Refrigerant metering system and method
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Solution Overview
Problem
HVAC systems face challenges in quickly restoring service when automated expansion valves (AEVs) fail, particularly due to unavailability of replacement parts, and refrigerant leaks pose health risks and require complete system evacuation for repairs.
Innovation Solution
Implementing a manual expansion valve (MEV) with condenser isolation valve (CIV) and flow isolation valve (FIV) to bypass or replace failing AEVs and isolate refrigerant coils for partial system operation and localized repairs, allowing for manual metering and isolation of refrigerant flow without complete system evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If automated expansion valves (AEV) are used for refrigerant metering, then refrigerant flow control precision is improved, but system reliability deteriorates when replacement parts are unavailable
Solution Approach 1:
The system is divided into two independent refrigerant metering pathways: an automated expansion valve pathway for normal precision control, and a manual expansion valve pathway for emergency operation. This segmentation allows the system to maintain reliability by switching to the manual pathway when the automated valve fails and parts are unavailable, while preserving measurement precision through the automated valve during normal operation.
Solution Approach 2:
The system changes the control parameter from fully automated electronic control to manual mechanical control when transitioning to the backup pathway. The manual expansion valve uses manual adjustment of a control rod position to meter refrigerant flow, changing the control mode parameter from automated to manual while maintaining the essential function of refrigerant metering.
2Object-affected harmful factors
If complete system evacuation is performed for refrigerant leak repairs, then safety is improved, but loss of time increases due to complete system shutdown
Solution Approach 1:
The isolation valves extract and isolate the leaking refrigerant coil from the rest of the system, allowing the repair to be confined to a localized section. This extraction enables the non-leaking portions of the system to remain operational and prevents the need for complete system evacuation, thereby reducing downtime while maintaining safety through localized isolation.
Solution Approach 2:
The refrigerant system is segmented into isolated sections using isolation valves at the coil connections. This segmentation allows independent repair of individual coils without affecting the entire system, enabling safety repairs while minimizing system-wide shutdown and reducing overall downtime.
3Ease of repair
If manual expansion valve with isolation valves is added to the system, then ease of repair is improved, but device complexity increases
Solution Approach 1:
The manual expansion valve and isolation valves serve multiple functions: they act as backup refrigerant metering devices when the automated valve fails, provides isolation capability for coil repairs, and enable localized refrigerant containment. This multi-functionality improves ease of repair while minimizing the addition of separate dedicated repair components, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The manual expansion valve is merged with the automated expansion valve assembly, sharing the same mounting location and refrigerant flow path. The isolation valves are integrated at the coil connection points, combining the repair isolation function with the existing refrigerant distribution infrastructure. This merging reduces the number of separate components and simplifies the overall system architecture.
Data Source
AI summary
A refrigerant metering system/method incorporating a manual expansion valve (MEV), condenser isolation valve (CIV), flow isolation valve (FIV), and evaporator isolation valve (EIV) is disclosed. The MEV is configured to replace a conventional automated expansion valve (AEV) that controls a refrigerant flow valve (RFV) that is positioned in a heating, ventilation, and air conditioning (HVAC) system between a refrigerant condenser coil (RCC) and a refrigerant evaporator coil (REC) and permits manual metering of refrigerant by the RFV from the RCC to the REC and also allows complete shutoff of refrigerant flow by the RFV from the RCC to the REC. The MEV allows rapid HVAC repair and restoration of service where a replacement AEV is not readily available. The CIV/FIV/EIV are positioned in the refrigerant flow lines to permit the AEV and/or REC to be isolated from HVAC refrigerant flow for repairs to the AEV and/or REC.