Refrigerant vapor compression system
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Solution Overview
Problem
Refrigerant vapor compression systems operating with carbon dioxide as a natural refrigerant face challenges in energy efficiency and cooling capacity, particularly in transcritical pressure regimes, where existing designs do not fully optimize heat exchange and compression stages for improved performance.
Innovation Solution
The system incorporates a series arrangement of compression stages with intercoolers and economizer circuits, including a vapor line in communication with the suction inlet of the second compression stage, and utilizes various heat exchanger configurations such as round tube plat fin and brazed plate heat exchangers, to enhance heat exchange efficiency and energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single-stage compression system is used, then the device complexity is reduced, but the energy efficiency and cooling capacity are insufficient in transcritical pressure regimes
Solution Approach 1:
The compression system is divided into multiple compression stages (first compression stage, second compression stage, and optionally third and fourth stages) with intercooling between stages. This segmentation allows the system to handle transcritical pressure regimes more efficiently by progressively compressing the refrigerant while removing heat at intermediate stages, thereby improving energy efficiency without requiring an overly complex single-stage design.
Solution Approach 2:
Intercooling is applied between compression stages to pre-cool the refrigerant before it enters the next compression stage. This preliminary cooling action reduces the work required in subsequent compression stages, improving overall energy efficiency while maintaining a manageable system complexity through standardized heat exchanger components.
2Productivity
If heat exchange processes are simplified, then the device complexity is reduced, but the cooling capacity and energy efficiency deteriorate
Solution Approach 1:
The heat exchange system is segmented into multiple heat exchangers including condenser, evaporator, intercoolers, and economizers. Each heat exchanger performs a specific thermal function at a different stage of the refrigeration cycle, maximizing cooling capacity through optimized heat transfer at each stage while using modular components that manage overall system complexity.
Solution Approach 2:
The refrigerant circuit is designed to operate in multiple modes (subcritical and transcritical) using the same basic heat exchanger components. The system can switch between operating modes by adjusting valve positions and refrigerant flow paths, providing universal functionality that maintains high cooling capacity across different operating conditions without requiring entirely different heat exchange systems.
3Object-affected harmful factors
If carbon dioxide is used as refrigerant in transcritical regime, then environmental friendliness is improved, but the system requires specialized design for optimal performance
Solution Approach 1:
The system is designed to operate in transcritical pressure regime with carbon dioxide refrigerant, utilizing parameter changes in pressure and temperature to achieve efficient heat transfer. The multiple compression stages with intercooling and the economizer circuit are specifically configured to handle the unique thermodynamic properties of CO2 in transcritical operation, optimizing performance while using standard heat exchanger types that manage design complexity.
Solution Approach 2:
Secondary fluids (such as air or water) are used as intermediaries in the heat exchangers to transfer heat between the CO2 refrigerant and the environment or process streams. This intermediary approach allows the system to leverage the high pressure and temperature characteristics of transcritical CO2 effectively while simplifying the direct interaction with ambient conditions or process fluids.
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 improves energy efficiency and cooling capacity by optimizing heat exchange processes across multiple stages, allowing for better refrigerant management and secondary fluid interaction, thereby enhancing the overall performance of refrigerant vapor compression systems.
Implementation Method 1
A first refrigerant heat rejection heat exchanger is disposed downstream with respect to refrigerant flow of the second compression stage for passing the refrigerant in heat exchange relationship with a flow of a first secondary fluid
Implementation Method 2
passing the refrigerant in heat exchange relationship with a flow of a first secondary fluid
Implementation Method 3
round tube plat fin heat exchanger or a louver fin mini-channel flat tube heat exchanger
Implementation Method 4
A first refrigerant intercooler is disposed intermediate the first compression stage and the second compression stage for passing the refrigerant passing from the first compression stage to the second compression stage in heat exchange relationship with the flow of the first secondary fluid
Implementation Method 5
passing the refrigerant... in heat exchange relationship with the flow of the first secondary fluid
Implementation Method 6
The economizer circuit includes a vapor line in fluid communication with a suction inlet to the second compression stage
Implementation Method 7
a compression device having at least a first compression stage and a second compression stage arranged in series refrigerant flow relationship
Data Source
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AI summary
A refrigerant vapor compression system includes a compression device having at least a first compression stage and a second compression stage arranged in series refrigerant flow relationship. A first refrigerant heat rejection heat exchanger is disposed downstream with respect to refrigerant flow of the second compression stage. A first refrigerant intercooler is disposed intermediate the first compression stage and the second compression stage. The first refrigerant intercooler is disposed downstream of the first refrigerant heat rejection heat exchanger with respect to the flow of the first secondary fluid. An economizer includes a vapor line in fluid communication with a suction inlet to the second compression stage. A second refrigerant heat rejection heat exchanger is disposed intermediate with respect to refrigerant flow of the second compression stage and the first refrigerant heat rejection heat exchanger. A second refrigerant intercooler is disposed intermediate the first compression stage and the second compression.