Pump-Down Refrigerant Storage Using a Large-Diameter Tube
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Solution Overview
Problem
In refrigeration apparatuses, when the capacity of the usage-side heat exchanger is greater than the capacity of the heat source-side heat exchanger, there is a risk that refrigerant cannot be accommodated in the heat source-side unit during a pump down operation, leading to insufficient refrigerant collection.
Innovation Solution
Incorporating a large-diameter tube with a capacity greater than the difference between the usage-side and heat source-side heat exchangers, along with a refrigerant container and heat source-side heat exchanger, to accumulate refrigerant during the pump down operation, ensuring sufficient collection in the heat source-side unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small high-performance heat exchanger is used as a heat source-side heat exchanger, then heat exchange performance is improved, but the capacity of the heat source-side heat exchanger becomes less than the capacity of the usage-side heat exchanger, causing refrigerant accommodation failure during pump down operation
Solution Approach 1:
The refrigerant accommodation function is segmented between multiple components: the heat source-side heat exchanger (outdoor heat exchanger), the accumulator, and the newly added large-diameter tube. This segmentation allows each component to contribute to the total refrigerant storage capacity, ensuring sufficient accommodation space during pump down operation while maintaining high heat exchange performance of the compact heat exchanger.
Solution Approach 2:
The large-diameter tube acts as an intermediary component between the heat source-side heat exchanger and the liquid refrigerant-side shutoff valve. It provides additional refrigerant storage capacity and serves as a buffer to ensure smooth refrigerant flow and accommodation during pump down operation, bridging the capacity gap created by using a compact heat exchanger.
2Volume of moving object
If the capacity of the heat source-side heat exchanger is reduced to match smaller installations, then the apparatus size is reduced, but the total refrigerant circuit capacity becomes insufficient for effective pump down operation
Solution Approach 1:
The refrigerant storage capacities of multiple components are merged to achieve the total required circuit capacity. The compact heat source-side heat exchanger, accumulator, and large-diameter tube are combined in series, where their individual capacities sum up to provide sufficient total refrigerant accommodation space, enabling effective pump down operation despite the reduced size of the heat exchanger itself.
Solution Approach 2:
Instead of increasing the capacity of the heat source-side heat exchanger in the traditional horizontal dimension, the solution adds volume in another dimension by introducing the large-diameter tube. This vertical/dimensional addition provides the necessary refrigerant storage capacity without increasing the footprint or complexity of the heat exchanger itself.
3Reliability
If a large-diameter tube is added to increase refrigerant capacity, then refrigerant accommodation is improved, but device complexity increases
Solution Approach 1:
The large-diameter tube serves multiple functions: it acts as a refrigerant storage reservoir during pump down operation, provides a flow buffer to smooth refrigerant movement, and maintains system pressure stability. By combining multiple functions in a single simple component, the overall device complexity is minimized while achieving reliable refrigerant collection.
Solution Approach 2:
The large-diameter tube is implemented as a simple, inexpensive cylindrical component without complex internal structures or additional functions. This straightforward design prioritizes cost-effectiveness and ease of installation over high-tech complexity, providing the necessary refrigerant capacity through basic geometric volume rather than sophisticated engineering.
Data Source
AI summary
An air-conditioning apparatus includes an outdoor unit, an indoor unit having an indoor heat exchanger, and a controller for executing a pump down operation. The outdoor unit has an accumulator of a capacity (Va), a compressor, an outdoor heat exchanger, an expansion valve, a large-diameter tube, which are joined by refrigerant pipes. The capacity (Vhi) of the indoor heat exchanger is greater than the capacity (Vho) of the outdoor heat exchanger. The large-diameter tube, which is larger in diameter than the refrigerant pipes, is provided so that the capacity (Vt) of the large-diameter tube satisfies the formula: capacity (Vt)>capacity (Vhi)−capacity (Vho)−capacity (Va).