What is Hot Wire Anemometer? – Definition, Working Principle, Construction

Hi, friends, welcome to the new post. In this article, we will discuss the question, What is a hot s a hot wire anemometer?” The hot wire anemometer is used for measuring the speed and wind direction. It is used as a wind speed device in meteorology. It was invented by Leon Battista Alberti in the 15th century. In this post, we will discuss its different factors, such as construction, applications, limitations, and working. So, let’s get started. Introduction to Hot Wire Anemometer

What is a hot wire anemometer?

• A hot wire anemometer (HWA) is used for measuring the velocity and fluid direction. It is measured through the heat loss of wire that is dipped in the fluid stream. The wire is heated through an electrical current.
• The hot wire, when placed in a fluid stream, resulted in heat shifting from the wire to the fluid, and the temperature of the wire was reduced. Wire resistance measures the flow rate of the fluid.
• Hot wire anemometer used as a research tool in fluid mechanics. It operated on the principle of heat transfer from high temperature to low temperature.

Working Principle of Hot Wire Anemometer?

There are many designs of hot wire anemometers, but some come with two probes having tungsten, platinum, or platinum-iridium wire stretched for constant temperature circuit types of anemometers, glass-coated thermistor beads connected. It works by sending current through the wire. That current causes the wire to heat. If gas or fluid flows over the device, it cools the wire.

The cooling process shows the existence of motion energy and the amount of time it takes the wire to cool, making it possible to find the velocity of fluid when moving over the wire.

 Construction

There are two main parts of a hot wire anemometer

1. Conducting wire
2. Wheat stone bridge.

Constant Current Method of Hot Wire Anemometer

In this configuration, an anemometer is connected to the flow of fluid for which the rate has to be measured. The current of constant value is flowing through gh the wire. The Wheatstone bridge is at a constant voltage.

If the wire is positioned in the stream of liquid, heat is shifted from wire to fluid. The heat is directly proportional to the resistance of a wire. If heat decreases, that means the resistance of the wire also decreases. The Wheatstone bridge measures change in resistance that is the flow rate of liquid.

Constant Temperature Anemometer

In this design, the wire is heated with current. The hot wire, when connected to the stream of fluid, transfers heat from wire to fluid. So the temperature of the wire varies and also varies resistance. It operated on the rule that the temperature of the wire is constant. The total current needed to get the wire in the starting condition is equal to the gas flow rate.

How to Measure the Rate of a Fluid with a Hot Wire Anemometer

The wire was heated with an electrical current, then the hot wire was placed in the stream of fluid, and the heat shifted from wire to fluid, and the temperature reduced. Resistance of wire measures the flow rate of the fluid.

Applications of a hot wire anemometer

Some applications of hot wire anemometers are listed here.

• It is used for monitoring and checking flow hoos, HVAC systems, and exhaust systems.
• It measures the instantaneous velocity of the fluid.
• It also measures areas with constant ambient temperature and low wind velocity.
• It is also part of the automotive industry for monitoring air use of engine
• It also measures airflow, humidity, and temperature on electronic components.
• In the pharmaceutical industry, used for monitoring airflow in biosafety cabins, chemical fume, and laminar flow hoods

What is Hotwire flow meter?

The principle of a hot wire anemometer is that a metal wire in fluid, with current heating wire, makes the temperature higher than the temperature of the fluid; if fluid passes through the wire, the analog vertical direction will take part of the wire heat used to make the wire temperature loss. The heat dissipating capacity is related to velocity; hot wire temperature changes result in resistance from the heat dissipating capacity of velocity in the signal.

Advantages

• It was used due to low cost and accurate results.
• It is sensitive.
• The spatial resolution of the hot wire anemometer is good.
• It has a high-frequency response higher than 10 kHz.
• It operates on high temperature.
• It has a feature to measure turbulent and laminar flows.
• It has a signal-to-noise ratio low.
• It has good data-handling features for gathering the required data.

Disadvantages

• It is fragile and used in clean glass fluids.
• Its turbulence intensity is high.
• It also faces contamination issues.
• Orobes of instruments can break.
• It has heat transfer problems between the probe and the surface.
• It also faces pointer deflection problems due to changes in atmospheric temperature.

What is a hot wire anemometer used for measuring gases?

FAQs

What is the working principle of a hot wire?

• The hot wire instrument is used for both AC and DC. Hotwire devices work on the principle of thermal effect that the length of wire increases due to the heating effect of the current flow.

What is the work of a hot wire anemometer?

• The hot wire anemometer is a thermal transducer that is used for measuring instantaneous flow velocity. The use of a hot wire anemometer helps instantaneous flow velocity to be calculated from electric voltage measurements.

How is a hot wire anemometer based on the principle of heat transfer?

• A hot wire anemometer uses the amount of heat removed from a heated temperature sensor through flowing fluid related to fluid velocity. These sensors use a 2nd, unheated temperature sensor for compensation variations in the air temperature.

What is the material of construction for a hot wire anemometer?

• The hot wire anemometer comes with two probes having wires stretched between them. The wire is normally made with tungsten, platinum, or platinum-iridium.

What is the construction of a hot wire anemometer?

• The hot wire anemometer comes with a thin, electrically heated wire put in gas flow. The flowing gas comes with a cooling effect on the wire that reduces resistance.

Which metal is used in an anemometer?

• Tungsten is mostly used in an anemometer.

What are the applications of an anemometer?

• For measuring the flow of wind, measure the direction of the wind and use it by drone users or RC plane users to check weather conditions before testing the devices.

What is the common name for an anemometer?

What is the range of a hot wire anemometer?

• Its range is between 0.3 … 30.0 m/s / 0.98 … 98.4 ft/s.

What is a constant temperature anemometer?

• Constant temperature anemometry, also called thermal anemometry Hot-wire, or hot-film Anemometry is used for measuring turbulence in 1D, 2D, or 3D gas and liquid flows with the use of hot-wire or hot-film probes inserted into the flow.