Heat Exchanger Trough and Guide Layout for Low Refrigerant Charge
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Solution Overview
Problem
Conventional vapor compression refrigeration systems face challenges in reducing refrigerant charge, managing lubrication oil accumulation, and guiding scattered refrigerant back to heat transfer tubes, leading to inefficient heat transfer and performance degradation.
Innovation Solution
A heat exchanger design incorporating a shell, distributing part, tube bundle, trough part, and guide part, where the trough part accumulates refrigerant and guides scattered refrigerant back to heat transfer tubes, reducing refrigerant charge while ensuring good heat transfer performance and managing lubrication oil accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flooded evaporator is used to ensure good 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. The upper section operates as a falling film evaporator with refrigerant distributed onto the tubes, while the lower section operates as a flooded evaporator with tubes immersed in liquid refrigerant. This segmentation allows the system to achieve good heat transfer performance while reducing overall refrigerant charge compared to a fully flooded design.
Solution Approach 2:
Different regions of the evaporator are assigned different operational characteristics. The upper portion uses falling film heat transfer where refrigerant flows over the tube surfaces, requiring minimal refrigerant charge. The lower portion uses flooded heat transfer where tubes are immersed in liquid refrigerant for efficient heat transfer. This local differentiation optimizes both heat transfer performance and refrigerant charge reduction.
2Reliability
If liquid refrigerant is recirculated from the lower portion to maintain falling film operation, then heat transfer performance is maintained, but lubrication oil accumulates in the evaporator
Solution Approach 1:
The harmful element (lubrication oil) is extracted from the recirculating refrigerant stream. A oil separation device is installed in the refrigerant recirculation line to remove accumulated lubrication oil from the liquid refrigerant before it is pumped back to the distributor. This prevents oil buildup in the evaporator while maintaining continuous recirculation for heat transfer performance.
Solution Approach 2:
An oil separation device serves as an intermediary component between the refrigerant collection and distribution systems. It intercepts the lubrication oil from the recirculating refrigerant flow and separates it before the refrigerant returns to the evaporator, preventing the harmful effect of oil accumulation while maintaining the beneficial recirculation process.
3Ease of operation
If refrigerant is scattered from heat transfer tubes, then refrigerant distribution becomes inefficient, but heat transfer performance degrades
Solution Approach 1:
A refrigerant recirculation system provides feedback to correct scattered refrigerant. Liquid refrigerant that falls to the lower portion of the evaporator is collected and pumped back to the distributor, which redistributes it onto the heat transfer tubes. This feedback loop ensures that scattered refrigerant is recovered and reused, maintaining efficient refrigerant distribution and heat transfer performance.
Solution Approach 2:
The recirculation system ensures continuous useful action by constantly returning liquid refrigerant to the heat transfer tubes. Instead of allowing scattered refrigerant to be lost or to form inefficient pools, the system continuously pumps refrigerant from the lower collection region back to the distributor, maintaining continuous film formation on the tubes and sustaining optimal heat transfer performance.
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 charge, prevents dry patches, and improves heat transfer efficiency by guiding scattered refrigerant and managing lubrication oil, enhancing overall system performance.
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
the guide part includes at least one lateral side portion extending upwardly and laterally outwardly from the tube bundle at a vertical position at an upper end of the trough part
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
Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film
Implementation Method 5
the evaporator, which is a heat exchanger that allows the refrigerant to evaporate from liquid to vapor while absorbing heat from liquid to be cooled
Implementation Method 6
the refrigerant to evaporate from liquid to vapor while absorbing heat
Data Source
AI summary
A heat exchanger for a vapor compression system includes a shell with a longitudinal center axis extending generally parallel to a horizontal plane, a distributing part, a tube bundle, a trough part and a guide part. The distributing part distributes a refrigerant. The tube bundle includes a plurality of heat transfer tubes disposed below the distributing part so that the refrigerant discharged from the distributing part is supplied onto the tube bundle. The heat transfer tubes extend generally parallel to the longitudinal center axis of the shell. The trough part extends generally parallel to the longitudinal center axis of the shell under at least one of the heat transfer tubes to accumulate the refrigerant in the trough part. The guide part includes at least one lateral side portion extending upwardly and laterally outwardly from the tube bundle at a vertical position at an upper end of the trough part.