Multi-stage heat engine
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Solution Overview
Problem
Existing heat pump systems, particularly single-stage systems, are inefficient for large temperature lifts due to high investment costs and energy consumption, while multi-stage systems are costly and not widely used for lower temperature lifts despite their potential for higher performance.
Innovation Solution
A multi-stage heat engine or heat pump system with multiple evaporator and condenser stages, where the compression of the medium occurs in different steps, with liquid medium cooling by evaporating a fraction and admixing vapour, maintaining fluid in a superheated or saturated state, and using smaller compression ratios to enhance efficiency, allowing for efficient heating and cooling at varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multi-stage heat pump systems are used to achieve higher performance and lower energy consumption, then the Coefficient of Performance (COP) increases and energy consumption decreases, but the device complexity and investment costs increase considerably
Solution Approach 1:
The heat pump system is divided into multiple compression stages with intermediate cooling steps. Each stage compresses the refrigerant to a higher pressure level, with intercooling between stages to reduce the work required. This segmentation of the compression process into discrete steps allows the system to achieve higher COP values by approaching the ideal Carnot cycle more closely, while managing the complexity through modular stage design.
Solution Approach 2:
The system changes the operating parameters of the refrigerant at each stage, specifically controlling temperature and pressure levels. By adjusting the compression ratio and intercooling temperature at each stage, the system optimizes the COP for different operating conditions. This parameter optimization allows achieving double the COP of single-stage systems while managing complexity through controlled parameter variations.
2Reliability
If two stage heat pump systems are used for high temperature lifts, then the pressure ratio per compressor is halved and performance is improved, but the investment costs increase
Solution Approach 1:
The compression process is segmented into two distinct stages, each handling a portion of the total pressure ratio. The first compressor raises the pressure from evaporator pressure to an intermediate pressure, while the second compressor raises it from intermediate to condenser pressure. This segmentation reduces the pressure ratio per compressor, improving reliability and performance, while the modular two-stage design manages investment costs through standardized component selection.
Solution Approach 2:
An intermediate pressure level is introduced as a mediator between the evaporator and condenser pressures. This intermediate stage allows two compressors to share the total pressure ratio, with each operating at more efficient and reliable pressure ratios. The intermediate cooling step also serves as a mediator to reduce the temperature of the refrigerant between compression stages, further improving system performance while managing complexity.
3Productivity
If the number of stages in heat pump systems is increased, then the performance increases, but the investment required increases considerably
Solution Approach 1:
The system is segmented into a specific number of compression stages (two or more) that provide the optimal balance between performance improvement and investment cost. Each additional stage provides diminishing returns in terms of COP improvement, so the invention identifies and implements the optimal number of stages where the marginal performance gain justifies the marginal investment cost, avoiding excessive complexity while achieving significant performance over single-stage systems.
Solution Approach 2:
The system optimizes parameters such as compression ratio per stage, intercooling temperature, and refrigerant flow distribution to maximize performance for a given number of stages. By carefully controlling these parameters, the system achieves high performance with a manageable number of stages, avoiding the need for excessive stages that would dramatically increase investment costs while providing sufficient performance improvement over single-stage systems.
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 multi-stage system achieves double the Coefficient of Performance (COP) of single-stage systems, consuming half the energy, and allows for efficient heating and cooling at different temperatures, reducing investment costs and energy consumption.
Implementation Method 1
compressing the gaseous phase in a first pressure vessel to a higher pressure
Implementation Method 2
expanding a fraction of the liquid phase in a second pressure vessel to a lower pressure
Implementation Method 3
cooling by evaporating a fraction of the liquid phase
Implementation Method 4
condenser for condensing the gaseous phase
Data Source
AI summary
A multi-stage heat engine having an evaporator, a condenser, expander stages; vapour compression stages; tanks for holding gaseous phases of a fluid. The compressor stages is adapted to compress the gaseous phase in the adjacent tank with a higher pressure than which occurred at expansion and to move the compressed fluid to the next adjacent tank at a higher pressure, the expander stages are adapted to expand a part of the compressed fluid in each tank, to expand the fluid in the adjacent tank at a lower pressure, the compressor and expander sections are adapted to output the gaseous phase at the highest pressure to the condenser and the liquid phase at the lowest pressure to the evaporator, where the output of the condenser are fed back to the tank at the highest pressure and the output of the evaporator is fed back to the tank at the lowest pressure.