Outdoor Heat Exchanger Capillary Layout for Balanced Condensation

Solution Overview

Problem

In heat exchangers for outdoor units, there is a challenge with liquid refrigerant accumulation in the lowermost stage and excessive subcooling when functioning as a condenser, and refrigerant maldistribution between stages due to liquid head and capillary tube length adjustments.

Innovation Solution

The height from the lower end of the refrigerant flow path of the lowermost stage to the upper end of the refrigerant flow distributor is reduced to 1/4 times the height to the uppermost stage, and the lowermost stage capillary tube length is set to at least 2/5 times the longest capillary tube, with optional U-shaped or coil configurations to enhance refrigerant flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the heat exchanger functions as a condenser with plural refrigerant flow paths arranged in multiple stages, then condensation capacity is improved, but liquid refrigerant accumulates in the lowermost stage and subcooling degree becomes excessively large

Engineering Contradiction:

Improvecondensation capacityVSAvoidrefrigerant flow balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by making the capillary tube of the lowermost stage longer than those of upper stages. This creates a stage-specific characteristic where the lowermost stage has increased flow resistance, preventing liquid refrigerant accumulation and excessive subcooling while maintaining overall condensation capacity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of capillary tube length specifically for the lowermost stage, making it longer than capillary tubes of upper stages. This parameter modification adjusts the flow characteristics to prevent liquid accumulation while preserving condensation efficiency.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If capillary tube length is adjusted to prevent refrigerant maldistribution, then refrigerant flow balance is improved, but liquid refrigerant accumulation and excessive subcooling are exacerbated

Engineering Contradiction:

Improverefrigerant flow balanceVSAvoidliquid refrigerant accumulation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by making the capillary tube of the lowermost stage longer than those of upper stages. This creates a stage-specific characteristic where the lowermost stage has increased flow resistance, preventing liquid refrigerant accumulation and excessive subcooling while maintaining overall condensation capacity.

Inventive Principle:

Principle #3Local quality

3Productivity

If refrigerant flow paths are arranged in multiple stages vertically, then heat exchange efficiency is improved, but liquid head causes difficulty in refrigerant flow to upper stages

Engineering Contradiction:

Improveheat exchange efficiencyVSAvoidrefrigerant flow distribution

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The patent applies local quality by making the capillary tube of the lowermost stage longer than those of upper stages. This creates a stage-specific characteristic where the lowermost stage has increased flow resistance, preventing liquid refrigerant accumulation and excessive subcooling while maintaining overall condensation capacity.

Inventive Principle:

Principle #3Local quality

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 prevents liquid refrigerant accumulation and excessive subcooling in the lowermost stage during condensation and ensures balanced refrigerant distribution across stages, improving operational efficiency.

Implementation Method 1

one end side of these plural refrigerant flow paths being connected to a refrigerant flow distributor via capillary tubes

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

distribution of refrigerant to each of the refrigerant flow paths

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 3

heat exchanger for an outdoor unit that is installed inside the blower chamber of the outdoor unit

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 4

heat exchanger

Methodology Applied

Scientific EffectConduction (thermal): Conduction (thermal)

Data Source

PatentEP1953480B1Heat exchanger for outdoor unit

Publication Date: 2012.06.13 DAIKIN INDUSTRIES LTD

Figure 1
Figure 2
Figure 3

AI summary

To prevent, in a heat exchanger for an outdoor unit that has a structure where mutually independent plural refrigerant flow paths are arranged in multiple stages in a vertical direction and where one end side of these plural refrigerant flow paths is connected to a refrigerant flow distributor via capillary tubes, a situation where liquid refrigerant accumulates in the refrigerant flow path of the lowermost stage and the subcooling degree ends up becoming excessively large when the heat exchanger is caused to function as a condenser of refrigerant. An outdoor heat exchanger (26) includes plural refrigerant flow paths (26a to 26f) that are mutually independent and arranged in multiple stages in a vertical direction, capillary tubes (64a to 64f) that are respectively connected to one end side of the plural refrigerant flow paths (26a to 26f), and a refrigerant flow distributor (65) with which the capillary tubes (64a to 64f) merge. The lowermost stage capillary tube (64f) that is connected to the refrigerant flow path (26f) of the lowermost stage of the plural refrigerant flow paths (26a to 26f) includes a coil portion (70) having a coiled shape.