Description
A benchtop unit designed to introduce students to the characteristics of saturated water vapour.
The apparatus consists of a Marcet Boiler, with an additional pipe loop, which enables saturated steam to be generated and returned to the base of the boiler as condensate.
Pure water in the boiler is heated to its boiling point using a pair of cartridge heaters with variable power control. A sight glass on the front of the boiler enables the internal processes to be observed, namely boiling patterns at the surface of the water, and also permits the water level in the boiler to be monitored. Saturated steam leaving the top of the boiler passes around the pipe loop before condensing and returning to the base of the boiler for reheating. The operating range of the boiler and loop is 0-7 bar gauge. The top limb of the pipe loop incorporates a Platinum Resistance Thermometer (PRT), temperature sensor and an electronic pressure sensor to measure the properties of the saturated steam. A filling point on the top limb enables the loop to be filled with pure water and permits all air to be vented safely before sealing the loop for pressurised measurements. A vapour offtake, with isolating valve, enables steam from within the loop to be passed through a throttling calorimeter, the purpose of which is to demonstrate how the dryness fraction of the saturated steam in the loop can be determined. The steam expands to atmospheric pressure as it is throttled and a second PRT temperature sensor measures the temperature of the steam following expansion.
The apparatus is designed for safe operation with a pressure relief valve set to operate if the pressure rises above the working pressure and a Bourdon gauge that remains operational when power is disconnected from the electrical console.
All power supplies, signal conditioning, circuitry etc, are contained in an electrical console with appropriate current protection devices and an RCD for operator protection. Readings from the sensors are displayed on a common digital meter with selector switch and all corresponding signals are routed to an I/O port for connection to a PC using an optional parallel interface/educational software package.
Specification
A benchtop unit comprising a boiler vessel and pipe loop with a pressure-relief valve to limit the operating pressure to eight bar gauge. A sight glass on the front of the boiler enables the boiling patterns to be observed and a Bourdon-type gauge indicates the pressure in the apparatus at all times for safe operation
A throttling calorimeter mounted adjacent to the pipe loop enables the condition of the saturated steam to be determined by measuring the temperature of the steam following throttling to atmospheric pressure. Temperatures in the pipe loop and inside the throttling calorimeter are measured using PRT sensors and pressure in the loop is measured using an electronic pressure sensor
An electrical console houses the necessary electronics with current protection devices and an RCD for operator protection. A digital meter with selector switch displays all sensor measurements. Corresponding signals are routed to an I/O port for connection to a PC. An optional interface device and educational software package is available
The boiler is heated by a pair of 500W electric heating elements with variable power control and overtemperature protection
A comprehensive instruction manual is included with a range of fully detailed laboratory teaching exercises
Key Features
Measurement of the relationship between temperature and pressure of the saturated vapour in the loop
Convenient control of heat input to the boiler using variable power control
Sight glass in the boiler enables observation of the boiling patterns in the water
Safe operation with pressure relief valve and permanent indication of system pressure