Dual-Loop Air Conditioning for Compressor Lubricant Return
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Solution Overview
Problem
Conventional Variable Refrigerant Volume (VRV) air conditioning systems face issues with lubricant retention and return due to the same refrigerant circulation loop, leading to compressor failure from insufficient lubrication, especially with large vertical or horizontal piping designs.
Innovation Solution
The system employs a secondary circulation module independent of the first circulation module, utilizing a vapor propelling device and a main liquid storage tank to facilitate the return of lubricant, with a control device and pump system to manage fluid flow and prevent lubricant accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single refrigerant circulation loop is used in VRV systems, then system simplicity is maintained, but lubricant cannot return to the compressor causing compressor failure
Solution Approach 1:
The patent divides the refrigerant circulation system into two separate loops: a first circulation loop containing the compressor and high-pressure components, and a second circulation loop containing the heat exchangers and low-pressure components. This segmentation allows the lubricant to remain in the first loop and return to the compressor, while refrigerant flows through both loops, thus resolving the lubricant return problem without requiring a completely complex new system architecture.
Solution Approach 2:
The patent introduces a liquid storage tank as an intermediary component that stores liquid refrigerant and facilitates the separation and return paths. The tank enables the liquid refrigerant (carrying lubricant) to be separated from vapor refrigerant, allowing the lubricant-laden liquid to return to the compressor while vapor continues to the heat exchangers, thus mediating the lubricant return issue.
2Reliability
If high-efficiency oil separator is added to intercept lubricant, then lubricant retention is improved, but system complexity increases
Solution Approach 1:
The patent extracts the lubricant separation function from the main refrigerant flow by using the phase separation that naturally occurs in the liquid storage tank. Instead of adding an oil separator in the refrigerant line, the system allows liquid refrigerant (which carries most lubricant) to separate from vapor refrigerant through gravity in the tank, thus achieving lubricant retention without adding complex separation devices to the refrigerant circulation path.
3Reliability
If compressor running speed is increased under low load, then lubricant return is improved, but energy efficiency deteriorates
Solution Approach 1:
The patent enables the lubricant return process to occur naturally through the system's own operation without requiring active control adjustments. The liquid storage tank's gravity-based phase separation and the natural flow dynamics allow lubricant to return to the compressor during normal low-speed operation, eliminating the need for artificial speed increases and thus maintaining energy efficiency while ensuring reliable lubricant return.
4Adaptability or versatility
If large vertical piping distance is used, then system flexibility is improved, but lubricant accumulation in pipes occurs
Solution Approach 1:
The patent changes the dimension of lubricant return from vertical pipe flow (relying on vapor velocity) to a horizontal/gravitational flow path through the liquid storage tank. By introducing this intermediate storage dimension, the system allows lubricant to return to the compressor through the tank's bottom outlet regardless of vertical piping distance, thus enabling flexible vertical piping design without lubricant accumulation issues.
5Adaptability or versatility
If long horizontal piping is used, then system coverage is improved, but lubricant accumulation in pipes occurs
Solution Approach 1:
The liquid storage tank acts as an intermediary that breaks the continuous horizontal pipe path into segments. Lubricant carried by liquid refrigerant flows into the tank, separates from the vapor phase, and returns to the compressor through the tank's bottom outlet. This intermediary allows long horizontal piping to be used for system coverage while preventing lubricant accumulation in the pipes.
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 prevents lubricant retention in the refrigeration system, ensuring proper lubrication and reducing compressor failure risks, regardless of piping design constraints, by maintaining efficient lubricant circulation and distribution.
Implementation Method 1
The compressor is used for compressing the first working fluid from a low-pressure vapor state to a high-pressure vapor state
Implementation Method 2
in the second heat exchanger, heat exchange is performed between the second working fluid and the first working fluid
Implementation Method 3
heat exchange is performed between the second working fluid and the first working fluid
Implementation Method 4
The vapor propelling device propels the second working fluid in a saturated vapor state to flow between the heat exchange device and the second heat exchanger
Data Source
AI summary
An air conditioning system includes a first circulation module and a second circulation module. Two circulation modules are joined by a heat exchanger. The first circulation is a modular refrigeration system includes a compressor, expansion device, and heat exchangers. The second circulation module includes a main liquid refrigerant tank, a number of distributed liquid refrigerant tanks, liquid pumps and a plurality of indoor units which includes a heat exchange device and a vapor propelling device. The heat exchange device is connected to the main liquid tank. The vapor propelling device propels the working fluid in a saturated vapor state to the first heat exchanger, thus forming a working fluid loop. It can be switched between the heating and cooling modes.