Two-Stage Refrigeration Compression for Fast Discharge Pressure Recovery
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Solution Overview
Problem
The existing heat source units with multi-stage compression systems face challenges in quickly restoring the system when the pressure switchgear of the low-stage compressor is activated, as there is no effective means to reduce the pressure in the discharge pipe, leading to prolonged system downtime and potential damage.
Innovation Solution
The heat source unit incorporates a configuration where the high-stage compression element operates while the low-stage compression element is paused, allowing the high-stage compressor to suck refrigerant gas from the discharge pipes and reduce pressure, and includes a pressure equalization circuit to facilitate the restart of the high-stage compressor after pausing, ensuring no pressure abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire compression system is paused when HPS of the low-stage compressor is activated, then the low-stage compressor is protected from high-pressure refrigerant, but the pressure in the discharge pipe remains increased and the system cannot be restored quickly
Solution Approach 1:
The compression system is segmented into high-stage and low-stage compressors that can operate independently. When HPS is activated, only the low-stage compressor is paused while the high-stage compressor continues to operate, allowing selective protection and pressure reduction without complete system shutdown.
Solution Approach 2:
The high-stage compressor acts as an intermediary to reduce pressure in the low-stage discharge pipe by suctioning refrigerant gas. This mediator component enables pressure reduction without requiring the low-stage compressor to run, resolving the contradiction between protection and quick restoration.
2Speed
If the high-stage compression element operates while the low-stage compression element is paused, then pressure is reduced quickly in the discharge pipe, but the high-stage compression element must restart after pausing which requires pressure equalization
Solution Approach 1:
The pressure equalization circuit is pre-configured with equalization valves that can be activated before the high-stage compressor restarts. This preliminary preparation of the pressure equalization path simplifies the restart process and reduces control complexity despite the added circuitry.
Solution Approach 2:
The pressure equalization circuit acts as an intermediary mechanism that facilitates the restart of the high-stage compressor by balancing pressures between suction and discharge sides, making the restart process smoother and more controlled.
3Ease of operation
If a pressure equalization circuit is added to facilitate high-stage compressor restart, then restart is simplified and pressure abnormalities are prevented, but the device complexity increases
Solution Approach 1:
The pressure equalization circuit serves multiple functions: it equalizes pressures before restart, prevents pressure abnormalities during operation, and can be integrated with existing pressure switchgear and control systems. This multi-functionality justifies the added complexity by providing comprehensive protection and ease of operation.
Solution Approach 2:
The pressure equalization circuit automatically equalizes pressures when needed without requiring manual intervention. The equalization valves open and close based on pressure differential, making the system self-regulating and reducing operational complexity despite the additional components.
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 approach allows for rapid pressure reduction in the discharge pipes, enabling quicker system restoration and reducing damage to the utilization-side units by shortening the time required to restore the compression system.
Implementation Method 1
The high-stage compression element (21) compresses a refrigerant discharged from the low-stage compression element (22, 23)
Implementation Method 2
the refrigerant gas remaining in the discharge pipes (22b, 23b) of the low-stage compression element (22, 23) can be sucked by the high-stage compression element (21)
Implementation Method 3
the pressure equalization circuit (37, 38) configured to equalize a suction pressure and a discharge pressure of the high-stage compression element (21) after the high-stage compression element (21) is paused and before the high-stage compression element (21) is restarted
Data Source
Figure 1
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Figure 3
AI summary
A heat source unit (10) constitutes a refrigeration apparatus (1) by being connected to a utilization-side unit (50, 60). The heat source unit (10) includes a low-stage compression element (22, 23), a high-stage compression element (21), and a heat exchanger (13). The low-stage compression element (22, 23) has a discharge pipe (22b, 23b) provided with a pressure switchgear (82, 83). The high-stage compression element (21) compresses a refrigerant discharged from the low-stage compression element (22, 23). When the low-stage compression element (22, 23) is paused in response to activation of the pressure switchgear (82, 83), the high-stage compression element (21) operates while the low-stage compression element (22, 23) is kept paused.