The Hilton Film & Dropwise Condensation Unit has been specifically designed for student use and to provide visual and quantitative results related to heat transfer during condensation. The unit is self-contained, having its own steam generator and air extraction system as well as condensers’ to provide filmwise and dropwise condensation.
Steam generation and both types of condensation take place in the same thick walled glass cylinder with metal cover plates. The lower cover houses an electric heating element, a thermocouple to measure the saturation temperature of the H2O and a combined filling and draining valve from 0.4kW to 3kW by a manual triac control. The upper cover housed two water cooled copper condensers, one of which is gold plated to promote dropwise condensation, and the other is in its natural state to give filmwise condensation. The cover is also fitted with a pressure relief valve and has connection to a pressure gauge, a pressure switch and to an air extraction system.
Considerable effort has been devoted to the design of the condensers, so that, although water cooled, there is little variation of the surface temperature and also that the mean metal temperature is obtained without the use of external thermocouples. The water flow rate through the condenser is measured by flow meters which are fitted with control valves.
A water jet vacuum pump is used intermittently to draw air (plus a certain amount of steam) from the chamber. Before entering the pump, the mixture is allowed to cool slightly so that some of the steam condenses. The condensate is removed by a separator and turned to the chamber, while the saturated air passes to the vacuum pump.
A multi-point electronic thermometer indicates all important temperatures and the rate of heat transfer is calculated from the water flow rate and its temperature rise.
