Showcase Cooler Fin Layout to Limit Frost and Ease Assembly
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Solution Overview
Problem
In fin-and-tube type coolers used in open showcases, the fins and refrigerant pipes are prone to frosting due to outside air entering and cooling, especially when the gaps between fins are small, making it difficult to maintain a predetermined interval without special jigs, and CO2 refrigerant pipes require narrower diameters, complicating the assembly process.
Innovation Solution
The use of long and short fins with projecting portions formed by burring, where long fins are arranged upstream and short fins downstream, with the short fins' projecting portions abutting adjacent fins to maintain the interval, and U-shaped hair pins with varying pitches to prevent dense arrangement and frost formation, allowing for stable cooling performance without special jigs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the gap between neighboring fins is kept small to increase heat exchange area, then the cooling efficiency is improved, but the fins are prone to frosting due to supercooling in gap portions
Solution Approach 1:
The fins are segmented into multiple types (first fins, second fins, third fins, fourth fins) with different structures and positions. The second fins have through-holes for refrigerant pipes while the fourth fins are solid without through-holes. This segmentation allows different fin regions to serve different functions - some optimized for heat exchange, others for preventing frost accumulation.
Solution Approach 2:
Different fin portions have different properties: the second fins have through-holes for refrigerant penetration to enhance local cooling, while the fourth fins are solid to prevent frost. The gap portions between fins are strategically positioned to allow air flow while preventing frost accumulation. This local differentiation resolves the contradiction between heat exchange efficiency and frost prevention.
2Quantity of substance
If the refrigerant pipe diameter is narrowed to reduce refrigerant amount and improve efficiency, then the system complexity is reduced, but the through-hole diameter of fins must be reduced making assembly difficult
Solution Approach 1:
The fin assembly is segmented into multiple types of fins (first, second, third, fourth fins) with different through-hole configurations. The second fins have through-holes for refrigerant pipes while the fourth fins are solid. This segmentation allows the refrigerant pipes to pass through specific fins without requiring all fins to have reduced-diameter holes, simplifying the assembly process while maintaining narrow pipe dimensions for CO2 refrigerant.
Solution Approach 2:
The refrigerant pipes act as intermediaries that pass through the fin structure. By positioning the pipes to pass through specific fins (second fins) rather than all fins, and by using solid fins (fourth fins) in certain positions, the assembly process is facilitated while maintaining the narrow pipe diameter required for CO2 refrigerant efficiency.
3Use of energy by moving object
If the straight portions of hair pins are locally densely arranged to maximize heat exchange, then the cooling performance is improved, but the gap portions become small causing supercooling and frost formation
Solution Approach 1:
The refrigerant pipe system is segmented into multiple hair pins with straight portions positioned at different locations. The first and second hair pins have straight portions in different positions, creating a distributed arrangement rather than local density. This segmentation ensures adequate spacing between refrigerant pipes to prevent supercooling and frost while maintaining overall heat exchange effectiveness.
Solution Approach 2:
The refrigerant pipes are arranged in multiple dimensions and positions rather than being densely packed in a single location. The hair pins extend in different directions and positions within the fin structure, distributing the cooling function across multiple spatial dimensions. This dimensional distribution prevents local density issues while maintaining effective heat exchange.
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 configuration maintains the required interval between fins without special jigs, reduces frost formation, and ensures stable cooling performance by preventing dense refrigerant pipe arrangement, thus enhancing the efficiency and reliability of the cooling system.
Implementation Method 1
air in the neighborhood of the fins is cooled by the endothermic action of refrigerant flowing in the refrigerant pipes formed by the hair pins
Implementation Method 2
the edge portions of the through-holes of the fins are projected by the burring method so that the projecting portions 36 have a predetermined length or more, and the fins are assembled while the projecting portions abut against the adjacent fins
Implementation Method 3
outside air freely enters the storage room. Therefore, water components contained in the outside air are cooled by the fins, so that the fins are frosted in some cases
Implementation Method 4
CO2 refrigerant is used while pressurized till pressure in the neighborhood of the critical point, and the pressure loss is little
Data Source
AI summary
A showcase having a fin-and-tube type cooler includes planar fins and a refrigerant pipe penetrating through the planar fins. The planar fins include long fins arranged in parallel to an air flow direction through the cooler, and short fins shorter in length than the long fins and arranged between adjacent long fins at a downstream side of the cooler. The refrigerant pipe includes first U-shaped hair pins having two straight pipe portions, and second U-shaped hair pins having two straight pipe portions. The pitch between the two straight pipe portions of each second U-shaped hair pin is set to double the pitch between the two straight pipe portions of each first U-shaped hair pin. The first and second U-shaped hair pins penetrate through the hole portions formed in the plural planar fins so as to be arranged in a predetermined style.