Measuring equipment One of the biggest problems in the project is to determine the position of the robot inside the cooling tower. The environment in the tower is very humid and hot, with the lot of fog. We have tried almost all standard solutions for determination of a robot's position, but none of them was possible. Laser range-finding method (LIDAR) is not possible due to a fog, satellite GPS is not possible, because the tower is almost closed at the top, direct measurement of a passed path with the positioning of an electronic compass is not possible due to a rough tower floor surface, etc.

The only possible solution is as we see so called Ultrasonic GPS. This measuring method defines the position of a robot with the triangulation of several ultrasonic transponders. On the robot is a special Ultrasonic transmitter unit which sends ultrasound signals. Those sound signals are detected with the Transponder units which are positioned on the known locations inside the tower. To sinhronise all signals, all of the remote transponders and the robots Ultrasonic transmitter are linked together with the radio 433MHz signal.

Because of a harsh environment a special version of a ultrasonic transponder was tested. This is the State of the art unit, sealed and water proof, because of its power it can also be used for bigger distances. It's high resonant frequency (92 kHz) allows to use it even in the environment full of noise. Several test were made with the new transducer in the lab and we plan to put it on the test in real cooling tower environment in the beginning of the year 2000. Up to now some real time distance measurement with the prototype lab units were made to show the use of the method and to evaluate the final version. The prototype Ultrasonic transponder unit and a LCD display type Ultrasonic receiver were made and tested. We can with those measure the distances up to 30 m. With the final version of the Ultrasonic GPS the computer will through it's attached A/D card read the distance to all remote Ultrasonic Transponders and transmit the data of all distances via Radio link to the external host computer. This method didn't work at the final testing.

Measurement parameters are basic parameters, measured on-line simultaneously with aid of computer system, additional parameters, measured in different time intervals, and system parameters which were taken from the power plant control room. The measurements are performed according to the standard DIN 1947.

Air velocity field of the cooling tower Air velocity field of the cooling tower is measured with a current-meter mounted on the vehicle. Measurement error is approximately 2% of the measuring value. Current-meter made on TURBOINSTITUTE have 100mm diameter and spiral pitch 125 mm. Propeller is made of polished aluminium alloy and is able to measure fluid velocities up to 4 m/s. Current-meter holder is made of stainless-steel with magnetic relay to detect rotation of the current-meter. Special petroleum lubricated bearings allow durable operation with invariable characteristics. Well-balanced and calibrated current-meter has high time-stability and accuracy. Current-meter is pre-calibrated. With each rotation of the current-meter four signal changes are generated (from 0 to 1 or reverse) which are sensed by the measuring system. The measurement time of one operational point is 1 minute. Software for current-meters calibration and flow measurement was developed by TURBOINSTITUTE.

Air temperature field in the cooling tower Air temperature field in the cooling tower is measured by Pt-100 temperature sensor located beside current-meter on the tracked vehicle. Time interval of temperature measurement at respective measurement position is 1 minute.

Water flow in the outlet channel Water flow in the outlet channel is obtained indirectly with measurement of water level and water velocity. The water velocity is measured with the ultrasonic type of a flow meter.

MEASURING RESULTS The Figures 3 to 5 should be given as an example of final measuring results in the cooling tower measurement plane.

FIGURE 1: Topological structure of the velocity profile; P = 331 MW.

FIGURE 2: Topological structure of the temperature profile; P = 331 MW. EFFICIENCY INCREASE AFTER RECONSTRUCTION OF COOLING TOWER