Abstract: An instrument for monitoring the build-up of fouling deposits on the liquid-handling surfaces of cooling towers, heat exchangers and other apparatus, subject to liquid fouling, is disclosed in this application. The build-up is monitored by sensing the increasing drag on a rotor immersed in the liquid, as the rotor and adjacent stationary surfaces become fouled. The drag is measured by a torque transducer, which is connected to read-out devices by means of a computer. The instrument may be used as an integral part of a feedback control system, or for evaluating fouling control strategies. The computer enables the instrument to operate in different modes, as desired.

Abstract: A test apparatus is provided for testing the heat transfer resistance of a tube, such as a tube of a heat exchanger, the apparatus including a heating means, such as a block of metal surrounding and engaging a part of the tube, with an electric heater for heating the block, the block including at least two termistors at different distances from the tube to measure heat flux. A pump causes water to flow through the tube, and a thermistor measures the water temperature. A flow meter and a pressure drop sensor for sensing the drop in pressure across the block are also provided. The measuring devices other than the flow meter provide, preferrably, analog output signals, which are converted and supplied to a computer for computation of total heat transfer resistance, convective heat transfer resistance, conductive heat transfer resistance of the tube and friction factor.