Two-Stage Refrigerant Intercooling for Transcritical CO2 Compression
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Solution Overview
Problem
Refrigerant vapor compression systems, particularly those operating in transcritical cycles with carbon dioxide, face challenges in energy efficiency and cooling capacity due to high refrigerant pressures, making it impractical to incorporate intercoolers, especially in transport refrigeration applications where space, weight, and cost are concerns.
Innovation Solution
Incorporating a refrigerant intercooler between the compression stages of a two-stage compression device, with a secondary fluid such as air or water, to enhance energy efficiency and cooling capacity, and optionally including an intercooler bypass circuit to prevent refrigerant condensation under low ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an intercooler is incorporated into the refrigerant circuit between compression stages, then energy efficiency and cooling capacity are improved, but device complexity and weight increase
Solution Approach 1:
The intercooler is combined with the existing condenser assembly, sharing common structural support and airflow paths. The intercooler utilizes the same ambient air flow that passes through the condenser, merging two cooling functions into a integrated thermal management system that reduces overall device complexity while maintaining energy efficiency improvements
Solution Approach 2:
The intercooler is designed to serve multiple functions: it cools the refrigerant between compression stages, utilizes waste heat for potential pre-heating applications, and shares the common airflow system with the condenser. This multi-functionality justifies the added complexity by providing multiple benefits from a single integrated component
2Productivity
If an intercooler is incorporated into the refrigerant circuit, then cooling capacity is improved, but weight and cost increase
Solution Approach 1:
The intercooler is nested within the existing condenser assembly structure, with refrigerant passages integrated into the same heat exchanger core. This nesting approach allows the intercooler to share structural weight with the condenser framework and utilizes existing mounting points and support structures, minimizing additional weight while maximizing cooling capacity improvement
Solution Approach 2:
The intercooler employs thin-walled refrigerant passages and flexible heat exchanger fins that provide high surface area for heat transfer with minimal material weight. The thin-film construction allows efficient thermal coupling between the refrigerant and ambient air while keeping the added weight to a minimum
3Use of energy by moving object
If the system operates in transcritical cycle with carbon dioxide, then energy efficiency is improved, but refrigerant pressure increases making intercooler incorporation impractical
Solution Approach 1:
The compression process is segmented into two stages with the intercooler positioned between them. This segmentation allows the high-pressure transcritical cooling to be achieved in two manageable steps, with the intercooler handling the intermediate pressure stage. The segmentation reduces the peak pressure requirements compared to single-stage compression while maintaining the energy efficiency benefits of transcritical operation
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
Improves energy efficiency and cooling capacity of refrigerant vapor compression systems, especially in transcritical cycles with carbon dioxide, while minimizing weight and cost, and allows for flexible operation across varying ambient conditions.
Implementation Method 1
a refrigerant intercooler disposed intermediate the first compression stage and the second compression stage
Implementation Method 2
with a secondary fluid such as air or water
Data Source
AI summary
A refrigerant vapor compression system includes a compression device having at least a first compression stage and a second compression stage, a refrigerant heat rejection heat exchanger disposed downstream with respect to refrigerant flow of the second compression stage, and a refrigerant intercooler disposed intermediate the first compression stage and the second compression stage. The refrigerant intercooler is disposed downstream of the refrigerant heat rejection heat exchanger with respect to the flow of a secondary fluid. A second refrigerant heat rejection heat exchanger may be disposed downstream with respect to refrigerant flow of the aforesaid refrigerant heat rejection heat exchanger, and a second refrigerant intercooler may be disposed intermediate the first compression stage and the second compression stage and downstream with respect to refrigerant flow of the aforesaid refrigerant intercooler.