receiver, enabling precise suction wetting control while maintaining compressor reliability through gas refrigerant injection.
Solution Approach 2:
The patent employs dynamic control of the second expansion valve (downstream side) to adjust refrigerant flow based on operating conditions. By dynamically adjusting the expansion valve opening, the system achieves high controllability of suction wetting while maintaining the gas injection function for compressor protection.
2Ease of operation
If the number of expansion valves is increased to two, then the suction wetting control is improved, but the device complexity increases
Solution Approach 1:
The first expansion valve (upstream side of receiver) serves dual functions: it controls refrigerant flow into the receiver and simultaneously enables gas refrigerant injection to the compressor. This multi-functionality reduces the need for additional components, offsetting the complexity increase from adding a second expansion valve.
Solution Approach 2:
The patent combines the functions of refrigerant flow control and gas injection control into the first expansion valve assembly. By merging these functions, the system achieves improved suction wetting control without proportionally increasing device 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 enables precise suction wetting control and discharge temperature protection, enhancing compressor reliability and preventing liquid compression, while maintaining stable refrigerant flow and temperature management.
Implementation Method 1
the receiver gas vent pipe 30 which leads the gas refrigerant accumulated in the receiver 25 to the suction side of the compressor 21
Implementation Method 2
an upstream side expansion valve subcooling control is performed so as to set a subcooling of the refrigerant to a target subcooling
Data Source
AI summary
An air conditioning apparatus includes a refrigerant circuit having a compressor, a radiator, an upstream side expansion valve, a receiver, a downstream side expansion valve, an evaporator, and a receiver gas vent pipe. Gas vent control is performed so that gas refrigerant is led from a receiver to the suction side of a compressor via a receiver gas vent pipe by opening a receiver gas vent valve. Upstream side expansion valve subcooling control is performed so that the opening of an upstream side expansion valve is changed such that the subcooling of refrigerant is set to target subcooling at the outlet of a radiator. Downstream side expansion valve suction wetting control is performed so that the opening of a downstream side expansion valve is changed such that refrigerant is in a wetting state and the dryness is set to target dryness at the outlet of an evaporator.