Subcooling Circuit Control for Refrigeration Energy Efficiency
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Solution Overview
Problem
Refrigeration circuits require significant energy due to a high gas phase fraction in the refrigerant, which reduces their efficiency, and existing subcooling systems increase power consumption, counteracting efficiency gains.
Innovation Solution
A cooling system with a refrigeration circuit and a subcooling circuit, where the operation of compressors and subcooler compressors are controlled to maintain specific temperature ranges in heat exchangers, optimizing heat transfer and energy efficiency by adjusting the temperature of the refrigerant and heat transfer fluid based on load and ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a subcooling circuit is added to increase refrigeration efficiency, then the cooling capacity is improved, but the power consumption increases
Solution Approach 1:
The patent applies dynamic control by adjusting the operating parameters of compressors and expansion devices based on real-time system conditions. The control unit dynamically adjusts the degree of subcooling and flash gas bypass to optimize the balance between cooling capacity and power consumption, preventing the system from operating at fixed inefficient points.
Solution Approach 2:
The system changes operational parameters including refrigerant flow rates, compression ratios, and expansion device openings to optimize performance. By varying these parameters in response to load conditions and ambient temperature, the system achieves efficient operation across different operating conditions without excessive power consumption.
2Loss of energy
If the gas phase fraction in refrigerant is reduced to improve efficiency, then the refrigeration efficiency increases, but the system complexity increases
Solution Approach 1:
The patent segments the refrigeration system into distinct functional zones: a subcooling circuit with dedicated heat exchangers and expansion devices, and a flash gas bypass system with separate control. This segmentation allows independent optimization of each subsystem to manage refrigerant phases effectively without requiring complete system redesign.
Solution Approach 2:
The patent introduces intermediate components such as economizer heat exchangers and flash gas heat exchangers that act as mediators between the high-pressure and low-pressure sides of the system. These intermediaries enable controlled heat transfer and phase adjustment, reducing gas phase fraction in the evaporator while maintaining system stability.
3Productivity
If compressors are operated at higher capacity to meet cooling demand, then the cooling capacity is sufficient, but the energy consumption increases
Solution Approach 1:
The patent applies partial action by using multiple compressors operating at partial loads rather than a single compressor at full load. The system can operate one or two compressors depending on demand, and the subcooling circuit provides additional cooling capacity when needed, avoiding the inefficiency of operating a single compressor at excessive capacity.
Solution Approach 2:
The control unit implements feedback control by continuously monitoring system parameters such as suction pressure, discharge pressure, and temperature differentials. Based on this feedback, the control unit adjusts compressor operation and expansion device openings to maintain optimal efficiency while meeting cooling demand, preventing energy waste from over-compression.
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 significantly improves the overall energy efficiency of the cooling system, reducing power consumption and maintaining optimal cooling capacity, allowing for efficient operation comparable to CO2-based systems without losing efficiency.
Implementation Method 1
an economizer heat exchanger (6), a high pressure expansion device (8)... The economizer heat exchanger (6) is coupled to a fluid cycle (9) further comprising a subcooler heat exchanger (7)...
Implementation Method 2
a subcooler heat exchanger (7)... configured for circulating a heat transfer fluid, especially water, within the fluid cycle (9)
Implementation Method 3
an high pressure expansion device (8)... a two-stage expansion by successive expansions by means of the high pressure expansion device (8) and the medium pressure expansion device (10)
Implementation Method 4
a medium pressure expansion device (10)... configured for expanding the subcooler refrigerant delivered from the subcooler condensers (24, 26)
Implementation Method 5
an evaporator (11)... During evaporation in the evaporator (11) the refrigerant absorbs heat thereby cooling the evaporator's (11) environment
Implementation Method 6
a set of compressors (2a, 2b, 2c, 2d) connected in parallel to each other... a one-stage compression by means of the compressors (2a, 2b, 2c, 2d)
Data Source
Figure 1
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AI summary
A cooling system comprises a refrigeration circuit (1) circulating a refrigerant and comprising in the flow direction of the refrigerant at least one compressor (2a, 2b, 2c, 2d); at least one condenser (4); at least one expansion device (8, 10); and at least one evaporator (11) for providing a cooling capacity. The cooling system further comprises a subcooling circuit (20) for subcooling the refrigerant circulating in the refrigeration circuit (1), the subcooling circuit (20) being configured to circulate a subcooling refrigerant and comprising at least one subcooler compressor (22, 23); at least one heat exchange means (6, 7) being arranged downstream of the at least one condenser (4) and being configured for heat exchange between the refrigeration circuit (1) and the subcooling circuit (20), the at least one heat exchange means (6, 7) comprising at least one temperature sensor; and a control unit (15) which is configured for controlling at least one compressor (2a, 2b, 2c, 2d) of the refrigeration circuit (1) and at least one subcooler compressor (22, 23) of the subcooling circuit (20) such that the cooling capacity to be provided by the at least one evaporator (11) is met and such that the temperature at the at least one heat exchange means (6, 7) measured by at least one temperature sensor is in a predetermined range.