Flat-Tube Condenser Path Layout for Partial-Load Heat Exchange
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Solution Overview
Problem
In air-conditioning systems using flat tubes, the efficiency of heat exchange is decreased during partial load operations due to increased liquid-phase portions in the refrigerant paths, leading to reduced refrigerant flow rates and heat exchange capacity.
Innovation Solution
The air-conditioning apparatus incorporates a heat exchanger with flattened heat transfer tubes arranged in parallel, where two-phase paths are positioned in regions of higher air velocity and liquid-phase paths in regions of lower air velocity, along with a fan generating air flows to optimize heat exchange efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flat tubes are used in the heat exchanger to increase heat transfer efficiency and mounting density, then heat exchange capacity (AK value) is improved, but refrigerant frictional pressure loss is increased particularly when used as an evaporator
Solution Approach 1:
The heat exchanger is divided into multiple refrigerant paths arranged in parallel, with each path containing multiple flat tubes. This segmentation allows the refrigerant flow to be distributed across multiple paths, reducing the flow rate in each individual path and thereby reducing frictional pressure loss while maintaining overall heat exchange capacity through the combined effect of multiple paths.
2Loss of energy
If the number of refrigerant paths is increased to reduce refrigerant frictional pressure loss, then pressure loss is improved, but the proportion of liquid-phase portions in each path is increased during partial load operation, decreasing heat exchange efficiency
Solution Approach 1:
Different regions of the heat exchanger are designed with different tube arrangements and flow characteristics. The heat exchanger incorporates both single-phase regions and two-phase regions with optimized tube configurations in each region, allowing the system to maintain efficient heat exchange in both evaporator and condenser modes while managing liquid-phase portions effectively during partial load operations.
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 reduces the proportion of liquid-phase portions in the heat transfer tubes, enhancing the overall efficiency of heat exchange and preventing refrigerant stagnation, thereby improving the energy efficiency of the air-conditioning system.
Implementation Method 1
a fan for generating flows of air passing through the heat exchanger in a predetermined air velocity distribution
Implementation Method 2
the heat exchanger being configured to exchange heat between the air and refrigerant flowing through the plurality of heat transfer tubes
Implementation Method 3
a plurality of first refrigerant paths for allowing gas refrigerant to flow into the plurality of first refrigerant paths and allowing the gas refrigerant to flow out as two-phase refrigerant
Implementation Method 4
a plurality of second refrigerant paths for allowing the two-phase refrigerant flowing out of the plurality of first refrigerant paths to flow into the plurality of second refrigerant paths, and to flow out as subcooled liquid refrigerant
Data Source
AI summary
An air-conditioning apparatus, including: a heat source-side heat exchanger including a plurality of heat transfer tubes each having a flattened shape and being arranged in parallel, the heat source-side heat exchanger being used at least as a condenser of a refrigeration cycle; and an outdoor fan for generating flows of air passing through the heat source-side heat exchanger in a predetermined air velocity distribution. The heat source-side heat exchanger is configured to exchange heat between the air and refrigerant flowing through the heat transfer tubes and includes a plurality of refrigerant paths, each including at least one of the plurality of heat transfer tubes and a plurality of two-phase paths for allowing gas refrigerant to flow into and out as two-phase refrigerant; and a plurality of liquid-phase paths for allowing the two-phase refrigerant flowing out of the plurality of two-phase paths to flow out as subcooled liquid refrigerant.