Nested Helical Heat Exchanger for Uniform Refrigerant Flow
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Solution Overview
Problem
Traditional cascade heat exchangers in refrigeration systems face issues such as high strain and stress due to temperature and pressure changes, leading to potential rupture and cross-contamination, non-uniform refrigerant flow distribution, high construction costs, and large spatial requirements, especially under two-phase flow conditions.
Innovation Solution
A heat exchanger design featuring a cylindrical exterior container with a refrigerant distribution tube and multiple closely nested, helically shaped refrigerant tubes of equal length, oriented in a radially outward and nested configuration, which reduces physical strain and stress by allowing resilient expansion and contraction, ensuring uniform flow distribution and preventing refrigerant mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shell and tube heat exchangers are used with rigid tube construction, then structural strength is improved, but high axial strain and stress occur during temperature and pressure changes leading to tube rupture
Solution Approach 1:
The patent employs flexible bellows-shaped diaphragms instead of rigid tubes. These diaphragms can expand and contract axially in response to temperature and pressure changes, absorbing thermal stress without rupturing. The bellows configuration provides flexibility while maintaining structural integrity, resolving the contradiction between strength and stress resistance.
Solution Approach 2:
The heat exchanger transitions from a static rigid structure to a dynamic flexible structure. The diaphragms can change shape and volume dynamically in response to operating conditions, allowing the system to adapt to thermal and pressure variations without failure.
2Volume of moving object
If plate heat exchangers are used with rigid plate construction, then compactness is improved, but high strains and stresses form in plate material during temperature and pressure changes
Solution Approach 1:
The patent replaces rigid plates with flexible bellows-shaped diaphragms that maintain the compact form factor while providing flexibility to accommodate thermal expansion and pressure changes. The diaphragms can deform elastically, preventing stress concentration and rupture while maintaining compact dimensions.
3Ease of manufacture
If conventional shell and tube or plate heat exchangers are used, then manufacturing simplicity is improved, but non-uniform flow distribution occurs under two-phase flow conditions
Solution Approach 1:
The heat exchanger is divided into multiple independent chambers separated by diaphragms, with each chamber containing a specific number of tubes. This segmentation allows independent flow path control, enabling uniform two-phase flow distribution across all tubes while maintaining relatively simple construction.
Solution Approach 2:
Multiple tubes are nested within chambers defined by the diaphragms, creating a hierarchical structure that facilitates uniform flow distribution. The nested arrangement ensures that refrigerant flows evenly through all tubes while maintaining manufacturing simplicity.
4Strength
If shell and tube heat exchangers are used with traditional construction, then structural robustness is improved, but large spatial volume is required for given heat transfer duty
Solution Approach 1:
The patent nests multiple tubes within compact chambers defined by diaphragms, arranging them in a space-efficient configuration. This nested structure achieves high heat transfer duty in a compact volume while maintaining structural robustness through the flexible diaphragm construction.
Solution Approach 2:
The bellows-shaped diaphragms introduce a third dimension (axial flexibility) to the traditionally planar plate or cylindrical shell structure, allowing compact packaging of heat transfer surfaces while maintaining structural integrity.
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 design enhances the robustness and compactness of the heat exchanger, preventing damage from refrigerant pressure and temperature changes, achieving uniform refrigerant flow and efficient heat transfer while maintaining a compact size.
Implementation Method 1
allowing resilient expansion and contraction
Implementation Method 2
efficient heat transfer
Data Source
AI summary
A heat exchanger is described and which includes an exterior container having an internal cavity; a refrigerant distribution tube is positioned within the internal cavity and which is further coupled in fluid receiving relation relative to a first source of refrigerant; and a multiplicity of closely nested refrigerant tubes are located within the internal cavity and are further disposed in a closely spaced, radially outwardly oriented positions relative to the refrigerant distribution tube, and which additionally have a predetermined and similar length dimension, and individually form helical coils which have a given and similar length dimension, and a variable pitch, and which are further coupled to a second source of a refrigerant.