Refrigeration cycle apparatus
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Solution Overview
Problem
Refrigeration cycle apparatuses face challenges in preventing liquid backflow into the compressor during mode transitions, particularly when switching from defrost to heating mode, due to insufficient gasification of refrigerant and differences in refrigerant amounts required for cooling and heating modes, leading to potential compressor breakdown and increased accumulator size.
Innovation Solution
A refrigeration cycle apparatus with a compressor, first and second heat exchangers, a flow path switching device, and a refrigerant tank circuit with a controller that adjusts the flow rate and path to bring the degree of superheat close to a target value, performing refrigerant release and collection operations to inhibit liquid backflow by managing the flow of refrigerant between the heat exchangers and a tank, thereby reducing the need for a large accumulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large accumulator is provided to inhibit liquid backflow into the compressor, then the reliability of the compressor is improved, but the volume of the machine chamber increases
Solution Approach 1:
The patent performs preliminary action by controlling the degree of superheat at the compressor suction side to be greater than or equal to a predetermined value before liquid backflow can occur. The controller adjusts the expansion valve opening degree in advance to ensure refrigerant is sufficiently gasified, preventing liquid refrigerant from entering the compressor during mode transitions.
Solution Approach 2:
The patent changes the parameter of degree of superheat from a passive to an actively controlled variable. By monitoring and adjusting the degree of superheat at the compressor suction side, the system ensures refrigerant remains in gas phase, eliminating the need for a large accumulator while protecting the compressor.
2Reliability
If the degree of superheat at the compressor suction side is controlled to be greater than or equal to a predetermined value, then liquid backflow is inhibited, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent implements feedback control by using a temperature sensor to detect the degree of superheat at the compressor suction side and feeding this information back to the controller. The controller then adjusts the expansion valve opening degree based on this feedback to maintain the degree of superheat at or above the predetermined value, creating a closed-loop control system.
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 effectively inhibits liquid backflow during mode transitions, reduces the size of the accumulator, and prevents compressor breakdown, allowing for a more compact machine chamber while maintaining efficient operation.
Implementation Method 1
the first pressure reducing device being configured to adjust a flow rate of the refrigerant to bring a degree of superheat of the refrigerant at a suction side of the compressor close to a target value
Implementation Method 2
a refrigerant tank circuit branching from between the first heat exchanger and the first pressure reducing device and joining between the first pressure reducing device and the second heat exchanger, being in parallel with the first pressure reducing device, and including, in series, a second pressure reducing device, a refrigerant tank, and a valve
Data Source
AI summary
In a refrigeration cycle apparatus, a controller is configured to, when a defrost mode is started, control a first pressure reducing device is controlled to adjust a flow rate of refrigerant to bring a degree of superheat of the refrigerant at a suction side of a compressor close to a target value, control a flow path switching device to form a first flow path through which the refrigerant released from the compressor flows to a first heat exchanger; perform a refrigerant release operation of opening one of a second pressure reducing device and a valve and closing the other of the second pressure reducing device and the valve, and perform a refrigerant collection operation of opening the second pressure reducing device and the valve, with the flow path switching device retained to form the first flow path, after the refrigerant release operation.