CO2 Refrigeration Pressure Control to Prevent Expansion Valve Flow Noise
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Solution Overview
Problem
Refrigeration apparatuses using supercritical refrigerants often generate noise due to the flow of refrigerant in a gas-liquid two-phase state at the inlet of the expansion mechanism, especially when the high pressure or temperature is not at a fully pressurized or critical level, leading to flow sound issues.
Innovation Solution
Incorporating a control section that regulates the opening degree of the expansion mechanism to ensure the discharge pressure is equal to or greater than the critical pressure, changing the state of the supercritical refrigerant from a gas-liquid two-phase state to a supercritical or liquid phase state, thereby inhibiting flow sound generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the expansion mechanism is opened during activation or at low external temperature, then the refrigeration apparatus can operate, but refrigerant in gas-liquid two-phase state flows into the expansion mechanism causing flow sound and noise
Solution Approach 1:
The control section performs preliminary action by detecting discharge pressure before opening the expansion mechanism and regulating it to reach the critical pressure threshold. This preliminary pressure regulation ensures the refrigerant is in supercritical state before expansion, preventing gas-liquid two-phase flow and the associated noise during subsequent operation.
Solution Approach 2:
The invention changes the physical parameter of the refrigerant from gas-liquid two-phase state to supercritical state by controlling the discharge pressure to be equal to or greater than the critical pressure. This parameter change eliminates the harmful gas-liquid two-phase flow condition that causes flow sound noise while maintaining operational capability.
2Productivity
If the discharge pressure is not controlled to be equal to or greater than the critical pressure, then the expansion mechanism can open freely, but the refrigerant remains in gas-liquid two-phase state generating flow sound
Solution Approach 1:
The control section implements feedback control by continuously monitoring the discharge pressure and adjusting the expansion mechanism opening degree accordingly. When discharge pressure is below the critical threshold, the control section restricts opening; when it reaches or exceeds the threshold, normal operation is permitted. This feedback loop ensures refrigerant remains in supercritical state, eliminating flow sound while 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
This solution effectively reduces noise by maintaining the refrigerant in a supercritical or liquid phase state, optimizing discharge pressure control, minimizing energy consumption, and reducing environmental impact using CO2 as a refrigerant with zero ozone depletion potential and low global warming potential.
Implementation Method 1
The compressor is configured to compress the supercritical refrigerant
Implementation Method 2
The gas cooler is configured to cool the supercritical refrigerant compressed by the compressor
Implementation Method 3
The expansion mechanism is configured to decompress the supercritical refrigerant
Implementation Method 4
The evaporator is configured to evaporate the supercritical refrigerant decompressed by the expansion mechanism
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
It is an object of the present invention to reduce occurrence of noise in an operation by inhibiting occurrence of flow sound of refrigerant. A refrigeration apparatus (1) is a refrigeration apparatus using supercritical refrigerant operating in a zone that high pressure of the supercritical refrigerant is equal to or greater than the critical pressure. The refrigeration apparatus (1) includes a compressor (21), a gas cooler (23, 31), an expansion mechanism (V2, V5), an evaporator (31, 23), discharge pressure detection means (P1, T2, T3) and a control section (5). The compressor is configured to compress the supercritical refrigerant. The gas cooler is configured to cool the supercritical refrigerant compressed by the compressor. The expansion mechanism is configured to decompress the supercritical refrigerant. The evaporator is configured to evaporate the supercritical refrigerant decompressed by the expansion mechanism. The discharge pressure detection means is capable of detecting discharge pressure of the compressor. The control section is configured to regulate the opening degree of the expansion mechanism for controlling the discharge pressure to be equal to or greater than the critical pressure when the refrigeration apparatus is activated and the discharge pressure is less than the critical pressure.