Phase change material-based enhancement for reversed-cycle defrosting in vapour compression refrigeration systems
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Solution Overview
Problem
Existing defrosting methods for evaporators in heat pumps and vapor compression refrigeration systems, such as reverse-cycle defrosting, consume energy meant for heat delivery to the condenser, leading to reduced comfort in ancillary systems like hot water tanks and radiators.
Innovation Solution
A thermal energy storage system with phase change materials and bypass mechanisms that allows for defrosting without affecting the energy delivered to the condenser, using thermal storage units positioned between the condenser and expansion valve, and employing phase change materials like waxes, paraffin, or fatty acids to enhance heat transfer and store energy for defrosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse-cycle defrosting is used to melt ice on the evaporator, then the evaporator can be defrosted, but the energy previously provided to the heat sink (condenser) is consumed, cooling down the hot water tank or radiators and reducing comfort
Solution Approach 1:
The system segments the refrigeration cycle into separate defrosting and heating functions by introducing a bypass line that allows the evaporator to be isolated from the main cycle during defrosting, enabling independent operation of these functions without interfering with heat sink performance
Solution Approach 2:
A defrosting fluid circulates through the evaporator during defrosting mode, acting as an intermediary heat transfer medium that absorbs heat from the evaporator coils to melt ice, while the condenser continues operating independently to provide heat to the heat sink
2Reliability
If reverse-cycle defrosting is implemented, then ice on the evaporator is melted, but the condenser must be bypassed and heat delivery to the heat sink is interrupted
Solution Approach 1:
The refrigeration system is segmented into independent defrosting and heating circuits, allowing the defrosting operation to occur in one part of the system while the heating function continues uninterrupted in another part through the condenser
Solution Approach 2:
The condenser maintains continuous heat delivery to the heat sink during defrosting operations by keeping the refrigerant flow through the condenser active and uninterrupted, while separate defrosting fluid circulation handles the evaporator defrosting function
3Reliability
If the condenser is bypassed during defrosting to direct hot vapour to the evaporator, then defrosting is achieved, but the energy meant for heat delivery is diverted
Solution Approach 1:
A defrosting fluid serves as an intermediary medium that circulates through the evaporator during defrosting, absorbing heat locally from the evaporator coils to melt ice, while the main refrigerant flow continues through the condenser to deliver heat to the heat sink without diversion
Solution Approach 2:
The defrosting system uses the heat already present in the refrigerant and defrosting fluid to melt the ice on the evaporator, achieving defrosting through self-contained heat transfer within the defrosting circuit without requiring external energy sources or diverting energy from the heat sink
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 enables efficient defrosting of evaporators without impacting the energy delivered to the condenser, maintaining comfort levels in associated systems and optimizing energy use by recovering and reusing retained heat energy.
Implementation Method 1
at least one coil is surrounded by a suitable phase change material
Implementation Method 2
employing phase change materials like waxes, paraffin, or fatty acids to enhance heat transfer and store energy for defrosting
Implementation Method 3
a thermal store comprising a heat exchanger with at least one coil, wherein said at least one coil is surrounded by a suitable phase change material
Data Source
AI summary
There is provided a thermal energy storage system suitable for use with systems adapted to transfer heat from at least one heat source to at least one heat sink (heat transfer system), comprising at least one thermal energy storage unit. There is additionally provided a thermal energy storage system for use with a heat pump, or vapour compression refrigeration systems, a method of defrosting evaporators without affecting the energy delivered in the condenser before the defrosting cycle, and system architecture for defrosting evaporators in heat pumps or in vapour compression refrigeration systems.