Multi-Evaporator Refrigeration Circuit With Liquid Separator Overfeed
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Solution Overview
Problem
Commercial refrigeration plants with multiple evaporation levels face inefficiencies due to superheating, which reduces heat exchange efficiency and complicates system design, leading to higher costs and complexity, while existing solutions like flooded evaporator systems are costly and complex, and trans-critical booster plants require complex components and high installation constraints.
Innovation Solution
A refrigeration plant with multiple evaporation levels that employs the technique of overfeeding evaporators to improve heat exchange efficiency without negative effects on compressors, using a liquid separator to collect and redistribute liquid refrigerant, eliminating the need for recirculation devices like pumps and ejectors, and simplifying the system design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superheating is maintained at evaporator outlet to prevent liquid return to compressors, then compressor reliability is improved, but heat exchange efficiency deteriorates
Solution Approach 1:
The system segments the refrigeration circuit into multiple independent low-pressure branches (LP1, LP2, LP3) operating at different evaporation levels, each with its own evaporator and compressor group. This allows independent optimization of each branch, enabling some branches to operate in overfeeding mode for efficiency while others maintain superheating for reliability.
Solution Approach 2:
The invention changes the operating parameters by allowing evaporators to operate in overfeeding conditions (without superheating) when thermal load justifies it, and by dynamically adjusting the degree of superheating based on instantaneous thermal load. This parameter flexibility resolves the contradiction between efficiency and reliability.
2Loss of energy
If flooded evaporator systems are used to eliminate superheating and improve heat exchange efficiency, then energy efficiency is improved, but system complexity and cost increase
Solution Approach 1:
Instead of implementing a complete flooded evaporator system throughout, the invention applies overfeeding operation partially to specific evaporators in specific low-pressure branches when thermal load conditions justify it. This partial application achieves efficiency improvements without the full complexity of flooded systems.
Solution Approach 2:
The system dynamically adjusts the degree of superheating and overfeeding operation based on instantaneous thermal load conditions. This dynamic control allows the system to optimize efficiency when possible while maintaining simplicity and reliability when needed, avoiding the fixed complexity of flooded evaporator designs.
3Quantity of substance
If trans-critical booster plants with liquid ejectors are used to manage liquid refrigerant, then liquid removal is improved, but device complexity and installation constraints increase
Solution Approach 1:
The invention extracts and removes liquid refrigerant at the evaporator outlet using a liquid separator before the refrigerant enters the compressor. This simple extraction approach eliminates the need for complex trans-critical components like liquid ejectors while effectively managing liquid refrigerant quantity.
Solution Approach 2:
The liquid separator acts as an intermediary device between the evaporator and compressor, removing liquid refrigerant and preventing it from reaching the compressor. This simple intermediary component replaces complex trans-critical liquid management systems.
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 enhances heat exchange efficiency, reduces energy consumption, increases evaporator temperature, decreases compressor discharge temperatures, and improves system reliability by preventing liquid return to compressors, all while maintaining simplicity and cost-effectiveness comparable to conventional plants.
Implementation Method 1
a liquid separator (20') that is fluidically connected: to the evaporator outlet (12') of said first low-pressure branch (LP1) to collect the liquid exiting the evaporator (12')
Implementation Method 2
at least one evaporator (12'), (12''), (12''') made to operate in overfeeding conditions
Implementation Method 3
a compressor group (13'), (13''), (13''') for each low-pressure branch
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a refrigeration plant with multiple evaporation levels, operating according to a vapour compression cycle and comprising a circuit 2 having a high-pressure branch HP, wherein is arranged at least one heat exchanger 10, and two or more low-pressure branches LP1,LP2,LP3, each of which operates at a different evaporation level to serve users having different refrigeration requirements. In each of the low-pressure branches the plant comprises an expansion device 11',11",11"', at least one evaporator 12',12",12"' and a compressor group 13',13",13"'. Said at least one evaporator of each low-pressure branch LP1, LP2, LP3 is connected directly to said high-pressure branch HP. At least a first low-pressure branch LP1 comprises a liquid separator 20' that is fluidically connected: - to the evaporator outlet 12' to collect the liquid exiting the evaporator itself in the case in which the latter is operating in overfeeding conditions; and - to the intake of the compressor group 13'. Such liquid separator 20' is fluidically connected to a second low-pressure branch LP2 upstream of the expansion device 11" of such second low-pressure branch through a first connection duct 21'. The circuit comprises controllable first valve means 22", 23'.