Refrigerator Heat Accumulator Using Subzero Phase-Change Medium
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Solution Overview
Problem
Refrigeration appliances face inefficiencies in maintaining a temperature range above 0°C due to the deformation of flexible walls in heat storage tanks, affecting heat transfer and compressor performance, especially when using water as a storage medium that expands upon freezing.
Innovation Solution
Employing a storage medium with a melting temperature below 0°C, such as an aqueous solution of ethylene glycol or urea, which acts as a heat accumulator during evaporator operating phases, maintaining high vapor pressure and reducing pressure differences for the compressor, while being encapsulated in capsules for stability and ease of manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If water is used as a storage medium in a heat storage tank with flexible walls, then the tank can accommodate volume changes during freezing, but the wall deformation affects heat transfer between the evaporator and the heat accumulator
Solution Approach 1:
The storage medium is divided into multiple capsules distributed throughout the heat accumulator, allowing each capsule to expand independently upon freezing without causing overall deformation of the heat accumulator structure, thus maintaining stable heat transfer surfaces
Solution Approach 2:
The patent introduces a rigid or semi-rigid heat accumulator structure as an intermediary between the evaporator and the storage medium, decoupling the volume expansion of water during freezing from the heat transfer surface, thereby preventing deformation-induced heat transfer degradation
2Temperature
If the evaporator cools down significantly during operating phases, then cooling capacity is increased, but the vapor pressure of the refrigerant decreases and compressor workload increases
Solution Approach 1:
The heat accumulator is pre-chilled during idle phases by absorbing heat from the evaporator, so that at the beginning of each operating phase, the evaporator starts from a higher temperature, maintaining higher vapor pressure and reducing compressor workload during the critical initial cooling period
Solution Approach 2:
The storage medium undergoes phase transition (freezing/melting) to store and release heat at constant temperature, providing thermal buffering that stabilizes evaporator temperature and prevents excessive cooling that would otherwise occur during operating phases
3Temperature
If the melting temperature of the storage medium is lowered to maintain effect during evaporator operation, then vapor pressure is maintained, but the defrosting process is prolonged
Solution Approach 1:
The patent optimizes the melting temperature parameter of the storage medium to be just below 0°C, which is sufficient to maintain effective vapor pressure during evaporator operation while ensuring complete melting occurs before the evaporator temperature rises above 0°C during idle phases, thus avoiding prolonged defrosting
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 approach enhances refrigeration efficiency by maintaining high vapor pressure during evaporator operation, reducing compressor workload, and minimizing defrosting duration, allowing for effective cooling and reduced energy consumption.
Implementation Method 1
a heat accumulator which is assigned to the evaporator and contains a storage medium which in Operating and idle phases of the evaporator changes its state of aggregation
Implementation Method 2
the use of a storage medium with a melting temperature below 0°C enables a significant increase in efficiency
Implementation Method 3
an evaporator which is arranged in thermal contact with the storage chamber
Implementation Method 4
reduces the pressure difference against which a compressor has to work in order to condense the refrigerant again
Implementation Method 5
a compressor has to work in order to condense the refrigerant again
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a refrigerator, especially a household refrigerator, comprising a storage chamber (3) for chilled goods, an evaporator (5) arranged in thermal contact with the storage chamber (3), operating intermittently in order to maintain the storage chamber (3) within a pre-determined temperature range, and a heat accumulator (10) associated with the evaporator (5), said heat accumulator containing an accumulation medium (12) that respectively changes its state of aggregation in operating and idle phases of the evaporator (5). In said refrigerator, the pre-determined temperature range of the storage chamber (3) is above 0?C and the melting temperature of the accumulation medium (12) is below 0?C.