Variable Heat Exchanger Surface for Frost-Stable Refrigeration
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Solution Overview
Problem
Existing refrigeration systems face challenges in maintaining precise temperature control during chilling or freezing processes due to limited heat transfer rates and frost buildup on heat exchanger surfaces, leading to potential product damage and reduced system efficiency.
Innovation Solution
A heat exchanger apparatus with a movable insulation member and knife edge design that adjusts the heat transfer surface area and removes frost, using cryogens like dry ice or liquid CO2, to provide a more uniform temperature and efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the heat exchanger surface area is increased to improve heat transfer rate, then cooling efficiency is improved, but frost buildup on the surface increases causing temperature control instability
Solution Approach 1:
The patent applies the dynamics principle by making the heat exchanger surface area variable rather than fixed. The insulation member can be moved to expose or cover portions of the heat exchanger surface, allowing the system to dynamically adjust the active heat transfer area based on cooling demands and frost conditions, thus maintaining both high productivity and temperature control stability.
Solution Approach 2:
The patent changes the parameter of heat transfer surface area from a constant value to a variable parameter. By adjusting the position of the insulation member, the exposed surface area of the heat exchanger can be modified, enabling the system to optimize heat transfer rate while preventing excessive frost buildup that would destabilize temperature control.
2Power
If the refrigerant temperature is lowered to increase heat transfer rate, then cooling capacity is improved, but the temperature difference between refrigerant and air becomes too small reducing heat transfer efficiency
Solution Approach 1:
The system dynamically adjusts the heat exchanger surface area available for heat transfer by moving the insulation member. This allows the system to maintain optimal heat transfer efficiency by exposing only the necessary surface area, compensating for the reduced temperature difference and maintaining adequate cooling capacity and heat transfer rate.
3Temperature
If the heat exchanger surface is kept cold to maintain cooling effect, then temperature control is improved, but frost from external air condensation reduces heat transfer rate
Solution Approach 1:
The patent uses a movable insulation member that can dynamically adjust the exposed surface area of the heat exchanger. When frost buildup occurs from external air condensation, the insulation member can be moved to cover portions of the surface, reducing further frost accumulation while maintaining cooling effect on the necessary surfaces, thus preserving heat transfer rate.
Solution Approach 2:
The insulation member provides preliminary protection by covering portions of the heat exchanger surface before external moist air can condense and form frost. This preventive action reduces frost buildup on the heat exchanger surface, maintaining heat transfer efficiency while the cold surface continues to provide the necessary cooling effect.
4Ease of operation
If trailer doors are opened frequently for deliveries, then product accessibility is improved, but rapid heat load increases make temperature control difficult
Solution Approach 1:
The variable surface area heat exchanger provides dynamic adjustment capability that allows the system to respond to rapid heat load changes from door openings. By adjusting the exposed heat exchanger surface area, the system can compensate for sudden heat ingress and maintain better temperature control despite frequent door operations and product accessibility requirements.
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 apparatus ensures consistent temperature control and prevents frost buildup, enhancing the efficiency and reliability of refrigeration systems by varying the heat transfer surface area and using cryogens effectively.
Implementation Method 1
The air inside the refrigerated space is cooled by forced or natural convection over the surface of the heat exchanger
Implementation Method 2
a first insulation member movably mounted for coaction with the sidewall... to provide a heat transfer effect
Implementation Method 3
The air inside the refrigerated space is cooled by forced or natural convection over the surface of the heat exchanger
Data Source
Figure 1
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Figure 6
AI summary
In order to eliminate the frost build up on the heat exchanger surface and to provide for a more uniform and consistent temperature of the product and the refrigeration space, a heat exchanger apparatus (10) is proposed, comprising - a housing having a sidewall (12) defining a chamber (14) in the housing for containing a cryogen; and - a first insulation member (30) movably mounted for coaction with the sidewall (12), the first insulation member (30) moveable to a position to expose or cover a select portion of the sidewall (12) to provide a heat transfer effect.