Trusted flow measurement is essential in maximizing HVAC system efficiency and ensuring occupant comfort. Glycol prevents heat transfer fluids from freezing in heating, cooling, and air conditioning systems. In systems where pipework is exposed to the exterior environment – rooftop units, free cooling, cooling towers – and green energy applications, such as solar thermal collectors. Glycol is also used in district cooling systems – such as high rise properties where low-temperature energy networks serve several customers.
The addition of glycol in any system can result in thermal energy measurement errors when using a meter intended for water. Heat transfer fluids are mixtures of water and glycols. Typically, additives such as corrosion inhibitors or oxygen scavengers and anti-fouling components are also part of the mix to protect the piping. Glycol is necessary for applications where water could freeze and damage the pipe system.
But glycols also have disadvantages compared to water:
- more expensive
- lower heat capacity – so you need more flow and therefore more pump power
- higher viscosity – so you need even more pump power in total up to 4x the pump power compared to water
Changes in the heat transfer fluid composition will impact the physical parameters involved in the measurement of volumetric flow and thermal energy - density, heat capacity, and viscosity. When using a thermal energy meter intended for water is employed with a glycol-water mixture, changes in these fluid properties can result in a cumulative heat measurement error of up to 40 percent. If the correct fluid parameters are known, it is possible to compensate. Thermal energy, Q, is defined.
By using a Belimo ultrasonic transit-time technology flow sensor, you can achieve accurate energy measurement with automatic glycol compensation to ensure correct consumer billing and optimal system performance. The inline flow sensor also offers continuous glycol concentration monitoring to ensure freeze protection.
It is very robust, insensitive to magnetite problems, and has no moving parts that could wear out or have dirt problems. It is suitable for use with glycols of a wide concentration range.
Join the ASHRAE webinar, September 10th at 2:00 PM (Eastern Time). During this webinar, you will learn
- Fundamentals of heat transfer
- How glycol is used in HVAC systems
- Measuring heat transfer (with water)
- The influence of glycol on the measurement of heat
- How important it is to monitor the glycol concentration constantly
- Alternative ways to measure heat transfer