What are the commonly used measuring media in HVAC pressure thermometers

The measuring medium of the pressure thermometer in the HVAC system directly affects the accuracy, durability and operating efficiency of the instrument. The physical properties and chemical composition of different media determine the specific requirements of the pressure thermometer when selecting and maintaining it. A deep understanding of the commonly used measuring media in HVAC pressure thermometers is of great significance for ensuring the stable operation of the system and improving the performance of the equipment.

Refrigerant (coolant)
Refrigerant is the most common measuring medium in the HVAC system and undertakes the key task of transferring cold and hot energy. The type and properties of the refrigerant directly affect the design of the pressure thermometer and its material selection.
Freon refrigerant
Traditional Freon (such as R22) was widely used in air conditioning and refrigeration equipment with good thermal physical properties. However, Freon has the problem of damaging the ozone layer and is gradually being eliminated. The pressure thermometer needs to be compatible with the chemical properties of Freon to avoid corrosion and leakage.
Hydrofluorocarbon refrigerant (HFC)
New environmentally friendly refrigerants such as R134a and R410a have low ozone depletion potential. This type of refrigerant has high requirements for equipment materials, and the pressure thermometer needs to have corrosion resistance and high pressure resistance to adapt to higher working pressures.
Natural refrigerants
Includes carbon dioxide (CO2), ammonia (NH3) and hydrocarbons (such as propane R290). Natural refrigerants have excellent environmental performance, but some media are corrosive and flammable, which puts higher requirements on the sealing, material and safety standards of pressure thermometers.
Water and water-based solutions
Water is commonly used as a heat carrier in chilled water and hot water systems in HVAC systems. The measurement of water and its mixed liquids poses special challenges to the adaptability and corrosion resistance of pressure thermometers.
Chilled water and hot water
Commonly used as circulating media in central air-conditioning systems, water pressure and temperature changes directly affect system efficiency. Pressure thermometers need to have anti-scaling and anti-corrosion functions to prevent water quality changes from causing equipment performance degradation.
Antifreeze mixtures
Common in low-temperature environments, antifreeze such as ethylene glycol or propylene glycol is added to water. Antifreeze has a certain degree of corrosiveness, and the material of the pressure thermometer needs to be chemically resistant and ensure sealing performance to prevent medium leakage.

Air and other gases
As the gas medium in the HVAC system, accurate measurement of pressure and temperature is essential for system regulation and control.
Compressed air
It is widely used in the auxiliary parts of pneumatic control and air conditioning systems. The pressure thermometer needs to adapt to the pressure fluctuations and temperature changes of the gas, and has good sensitivity and durability.
Nitrogen and inert gas
It is used for protective atmosphere or special refrigeration scenarios. The selection of pressure thermometers needs to consider the chemical stability of the gas and the working pressure range.

Oil media
Lubricating oil and hydraulic oil are indispensable in the drive and control systems of some HVAC equipment. The pressure thermometer monitors the pressure and temperature of the oil, which helps to maintain the stable operation of the equipment.
Lubricating oil
It needs to be resistant to high temperature and grease corrosion. The seal and material selection of the pressure thermometer must prevent performance degradation caused by changes in oil quality.
Hydraulic oil
The pressure fluctuation is large, which puts high requirements on the response speed and pressure resistance of the pressure thermometer.

Special coolant and heat transfer medium
Some HVAC systems use special coolants or heat transfer media to improve energy efficiency or meet special working conditions.
Organic heat carrier fluid
Used in high-temperature heat recovery systems, the medium temperature is high, and the pressure thermometer needs to have high temperature resistance and good chemical corrosion resistance.
Brine solution
Used in some ice storage systems, brine is highly corrosive, and the material and sealing design of the pressure thermometer must adapt to harsh environments.

The impact of the measuring medium on the performance of the pressure thermometer
Accuracy and response speed
The density, viscosity and thermal conductivity of different media affect the response speed and measurement accuracy of the pressure thermometer. The instrument needs to be calibrated according to the characteristics of the medium.
Corrosion resistance requirements
The chemical properties of the medium determine the choice of pressure thermometer material to avoid metal corrosion, scaling and seal failure.
Safety and environmental considerations
The safety and environmental protection of the measuring medium affect the design standards of the instrument, especially in the environment of flammable, explosive or toxic media, the pressure thermometer must meet strict safety regulations.