Double-Column Heat Exchanger Flow Layout for Reversible Air Conditioning
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Solution Overview
Problem
Heat exchangers with a double-column structure face performance issues as an evaporator or condenser due to the direction of refrigerant flow, leading to inadequate heat exchange efficiency, particularly when the refrigerant flows from the windward to the leeward tube bank or vice versa.
Innovation Solution
A heat exchanger design with a windward and leeward tube bank divided into principal and auxiliary sections, where the refrigerant flows through the auxiliary sections first when functioning as an evaporator and through the principal sections first when functioning as a condenser, ensuring consistent temperature differences and mass flow rates across the banks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the refrigerant flows from the windward tube bank to the leeward tube bank in a double-column heat exchanger with flat tubes arranged one above the other, then the refrigerant temperature decreases due to pressure loss, but the refrigerant may turn into a gas single phase state in the windward tube bank when wetness is non-uniform, reducing heat exchange efficiency
Solution Approach 1:
The windward tube bank is divided into a principal windward bank portion and an auxiliary windward bank portion, with the auxiliary portion positioned below the principal portion. This segmentation allows different sections to handle refrigerant flow at different stages, ensuring that gas-liquid two-phase refrigerant flows through the auxiliary portion first and then the principal portion, preventing premature phase change and maintaining heat exchange efficiency.
Solution Approach 2:
The patent applies different functional qualities to different parts of the tube bank. The auxiliary windward bank portion is designed to receive gas-liquid two-phase refrigerant first, while the principal windward bank portion receives refrigerant after it has mixed in the header. This local differentiation ensures optimal heat exchange performance in each section based on the refrigerant state.
2Area of stationary object
If the heat exchanger is designed with a double-column structure to improve heat exchange capacity, then the heat exchange area increases, but the refrigerant flow distribution becomes complex and performance varies depending on flow direction
Solution Approach 1:
The double-column heat exchanger is segmented into principal and auxiliary portions in each tube bank, with clear spatial arrangement (auxiliary below principal). This segmentation simplifies the flow path design by creating a logical sequence for refrigerant flow through different sections, reducing the complexity associated with double-column structures.
Solution Approach 2:
Instead of having the refrigerant flow directly from windward to leeward tube banks, the patent inverts the expected flow sequence by introducing auxiliary portions that receive refrigerant first. This inversion creates a more controlled flow distribution pattern that simplifies the overall system performance.
3Ease of operation
If the refrigerant flow path is simplified to improve ease of operation, then the flow direction is straightforward, but the heat exchange performance as both evaporator and condenser is compromised
Solution Approach 1:
The heat exchanger is designed with principal and auxiliary portions that enable it to function effectively as both an evaporator and a condenser. The same structural configuration supports dual functions by allowing refrigerant to flow through different sections in different operational modes, achieving multi-functionality without requiring separate systems.
Solution Approach 2:
The refrigerant flow path is made dynamic through the header design that allows gas-liquid two-phase refrigerant to mix and distribute to different tube bank portions based on operational conditions. This dynamic flow distribution adapts to maintain optimal performance whether the system is operating as an evaporator or condenser.
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 design ensures both evaporator and condenser performance by maintaining lower refrigerant temperatures relative to air when functioning as an evaporator and higher temperatures when functioning as a condenser, securing heat exchange efficiency.
Implementation Method 1
a heat exchanger configured to exchange heat between a refrigerant flowing through a plurality of flat tubes (31, 61) and air
Implementation Method 2
the temperature (the saturation temperature) of the refrigerant flowing through the windward tube bank (502) decreases from 2° C. to 1° C. due to a pressure loss caused when the refrigerant passes through the flat tubes (501)
Data Source
AI summary
In a heat exchanger, a principal windward heat exchange region includes a principal windward bank portion, a principal leeward heat exchange region includes a principal leeward bank portion, an auxiliary windward heat exchange region includes an auxiliary windward bank portion, and an auxiliary leeward heat exchange region includes an auxiliary leeward bank portion. Each of the principal and auxiliary bank portions is constituted of a plurality of flat tubes. In the heat exchanger functioning as an evaporator, a refrigerant flows sequentially through the auxiliary windward, auxiliary leeward, principal leeward, and principal windward bank portions. In the heat exchanger functioning as a condenser, a refrigerant flows sequentially through the principal windward, principal leeward, auxiliary leeward, and auxiliary windward bank portions. Consequently, the heat exchanger exhibits performance sufficient for functioning as both an evaporator and a condenser.