Heating Circuit Antifreeze Detection via Viscosity-Corrected Flow
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Solution Overview
Problem
Existing hydraulic circuits in heating systems, such as solar thermal and heat pump systems, face challenges in ensuring sufficient antifreeze content in the heat transfer medium, leading to potential freezing issues due to incomplete or insufficient antifreeze addition during installation and maintenance.
Innovation Solution
A method that calculates the antifreeze content by measuring and correcting the volume flow of the circulating pump using a combination of pump model data, actual volume flow measurements, and temperature data, leveraging the viscosity differences between antifreeze and water to determine the antifreeze proportion in the heat transfer medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mixture of water and antifreeze is used as heat transfer medium, then frost protection is achieved, but the viscosity of the medium changes making flow rate measurement inaccurate
Solution Approach 1:
The system continuously monitors the difference between calculated volume flow rate (from pump characteristics) and measured volume flow rate (from flow sensor). This feedback loop detects viscosity changes caused by antifreeze concentration variations, enabling the system to identify when antifreeze content deviates from expected levels and alert operators to potential filling errors.
Solution Approach 2:
The invention replaces direct viscosity measurement with an indirect measurement approach. Instead of measuring viscosity directly, the system uses electrical parameters (pump current, power consumption) and hydraulic parameters (pressure differential) combined with pump characteristic curves to calculate volume flow rate, then compares it with actual flow sensor measurements to infer viscosity and antifreeze concentration.
2Ease of manufacture
If antifreeze is added in insufficient quantity during installation and maintenance, then system filling is completed, but sufficient frost protection is not achieved
Solution Approach 1:
The system performs preliminary verification of antifreeze concentration immediately after system filling or maintenance operations. By comparing calculated versus measured volume flow rates right after the hydraulic circuit is filled, the system can detect insufficient antifreeze addition before the system goes into operation, preventing potential freezing damage.
Solution Approach 2:
The heating system automatically monitors its own heat transfer medium properties without requiring external testing equipment or manual intervention. The control unit uses existing sensors (flow sensor, temperature sensors, pressure sensors) and pump parameter data to self-diagnose whether the antifreeze concentration is adequate, enabling the system to verify its own proper filling status.
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 method provides reliable antifreeze content measurement, especially at low temperatures, ensuring frost protection and preventing system failures by accurately determining the antifreeze levels in real-time, thus ensuring the system operates effectively even at sub-freezing conditions.
Implementation Method 1
The heat transfer medium is circulated within the circuit by a circulation pump
Implementation Method 2
the actual volumetric flow rate V̇ist is measured using a suitable measuring device
Implementation Method 3
the temperature of the heat transfer medium pumped by the circulation pump and measured by the volume flow sensor is measured by means of a temperature sensor
Implementation Method 4
The invention takes advantage of the fact that the antifreeze content influences the viscosity of the heat transfer medium. This viscosity is determined indirectly by comparing a volume flow rate V̇p calculated from the characteristics of the circulation pump with a volume flow rate V̇ist measured by a volume flow sensor and correcting for the influence of temperature on viscosity
Data Source
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AI summary
The invention relates to a method for determining the antifreeze content of a water-based heat transfer medium in a hydraulic circuit 3 of a heating system circulated by a circulating pump 4 . The method according to the invention makes use of the fact that the measured values of a volume flow sensor 9 and the calculated values for the volume flow of the circulating pump 4 change with increasing viscosity.