Cooling system having a condenser with a micro-channel cooling coil and sub-cooler having a fin-and-tube heat cooling coil
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Solution Overview
Problem
Cooling systems with micro-channel condensers are sensitive to refrigerant charge differences, leading to issues with sub-cooling and efficiency when the evaporator volume is larger than the condenser volume, causing refrigerant migration and reduced capacity and efficiency across varying ambient temperatures.
Innovation Solution
Incorporating a sub-cooler with a fin-and-tube cooling coil in series between the condenser and expansion device, where the fin-and-tube coil has a hydraulic volume equivalent to the micro-channel coil but a smaller face area, allowing the sub-cooler to hold most of the liquid refrigerant and reducing the condenser's sensitivity to charge variations, thereby maintaining system functionality and efficiency across extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If a micro-channel condenser is used, then the condenser volume is reduced, but the system becomes sensitive to refrigerant charge differences causing sub-cooling issues
Solution Approach 1:
The condenser is segmented into two distinct sections: a micro-channel condenser section for heat rejection and a sub-cooler section with larger internal volume for refrigerant charge storage. This segmentation allows each section to perform its specialized function optimally while together they resolve the charge sensitivity problem.
Solution Approach 2:
The sub-cooler is integrated within or adjacent to the micro-channel condenser structure, with the two components working in series. The sub-cooler acts as a nested volume within the overall condenser assembly, allowing the compact micro-channel design to maintain its space efficiency while incorporating the necessary charge storage capacity.
2Productivity
If the evaporator volume is larger than the condenser volume, then cooling capacity is improved, but refrigerant migration occurs reducing system efficiency
Solution Approach 1:
The sub-cooler is positioned to receive and hold liquid refrigerant before it enters the expansion device, performing preliminary action to prevent refrigerant migration. By maintaining proper sub-cooling and charge distribution in advance, the system prevents energy losses from migration even when evaporator volume exceeds condenser volume.
3Volume of stationary object
If the condenser volume is reduced for compactness, then system footprint is minimized, but the system cannot maintain functionality across extreme temperature variations
Solution Approach 1:
Different sections of the condenser assembly have different volumetric qualities: the micro-channel section provides compact heat exchange with minimal volume, while the sub-cooler section provides larger internal volume for charge management. This local differentiation of qualities allows the overall system to be compact yet adaptable to extreme temperature variations.
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 enables the cooling system to operate effectively throughout a wide range of temperatures with increased efficiency and capacity, minimizing the impact on input power and maintaining sub-cooling, thus enhancing the seasonal coefficient of performance (SCOP).
Implementation Method 1
condenser with a micro-channel cooling coil
Implementation Method 2
condenser has a micro-channel cooling coil
Implementation Method 3
sub-cooler having a fin-and-tube heat cooling coil
Implementation Method 4
maintaining sub-cooling
Implementation Method 5
evaporator having a fin-tube cooling coil
Implementation Method 6
evaporator
Data Source
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Figure 3
AI summary
In an aspect, a cooling system has a cooling circuit that includes an evaporator, a condenser, a compressor, a sub-cooler and an expansion device configured in a direct expansion cooling circuit with the sub-cooler coupled in series between an outlet of the condenser and an inlet of the expansion device. The condenser has a micro-channel cooling coil and the sub-cooler has a fin-and-tube cooling coil. In an aspect, the fin-and-tube cooling coil of the sub-cooler has a total hydraulic volume equivalent to the total hydraulic volume of the micro-channel cooling coil of the condenser but the fin-and-tube cooling coil of the sub-cooler has a face area more than two times smaller than a face area of the micro-channel cooling coil of the condenser.