Modified two-phase refrigeration cycle
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Solution Overview
Problem
Conventional refrigeration cycles experience inefficiencies due to irreversibilities introduced by expansion valves, leading to reduced cooling capacity and increased compressor work, as they fail to capture energy during the expansion process.
Innovation Solution
A modified two-phase refrigeration cycle utilizing a two-phase expander to expand high-pressure saturated or supercooled liquids into a two-phase fluid at constant or near-constant entropy, reducing irreversibilities and capturing energy, and a two-phase compressor to optimize for varying loads and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If an expansion valve is used to reduce pressure of the working fluid, then the pressure reduction function is achieved, but entropy increases and cooling capacity is reduced
Solution Approach 1:
The patent replaces the conventional expansion valve (mechanical throttling device) with a two-phase expander that functions as both a pressure reduction device and an energy recovery device. The expander uses the pressure differential to drive a rotor that generates electricity, substituting the passive throttling mechanism with an active energy-converting mechanism.
Solution Approach 2:
The patent converts the previously harmful effect of pressure differential (which caused entropy increase and energy loss in expansion valves) into a beneficial resource by using it to drive the expander rotor. The pressure drop that formerly represented energy loss now drives the expansion process while generating electrical energy, turning the 'harmful' pressure differential into a useful power source.
2Loss of energy
If a turbine is used to extract energy and decrease pressure of the working fluid, then energy extraction is achieved, but turbines are not suited to handle two-phase fluids
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the expander: the expansion chambers handle two-phase fluid expansion while the rotor and stator components are designed for energy extraction. The system maintains different conditions in different locations - two-phase expansion in chambers, single-phase or controlled two-phase flow in the rotor path - allowing each component to operate in its optimal regime.
Solution Approach 2:
The patent changes the operating parameters of the expander to accommodate two-phase fluids, specifically designing the expansion ratio, rotor speed, and chamber geometry to handle the unique properties of two-phase flow. The system operates at parameters that allow efficient energy extraction while managing the complexities of two-phase fluid dynamics, including variable density and compressibility.
3Device complexity
If conventional refrigeration cycle is used, then the system structure is simple, but irreversibilities reduce cooling capacity and increase compressor work
Solution Approach 1:
The two-phase expander serves multiple functions simultaneously: it acts as a pressure reduction device (replacing the expansion valve), an energy extraction device (generating electricity), and a flow control device (regulating refrigerant flow to the evaporator). This multi-functionality consolidates several components into one, maintaining relatively simple system structure while achieving improved performance.
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 increases the cooling capacity of the working fluid, reduces the work required by the compressor, and improves overall efficiency by minimizing entropy increase and capturing enthalpy, resulting in enhanced coefficient of performance and energy savings.
Implementation Method 1
utilizing a two-phase expander to expand high-pressure saturated or supercooled liquids into a two-phase fluid at constant or near-constant entropy, reducing irreversibilities and capturing energy
Implementation Method 2
Within the evaporator, the low-pressure two-phase fluid absorbs heat from an environment, therein becoming the low-pressure superheated vapor
Implementation Method 3
the working fluid enters the compressor as a low-pressure superheated vapor and is compressed to a high-pressure superheated vapor
Implementation Method 4
The high-pressure superheated vapor then condenses or cools within the condenser to become a high-pressure supercooled liquid
Data Source
AI summary
A modified two-phase refrigeration cycle compresses a working fluid, condenses the working fluid into a saturated or supercooled liquid, expands the saturated or supercooled liquid into a two-phase fluid, and evaporates the two-phase working fluid. The modified two-phase refrigeration cycle reduces irreversibilities imposed by conventional refrigeration cycles and extracts energy from the working fluid during the expansion process. For instance, a system that employs the modified two-phase refrigeration cycle includes a two-phase expander to reduce irreversibilities during an expansion process and extract energy. In some instances, the system includes a two-phase compressor to compress two-phase fluids for varying loads and environmental conditions of the system.