PCM Thermal Storage Circuit for Heat Pump Energy Shifting
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Solution Overview
Problem
Climate-control systems, such as heat-pump and refrigeration systems, face inefficiencies in thermal management and energy storage, particularly in effectively utilizing phase-change materials for temperature regulation and energy efficiency across varying operational modes.
Innovation Solution
A climate-control system incorporating a working fluid circuit with a compressor, heat exchangers, expansion devices, a flash tank, and a thermal storage tank containing phase-change material, where the system operates in charge and discharge modes to optimize energy transfer and storage using a bypass valve and expansion devices to control fluid flow and temperature regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermal storage is implemented using phase-change material, then energy efficiency is improved, but device complexity increases due to additional components like storage tank, flash tank, and multiple expansion devices
Solution Approach 1:
The system divides the thermal management function into separate components: a storage tank containing phase-change material for thermal energy storage, a flash tank for flash evaporation, and multiple heat exchangers (first, second, and third) for different thermal exchange functions. This segmentation allows each component to specialize in a specific thermal process, improving overall energy efficiency while managing complexity through functional decomposition
Solution Approach 2:
The phase-change material in the storage tank is pre-charged and maintained at optimal temperature conditions before peak demand periods. During off-peak hours, the system pre-cools or pre-heats the phase-change material, so that when high electricity cost periods occur, the stored thermal energy is already available, eliminating the need for real-time thermal adjustment and reducing operational complexity during critical periods
2Temperature
If multiple expansion devices and flash tank are added for optimized fluid flow control, then temperature regulation is improved, but device complexity increases
Solution Approach 1:
Different expansion devices are positioned at different locations in the fluid circuit, each controlling temperature and pressure for specific downstream components. The first expansion device regulates flow to the second heat exchanger, the second expansion device controls flow to the third heat exchanger, and the third expansion device manages flash tank operation. This localized control allows precise temperature regulation at each thermal exchange point without requiring complex centralized control
Solution Approach 2:
The flash tank serves as an intermediary component between the compression stage and the expansion devices. It receives high-pressure refrigerant from the compressor, performs flash evaporation to separate liquid and vapor phases, and then directs the separated phases to different expansion devices. This intermediary function simplifies the overall control logic by providing natural phase separation before the refrigerant reaches the expansion devices, reducing the complexity of temperature and pressure management
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 system enhances energy efficiency by utilizing thermal storage to reduce operational costs, especially during high electricity times, and maintains efficient cooling and heating capabilities by optimizing the phase-change material's temperature through controlled fluid flow and expansion device operations.
Implementation Method 1
The storage tank contains phase-change material that is thermally coupled with the second heat exchanger of the working fluid circuit
Implementation Method 2
The system enhances energy efficiency by utilizing thermal storage to reduce operational costs
Implementation Method 3
The first heat exchanger receives working fluid discharged from the first compressor. The second heat exchanger is disposed within the storage tank such that the second heat exchanger is fluidly isolated from the phase-change material contained in the storage tank and in fluid communication with the first heat exchanger and the flash tank
Implementation Method 4
The working fluid circuit includes a first expansion device disposed between the second heat exchanger and the first heat exchanger
Data Source
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AI summary
A climate-control system includes a working fluid circuit and a storage tank. The working fluid circuit has a first compressor, a first heat exchanger, a second heat exchanger, a flash tank, and a third heat exchanger. The first heat exchanger receives working fluid discharged from the first compressor. The flash tank is disposed downstream the first heat exchanger and includes an inlet and first and second outlets. The first outlet provides working fluid to the third heat exchanger disposed between the flash tank and the first compressor. The second outlet provides working fluid to the first compressor. The storage tank contains phase-change material that is thermally coupled with the second heat exchanger of the working fluid circuit.