Compression cooling system and method for regulating a compression cooling system
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Solution Overview
Problem
Compression refrigeration systems face the risk of the compressor oil reservoir running dry due to imbalances between oil throw and return rates, particularly at low load ranges or high overheating conditions, leading to potential damage from insufficient oil return.
Innovation Solution
A method and system for controlling the compression refrigeration system that detects overheating and regulates the throttle element to ensure safe operation by determining oil throw and return rates based on compressor speed, pressure, and process variables, and performs an oil return sequence when the oil level becomes critical.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor operates at low load ranges or high overheating conditions, then the refrigeration effect is maintained, but the oil return rate decreases and the oil reservoir may run dry
Solution Approach 1:
The control unit continuously monitors the oil level in the compressor and dynamically adjusts the expansion valve opening degree based on feedback signals. When the oil level drops below a threshold, the control unit increases the expansion valve opening to enhance oil return, creating a closed-loop control system that maintains reliable oil levels during low load or high overheating conditions
Solution Approach 2:
The expansion valve opening degree is made dynamically adjustable rather than fixed. The control unit varies the opening degree in real-time based on operating conditions (load range, overheating degree, oil level), allowing the system to optimize both refrigeration effect and oil return rate under different operational scenarios
2Reliability
If the expansion valve opening is increased to improve oil return, then the oil level is maintained, but the refrigeration efficiency decreases
Solution Approach 1:
The expansion valve opening degree is dynamically adjusted based on real-time operating conditions. The control unit increases the opening only when and to the extent necessary for oil return, rather than maintaining a constantly large opening, thus minimizing the impact on refrigeration efficiency while ensuring adequate oil supply
Solution Approach 2:
The system changes the opening degree parameter of the expansion valve in response to varying operating conditions. By adjusting this parameter dynamically rather than keeping it fixed, the system can optimize the balance between oil return and refrigeration efficiency for each specific operating scenario
3Productivity
If the compressor speed is increased to improve refrigeration capacity, then the cooling effect is enhanced, but the oil throw rate increases and oil return becomes insufficient
Solution Approach 1:
The control unit monitors compressor speed, refrigeration load, and oil level simultaneously. When high compressor speed causes insufficient oil return, the feedback mechanism triggers an increase in expansion valve opening to compensate, allowing the system to maintain high refrigeration capacity while ensuring adequate oil supply through dynamic adjustment
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 effectively prevents the compressor oil reservoir from running dry by ensuring adequate oil return, even in critical operating conditions, thereby maintaining system safety and performance.
Implementation Method 1
The refrigerant, now at low pressure, evaporates in the evaporator, absorbing heat from the surrounding environment
Implementation Method 2
The refrigerant is forced through the condenser, where it releases heat to a heating medium in a heat sink system
Implementation Method 3
Internal heat is transferred in an optional internal heat exchanger, for example in the form of a recuperator, between the refrigerant flowing under high pressure from the condenser to the expansion valve and the refrigerant flowing under low pressure from the evaporator to the compressor
Data Source
AI summary
The present invention relates to a method for controlling a compression refrigeration system (200) and an associated compression refrigeration system (200). The method comprises the following steps: determining an oil discharge rate of the compressor (210) into the refrigeration circuit as a function of at least one speed of the compressor (210); determining an oil return rate from the refrigeration circuit as a function of at least one process variable of the refrigeration circuit, wherein the process variables are selected from the list containing: low pressure (LP), high pressure (HP), speed of the compressor (210), superheat of the refrigerant; evaluating an oil level from the oil discharge rate, oil return rate, and operating mode of the compression refrigeration system (200); and performing an oil return sequence in the case where the evaluated oil level is in a range critical for the operation of the compressor.