Freezing apparatus
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Solution Overview
Problem
Existing freezing devices with screw compressors face issues with refrigerant pressure equalization during braking control, leading to potential damage or wear of the compression mechanism due to prolonged oil flow and counter-rotation of the screw rotor.
Innovation Solution
A freezing device with a flow control valve that equalizes pressure between the high and low pressure units by controlling the flow rate, integrated with rotation braking control to prevent counter-rotation and reduce the pressure equalization time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotation braking control is performed by applying direct-current voltage to the motor stator, then counter-rotation of the screw rotor is suppressed, but refrigerant pressure equalization takes a long time causing oil flow issues and potential damage to the compression mechanism
Solution Approach 1:
The flow control valve is opened in advance during the braking control period to equalize refrigerant pressure between the high-pressure and low-pressure units before the braking control ends. This preliminary action ensures pressure equalization is completed within the braking control time window, preventing oil flow issues and potential damage to the compression mechanism while maintaining the effectiveness of counter-rotation suppression.
Solution Approach 2:
The flow control valve acts as an intermediary device that facilitates refrigerant flow between the high-pressure and low-pressure units during braking control. By controlling the valve opening, the system mediates the pressure equalization process, enabling controlled refrigerant migration that balances pressure without causing harmful oil flow or extending the braking control duration.
2Loss of time
If the flow control valve is opened to equalize pressure between high and low pressure units, then pressure equalization time is reduced, but refrigerant flow control becomes more complex
Solution Approach 1:
The flow control valve serves multiple functions: it equalizes refrigerant pressure during braking control, controls refrigerant flow rates, and prevents harmful oil flow. By integrating these functions into a single valve system controlled by the existing controller, the patent achieves pressure equalization without significantly increasing overall system complexity.
3Reliability
If braking control is extended to ensure complete pressure equalization, then compression mechanism protection is improved, but the compressor stops operating for a longer period reducing productivity
Solution Approach 1:
By opening the flow control valve in advance during the braking control period, the system performs pressure equalization proactively before the braking control ends. This ensures complete pressure equalization within the original braking control time window, protecting the compression mechanism without extending the stop duration and maintaining productivity.
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 reduces the time needed for pressure equalization, preventing damage to the compression mechanism and minimizing oil flow issues, thus reducing the risk of liquid compression and subsequent damage to the gate rotor.
Implementation Method 1
a flow control valve that is provided in the communication flow path and that controls a flow rate of the refrigerant flowing through the communication flow path
Implementation Method 2
an inverter that supplies a voltage to the compressor and drives or stops the motor
Data Source
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Figure 6
AI summary
A freezing device including a compressor that compresses sucked refrigerant using a compression mechanism and discharges compressed refrigerant includes a compressor, an inverter, and a controller. The compressor includes a motor that drives the compression mechanism, a low pressure unit in which the sucked refrigerant flows, a compression space in which the refrigerant flowing in the low pressure unit is compressed, a high pressure unit in which the refrigerant compressed in the compression space flows, a communication flow path through which the low pressure unit and the high pressure unit communicate, and a flow control valve that is provided in the communication flow path and that controls a flow rate of the refrigerant flowing through the communication flow path. The inverter supplies a voltage to the compressor and drives or stops the motor. The controller controls the inverter and the flow control valve. The controller performs, in stop control in which an operation of the compressor is stopped, braking control in which driving of the compression mechanism is prevented or suppressed by controlling the inverter, and pressure equalization control in which pressure in the high pressure unit is equalized with pressure in the low pressure unit by opening the flow control valve.