Multi-Stage Refrigeration Pressure Control for Intermediate Precooling
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Solution Overview
Problem
Multi-stage refrigeration systems face inefficiencies due to the dependence of auxiliary refrigerant streams on the performance of intermediate heat exchangers, particularly in regulating the auxiliary expansion value to effectively precool the main stream.
Innovation Solution
A refrigeration cycle with a compression element, radiator, auxiliary expansion means, intermediate heat exchanger, main expansion means, and evaporator, where the refrigerant is branched into two streams for heat exchange, with the pressure in the intermediate pressure part of the compression element controlled using expressions like Pint,opt=Kint,opt*(Psuc*Pdis)^0.5 to optimize intermediate pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the auxiliary expansion value is not properly regulated, then the intermediate heat exchanger cannot effectively precool the main stream, but increasing control complexity may be required to optimize the auxiliary expansion value
Solution Approach 1:
The patent implements feedback control by using the measured intermediate pressure from the intermediate pressure part of the compression element to dynamically adjust the auxiliary expansion valve opening. The control unit continuously monitors the intermediate pressure and modifies the auxiliary expansion value accordingly, creating a closed-loop control system that optimizes precooling effectiveness without requiring overly complex control architecture.
Solution Approach 2:
The system achieves self-regulation where the auxiliary expansion valve automatically adjusts based on the intermediate pressure conditions. The control methodology enables the system to self-optimize the auxiliary refrigerant stream flow rate according to actual operating conditions, eliminating the need for external manual intervention or complex external control systems.
2Power
If the intermediate pressure is not optimized, then the compressor works harder due to lower suction side pressure, but implementing pressure control requires sophisticated control algorithms
Solution Approach 1:
The control unit uses feedback from the intermediate pressure sensor to dynamically adjust the auxiliary expansion valve, maintaining optimal intermediate pressure that minimizes compressor power consumption. This feedback mechanism allows the system to adapt to varying operating conditions while using a relatively simple control algorithm based on the geometric mean relationship.
Solution Approach 2:
The patent applies parameter changes by utilizing the geometric mean relationship between suction pressure, discharge pressure, and intermediate pressure. The control algorithm adjusts the auxiliary expansion parameter based on the formula Pint,opt = Kint,opt × (Psuc × Pdis)^0.5, where the intermediate pressure parameter is optimized as a function of suction and discharge pressures, simplifying the control requirement.
3Adaptability or versatility
If a fixed auxiliary expansion value is used, then the system is simple to operate, but it cannot adapt to varying operating conditions to maintain optimal efficiency
Solution Approach 1:
The patent transforms the static auxiliary expansion valve into a dynamic control element that automatically adjusts its opening based on real-time intermediate pressure measurements. This dynamic adjustment enables the system to adapt to varying operating conditions such as changes in ambient temperature, refrigerant charge, or load conditions, while the control unit handles the complexity, maintaining ease of operation for the user.
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 control methodology enhances the efficiency of the refrigeration cycle by optimizing intermediate pressure, leading to improved performance and coefficient of performance (COP) across various operating conditions.
Implementation Method 1
Heat exchange is performed between the two refrigerant stream within said intermediate heat exchanger
Implementation Method 2
The effectiveness of the auxiliary stream in precooling the main stream depends on the performance of the intermediate heat exchanger... what is needed is a control methodology to regulate the auxiliary expansion value that controls the flow rate intermediate heat exchanger
Implementation Method 3
the refrigerant flowing out of said evaporator is sucked by low pressure part of said compression element, and the refrigerant flowing out of said intermediate heat exchanger is sucked by intermediate pressure part of said compression element
Data Source
AI summary
A multi-stage refrigeration system is provided. The refrigeration system includes a first compression element which produces a first compressed refrigerant stream. A mixer combines the first compressed refrigerant stream with an auxiliary refrigerant stream. A second compression element is coupled to the mixer and produces a second compressed refrigerant stream. A first heat exchanger receives the second compressed refrigerant stream and generates a cooled stream. A stream splitter receives the cooled stream and provides first and second output streams. A first expansion valve receives the first output stream and controls the flow of the first output stream and a second expansion valve receives the second output stream and controls the flow of the second output stream. A second heat exchanger generates the auxiliary refrigerant stream provided to the mixer. An evaporator is coupled to the first expansion valve and the first compression element to evaporate the first output stream and provide an evaporated stream to the first compression element.