Heat Exchanger with Variable Tube Diameter to Reduce Pressure Loss
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Solution Overview
Problem
Existing heat exchangers for air conditioners face challenges in optimizing heat transfer tube diameters to accommodate changing refrigerant states during heat exchange, leading to suboptimal performance and increased pressure loss.
Innovation Solution
A heat exchanger design with three rows of heat transfer tubes arranged along the air flow direction, where the inlet or outlet side tube has the smallest diameter, and the adjacent tubes have larger diameters within specific ratios, optimizing tube diameters and fin widths to enhance heat transfer efficiency while minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform diameter heat transfer tubes are used throughout the heat exchanger, then manufacturing is simplified, but heat transfer efficiency decreases due to inability to accommodate changing refrigerant states
Solution Approach 1:
The heat exchanger employs heat transfer tubes with different diameters at different locations along the air flow direction. The first row has a smaller diameter suitable for liquid refrigerant, while the second row has a larger diameter suitable for two-phase or superheated refrigerant. This local differentiation optimizes heat transfer efficiency for each refrigerant state without requiring complex manufacturing processes, as the diameter change occurs only between adjacent rows rather than along the entire tube length.
2Productivity
If smaller diameter tubes are used to increase flow velocity and heat transfer, then heat transfer efficiency improves, but pressure loss increases
Solution Approach 1:
The invention applies different tube diameters at different locations corresponding to different refrigerant states. The smaller diameter in the first row increases flow velocity and heat transfer efficiency for liquid refrigerant, while the larger diameter in the second row reduces pressure loss for two-phase or superheated refrigerant. This local optimization balances heat transfer enhancement with pressure loss reduction.
Solution Approach 2:
The invention changes the geometric parameter (tube diameter) to match the changing state of the refrigerant. By transitioning from a smaller diameter suitable for liquid refrigerant to a larger diameter suitable for two-phase or superheated refrigerant, the system optimizes both heat transfer efficiency and pressure loss characteristics for each refrigerant state.
3Loss of energy
If larger diameter tubes are used to reduce pressure loss, then pressure loss decreases, but heat transfer efficiency reduces due to lower flow velocity
Solution Approach 1:
The heat exchanger uses smaller diameter tubes in the first row where liquid refrigerant flows to maximize heat transfer efficiency through higher flow velocity, and larger diameter tubes in the second row where two-phase or superheated refrigerant flows to minimize pressure loss. This spatial differentiation resolves the contradiction between heat transfer efficiency and pressure loss.
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 improves heat exchanging performance by increasing flow velocity and heat transfer efficiency, particularly during cooling and heating operations, while maintaining low pressure loss and enhancing the coefficient of performance (COP).
Implementation Method 1
a heat exchanger in which three rows of heat transfer tubes are arranged along an air flow direction, among the three rows of heat transfer tubes, a refrigerant inlet side heat transfer tube in a case of using as an evaporator or a refrigerant outlet side heat transfer tube in a case of using as a condenser has the smallest diameter
Implementation Method 2
performing heat exchange with the air
Implementation Method 3
a refrigerant for performing heat exchange with the air is in a two-phase state of containing a large volume of a liquid refrigerant in an inlet part of the heat exchanger, and in a wet state or a superheated state in an outlet part of the heat exchanger
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A heat exchanger capable of improving the heat exchanging performance while suppressing the increase in the pressure loss is provided. A heat exchanger (1), in which a large number of plate-shaped fins (21) are attached to outer peripheries of heat transfer tubes (20) through which a refrigerant flows, the heat exchanger (1) being for performing heat exchange with the air. Three rows of heat transfer tubes (20a, 20b, 20c) are arranged along an air flow direction. Among the three rows of the heat transfer tubes (20a, 20b, 20c), an inlet side heat transfer tube in a case of using as an evaporator or an outlet side heat transfer tube in a case of using as a condenser has the smallest diameter. In a case where the most windward side heat transfer tube has the smallest diameter, a tube diameter of the most windward side heat transfer tube is D1, a tube diameter of the middle heat transfer tube is D2, and a tube diameter of the most leeward side is D3, D1 < D2 = D3, 4 mm ≤ D3 ≤ 10 mm, and 0.6 ≤ D1/D3 < 1 are satisfied. In a case where the most leeward side heat transfer tube has the smallest diameter, the tube diameter of the most leeward side heat transfer tube is D1, the tube diameter of the middle heat transfer tube is D2, and the tube diameter of the most windward side is D3, D1 < D2 = D3, 4 mm ≤ D3 ≤ 10 mm, and 0.6 ≤ D1/D3 < 1 are satisfied.