HVAC Zone Airflow Monitoring for Sensor Fault and Infiltration Detection
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Solution Overview
Problem
HVAC systems face challenges in accurately monitoring air flow in zones due to sensor malfunctions and infiltration/exfiltration issues, which affect the reliability of air flow data and require frequent maintenance.
Innovation Solution
A method and control system that utilize dual flow sensors to record supply and return flows, determine infiltration and exfiltration components, and assess sensor operational states by analyzing deviations in flow ratios and temporal patterns, potentially aided by additional sensors and temperature measurements to enhance accuracy and reduce maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual flow sensors are used to monitor supply and return flows, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control system continuously monitors the relationship between supply flow and return flow measurements, using feedback loops to detect deviations that indicate sensor malfunctions or infiltration events. The system compares expected flow relationships with actual measurements and adjusts or alerts based on the deviation analysis.
Solution Approach 2:
The sensor system performs self-diagnosis by analyzing the consistency between supply and return flow measurements. The control system automatically detects sensor malfunctions through mathematical relationships (supply flow should equal return flow plus infiltration), eliminating the need for separate monitoring systems or manual diagnostics.
2Reliability
If sensor malfunction detection is implemented through flow ratio analysis, then reliability is improved, but loss of information increases due to infiltration/exfiltration interference
Solution Approach 1:
The total return flow is segmented into two distinct components: the controlled supply flow component and the uncontrolled infiltration/exfiltration component. By mathematically separating these components, the system can independently analyze sensor accuracy without the confounding influence of infiltration, allowing reliable malfunction detection even in leaky buildings.
Solution Approach 2:
The control system acts as an intermediary that processes raw sensor data through mathematical relationships to extract meaningful information. By using the known relationship between supply and return flows as an intermediary model, the system can distinguish between legitimate flow variations due to infiltration and actual sensor malfunctions.
3Measurement precision
If frequent maintenance is performed to ensure sensor accuracy, then measurement precision is maintained, but productivity decreases
Solution Approach 1:
The system performs preliminary diagnostic actions continuously in the background by monitoring flow relationships. Instead of waiting for scheduled maintenance or performance degradation to trigger service calls, the system proactively detects sensor issues through mathematical analysis of supply and return flow data, enabling maintenance to be performed only when actually needed.
Solution Approach 2:
The patent replaces physical maintenance mechanisms (manual sensor cleaning, calibration, and replacement) with an information-based diagnostic system. The control system uses mathematical analysis of flow data to detect sensor degradation, substituting automated digital monitoring for manual mechanical maintenance activities.
Data Source
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AI summary
A method of monitoring an air flow in a zone (1) of an HVAC system (10) is described, the zone (1) comprising a supply port (11) and a return port (1 2), a first flow sensor (111) configured to measure a supply flow (φ1) through the supply port (11), and a second flow sensor (121) configured to measure a return flow (φ2) through the return port (12), the method comprising: recording by a control system (20, 20') the supply flow (φ1) measured by the first flow sensor (111) and the return flow (φ2) measured by the second flow sensor (121); determining by the control system (20, 20') an infiltration and exfiltration component (φinf/exf), using the supply flow (φ1) and the return flow (φ2) recorded by the control system (20, 20'); and determining by the control system (20, 20') an operational sensor state of at least one of the first flow sensor (111) and the second flow sensor (121), using the supply flow (φ1), the return flow (φ2), and the infiltration and exfiltration component (φinf/exf).