Transcritical CO2 Compression Staging for Capacity Boost
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Solution Overview
Problem
Refrigerant vapor compression systems operating in transcritical cycles, particularly in transport refrigeration, face challenges in maintaining refrigeration capacity equivalent to subcritical cycles, especially under high-capacity operations, and struggle with energy efficiency across varying load conditions.
Innovation Solution
A refrigerant vapor compression system with a multi-stage compression device and an economizer circuit, allowing for selective operation of compression stages in series or parallel flow relationships, and utilizing flow control devices to manage refrigerant flow through various heat exchangers, enabling operation in economized, non-economized, and capacity-boosted modes to optimize cooling capacity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a refrigerant vapor compression system operates in transcritical cycle with carbon dioxide, then environmental capability is improved, but refrigeration capacity under high-demand conditions deteriorates compared to subcritical systems
Solution Approach 1:
The system dynamically switches between series and parallel compression stage configurations based on operating conditions. The compression stages can be selectively connected in series for normal operation or in parallel for capacity-boosted operation, allowing the system to adapt its refrigeration capacity to match demand while maintaining transcritical carbon dioxide operation for environmental benefits
Solution Approach 2:
The system changes operational parameters by altering the flow relationship between compression stages. Flow control devices adjust refrigerant flow distribution to switch between series and parallel configurations, thereby changing the effective compression capacity and ratio to match varying load conditions while maintaining transcritical operation
2Loss of energy
If compression stages operate in series configuration, then energy efficiency is improved, but refrigeration capacity under high-demand conditions deteriorates
Solution Approach 1:
The system provides dynamic configuration switching between series and parallel compression stage arrangements. During normal operation, stages operate in series for energy efficiency. During high-demand periods, the system switches to parallel configuration to boost refrigeration capacity, and during pull-down operations, it can operate in capacity-boosted mode with both stages compressing simultaneously
3Productivity
If compression stages operate in parallel configuration, then refrigeration capacity is boosted, but energy efficiency deteriorates
Solution Approach 1:
The system dynamically selects parallel configuration only when high refrigeration capacity is required. Flow control devices enable switching between series and parallel modes based on real-time operating conditions, ensuring parallel operation is used strategically during capacity-boosted需求的 periods rather than continuously, thereby minimizing energy waste
Solution Approach 2:
The system changes operational parameters by adjusting the flow relationship between compression stages. During pull-down operations or high-demand periods, the system switches to parallel configuration with adjusted refrigerant flow distribution to maximize capacity. During normal steady-state operation, it returns to series configuration for 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
The system achieves refrigeration capacity comparable to subcritical systems, enhances cooling performance during high-demand periods, and reduces energy consumption by adjusting compression stage configurations, resulting in improved efficiency and potential displacement volume reduction of up to 25-30%, leading to overall system efficiency gains of 5-10%.
Implementation Method 1
a compression device having a first compression stage and a second compression stage
Implementation Method 2
a first refrigerant heat rejection heat exchanger and a second refrigerant heat rejection heat exchanger
Implementation Method 3
a refrigerant heat absorption heat exchanger
Implementation Method 4
a primary expansion device operatively associated with the evaporator
Implementation Method 5
a refrigerant heat absorption heat exchanger, hereinafter referred to as an evaporator
Data Source
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AI summary
A refrigerant vapor compression system and method of operation are disclosed wherein the first (30a) and second (30b) compression stages of a two stage compression device are selectively configurable in a first arrangement and a second arrangement. In the first arrangement, the first and second compression stages operate in a series refrigerant flow relationship. In the second arrangement, the first and second compression stages (30a), (30b) operate in a parallel refrigerant flow relationship.