Trough-Based Oil Separation for Hybrid Falling Film Heat Exchangers
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Solution Overview
Problem
Conventional vapor compression refrigeration systems, particularly hybrid falling film evaporators, require a large refrigerant charge and suffer from performance degradation due to lubrication oil accumulation, which affects heat transfer efficiency.
Innovation Solution
A heat exchanger design incorporating a trough part to accumulate refrigerant and separate lubrication oil, reducing the overall refrigerant charge while maintaining efficient heat transfer performance by redistributing refrigerant and discharging excess oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a flooded evaporator design is used to ensure high heat transfer performance, then heat transfer efficiency is improved, but refrigerant charge increases significantly
Solution Approach 1:
The evaporator is divided into multiple sections with different heat transfer modes. Some heat transfer tubes are arranged in a falling film section where refrigerant flows as a film, while other tubes are in a flooded section. This segmentation allows the system to achieve high heat transfer efficiency in the flooded section while reducing overall refrigerant charge through the falling film section.
Solution Approach 2:
Different regions of the evaporator are assigned different operational characteristics. The falling film section uses a different refrigerant distribution mechanism and heat transfer mode compared to the flooded section. This local differentiation optimizes the balance between heat transfer performance and refrigerant charge by applying the most efficient mode to each specific region.
2Quantity of substance
If hybrid falling film evaporator is used to reduce refrigerant charge, then refrigerant charge is reduced, but lubrication oil accumulation degrades performance
Solution Approach 1:
The harmful lubrication oil is extracted and removed from the refrigerant circulation system through a dedicated oil separation and discharge mechanism. The oil separator collects oil that accumulates in the evaporator, and the discharge device periodically removes it, preventing oil accumulation from degrading heat transfer performance while maintaining the reduced refrigerant charge benefits.
Solution Approach 2:
The system incorporates a feedback mechanism where oil accumulation is detected and triggers the oil discharge operation. The oil separator monitors oil levels and activates the discharge device when oil accumulation reaches a threshold, ensuring that heat transfer performance is maintained by continuously managing oil removal in response to actual operating conditions.
3Productivity
If refrigerant is recirculated in hybrid falling film evaporator, then heat transfer performance is maintained, but lubrication oil is also recirculated causing performance degradation
Solution Approach 1:
The oil separator extracts lubrication oil from the recirculating refrigerant stream before it re-enters the heat transfer tubes. This separation process removes the harmful oil component while allowing the refrigerant to continue circulating, maintaining heat transfer performance without the detrimental effects of oil accumulation.
Solution Approach 2:
The oil separator acts as an intermediary device between the refrigerant circulation system and the heat transfer tubes. It intercepts the recirculating refrigerant, removes oil through separation mechanisms, and returns only clean refrigerant to the heat transfer section, thereby protecting the heat transfer performance from oil contamination.
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
The design effectively reduces refrigerant consumption and prevents performance degradation by ensuring consistent refrigerant distribution and removing lubrication oil, thereby enhancing heat transfer efficiency in vapor compression systems.
Implementation Method 1
The liquid refrigerant that does not evaporate falls vertically from the heat transfer tube at an upper position toward the heat transfer tube at a lower position by force of gravity
Implementation Method 2
liquid refrigerant is deposited onto exterior surfaces of the heat transfer tubes from above so that a layer or a thin film of the liquid refrigerant is formed along the exterior surfaces of the heat transfer tubes
Implementation Method 3
Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film to the vapor-liquid interface
Implementation Method 4
part of the liquid refrigerant evaporates, and thus, heat is removed from the water flowing inside of the heat transfer tubes
Implementation Method 5
Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film
Data Source
AI summary
A heat exchanger is adapted to be used in a vapor compression system. The tube bundle includes a plurality of heat transfer tubes in a falling film region and in an accumulating region. The heat transfer tubes in the falling film region are arranged in a plurality of columns extending parallel to each other. The heat transfer tubes in the accumulating region are arranged in a plurality of rows extending parallel to each other. A trough part includes a plurality of trough sections disposed respectively below the rows of the heat transfer tubes in the accumulating region to accumulate the refrigerant therein. A ratio between a number of rows of the heat transfer tubes in the accumulating region and a number of the heat transfer tubes in each of the columns in the falling film region is about 1:9 to about 2:8.