Thermal Flow Meters: History And Evolution

Thermal Flow Meter Liquid

Source – Unsplash

Thermal flowmeters were introduced in the market after Coriolis meters came in the mid-1970s. Although the global market for Coriolis meters now reaches $1,932.5 million, the demand for thermal meters is about $150 million. 

Despite the difference in its market size and demand, the thermal flow meter is still one of the excellent technological innovations. In this post, we’ll walk you through a brief history and evolution of thermal flow meters. Read on to know more!

How It Started

The thermal meter’s history is undoubtedly enthralling. These meters were first made in the Western United States as a result of the independent development of three companies. One of the companies was Fluid Components International.

The company began by designing thermal flow switches for oil patches. These flow switches perceived the movement or flow of oil in the pipes. Even so, the switches did not turn into actual flow meters until 1981. 

Moreover, the collaboration of Jerry Jurz, Ph.D., and John Olin, Ph.D., was the second phase of the flowmeter market’s development. Both of them worked for Thermo Systems Incorporated, located in Minnesota. 

In this company, they manufactured hot-film and hot-wire anemometers for applications in air flows, turbulence, and gas dynamics. These devices were founded on thermal dispersion technology and involved sensors, which consisted of a thin platinum film or heated tungsten wires. 

Although Kurz and Olin were researching anemometers, they were more inclined to make measurement devices for many different industrial applications. Because of this, they established their own organization in 1973, incorporating Sierra Instruments.

In the year 1977, Sierra Instruments was producing both thermal flow meters and air sampling products. Also, in the same year, Kurz formed Kurz Instruments to become independent. In the early 80s, Fluid Components, Kurz, and Sierra were the only organizations to manufacture thermal flow meters. But over the years, more manufacturers and suppliers took place. 

How Thermal Flow Meters Work

Thermal meters are mainly used to measure gas flow. These meters bring heat into the flow and calculate the rate of heat loss. A couple of sensors computes the heat loss, and the process works excellently with the gas flow since the heat absorption ability of fluids quickly soaks the signal, resulting in a loss of resolution.

Although all thermal meters introduce heat into the flow, there are different ways to gauge the rate of heat loss. Take constant temperature differential, for instance. Thermal meters utilizing this method uses sensors to measure the gas temperature. 

The device tries to keep an unvarying difference in temperature between the sensors. On the other hand, the second method is using the principle that higher flow velocity makes a significant cooling effect. 

Environmental Applications

Thermal meters are utilized for many different applications. That said, there are two periods of thermal flow meters, wherein environmental applications drive sales in the market.

The first one was in the early 90s when the demand of CEMS (continuous emissions monitoring) need the measurement of nitrous oxides and sulfur dioxide. For this purpose, thermal flow meters were perfect. By merging the measurements of the concentrations, it can be identified how much SO2 and NOX are discharged or freed into the atmosphere. 

Keep in mind that this is very crucial because they’ve been deemed as the chief cause of acid rain. Thermal meters competed with ultrasonic and Pitot tube flow meters to deliver this measurement at that time.

Furthermore, the full acceptance or recognition of global warming as a scientific fact has allowed for a second prospect for thermal flow meters. Starting with Obama’s administration, the US government has prioritized the reduction and identification of greenhouse gases.

The following are some of the applications that have instigated or launched due to the efforts to minimize greenhouse gases:

  • Ethanol refining and distillation
  • Biomass gasification
  • Methane recovery from coal mines
  • Measuring emissions from steam generators, process heaters, and boilers
  • Monitoring and measurement of flare and flue gases
  • Recovery measurement of landfill gases

The government has declared the goal or objective of minimizing greenhouse gas emissions by at least 80% by 2050. Other countries have exerted much effort to cut down on greenhouse gases, as well. 


Thermal flowmeters are still considered as a pioneering technology to some extent. Manufacturers have reacted to the sharp volume of challenging and modern applications by bringing in many essential product improvements and enhancements. The market is continuing to drive more sales; thus, suppliers and manufacturers will respond with more accurate and feature-rich thermal flow meters. 
Although thermal flow meters might not be as extensively used compared to Coriolis flow meters, they have their own set of applications and niche. More importantly, competition in the flowmeter market will likely increase because suppliers will try to introduce higher-quality, better-performing products.


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