Liquid Door Heating Circuit Using Waste Heat in Refrigerated Cabinets
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Solution Overview
Problem
Existing door heating systems in refrigerated cabinets are inefficient due to reliance on air as the heating fluid, which has poor thermal conductivity and limited interaction time with the heat exchanger, restricting heating to only when the door is closed and resulting in low efficiency and suboptimal use of waste heat.
Innovation Solution
A liquid heating fluid circuit with a partially filled heating fluid reservoir, thermally connected to a cooling fluid circuit via a heat exchanger, utilizing a liquid heating fluid with higher thermal conductivity, allowing for continuous and efficient heating of the door while minimizing heat input into the cooling space, and using a corrosion-resistant material for the reservoir to avoid complex filling and corrosion issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air is used as heating fluid in the heating fluid circuit, then the door can be heated when the door is closed, but the heating efficiency is low due to poor thermal conductivity and short interaction time
Solution Approach 1:
The patent changes the physical state of the heating fluid from gaseous (air) to liquid (heating fluid with higher thermal conductivity). This parameter change enables more efficient heat transfer from the heat exchanger to the door while maintaining the door heating capability, thus resolving the contradiction between reliability and productivity.
2Reliability
If the heating fluid circuit is only formed when the door is closed, then the door can be heated, but heating can only occur when the door is closed and not continuously
Solution Approach 1:
The heating fluid circuit is pre-configured within the door structure, with the heat exchanger positioned to contact the door. This preliminary arrangement ensures that heating can immediately commence when the door is closed without requiring system reconfiguration, enabling continuous heating capability while maintaining the door heating function.
3Productivity
If a liquid heating fluid is used instead of air, then thermal energy can be transferred more quickly and efficiently, but the heating fluid must be contained in a closed circuit to prevent escape
Solution Approach 1:
The heating fluid circuit is nested within the door structure, with pipes and the heat exchanger integrated into the door's internal architecture. This nesting approach contains the liquid heating fluid efficiently within the door itself, achieving high heat transfer efficiency while minimizing the complexity of the overall closed circuit system.
4Quantity of substance
If the heating fluid reservoir is partially filled with heating fluid, then a large amount of heating fluid is available for heat absorption, but the remaining volume must be filled with air or gas which expands with temperature
Solution Approach 1:
The heating fluid reservoir is designed with localized functional zones: the lower portion contains the liquid heating fluid for heat absorption, while the upper portion contains air or gas as a compressible cushion. This local differentiation allows the system to accommodate thermal expansion of the gas phase without transmitting excessive pressure to the reservoir walls, while maintaining sufficient liquid volume for effective heat transfer.
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 continuous, efficient heating of the door with reduced energy input, optimized heat transfer, and minimized thermal energy input into the cooling space, using a liquid heating fluid with higher conductivity and a corrosion-resistant reservoir, allowing for improved waste heat utilization and reduced operational costs.
Implementation Method 1
a cooling fluid circuit (5) for the cooling unit (6) of the refrigerated cabinet (2), which cooling fluid circuit (5) is thermally connected to the heating fluid circuit (3) via a heat exchanger (4)
Implementation Method 2
a liquid heating fluid (7), which has a higher thermal conductivity than air, can be used instead of a gaseous one
Implementation Method 3
The heat absorbed by the heating fluid is transported in the heating fluid circuit to the door, where it releases thermal energy and thus heats the door
Data Source
Figure 1
Figure 2
AI summary
A device for heating the door (1) of a refrigerated display case (2) is described, comprising a heating fluid circuit (3) for the door (1) and a cooling fluid circuit (5) for the refrigeration unit (6) of the refrigerated display case (2), which is thermally connected to the heating fluid circuit (3) via a heat exchanger (4). To design a device of the type described above in such a way as to enable continuous, efficient heating of the door with the lowest possible energy expenditure, thereby minimizing heat input into the refrigerated compartment and, in particular, eliminating the need for additional heating elements, it is proposed that the heating fluid circuit (3) comprises a liquid heating fluid and that the heat exchanger (4) is a heating fluid reservoir partially filled with heating fluid and fluidly connected to the heating fluid circuit (3).