Method for controlling defrost in refrigeration systems
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Solution Overview
Problem
Standard defrost technologies in refrigeration equipment cause temperature fluctuations that exceed acceptable limits for maintaining product viability, particularly in applications like vaccine storage, where consistent temperatures between −58°F and 5°F are required, and existing methods fail to control these variations effectively.
Innovation Solution
A refrigeration defrost system utilizing temperature variation moderating heat reservoirs and a secondary chamber to regulate airflow and thermally isolate the product chamber, preventing temperature rises above 5°C during defrost cycles, and incorporating thermal reservoirs to extend the tolerance time during cooling capacity disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard defrost technologies are used to eliminate frost buildup, then the frost layer evaporates or drains away, but the air and product temperature within the freezer rises above acceptable limits
Solution Approach 1:
The freezer is divided into two separate chambers: an evaporator chamber where frost accumulates and is defrosted, and a product chamber where temperature must be maintained. This segmentation allows independent temperature control in each chamber, enabling effective defrosting without compromising product temperature stability.
Solution Approach 2:
A thermal mass (water reservoir) acts as an intermediary between the evaporator chamber and product chamber. During defrosting, the thermal mass absorbs excess heat from the evaporator chamber, preventing temperature rise in the product chamber. The thermal mass is thermally coupled to both chambers, mediating heat transfer to maintain temperature stability.
2Object-generated harmful factors
If heating is applied to defrost the freezer compartment, then frost is removed, but the temperature variation exceeds acceptable limits for product viability
Solution Approach 1:
A thermal mass (water reservoir) is pre-positioned in the product chamber before defrost cycles begin. This thermal mass is prepared to absorb heat during upcoming defrost events, preemptively stabilizing temperatures before harmful temperature variations can occur in the product chamber.
Solution Approach 2:
The thermal mass utilizes phase transition (freezing and melting of water) to regulate temperature. During defrosting, the water in the thermal mass absorbs heat and melts from frozen to liquid state, maintaining a constant temperature plateau that prevents product temperature from rising above acceptable limits.
3Temperature
If a secondary chamber and plenum are added to regulate airflow and contain heat reservoirs, then temperature control is improved, but device complexity increases
Solution Approach 1:
The evaporator chamber serves multiple functions: it acts as both the cooling chamber for the product and the defrost chamber for frost removal. The same evaporator is used for both refrigeration and defrosting operations, eliminating the need for separate chambers and reducing overall system complexity despite the added plenum structure.
Solution Approach 2:
The plenum chamber merges the airflow regulation function with the thermal mass containment function. This single integrated structure serves dual purposes: directing airflow between chambers and housing the thermal mass that stabilizes temperatures, thereby reducing the number of separate components needed.
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 maintains consistent temperatures within the required range during defrost cycles, ensuring product viability and extending the time during cooling capacity reductions without affecting product quality.
Implementation Method 1
temperature variation moderating heat reservoirs consisting of high specific or latent heat capacity materials
Implementation Method 2
the heat absorbing element of the cooling technology
Implementation Method 3
integrated evaporator heating element
Implementation Method 4
axial airflow induction fan
Implementation Method 5
refrigerant evaporation
Implementation Method 6
hermetically sealed compressor
Data Source
AI summary
Automatic defrost technology for refrigeration equipment, in particular, defrosting refrigeration equipment by acceleration defrosting sublimation effects in refrigeration chambers in continual operation below the freezing point of water. Useful for refrigeration equipment for storage of vaccines and other products having storage temperatures ranging from −58 degrees Fahrenheit and 5 degrees Fahrenheit.