VRF Outdoor Unit Flow Distribution for Lower Refrigerant Pressure Drop
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Solution Overview
Problem
The existing two-tube type heat recovery VRF air conditioning systems face an unacceptable pressure drop when using gas-liquid two-phase refrigerants through flow-distribution capillary tubes, leading to a worse flow distributing effect and performance of the heat exchanger.
Innovation Solution
The proposed outdoor unit for a VRF air conditioning system incorporates a compressor, reversing assembly, outdoor heat exchanger with flow-distribution capillary tubes, electronic expansion valve, and a refrigerant flow path with an adjusting valve assembly, which allows gaseous and liquid refrigerants to converge into a two-phase refrigerant, reducing pressure drop and improving flow distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If gas-liquid two-phase refrigerant flows through flow-distribution capillary tubes, then flow distribution is achieved, but unacceptable pressure drop is produced
Solution Approach 1:
The refrigerant flow path is segmented into multiple parallel channels instead of a single capillary tube. The flow distributor divides the incoming refrigerant into several separate flow paths, reducing the pressure drop in each individual channel while maintaining effective flow distribution across the heat exchanger.
Solution Approach 2:
A flow distributor is introduced as an intermediary component between the refrigerant source and the heat exchanger. This mediator device actively manages the refrigerant flow, distributing it evenly across multiple capillary tubes or channels, thereby reducing the overall pressure drop while achieving proper flow distribution.
2Stress or pressure
If flute-shaped tubes are used for flow distribution instead of capillary tubes, then pressure drop is reduced, but flow distributing effect becomes worse
Solution Approach 1:
The invention merges the functions of flow distribution and pressure reduction by combining multiple capillary tubes in parallel with a flow distributor. This hybrid approach captures the advantages of both flute-shaped tubes (lower pressure drop) and capillary tubes (better flow distribution), achieving both goals simultaneously.
Solution Approach 2:
The solution transitions from a single-dimensional flow path (single capillary tube or single flute-shaped tube) to a multi-dimensional flow distribution network. By arranging multiple channels in parallel and using a flow distributor to manage the distribution, the system adds spatial dimensionality to the flow path, reducing pressure drop while maintaining distribution effectiveness.
3Productivity
If refrigerant flow rate is increased to meet cooling and heating requirements, then system performance improves, but pressure drop increases
Solution Approach 1:
The total refrigerant flow is segmented into multiple parallel channels through the flow distributor. This allows the system to handle higher total flow rates to meet cooling and heating demands while each individual channel experiences reduced pressure drop, maintaining overall system 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
This configuration ensures an excellent flow distributing effect, reduces refrigerant pressure drop, and meets both cooling and heating requirements, thereby enhancing the performance of the outdoor unit.
Implementation Method 1
flow-distribution capillary tubes
Implementation Method 2
electronic expansion valve, having a first end connected to the flow distributor
Implementation Method 3
heat exchange portion includes a plurality of heat exchange tubes
Implementation Method 4
compressor, having an exhaust port and a gas return port
Data Source
AI summary
An outdoor unit (100) for a VRF air conditioning system and a VRF air conditioning system having the same are provided. The outdoor unit (100) comprises: a compressor (10); a reversing assembly (20); an outdoor heat exchanger (30) comprising an header (31), an heat exchange portion (32), a plurality of flow-distribution capillary tubes (33) and a flow distributor (34); an electronic expansion valve (40) connected to the flow distributor (34); an refrigerant flow path (50) and an adjusting valve assembly (60), in which the refrigerant flow path (50) is connected to the electronic expansion valve (40), and the adjusting valve assembly (60) is connected to the refrigerant flow path (50) in series; a reversing valve assembly (70) configured to make the refrigerant flow out of the outdoor unit (100) via the second stop valve (120), and make the refrigerant flow into the outdoor unit (100) via the first stop valve (110).