Solution:

Hot-wire anemometer is most well known thermal anemometer, measure fluid velocity by nothing the heat convected away by the fluid. Hot-anemometers are popular for unsteady flow of gas and liquid flow measurement. The basic system consists of electrically heated wire suitably is liquid.
Due to the change in velocity of flowing liquid the heat lost by the wire also changes. The loss in temperature causes the change in resistance of a hot wire. And this changes the current through the hot wire for a constant voltage. Flow can be measured by measuring the change in the resistance or current.