Capacity modulating an expansion device of a HVAC system
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Solution Overview
Problem
HVAC systems face inefficiencies at variable load conditions due to fixed orifice expansion devices, leading to ineffective refrigerant expansion and reduced thermal performance, especially when operating at partial loads, and challenges in distributing two-phase refrigerant mixtures in micro-channel heat exchangers.
Innovation Solution
A capacity modulating assembly with multiple expansion devices connected to flow control valves and outflow ports, allowing for the regulation of refrigerant flow by opening or closing orifices and valves based on load conditions, ensuring effective expansion and distribution of refrigerant in micro-channel heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed orifice expansion device is used, then the device structure is simple, but the thermal performance deteriorates at partial load conditions
Solution Approach 1:
The expansion device transitions from a fixed orifice design to a dynamic design with multiple orifices that can be selectively opened or closed based on load conditions. The controller dynamically adjusts which orifices are active, enabling the device to adapt its expansion capacity to match varying system demands and maintain optimal thermal performance across different operating conditions.
Solution Approach 2:
The single fixed orifice is segmented into multiple separate orifices (first orifice, second orifice, etc.), each controllable by its own flow control valve. This segmentation allows independent control of refrigerant flow paths, enabling the system to optimize performance at different load levels by selectively activating specific orifices based on operational requirements.
2Reliability
If multiple expansion devices are used for capacity modulation, then the thermal performance is improved, but the device complexity increases
Solution Approach 1:
Multiple expansion devices are merged into a single integrated expansion device structure that contains multiple orifices within one body. This consolidation maintains the capacity modulation functionality and thermal performance benefits of multiple devices while reducing system complexity by eliminating the need for separate expansion device housings and connections for each individual device.
Solution Approach 2:
The single expansion device is designed to perform multiple functions by incorporating multiple orifices that can be selectively activated. This multi-functional design allows the device to handle different capacity requirements (partial load and full load conditions) within a single component, replacing what would traditionally require multiple separate devices.
3Adaptability or versatility
If flow control valves are added to control refrigerant flow, then the capacity modulation capability is improved, but the device complexity increases
Solution Approach 1:
Flow control capability is applied locally at each orifice location rather than using a single centralized control mechanism. Each orifice has its own flow control valve, allowing independent local adjustment of refrigerant flow. This distributed control approach enables precise capacity modulation while maintaining relatively simple valve selection, as only two valves are needed for the two-orifice configuration.
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 solution maintains effective refrigerant expansion and thermal performance across varying loads, preventing liquid refrigerant from entering the compressor and ensuring even distribution in micro-channel heat exchangers, thus extending compressor lifespan and improving system efficiency.
Implementation Method 1
The liquid refrigerant can then be directed through the expansion device to reduce a temperature and become a liquid/vapor refrigerant mixture (two-phase refrigerant mixture)
Implementation Method 2
The two-phase refrigerant mixture can be directed into the evaporator to exchange heat with, for example, air moving across the evaporator
Implementation Method 3
air moving across the evaporator
Implementation Method 4
Outer surfaces of the micro-channel tubes and the fins may help heat exchange between the first fluid (such as refrigerant) in the micro-channel tubes and a second fluid (such as air) flowing across the outer surfaces
Data Source
AI summary
Methods, systems and apparatuses are directed to a capacity modulating assembly configured to distribute two-phase refrigerant mixture to an evaporator of a HVAC system, such as a micro-channel heat exchanger (MCHEX) evaporator. The capacity modulating assembly may include a plurality of expansion devices. During capacity modulation, at least one of the plurality of expansion devices can be closed so that a refrigerant flow rate through the remaining expansion devices can be maintained. The capacity modulating assembly can include a refrigerant outflow port, which may help direct refrigerant out of the heat exchanger. The capacity modulating assembly can be connected with the MCHEX. The plurality of expansion devices can be configured to extend inside a header of the MCHEX to help distribute refrigerant to the micro-channel tubes of the MCHEX.