Refrigeration cycle device and refrigeration cycle device control method
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Solution Overview
Problem
In refrigeration cycle devices, particularly heat pumps and air conditioners, the high-stage compressor faces risks of liquid ingestion and overheating due to supercooled refrigerant, leading to potential damage and inefficiency, especially in low outside air temperatures.
Innovation Solution
A refrigeration cycle device with a bypass pipe and flow rate adjustment section that controls the refrigerant flow between the low-stage and high-stage compressors, adjusting the refrigerant flow based on discharge temperature and suction superheat to prevent liquid ingestion and maintain superheated gas, thereby preventing compressor damage and maintaining efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a large amount of supercooled liquid refrigerant is supplied to the suction pipe of the high-stage compressor, then the temperature of the refrigerant discharged from the high-stage compressor is lowered, but the refrigerant at the inlet of the compressor enters a gas-liquid two-phase state causing liquid compression and potential compressor damage
Solution Approach 1:
A bypass pipe is introduced as an intermediary pathway that allows controlled diversion of liquid refrigerant from the main flow between the low-stage compressor discharge and high-stage compressor suction. This intermediary structure enables precise regulation of refrigerant flow into the high-stage compressor, preventing direct uncontrolled supply of excessive liquid refrigerant while still allowing sufficient cooling effect.
Solution Approach 2:
The system changes the flow rate parameter of refrigerant supplied to the high-stage compressor by using an expansion valve to precisely control the amount of refrigerant entering the bypass pipe. By adjusting the expansion valve opening degree, the system optimizes the balance between cooling effect and preventing liquid ingestion, transforming the refrigerant state from excessive liquid to controlled amount with appropriate superheat.
2Productivity
If the outside air temperature is low, then the discharge pressure of the compressor must be raised to maintain heating performance, but the temperature of the refrigerant discharged from the compressor rises causing deterioration of lubricating oil and damage to components
Solution Approach 1:
The system performs preliminary cooling action by supplying controlled liquid refrigerant to the suction pipe of the high-stage compressor before the refrigerant enters the compression chamber. This preliminary action of introducing cool liquid refrigerant pre-cools the suction gas and reduces the temperature rise during compression, preventing overheating even when discharge pressure is raised for low-temperature heating operation.
Solution Approach 2:
The invention extracts a portion of the liquid refrigerant from the main condenser output flow and directs it through the bypass pipe to the high-stage compressor suction pipe. By taking out this specific refrigerant stream and applying it locally at the compressor inlet, the system achieves targeted cooling effect without disrupting the overall refrigeration cycle and maintains heating performance while controlling discharge temperature.
3Temperature
If the amount of liquid refrigerant supplied to the high-stage compressor is increased to lower discharge temperature, then the cooling effect is improved, but the risk of liquid ingestion and compressor damage increases
Solution Approach 1:
The system implements feedback control by monitoring the suction superheat degree of the high-stage compressor and adjusting the expansion valve opening degree accordingly. When suction superheat is low (indicating risk of liquid ingestion), the controller reduces the expansion valve opening to limit liquid refrigerant flow through the bypass pipe. When suction superheat is adequate, the valve opening is increased to enhance cooling effect, maintaining optimal balance between temperature control and liquid ingestion prevention.
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 lowers the temperature of the refrigerant sucked into the high-stage compressor, preventing liquid ingestion and maintaining a constant superheat degree, thus preventing compressor damage and ensuring efficient operation across varying temperature conditions.
Implementation Method 1
The refrigerant which is supplied to the suction pipe of the compressor is a supercooled liquid medium
Implementation Method 2
a flow rate adjustment section which is provided in the bypass pipe and adjusts the amount of a refrigerant flowing through the bypass pipe
Implementation Method 3
the temperature of the refrigerant which is sucked into the high-stage compressor is lowered
Implementation Method 4
an expansion section, and an evaporator are connected with one another by piping
Data Source
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AI summary
The purpose of the present invention is to reduce the temperature of a refrigerant sucked in by a high-stage compressor and prevent the high-stage compressor from sucking in a liquid medium. This refrigeration cycle device has a compression unit having a low-stage compressor (7) and a high-stage compressor (8), a condenser (11), a first expansion valve (12), and an evaporator (17). The refrigeration cycle device is equipped with: a liquid bypass circuit (32) which branches off from a pipe connecting the condenser (11) and the first expansion valve (12), and joins into a pipe connecting the low-stage compressor (7) and the high-stage compressor (8); a third expansion valve (33) which is provided to the liquid bypass circuit (32) and adjusts the amount of the refrigerant flowing through the liquid bypass circuit (32); and a controller (40) which controls the third expansion valve (33) and increases the amount of the refrigerant flowing through the liquid bypass circuit (32) when the discharge temperature of the high-stage compressor (8) is higher than a predetermined value, and which controls the third expansion valve (33) and adjusts the amount of the refrigerant flowing through the liquid bypass circuit (32) on the basis of the suction superheat degree of the high-stage compressor (8).