Heat Exchanger Defrost Heater Mounting for Thermal Expansion
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Solution Overview
Problem
Electric resistance heating elements in air-cooling heat exchangers experience significant thermal expansion and contraction during defrost cycles, leading to displacement and potential damage to the heating elements and the heat exchanger, as well as neighboring equipment, due to the anchoring ice melting and re-expansion.
Innovation Solution
A resilient mounting arrangement using a biasing member, such as a coil spring, is employed to restrain the heating element within the heat exchanger, allowing for limited movement during expansion and contraction while maintaining proper positioning after each defrost cycle, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid mounting system is used to restrain the heating element, then the heating element is held firmly in position, but the thermal expansion and contraction forces cause internal damage to the heat exchanger tubes, fins, or casings
Solution Approach 1:
The patent employs a flexible resilient mounting system comprising a resilient member (such as a spring or elastomeric material) that allows the heating element to be restrained while accommodating thermal expansion and contraction. The resilient member flexes to absorb expansion forces and returns the heating element to its original position during contraction, preventing damage to the heat exchanger structure while maintaining positioning stability.
Solution Approach 2:
The resilient mounting system changes its mechanical properties (flexibility, stiffness) in response to temperature variations. During heating cycles, the resilient member becomes more compliant to accommodate expansion; during cooling cycles, it regains stiffness to maintain positioning. This dynamic parameter adjustment allows the system to handle thermal stresses without compromising structural integrity.
2Strength
If the heating element is allowed to expand freely during defrost cycles, then damage to the heat exchanger is avoided, but the heating element creeps or walks out of the heat exchanger over time
Solution Approach 1:
The resilient mounting system provides mechanical feedback through the resilient member that continuously pushes the heating element back toward its original position. As the heating element expands during defrost cycles, the resilient member compresses and stores energy; when the heating element contracts, the stored energy propels it back to its initial position, preventing cumulative displacement or 'creeping' over multiple cycles.
Solution Approach 2:
The mounting system transitions from a static rigid constraint to a dynamic resilient constraint that adapts to the heating element's thermal cycles. The resilient member allows controlled movement during expansion while maintaining overall positioning stability, creating a dynamic equilibrium that prevents both damage and displacement.
3Force
If a strong mounting arrangement is used to counter thermal expansion forces, then the heating element remains restrained, but the repeated thermal expansion and contraction cause internal damage to the heat exchanger components
Solution Approach 1:
The resilient mounting system provides beforehand cushioning by incorporating a resilient member that is pre-configured to absorb the anticipated thermal expansion forces. The resilient material acts as a cushion that deforms under expansion loads, protecting the heat exchanger structure from impact forces while maintaining sufficient restraining force to prevent displacement.
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 solution effectively absorbs the thermal expansion forces, preventing damage to the heating elements and the heat exchanger, and ensures the heating element remains correctly positioned, thus maintaining operational integrity throughout multiple defrost cycles.
Implementation Method 1
due to its coefficient of linear expansion, the metal sheath which typically encloses such heating elements will contract as the temperature of the heat exchanger drops... When the heat exchanger is warmed during a subsequent defrost cycle, the same metal sheath of the heating element expands due the same coefficient of linear expansion
Implementation Method 2
the coil spring which is oriented so as to absorb thermal expansion forces
Data Source
AI summary
A heat exchanger and method for defrosting a heat exchanger is disclosed and which includes a heat exchanger having a fluid receiving conduit, and at least one space which is defined, at least in part, by the fluid receiving conduit, an expandable and contractible heating element which is received within the space, and which is located in heat transmitting relation relative to the fluid receiving conduit, and a biasing member mounted on the heat exchanger and the heating element and which longitudinally, and resiliently restrains the movement of the heating element relative to the heat exchanger during the expansion and contraction of the heating element relative to the heat exchanger.