Parallel Capillary Expansion Tubes for Uniform Refrigerant Flow
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Solution Overview
Problem
Existing cooling systems face inefficiencies in refrigerant mass flow distribution across multiple parallel heat exchanger coils, leading to non-uniform energy exchange and reduced performance, particularly when compressor operating capacity varies.
Innovation Solution
Incorporating an oversized expansion valve and multiple capillary expansion tubes, where the valve position is adjusted to maintain choked flow and control refrigerant properties, ensuring uniform mass flow distribution across capillary tubes and evaporator coils, and using a subcooling heat exchange assembly to manage refrigerant subcooling and flow quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single expansion device is used to supply refrigerant to multiple parallel heat exchanger coils, then the device complexity is reduced, but the refrigerant mass flow distribution becomes non-uniform leading to reduced heat exchange efficiency
Solution Approach 1:
The single expansion device is segmented into multiple capillary expansion tubes (first capillary expansion tube, second capillary expansion tube, etc.), each supplying refrigerant to a corresponding heat exchanger coil. This segmentation enables independent refrigerant flow control to each coil, achieving uniform mass flow distribution and optimizing heat exchange efficiency while maintaining relatively simple system architecture.
2Adaptability or versatility
If the expansion valve opening is increased to accommodate higher compressor capacity, then the system can handle higher operating conditions, but the refrigerant mass flow distribution becomes non-uniform across parallel coils
Solution Approach 1:
The expansion device is divided into multiple independent capillary tubes, each with precisely controlled dimensions (length, inner diameter, wall thickness). This segmentation allows the system to maintain uniform refrigerant distribution across all coils even when the expansion valve is opened wide for high compressor capacity operation, as each capillary tube independently regulates flow to its associated coil.
3Manufacturing precision
If capillary expansion tubes are used to ensure uniform refrigerant distribution, then the refrigerant mass flow distribution improves, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The capillary expansion tubes utilize their own physical dimensions and flow characteristics to automatically regulate refrigerant distribution. By designing the tubes with specific lengths, inner diameters, and wall thicknesses, the system achieves uniform refrigerant mass flow distribution across all coils without requiring complex external control mechanisms, thereby balancing manufacturing precision requirements with acceptable device 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 approach enhances energy exchange efficiency, maintains uniform refrigerant mass flow distribution across evaporator coils, protects the compressor from liquid refrigerant, and improves system reliability and performance across varying operating conditions.
Implementation Method 1
a plurality of capillary expansion tubes fluidly coupled in parallel to an output of the first fluid line and that to exert a second pressure drop on the refrigerant circulated through the cooling system
Implementation Method 2
an expansion valve disposed along the second fluid line, in which the expansion valve exerts a first pressure drop on the second portion of the refrigerant that facilitates extracting heat from the first portion of the refrigerant flowing through the first fluid line using the second portion of the refrigerant flowing through the second fluid line
Implementation Method 3
in an evaporator heat exchanger, phase change of the refrigerant from a liquid phase to a gas phase may extract heat from air flowing around the evaporator coil, thereby cooling the air
Implementation Method 4
in an evaporator heat exchanger, the refrigerant may enter an evaporator coil as a liquid, evaporate (e.g., vaporize), and exit the evaporator coil as a vapor
Implementation Method 5
in a condenser heat exchanger, the refrigerant may enter a condenser coil as a vapor, condense, and exit the condenser coil as a liquid
Implementation Method 6
In operation, a heat exchanger may facilitate energy (e.g., heat) exchange between a circulated refrigerant (e.g., coolant) and a surrounding fluid (e.g., water or air)
Data Source
AI summary
A cooling system includes a subcooling heat exchange assembly, which controls magnitude of subcooling of refrigerant circulated through the cooling system. The subcooling heat exchange assembly includes a first fluid line fluidly coupled to an output of a condenser to enable a first portion of the refrigerant output from the condenser to flow through the first fluid line; a second fluid line fluidly coupled to the output of the condenser to enable a second portion of the refrigerant output from the condenser to flow through the second fluid line; and an expansion valve disposed along the second fluid line, in which the expansion valve exerts a first pressure drop on the second portion of the refrigerant that facilitates extracting heat from the first portion of the refrigerant flowing through the first fluid line using the second portion of the refrigerant flowing through the second fluid line when valve position of the expansion valve is greater than a threshold position. Additionally the cooling system includes a plurality of capillary expansion tubes fluidly coupled in parallel to an output of the first fluid line and that to exert a second pressure drop on the refrigerant circulated through the cooling system.