Systems and methods for multi-stage refrigeration
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Solution Overview
Problem
Existing multi-stage refrigeration systems, particularly cascade refrigeration cycles, are less energy efficient due to reliance on mechanical equipment and hydraulic expanders, which add complexity and capital cost, and do not effectively utilize staged flashes to recover energy.
Innovation Solution
The integration of one or more liquid motive eductors in combination with a pump into multi-stage refrigeration systems to raise lower stage vapor pressure, lower feed gas pressure, and enhance energy efficiency by optimizing energy recovery through staged flashes in both mixed refrigerant and cascade cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical equipment and hydraulic expanders are used in cascade refrigeration cycles, then the system can achieve multi-stage refrigeration, but the device complexity and capital cost increase
Solution Approach 1:
The patent extracts and eliminates the complex mechanical expanders and hydraulic equipment from the cascade refrigeration system. Instead, it uses a single compressor with intercooling stages and flash drums to achieve multi-stage refrigeration, thereby removing the problematic mechanical components while preserving the functional capability.
Solution Approach 2:
The patent introduces flash drums as intermediary devices between compression stages. These flash drums serve as mediators that enable pressure reduction and partial vaporization without requiring complex mechanical expanders, thus simplifying the overall system architecture while maintaining multi-stage refrigeration functionality.
2Ease of operation
If mechanical expanders are used for pressure reduction in cascade refrigeration, then the refrigeration stages can be achieved, but the energy efficiency decreases
Solution Approach 1:
The system uses self-service pressure reduction through flash drums where the refrigerant automatically expands from high to low pressure through a valve, utilizing the inherent pressure differential without requiring external mechanical work. This eliminates the need for energy-consuming mechanical expanders while achieving the necessary pressure reduction for cascade refrigeration stages.
3Ease of operation
If conventional cascade refrigeration cycle is used, then the system is easy to operate with single refrigerant, but the energy recovery through staged flashes is not effective
Solution Approach 1:
The patent implements preliminary cooling of the compressor discharge gas in the intercooler before it enters the second compression stage. This preliminary action recovers energy from the hot discharge gas to pre-cool the incoming refrigerant, reducing the compression work required in subsequent stages and improving overall energy efficiency while maintaining the simple single-refrigerant cascade architecture.
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 significantly reduces power consumption, as demonstrated by simulations showing power savings of up to 2% when a pump is used to raise the saturated liquid pressure, improving the overall energy efficiency of the refrigeration process.
Implementation Method 1
A liquid stream or a supercritical fluid stream from a source is supplied to an eductor. A vapor stream enters the eductor at a lower pressure than a pressure at the source of the liquid stream or the supercritical fluid stream to achieve partial liquefaction and produce a two-phase fluid stream.
Implementation Method 2
The two-phase fluid stream from the eductor enters a flashdrum where it is flashed to produce a liquid stream and a vapor stream at a higher pressure than a pressure of the vapor stream entering the eductor.
Data Source
AI summary
Systems and methods for multi-stage refrigeration in mixed refrigerant and cascade refrigeration cycles using one or more liquid motive eductors in combination with a pump.