H911 Film and Dropwise Condensation Unit

H911 Film and Dropwise Condensation Unit

Although the differences in the modes of boiling heat transfer are generally recognised many students are not aware that two distinct modes of condensation can occur. The H911 is a self-contained bench top unit that allows the investigation of heat fluxes and heat transfer coefficients during the condensation of steam.

The considerable difference between the appearance and heat transfer rates of dropwise and filmwise condensation are clearly demonstrated. Heat fluxes approaching 1000 kW/m2 can be obtained.

A vacuum pump is fitted to the unit so that the effect of non-condensable gases in condensers may be investigated. A computer upgrade allowing all temperatures, pressures and flow rates to be automatically recorded is available.

H911 Film and Dropwise Condensation Unit

High quality ABS Plastic Panel, having an attractive appearance, and on which the following components are mounted:

Steam Chamber:   Thick walled glass cylinder with flared ends and P.T.F.E. seals to nickel plated brass cylinder covers.

Condensers:   TWO - water cooled - mounted in upper cylinder cover. Dimensions: 12.7 mm external dia. X 90 mm effective length. Specially designed and fabricated from copper and brass, incorporating a heat exchanger to minimise variation of surface temperature.

Dropwise condenser – gold plated.

Filmwise condenser – natural finish.

Each condenser shell is fitted with three thermocouples connected to measure the mean metal temperature and two thermocouples to measure the inlet and outlet water temperatures respectively.

Heating Element:  Coiled 3 kW electric heating element with thermal protection.

Heater Control:  Triac control to manually vary heat input from approximately 0.4 to 3.0 kW.

Air Extraction System:  Air cooler, separator and water jet vacuum pump with the necessary valves.

Instrumentation

Temperature:  Digital Temperature Indicator to indicate all important temperatures.

Pressure Gauge:  100 mm dia. To measure chamber pressure. Range – 100 to +100 kNm-2 gauge.

Flow Meters:  TWO – variable area type, with control valve.  To measure the water flow rate through the condensers.

Ranges  ONE - 4 to 50 gm s-1 (Dropwise)       ONE – 1 to 12 gm s-1 (Filmwise)

Safety

Pressure Relief Valve:  Spring loaded valve fitted to upper cylinder cover – set to discharge at 20 kN m-2 gauge.

Pressure Switch:  Diaphragm type pressure switch to switch off heater when the chamber pressure exceeds 10 kN m-2 gauge.  Manually re-set.

Heater Thermal Protection:   To interrupt the heater circuit if the heater overheats due to inattention to the water level in the chamber.  Manually re-set.

All electrical components are earthed and fused.

  • Visual observation of filmwise and dropwise condensation, and of nucleate boiling.
  • Measurement of heat flux and surface heat transfer coefficient in both filmwise and dropwise condensation at pressures up to astmospheric.
  • Investigation of the saturation pressure/temperature relationship for H2O between about 20oC and 100oC.
  • Demonstration and investigation of the effect of air in condensers.
  • Demonstration of Daltons Law.

H910 Film and Dropwise Condensation