Header Pipe Cross-Section Control for Uniform Evaporator Flow
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Solution Overview
Problem
Conventional heat exchangers with flat tubes and header-collecting pipes face challenges in uniformly distributing refrigerant flow rates when functioning as evaporators, leading to insufficient performance due to non-uniform flow rates and inadequate distribution methods.
Innovation Solution
The heat exchanger is designed with a second header-collecting pipe that forms flow spaces with an effective cross-sectional area adjusted based on the mass flow rate of refrigerant, ensuring uniform distribution by optimizing the flow velocity and area to accommodate varying operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the heat exchanger uses conventional header-collecting pipes and flat tubes configuration, then the structure is simple and easy to manufacture, but the refrigerant flow distribution is non-uniform leading to insufficient performance
Solution Approach 1:
The patent changes the geometric parameters of the flow spaces in the header-collecting pipe by controlling the insertion depth of flat tubes. Specifically, the insertion depth is set to 0.05 to 0.15 times the length of the flat tube, which optimizes the flow space cross-sectional area and ensures uniform refrigerant distribution, thereby improving heat exchange performance while maintaining structural simplicity
Solution Approach 2:
The patent introduces a new dimensional parameter - the insertion depth of flat tubes into the header-collecting pipe - to control the flow space characteristics. This dimensional control enables uniform refrigerant distribution without complicating the overall structure, resolving the contradiction between manufacturing simplicity and performance
2Ease of operation
If the refrigerant flow rate into flat tubes is non-uniform, then the system operation is simple, but the refrigerant enters single-phase gas state at midpoints causing insufficient heat exchange performance
Solution Approach 1:
The patent optimizes the flow space cross-sectional area in the header-collecting pipe by controlling tube insertion depth, which equalizes refrigerant flow rates into all flat tubes. This ensures refrigerant remains in gas-liquid two-phase state throughout the flat tubes, maintaining high heat exchange performance while keeping operations simple
3Productivity
If the heat exchanger is designed for high performance evaporator operation, then the heat exchange efficiency is improved, but the design complexity and manufacturing difficulty increase
Solution Approach 1:
The patent achieves high performance by optimizing a single key parameter - the insertion depth of flat tubes into the header-collecting pipe. This parameter controls the flow space area to ensure uniform refrigerant distribution. The solution maintains conventional simple structure while achieving superior performance through precise parameter control, avoiding increased design and manufacturing complexity
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 configuration ensures uniform refrigerant distribution to flat tubes, enhancing the heat exchanger's performance by maintaining appropriate flow velocities and maximizing heat absorption, thereby providing sufficient performance even under varying operational conditions.
Implementation Method 1
a refrigerant being in a gas-liquid two-phase state flows upwardly when the heat exchanger functions as an evaporator
Implementation Method 2
The refrigerant flowing through the flat tubes dissipates heat into air and condensates
Implementation Method 3
causes a refrigerant flowing inside the flat tubes to exchange heat with air flowing outside the flat tubes
Data Source
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AI summary
In a heat exchanger, each of flat tubes (31) has an end portion inserted in a header-collecting pipe (70). When the heat exchanger functions as an evaporator, a refrigerant in a gas-liquid two-phase state upwardly flows in a subspace (71 a) located in the header-collecting pipe (70). An effective cross-sectional area A of the subspace (71 a) in the header-collecting pipe (70) is set based on a mass flow rate of the refrigerant flowing into the subspace (71a) in the header-collecting pipe (70). The effective cross-sectional area A is obtained by subtracting a projected area A1 which corresponds to a portion of each flat tube (31) located in the subspace (71a) and is projected onto a plane perpendicular to an axial direction of the header-collecting pipe (70) from an area A0 of a cross section of the subspace (71 a) which is perpendicular to the axial direction of the header-collecting pipe (70).