Polymeric Expansion Header for Fluid Coil Freeze Protection
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Solution Overview
Problem
Existing solutions for preventing fluid coils from splitting or rupturing due to thermal expansion in HVAC systems are either maintenance-intensive, costly, or degrade thermal-hydraulic performance, and often require interaction with the working fluid, leading to potential flooding and chemical interference.
Innovation Solution
A fluid coil system featuring a compressible polymeric material in the expansion headers that absorbs and contracts with the volume change of water as it freezes or turns to steam, preventing stress and rupture, and returns to its original shape upon phase change, without the need for pressure relief valves or expensive sensors, using materials like EPDM rubber that are chemically resistant and non-reactive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure relief devices are used to prevent freezing damage, then coil protection is improved, but maintenance requirements increase and flooding risk remains
Solution Approach 1:
The freeze protection device is designed to automatically detect freezing conditions through temperature sensing and self-activate to relieve pressure without requiring external control systems, sensors, or manual intervention. The device maintains itself through automatic operation and requires minimal maintenance after installation
Solution Approach 2:
The invention extracts the essential freeze protection function from complex sensor-valve assemblies and implements it through a simple temperature-activated mechanism that removes unnecessary components while retaining the core protective capability
2Reliability
If expansion relief headers with sensors and valves are used, then freeze protection is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts only the essential temperature-sensing and pressure-relief functions from complex sensor-valve assemblies, eliminating unnecessary electronic sensors, control systems, and multiple valves while retaining effective freeze protection capability
Solution Approach 2:
The device uses simple, inexpensive mechanical components that can be easily replaced if needed, avoiding costly electronic sensors and complex control systems while maintaining reliable protection functionality
3Stress or pressure
If flexible inserts are placed in water pipes, then expansion pressure absorption is improved, but thermal-hydraulic performance degrades
Solution Approach 1:
The invention introduces a flexible diaphragm as an intermediary element within the header that absorbs expansion pressures without directly contacting or interfering with the water flow path, thereby maintaining thermal-hydraulic performance while providing freeze protection
Solution Approach 2:
The flexible diaphragm is positioned in the header volume rather than directly in the water flow path, utilizing the third dimension (header space) to absorb expansion without impeding the primary thermal-hydraulic function of the coil
4Stress or pressure
If pressure relief valves are used, then pressure relief is improved, but fluid leakage and flooding risk increase
Solution Approach 1:
The invention converts the potential harm of pressure relief into a controlled benefit by designing the diaphragm to rupture internally within the header, transforming what would be external flooding into contained pressure relief that protects the coil while minimizing water damage
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 system effectively prevents fluid coil rupture and flooding by absorbing expansion pressures without bleeding fluid externally, reducing maintenance and costs, while maintaining thermal-hydraulic performance and chemical compatibility.
Implementation Method 1
thermal expansion of liquid, such as water, in freezing conditions and in steam conditions
Implementation Method 2
as it undergoes a phase change between a liquid state and a solid state, and between a liquid state and a gas state
Implementation Method 3
The material is capable of being compressed a sufficient amount to absorb the expansion pressures exerted by the water
Data Source
AI summary
A fluid coil includes a tube bundle having a series of straight tubing runs and a series of return bends extending between and fluidically connecting ones of the straight tubing runs, an expansion header fluidically connected to at least some of the return bends and a polymeric material disposed in the expansion header. The polymeric material has an initial shape and is compressible to repeatedly expand and contract between a first volume in which water is present in the tube bundle and a second volume in which the water undergoes a phase change. Contraction of the polymeric material absorbs an increase in volume as the water undergoes the phase change to prevent stressing and rupture of the tube bundle and upon an opposite phase change, the polymeric material returns to its initial shape. The polymeric material can be a pressurizable bladder. A system and method to prevent the rupture of a tube bundle in a fluid coil are also disclosed.