Methods and systems for compressor operation
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Solution Overview
Problem
Conventional refrigeration systems face failures and damage during compressor startup, especially at low ambient temperatures, due to refrigerant condensation in the compressor, which can mix with oil and cause lubrication issues and component damage.
Innovation Solution
A refrigeration system and method that involve preheating the compressor components, controlled opening of pressure equalization and liquid valves, and gradual startup at reduced speeds to prevent refrigerant condensation, maintaining oil and compressor temperatures above the saturated discharge temperature of the refrigerant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor is started at low ambient temperatures without preheating, then the startup time is reduced, but refrigerant condensation occurs in the compressor causing component damage and lubrication failure
Solution Approach 1:
The system performs preliminary actions before compressor startup by determining whether preheating is required based on the length of time the compressor has been inactive and the discharge temperature. If the discharge temperature is below a predetermined threshold or the compressor has been inactive for an extended period, the system activates preheating of the compressor discharge line and/or refrigerant before allowing normal startup to proceed, thereby preventing refrigerant condensation and oil dilution.
Solution Approach 2:
The system uses feedback from temperature sensors monitoring the compressor discharge temperature and operational status to dynamically control the startup sequence. The control means continuously monitors the discharge temperature and adjusts the preheating duration and intensity accordingly, creating a closed-loop control system that adapts to actual thermal conditions rather than following a fixed timing sequence.
2Reliability
If the compressor is preheated for extended periods before startup, then refrigerant condensation is prevented, but the startup time and energy consumption increase
Solution Approach 1:
The system dynamically adjusts preheating parameters including duration, temperature threshold, and heating intensity based on real-time measurements of compressor discharge temperature and inactive time. By changing these parameters adaptively rather than using fixed values, the system achieves sufficient preheating to prevent condensation while minimizing unnecessary heating time and energy consumption.
Solution Approach 2:
The system applies partial preheating action only when necessary - determining whether preheating is required based on whether the discharge temperature is below a predetermined threshold or the compressor has been inactive for an extended period. This selective application of preheating avoids unnecessary heating cycles while ensuring adequate preparation when conditions warrant it.
3Use of energy by moving object
If the compressor discharge temperature is low, then energy consumption is reduced, but refrigerant condensation occurs in the oil causing lubrication failure
Solution Approach 1:
The system applies preliminary anti-action by preheating the compressor discharge line and/or refrigerant before startup when the discharge temperature indicates a high risk of condensation. This counteracts the harmful effect of low temperature that would otherwise lead to refrigerant condensation in the oil and subsequent lubrication failure, addressing the problem before the compressor actually starts operating.
Solution Approach 2:
The system performs preliminary heating of the compressor and refrigerant based on the discharge temperature and inactive time assessment, preparing the system in advance to prevent condensation before the compression cycle begins, thereby ensuring reliable lubrication from the moment of startup.
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
Minimizes the risk of refrigerant condensation and subsequent damage by ensuring the compressor components and oil are above the saturated discharge temperature, maintaining optimal lubrication and preventing refrigerant mixing with oil during startup.
Implementation Method 1
the stator windings of a motor associated with the compressor, for example the internal electric alternating current motor (synchronous or asynchronous) of the compressor are electrically connected to an electrical source, e.g. a direct current source, to thereby heat the windings and thus heat the compressor
Implementation Method 2
the pressure equalisation valve is a bypass passage, the passage is opened as the compressor is started to allow pressure balancing between the compressor suction and discharge by bypassing the compressor
Implementation Method 3
the vapour refrigerant from the discharge valve in the compressor being hotter than the actual suction gas refrigerant and when passing through the bypass and the compressor suction, the vapour heats the mechanical parts of the compressor and the oil
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
There is provided a refrigeration system (10) comprising a compressor (12) having a suction (11) and a discharge (13), a heat rejecting heat exchanger. (14), an expansion valve (16), and a heat accepting heat exchanger (18). Preferably the system (10) comprises any one or more of: a pressure equalisation valve (4O3 42) for equalising the pressure differential between the compressor suction (11) and compressor discharge (13); a liquid valve (44), preferably a liquid solenoid valve or an electronic expansion valve, the liquid. valve (44) arranged in a flow line (24) between the heat rejecting heat exchanger (14) and the expansion valve (16); and a check valve (46), preferably a solenoid valve or an electronic expansion valve, arranged in a flow line (22) between the heat rejecting heat exchanger (14) and the compressor (12). The valves (40, 42, 44, 46) are operated in a variety of manners upon compressor shutdown and startup to avoid damage to the components of the compressor (12). Preferably the system further comprises means for heating at least one component of the compressor (12) and preferably also control means for activating the heating means when appropriate, such as when compressor startup is required, and starting the compressor after heating.