Two-Stage Refrigerant Expansion Control for Stable COP
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional refrigerating apparatuses using a multistage compression refrigeration cycle with supercritical refrigerants face challenges in maintaining coefficient of performance (COP) stability during load fluctuations, which can lead to increased device load and reliability issues.
Innovation Solution
The apparatus incorporates a two-stage compression system with a heat exchanger and expansion mechanisms, including a heat exchanger switching mechanism and temperature detectors, to manage refrigerant flow and pressure, ensuring efficient heat exchange and moderate superheat, thereby improving COP and maintaining device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the load of the refrigerating apparatus is increased to improve coefficient of performance, then energy efficiency improves, but device reliability deteriorates due to increased load on components
Solution Approach 1:
The compression process is divided into two stages with separate compression elements operating at different pressure levels. The first compression element compresses refrigerant to intermediate pressure, while the second compression element further compresses it to high pressure. This segmentation allows each compression element to operate within optimal load ranges, improving overall efficiency while preventing any single component from bearing excessive load that would compromise reliability.
Solution Approach 2:
The system utilizes parameter changes by operating the refrigerant through different thermodynamic states including supercritical conditions. By controlling the refrigerant to reach and maintain supercritical state in the heat exchanger, the system achieves improved heat transfer coefficients and energy efficiency while the expansion mechanism controls pressure parameters to keep device loads within safe operating limits.
2Use of energy by moving object
If a two-stage compression system is implemented to improve COP, then energy efficiency improves, but device complexity increases
Solution Approach 1:
The first and second compression elements are integrated into a single compression mechanism that shares common structural components, drive systems, and control mechanisms. This merging approach allows the two-stage compression system to achieve improved energy efficiency while minimizing the increase in device complexity through shared infrastructure rather than completely separate systems.
Solution Approach 2:
The heat exchanger is designed to serve multiple functions: it acts as a condenser for high-pressure refrigerant, provides subcooling, and enables heat exchange between refrigerant streams. This multi-functionality reduces the need for separate dedicated components for each function, thereby improving COP while limiting the growth of device complexity.
3Reliability
If the refrigerant temperature is increased to prevent liquid compression, then device reliability improves, but energy efficiency deteriorates
Solution Approach 1:
The system performs preliminary subcooling of the refrigerant in the heat exchanger before it reaches the expansion mechanism. By pre-cooling the refrigerant to a temperature well below its saturation point at the given pressure, the system ensures that the refrigerant remains in liquid form through the expansion process and into the evaporator, preventing liquid compression in the compressor while maintaining efficient heat transfer that preserves energy efficiency.
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 configuration enhances the coefficient of performance, prevents liquid compression, and maintains high discharge temperatures, ensuring reliable operation and efficient heat management even under fluctuating loads.
Implementation Method 1
The first heat exchanger causes heat exchange to be performed between the refrigerant flowing through the first refrigerant pipe and the refrigerant flowing through the second refrigerant pipe
Implementation Method 2
The expansion mechanism reduces the pressure of the refrigerant
Implementation Method 3
The evaporator is connected to the expansion mechanism and causes the refrigerant to evaporate
Implementation Method 4
The two-stage compression element has a first compression element that sucks in, compresses, and discharges the refrigerant and a second compression element that sucks in, further compresses, and discharges the refrigerant
Data Source
AI summary
A refrigerating apparatus, where refrigerant reaches a supercritical state in at least part of a refrigeration cycle, includes at least one expansion mechanism, an evaporator connected to the expansion mechanism, first and second sequential compression elements, a radiator connected to the discharge side of the second compression element, a first refrigerant pipe interconnecting the radiator and the expansion mechanism, a heat exchanger arranged to cause heat exchange between the first refrigerant pipe and another refrigerant pipe. Preferably, a heat exchanger switching mechanism is switchable so that refrigerant flows in the first refrigerant pipe through the first heat exchanger or in a heat exchange bypass pipe connected to the first refrigerant pipe. Alternatively, a heat exchanger switching mechanism increases refrigerant flowing through a second expansion mechanism when an air temperature at the evaporator and/or a compressed refrigerant temperature detected is higher and/or lower than predetermined values.