Non-invasive temperature-based diagnostic method
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Solution Overview
Problem
Existing methods for diagnosing refrigerant charge and airflow in HVAC systems are invasive, leading to refrigerant venting, introduction of non-condensables, and contamination, which contribute to global warming and reduce diagnostic accuracy.
Innovation Solution
A non-invasive temperature-based diagnostic method that uses measurements of return-air drybulb temperature, return-air wetbulb temperature, supply-air drybulb temperature, outdoor air temperature, suction temperature, and liquid temperature to diagnose refrigerant charge and airflow faults without connecting refrigerant pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If refrigerant pressure gauges are connected to Schrader valves for diagnosing refrigerant charge and airflow, then diagnostic information can be obtained, but refrigerant is vented to the atmosphere causing global warming
Solution Approach 1:
The patent replaces the mechanical connection of pressure gauges to the refrigerant system with a non-invasive thermal imaging system that detects temperature differentials across the evaporator coil. This substitution eliminates the need to connect to the refrigerant circuit, thereby preventing refrigerant venting while still providing diagnostic information about refrigerant charge and airflow conditions
Solution Approach 2:
The patent uses temperature differentials as an intermediary parameter to indirectly assess refrigerant charge and airflow conditions. Instead of directly measuring refrigerant pressure, the system measures temperature differences across the evaporator coil, which serve as a mediator that correlates to the underlying system conditions without requiring direct contact with the refrigerant
2Measurement precision
If refrigerant pressure gauges are connected to Schrader valves, then refrigerant charge can be diagnosed, but non-condensables (air and water vapor) are introduced into the system
Solution Approach 1:
The patent replaces the mechanical gauge connection process with an optical thermal imaging system that measures temperature fields. This substitution eliminates the opening and closing of Schrader valves, preventing the introduction of non-condensable gases and moisture into the sealed refrigerant system while still enabling accurate refrigerant charge diagnosis
3Reliability
If refrigerant pressure gauges are connected to Schrader valves, then system faults can be detected, but the refrigerant system is contaminated with incompatible materials
Solution Approach 1:
The patent substitutes the invasive mechanical gauge connection with a non-contact thermal imaging system. This replacement maintains comprehensive fault detection capability by monitoring temperature differentials that indicate various system conditions, while completely eliminating the risk of contaminating the refrigerant system with oils, incompatible refrigerants, or other materials that may be introduced during gauge connection and disconnection
4Ease of operation
If temperature split method is used to evaluate airflow, then airflow indication can be obtained, but information about AC system faults such as refrigerant undercharge, overcharge, and heat exchanger faults is not provided
Solution Approach 1:
The patent enhances the basic temperature split method by integrating multiple diagnostic functions into a single thermal imaging system. The system not only evaluates airflow through temperature differential measurement but also diagnoses refrigerant charge conditions, heat exchanger faults, and other system issues by analyzing the same thermal data through multiple diagnostic algorithms, thereby providing comprehensive fault information without additional invasive measurements
Data Source
AI summary
A Non-invasive Temperature-based Diagnostic (NTD) method for evaluating Air Conditioning (AC) system faults based on Return-air Drybulb Temperature (RDT), Return-air Wetbulb Temperature (RWT), Supply-air Drybulb Temperature (SDT), Suction Temperature (ST), Liquid Temperature (LT), Outdoor-Air Temperature (OAT), Delta Temperature Split (DTS) equal to Actual Temperature Split (ATS) minus Required Temperature Split (RTS), and Liquid Over Ambient Temperature (LOA) equal to LT minus OAT. The method diagnoses proper Refrigerant Charge and Airflow (RCA) based on DTS and LOA or at least one AC system fault based on DTS, ST, and LOA. The processing order comprises at least one diagnostic selected from the group consisting of: low cooling capacity, condenser heat exchanger, refrigerant restriction, evaporator heat exchanger, proper RCA, refrigerant undercharge, overcharge, non-condensables, and low airflow. DTS is used to determine an undercharge amount. The ratio of ATS measured before and after correcting AC system faults is used to calculate an energy-efficiency improvement.