Behaviour of a Piston Compressor ET 432

Behaviour of a Piston Compressor

Type: ET 432
Name: Behaviour of a Piston Compressor
Technical Description

  Smaller refrigeration systems usually have a piston compressor. Piston compressors are positive displacement machines. These differ in their characteristics decisively from flow equipment which include the turbo compressors that are common in very large systems.
  In piston compressors the flow rate is mainly dependent on the displaced volume and speed. Due to the unavoidable dead space the flow rate drops with increasing pressure ratio. Because the flow rate is a measure for the refrigeration capacity of the refrigeration system, the properties of the compressor are important for the capacity of the whole system.
  In this trainer a commercial open refrigerant compressor is operated in an open process with air. The inlet and outlet pressures and thus the pressure ratio can be adjusted via valves in wide ranges. The drive via a frequency converter permits variable speeds. Pressures, temperatures, electric power consumption, speed and torque are recorded. The measured values are transmitted directly to a PC via USB. The data acquisition software is included.

  The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.


Learning Objectives / Experiments

- determine characteristic variables of a piston

  compressor during experiments
- record of the pressure/volumetric flow rate

- determination of the volumetric efficiency at different

  intake pressures, pressure ratios and speeds
- determination of the isothermal compressor

- measurement of the mechanical and electrical

  power consumption in dependence of the intake

  pressure and pressure ratio
- determination of the mechanical efficiency and the

  overall efficiency


* Open 2-cylinder piston compressor from

* Record of the pressure/volumetric flow rate

* Measurement of intake volume and pressure ratio1
* Determination of volumetric and mechanical


* GUNT software for data acquisition


[1] experimental unit for piston compressor from refrigeration
[2] open process with air
[3] typical open 2-cylinder compressor
[4] drive via asynchronous motor with frequency converter for speed adjustment
[5] inlet pressure and outlet pressure (pressure ratio) adjustable via valves
[6] instruments: 2 manometers, flow meter, sensors for pressure, temperature, speed, torque (via force), flow rate, digital power indication

[7] GUNT software for data acquisition via USB under Windows Vista or Windows 7 


Technical Data

- speed: 465...975min-1

- number of cylinders: 2
- stroke: 26mm
- borehole: 35mm
- displaced volume: 50cm³
- max. displacement: 2,92m³/h

  (at 1450min-1 motor speed)
Drive motor

- power: 550W

- speed: 0...1400min-1
Measuring ranges
- torque: 0...10Nm
- speed: 0...2500min-1
- electric power: 0...600W
- temperature: 1x 0...100°C, 1x 0...200°C
- flow rate: 0,4...3,2Nm³/h

- pressure sensor: -1...1,5bar / -1...24bar

- manometer: -1...9bar / -1...24bar

Dimensions and Weight LxWxH: 1510x790x1750mm
Weight: approx. 148kg Required for Operation 230V, 50/60Hz, 1 phase or 120V, 60Hz, 1 phase Scope of Delivery

1 trainer

1 GUNT software CD + USB cable

1 set of instructional material

Order Details

061.43200  ET 432  Behaviour of a Piston