Cooling system with flexible evaporating temperature
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Solution Overview
Problem
Carbon dioxide refrigerant-based cooling systems operate inefficiently in high ambient temperatures due to difficulties in regulating pressure and removing heat, leading to reduced efficiency compared to systems using other refrigerants.
Innovation Solution
The cooling system implements processes such as flooding low side heat exchangers, directing vapor refrigerant to a flash tank instead of a compressor, and transferring heat from compressor suction to high side heat exchanger discharge to enhance efficiency in high ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If carbon dioxide refrigerant is used in cooling systems, then environmental friendliness is improved, but system efficiency deteriorates in high ambient temperatures
Solution Approach 1:
The system is divided into multiple low side heat exchangers (first and second low side heat exchangers) with separate separators, allowing independent control and optimization of refrigerant flow paths. This segmentation enables the system to handle carbon dioxide's temperature-pressure characteristics more effectively in high ambient conditions.
Solution Approach 2:
An accumulator is introduced as an intermediary component between the separators and the compressor. The accumulator receives liquid portions from both separators and provides a controlled interface to the compressor, helping to manage pressure fluctuations and improve system stability when using carbon dioxide refrigerant in high temperature environments.
2Object-affected harmful factors
If carbon dioxide refrigerant is used, then environmental benefits are achieved, but pressure regulation difficulty increases in high ambient heat
Solution Approach 1:
The system employs dynamic pressure management through the accumulator and multiple expansion valves that can adjust refrigerant flow based on real-time operating conditions. The accumulator's liquid portion separation and controlled discharge to the compressor enable adaptive pressure regulation, making the system more responsive to high ambient temperature variations.
Solution Approach 2:
The system changes the physical parameters of the refrigerant by separating it into liquid and vapor portions in the accumulator. By controlling the phase state and pressure of the refrigerant entering the compressor through the accumulator, the system optimizes pressure regulation and improves ease of operation with carbon dioxide in high temperature conditions.
3Object-affected harmful factors
If carbon dioxide refrigerant is used, then environmental friendliness is improved, but heat removal difficulty increases in high ambient heat
Solution Approach 1:
The cooling system is segmented into multiple independent low side heat exchangers, each with its own separator. This allows the system to optimize heat removal from different zones independently, improving overall heat transfer efficiency when using carbon dioxide refrigerant in high ambient temperatures.
Solution Approach 2:
The accumulator performs preliminary action by separating the refrigerant into liquid and vapor portions before it enters the compressor. This pre-separation optimizes the refrigerant state for subsequent compression and heat exchange processes, enhancing heat removal efficiency in high temperature operating conditions.
4Power
If vapor refrigerant is directed to the compressor, then compression function is maintained, but system efficiency decreases in high ambient temperatures
Solution Approach 1:
The accumulator serves as an intermediary between the heat exchangers and the compressor, receiving mixed refrigerant and separating it into liquid and vapor portions. Only the optimized vapor portion is then supplied to the compressor, improving compression efficiency and overall system productivity while maintaining the necessary compression function.
Solution Approach 2:
The system changes the parameters of the refrigerant by controlling its phase composition before it reaches the compressor. By adjusting the proportion of liquid and vapor portions in the accumulator and controlling the evaporating temperature, the system optimizes the refrigerant state for compression, thereby improving system efficiency in high ambient temperatures.
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
These processes improve the efficiency of carbon dioxide refrigerant-based cooling systems by achieving efficiency gains of up to 37% during high ambient temperatures, specifically through flooding low side heat exchangers, directing vapor to an ejector, and subcooling refrigerant entering the compressor.
Implementation Method 1
The high side heat exchanger removes heat from a refrigerant
Implementation Method 2
The first low side heat exchanger uses refrigerant from the flash tank to cool a first space
Implementation Method 3
The second low side heat exchanger uses refrigerant from the flash tank to cool a second space
Implementation Method 4
The accumulator separates refrigerant within the accumulator into a third liquid portion and a third vapor portion
Implementation Method 5
The compressor compresses the third vapor portion from the accumulator
Implementation Method 6
The first ejector receives refrigerant from the high side heat exchanger and directs refrigerant from the high side heat exchanger to the flash tank
Data Source
AI summary
A cooling system implements various processes to improve efficiency in high ambient temperatures. First, the system can flood one or more low side heat exchangers in the system. Second, the system can direct a portion of vapor refrigerant from a low side heat exchanger to a flash tank rather than to a compressor. Third, the system can transfer heat from refrigerant at a compressor suction to refrigerant at the discharge of a high side heat exchanger.