External Oven Cavity Coating to Reduce Radiant Heat Loss
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Solution Overview
Problem
Kitchen ovens experience high heat losses due to the high emissivity of the outer surface of their cavities, which are typically formed during the firing of enamel coatings, leading to inefficient energy use.
Innovation Solution
Applying a low emissivity coating on the outer surfaces of the oven cavity walls, composed of materials like aluminum or tin-oxide particles, to reduce the emissivity below that of oxidized steel, thereby minimizing heat radiation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the outer surface of the cavity walls is left as oxidized steel from enamel firing, then the manufacturing process is simple, but the emissivity is high causing significant heat loss
Solution Approach 1:
The patent applies a composite coating structure consisting of a primer layer and a topcoat layer with low emissivity materials (such as aluminum powder, stainless steel powder, or ceramic coatings). This composite structure reduces heat loss by combining the adhesion benefits of primer with the thermal reflection properties of the topcoat, directly addressing the high emissivity issue of oxidized steel surfaces.
Solution Approach 2:
The patent changes the surface emissivity parameter by applying coatings with specifically selected materials that have lower emissivity values than oxidized steel. The topcoat layer contains reflective materials that alter the thermal radiation characteristics of the cavity surface, reducing heat loss to the surrounding environment.
2Use of energy by moving object
If a low emissivity coating is applied to reduce heat loss, then energy efficiency improves, but the manufacturing process becomes more complex
Solution Approach 1:
The coating system is segmented into distinct functional layers: a primer layer for surface preparation and adhesion, and a topcoat layer for thermal reflection. This segmentation allows each layer to be optimized for its specific function while maintaining a manageable manufacturing process. The primer ensures proper bonding to the metal substrate, while the topcoat provides the low emissivity performance.
Solution Approach 2:
The primer layer acts as an intermediary between the metal substrate and the topcoat layer. It prepares the surface for optimal adhesion of the reflective topcoat, ensuring that the low emissivity coating remains firmly attached during thermal cycling and operation, thus maintaining energy efficiency without requiring overly complex application processes.
3Loss of energy
If the outer surface is coated to reduce emissivity, then heat radiation loss decreases, but the surface area and material usage increase
Solution Approach 1:
The patent applies low emissivity coating specifically to the outer surfaces of the cavity walls where heat loss occurs, rather than coating the entire oven structure. The topcoat with reflective materials is concentrated on the external surfaces that face the surrounding environment, optimizing heat retention while minimizing material consumption. Internal surfaces may use different or no coating depending on specific 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
Significantly reduces the emissivity of the oven cavity surfaces, leading to energy savings and improved efficiency by minimizing heat loss during operation.
Implementation Method 1
the coating comprises at least one material with a low emissivity... such that the emissivity of heatable cavities is lowered... minimizing heat radiation loss
Data Source
Figure 1
Figure 2~2B
Figure 3A~3C
AI summary
A heatable cavity (2) for a kitchen appliance (1), particularly for an oven, wherein the heatable cavity (2) comprises a plurality of cavity walls defining a cooking chamber (7) for cooking foodstuff, and a central opening for placing foodstuff into the cooking chamber (7), wherein the outer surface of at least one of the cavity walls comprises a coating (10)that comprises a material with a low emissivity, preferably wherein said material with a low emissivity has a lower emissivity than oxidized steel.