PCM Thermal Store Refrigeration for Peak Cooling Loads
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Solution Overview
Problem
Commercial refrigeration display cabinets, such as bottle coolers, face inefficiencies due to high peak cooling loads and the need for larger, less efficient vapour compression refrigeration systems, as well as compromised insulation for transparency, leading to higher operational costs and reduced efficiency.
Innovation Solution
A refrigerator design incorporating a phase change material thermal store with a vapour compression refrigeration system featuring two evaporators, where refrigerant flow is controlled between the evaporators based on cooling load, directing it primarily to the first evaporator during high loads and the second evaporator during low loads, and using air circulation to enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a larger vapour compression refrigeration system is used to cope with high peak cooling loads, then the cooling capacity is improved, but the energy efficiency deteriorates
Solution Approach 1:
The phase change material is pre-cooled during periods of low cooling demand so that it is ready to provide rapid cooling when peak loads occur. This preliminary preparation allows the system to respond to high cooling demands without requiring an oversized compressor, thereby maintaining energy efficiency while providing adequate cooling capacity.
Solution Approach 2:
The system changes the state of the phase change material between solid and liquid phases to store and release thermal energy. By utilizing the phase change transition, the system can accumulate cooling capacity during low-demand periods and release it during high-demand periods, avoiding the need for a continuously large compressor and improving overall energy efficiency.
2Illumination intensity
If the door is made transparent for display purposes, then the visibility of beverages is improved, but the thermal insulation deteriorates
Solution Approach 1:
The phase change material acts as a thermal buffer that compensates for the poor insulation of the transparent door. When the door is opened or when external heat enters through the transparent panels, the PCM absorbs excess heat during its phase transition, preventing temperature rise inside the cabinet and reducing the energy loss that would otherwise occur through the poorly insulating door.
3Productivity
If refrigerant flows to both evaporators during low cooling load, then the cooling efficiency is improved, but the complexity of refrigerant flow control increases
Solution Approach 1:
The refrigeration system is designed with multi-functionality where the refrigeration unit serves dual purposes: cooling the beverage storage chamber directly and pre-cooling the phase change material simultaneously. This universal approach allows the system to maintain high cooling efficiency during low-demand periods by utilizing both cooling paths, while the control complexity is managed through a single integrated refrigeration cycle rather than separate independent 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
This solution improves the overall efficiency of the refrigeration system by utilizing spare capacity to pre-cool the phase change material during low loads, allowing for faster cooling during high loads and reducing the need for a large compressor, while maintaining effectiveness and enabling continued cooling during power failures.
Implementation Method 1
a thermal store comprising a phase change material for cooling the cooling chamber
Implementation Method 2
a thermal store comprising a phase change material for cooling the cooling chamber
Implementation Method 3
a vapour compression refrigeration system including a first evaporator for cooling the cooling chamber and a second evaporator for cooling the phase change material
Data Source
Figure 1
Figure 2~3
AI summary
A refrigerator having a thermal store comprising a phase change material is disclosed. The refrigerator has a cooling chamber (6) for containing an object to be cooled, and a vapour compression refrigeration system including a first evaporator (10) for cooling the cooling chamber and a second evaporator (12) for cooling the phase change material. A valve (15) is provided to control the flow of refrigerant to the first and second evaporators depending on the cooling load on the refrigerator. When the refrigerator is subject to a relatively low cooling load, refrigerant flows to the second evaporator (12) to cool the phase change material and, when the refrigerator is subject to a relatively high cooling load, refrigerant flows to the first evaporator (10) such that increased cooling is provided to the cooling chamber by the first evaporator and the phase change material. In a preferred embodiment, refrigerant flows to both the first and second evaporators (10,12) when the refrigerator is subject to a relatively low cooling load and substantially only to the first evaporator (10) when the refrigerator is subject to a relatively high cooling load.