Refrigeration device and method for controlling same
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Solution Overview
Problem
Conventional refrigeration apparatuses face pressure increases in the low-temperature side cycle when circulation is stopped, leading to increased costs and weight due to the need for rigid components, especially when using refrigerants like CO2 in environments with outside air temperatures higher than the refrigerant's critical temperature.
Innovation Solution
A refrigeration apparatus with a receiver located under the cascade condenser, where the controller activates the high-temperature side compressor when the low-temperature side compressor is off, and controls the frequency and opening degree of the high-temperature side expansion device based on pressure, ensuring rapid collection of refrigerant in the receiver and suppressing pressure increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the circulation in the low-temperature side cycle is stopped to prevent pressure drop, then the compressor is protected from excessive refrigerant suction, but the pressure in the low-temperature side cycle increases when outside air temperature is higher than the refrigerant's critical temperature
Solution Approach 1:
The patent introduces a flow control valve as an intermediary device in the refrigerant line between the low-temperature side compressor and the cascade condenser. This valve partially restricts refrigerant flow to the cascade condenser when the low-temperature compressor is running, preventing excessive refrigerant accumulation and pressure increase in the low-temperature side cycle during stopped periods, while still allowing the compressor to be protected from excessive suction.
Solution Approach 2:
The patent employs dynamic control of the flow control valve opening degree based on operating conditions. The valve opening is adjusted according to the running state of the low-temperature compressor, the temperature difference between evaporator inlet and outlet, and pressure conditions, enabling adaptive management of refrigerant flow to balance compressor protection with pressure control.
2Stress or pressure
If rigid structures with sufficient wall thickness are used to cope with pressure increase, then the system can handle pressure variations, but the cost and weight of the refrigeration apparatus increase
Solution Approach 1:
The patent changes the operational parameters of the system by controlling the flow control valve to maintain pressure within acceptable ranges during compressor stop periods. This dynamic parameter control allows the use of components with lighter wall thickness that are sufficient for normal operating pressures, rather than requiring heavy structures designed for maximum possible pressure excursions.
3Stress or pressure
If rigid structures with sufficient wall thickness are used to cope with pressure increase, then the system can handle pressure variations, but the manufacturing cost increases
Solution Approach 1:
The patent changes the operational parameters of the system by controlling the flow control valve to maintain pressure within acceptable ranges during compressor stop periods. This dynamic parameter control allows the use of components with lighter wall thickness that are sufficient for normal operating pressures, rather than requiring heavy structures designed for maximum possible pressure excursions, thereby reducing material costs and manufacturing expenses.
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 effectively reduces pressure in the low-temperature side cycle, minimizing the need for robust components and lowering costs and weight, while maintaining efficient operation.
Implementation Method 1
a cascade condenser including the first evaporator and the second condenser and configured to heat exchange between the refrigerant flowing in the first evaporator and the refrigerant flowing in the second condenser
Implementation Method 2
the receiver is located under the cascade condenser... the refrigerant in the second refrigerant circuit, which has been condensed and liquefied by the refrigerant in the first refrigerant circuit, is rapidly collected in the receiver
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A refrigeration apparatus 1 includes a high-temperature side cycle 11 in which a refrigerant circulates, the high-temperature side cycle 11 including a high-temperature side compressor 12, a high-temperature side condenser 13, a high-temperature side expansion valve 14, and a high-temperature side evaporator 15 sequentially connected by piping, a low-temperature side cycle 21 in which a refrigerant circulates, the low-temperature side cycle 21 including a low-temperature side compressor 22, a low-temperature side condenser 24, a receiver 25, a low-temperature side expansion valve 43, and a low-temperature side evaporator 44 sequentially connected by piping, and a cascade condenser 51 including the high-temperature side evaporator 15 and the low-temperature side condenser 24 and configured to heat exchange between the refrigerant flowing in the high-temperature side evaporator 15 and the refrigerant flowing in the low-temperature side condenser 24. The receiver 25 is located under the cascade condenser 51.