Condenser Relative Subcooling Control for Stable Refrigerant Pressure
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Solution Overview
Problem
Refrigerant systems face inefficiencies due to unstable subcooling control, leading to either gaseous refrigerant exit from the condenser or unnecessarily high pressure, resulting in energetically inefficient operation.
Innovation Solution
A method for controlling the heat-rejection heat exchanging side of a refrigerant circuit involves calculating a relative subcooling value using refrigerant condensation and outlet temperatures, and secondary medium inlet temperatures, with a compensation value to adjust for high-pressure conditions, allowing for precise control of refrigerant condensation temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the reference subcooling value is set too low to prevent gaseous refrigerant exit, then refrigerant stability is improved, but condenser control stability deteriorates and energy efficiency decreases
Solution Approach 1:
The patent changes the parameter being controlled from absolute subcooling value to relative subcooling value (ratio of actual subcooling to maximum potential subcooling). This parameter transformation allows the system to maintain refrigerant stability while avoiding the instability caused by excessive subcooling, as the relative value inherently scales with operating conditions
Solution Approach 2:
The patent implements dynamic adaptation of the reference subcooling value based on current operating conditions (ambient temperature, heat exchanger type, refrigerant flow rate). Instead of using a fixed reference value, the system continuously adjusts the reference relative subcooling value to match varying conditions, preventing both gaseous exit and excessive pressure
2Reliability
If the reference subcooling value is set too high to ensure complete condensation, then refrigerant condensation is improved, but refrigerant pressure becomes excessively high and energy efficiency decreases
Solution Approach 1:
The patent transforms the control parameter from absolute subcooling to relative subcooling (actual subcooling divided by maximum potential subcooling). This ratio-based parameter naturally adapts to different operating conditions and heat exchanger sizes, ensuring complete condensation without requiring excessively high fixed subcooling values that would cause high pressure
Solution Approach 2:
The system dynamically adjusts the reference relative subcooling value based on ambient temperature, refrigerant flow rate, and heat exchanger characteristics. This dynamic adjustment ensures sufficient condensation at all operating conditions while avoiding the high pressure problems associated with fixed high subcooling settings
3Device complexity
If manual reference subcooling value setting is used to simplify control, then control complexity is reduced, but adaptability to different operating conditions and heat exchanger constructions deteriorates
Solution Approach 1:
The patent introduces relative subcooling value calculation that automatically adapts to different heat exchanger constructions and operating conditions. By using the ratio of actual to maximum potential subcooling, the system achieves universal applicability across different heat exchanger types and sizes without requiring complex individual calibration for each configuration
Solution Approach 2:
The system implements dynamic calculation of the reference relative subcooling value based on real-time operating parameters (ambient temperature, refrigerant flow rate, heat exchanger surface area). This dynamic approach provides automatic adaptation to varying conditions while maintaining relatively simple control logic through a unified calculation framework
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 method achieves stable and efficient refrigerant subcooling and pressure control, optimizing energy use and preventing gaseous refrigerant exit or excessive pressure, ensuring maximum energetic efficiency across varying conditions.
Implementation Method 1
a refrigerant is cooled against a secondary medium
Implementation Method 2
refrigerant condensation temperature
Implementation Method 3
subcooling of the refrigerant is then controlled... cooling the refrigerant below its condensation temperature
Data Source
Figure 1~2
Figure 3
AI summary
A method of controlling a heat-rejection heat exchanging side of a refrigerant circuit comprises the steps of providing a heat-rejection heat exchanging side comprising at least one heat-rejection heat exchanger (4), wherein a refrigerant is cooled against a secondary medium; obtaining a refrigerant condensation temperature (Tc) in the heat-rejection heat exchanging side; obtaining a refrigerant outlet temperature (Tro); obtaining a secondary medium inlet temperature (Tsmi); calculating a relative subcooling value by relating the refrigerant condensation temperature (Tc), the refrigerant outlet temperature (Tro), and the secondary medium inlet temperature (Tsmi); and controlling the relative subcooling value with regard to a reference relative subcooling value.