Heat pump system comprising two stages, method of operating a heat pump system and method of producing a heat pump system
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Solution Overview
Problem
Heat pump systems using water as the working liquid face issues with cavitation and inefficiency due to low pressures, leading to reduced service life and increased energy consumption, and require complex start-up and maintenance procedures.
Innovation Solution
A heat pump system design with multiple stages, where pumps are arranged at the bottom to prevent cavitation and the heat exchangers are positioned below the pumps, allowing for a compact and efficient layout with cascaded operation modes, and a self-regulating liquid transport system to maintain optimal pressure and flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If water is used as the working liquid in heat pump systems, then the enthalpy difference ratio is improved (6 times higher than R134a), but cavitation occurs due to low pressures leading to reduced service life
Solution Approach 1:
The heat pump system is divided into multiple stages (first heat pump stage and second heat pump stage), each handling a portion of the pressure ratio. The first stage compressor handles the initial compression from evaporator pressure to intermediate pressure, while the second stage compressor handles compression from intermediate pressure to condenser pressure. This segmentation prevents excessive pressure ratios in a single stage, avoiding cavitation while maintaining the high enthalpy difference ratio of water as working liquid.
Solution Approach 2:
A liquid subcooling heat exchanger is introduced as an intermediary component between the two heat pump stages. This heat exchanger subcools the liquid refrigerant after the first stage condensation and before it enters the second stage evaporator, ensuring adequate pressure and temperature conditions that prevent cavitation in the second stage compressor while utilizing the high enthalpy properties of water.
2Use of energy by moving object
If water is used as the working liquid, then energy efficiency is improved, but the system requires complex start-up and maintenance procedures
Solution Approach 1:
The system incorporates preliminary action through the liquid subcooling heat exchanger and expansion organs that automatically regulate liquid flow to the evaporators. These components are pre-configured to maintain optimal pressure and temperature conditions, eliminating the need for complex manual start-up procedures and reducing maintenance requirements. The expansion organs automatically adjust to system conditions, and the subcooling heat exchanger pre-conditiones the liquid refrigerant before each stage.
3Device complexity
If a single stage heat pump system is used, then device complexity is reduced, but efficiency is reduced due to low pressures and cavitation
Solution Approach 1:
The system uses two heat pump stages connected in series, where the first stage handles evaporation and initial compression, and the second stage handles intermediate evaporation and final compression. This segmentation allows each compressor to operate at optimal pressure ratios, preventing cavitation and maintaining high efficiency while using water as the working liquid. The multiple stages enable the system to achieve the necessary total pressure ratio without the drawbacks of a single-stage design.
Solution Approach 2:
The patent merges the functions of two heat pump stages into a single integrated system with shared components. The liquid subcooling heat exchanger serves both stages by subcooling liquid between them, and the expansion organs coordinate to distribute liquid to both evaporators. This merging achieves the efficiency benefits of multi-stage operation while consolidating components to manage complexity.
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 design prevents cavitation, enhances efficiency, reduces energy consumption, and simplifies start-up and maintenance by minimizing air inclusions and using a cascaded heat pump configuration for optimal performance across various operating conditions.
Implementation Method 1
a first evaporator configured to evaporate a first working liquid to generate first working vapor
Implementation Method 2
a first compressor configured to compress the first working vapor generated by the first evaporator
Implementation Method 3
a first condenser configured to condense the compressed first working vapor generated by the first compressor to generate the first working liquid
Implementation Method 4
a second evaporator configured to evaporate a second working liquid to generate second working vapor
Implementation Method 5
a second compressor configured to compress the second working vapor generated by the second evaporator
Implementation Method 6
a second condenser configured to condense the compressed second working vapor generated by the second compressor to generate the second working liquid
Implementation Method 7
a heat exchanger configured to cool the first working vapor generated by the first evaporator using the second working liquid
Data Source
AI summary
A heat pump system includes a heat pump stage having a first evaporator, a first liquefier, and a first compressor; and a further heat pump stage having a second evaporator, a second liquefier, and a second compressor, wherein a first liquefier exit of the first liquefier is connected to a second evaporator entrance of the second evaporator via a connecting lead.