Diagnostic mode of operation to detect refrigerant leaks in a refrigeration circuit

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

HVAC systems face challenges in reliably detecting refrigerant leaks, which compromise system performance and increase costs, as existing methods lack effectiveness in accurately determining leak presence and volume within the refrigeration circuit.

Innovation Solution

A diagnostic mode is implemented in HVAC systems, where a controller activates the compressor with the expansion valve closed, measuring pressure using a high-sensitivity sensor to determine the pump-down time and compare it to an expected time, thereby determining the presence of a refrigerant leak based on pressure threshold values and historical data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing leak detection methods are used, then system operation continues, but refrigerant leak detection reliability is insufficient

Engineering Contradiction:

Improverefrigerant leak detection reliabilityVSAvoidleak presence and volume detection accuracy

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system performs a pump-down operation before normal operation to isolate refrigerant in the condenser and create a controlled diagnostic state. This preliminary action enables accurate leak detection by establishing known initial conditions (pressure, temperature, valve positions) that facilitate reliable measurement of refrigerant mass changes over time, directly addressing the insufficient detection reliability problem.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors pressure differential across the condenser and compares it against expected values based on the pump-down model. This feedback mechanism provides real-time information about refrigerant mass in the system, enabling accurate detection of leaks and their volumes, thereby resolving the information loss about leak presence and volume.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If pump-down time measurement is used, then refrigerant leak detection accuracy improves, but diagnostic operation time increases

Engineering Contradiction:

Improverefrigerant leak detection accuracyVSAvoiddiagnostic operation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs a partial pump-down operation only sufficient to isolate enough refrigerant in the condenser for accurate measurement, rather than completing a full system shutdown. This partial action achieves the necessary measurement precision for leak detection while minimizing the time penalty by avoiding excessive pump-down duration and enabling quicker return to normal operation.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The pump-down operation serves dual purposes: it prepares the system for accurate leak detection measurement while also functioning as a normal system cycle phase. This multi-functionality reduces the overall diagnostic time by combining leak detection preparation with routine system operation, eliminating the need for separate dedicated diagnostic time.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If expansion valve is closed during compression, then refrigerant is isolated in condenser for measurement, but system operational flexibility is reduced

Engineering Contradiction:

Improverefrigerant isolation for measurementVSAvoidsystem operational flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system periodically enters pump-down mode with the expansion valve closed to perform leak detection measurements, then returns to normal operation with the valve open. This periodic action allows reliable refrigerant isolation for measurement when needed while maintaining full system operational flexibility during the majority of operation time, resolving the contradiction between measurement reliability and operational adaptability.

Inventive Principle:

Principle #19Periodic action

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 approach enables HVAC systems to accurately detect refrigerant leaks by measuring the time it takes for refrigerant to be pumped into an outdoor portion of the circuit, allowing for timely intervention and reducing operational costs associated with leak-related issues.

Implementation Method 1

measuring pressure using a high-sensitivity sensor to determine the pump-down time

Methodology Applied

Scientific EffectPressure measurement:

Data Source

PatentUS10684052B2Diagnostic mode of operation to detect refrigerant leaks in a refrigeration circuit

Publication Date: 2020.06.16 TYCO FIRE & SECURITY GMBH

AI summary

The present disclosure relates to a refrigeration circuit that includes a controller communicatively coupled to a compressor, an expansion valve, and a sensor of the refrigeration circuit. The controller may activate the compressor and actuate the expansion valve such that the compressor is active while the expansion valve is closed. The controller may also measure a pressure of a refrigerant in the refrigeration circuit using the sensor while the compressor is active and the expansion valve is closed. Additionally, the controller may determine whether a refrigerant leak exists based on a maximum measurement time being reached or a time difference between a first time associated with the compressor being active while the expansion valve is closed and a second time associated with the measured pressure falling below a threshold value.