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ET 422

- Practice-oriented model of a commercial refrigeration system
- Refrigeration and freezing chamber to investigate different methods for capacity control
- Simulation of 12 faults
- 2 defrosting methods for freezing chambe


Technical Description

The efficient control of the capacity and temperature in refrigeration systems is an important topic in refrigeration technology. With ET 422 different methods of capacity control can be investigated.

The components of a refrigeration circuit with refrigeration and freezing chambers are arranged clearly in the trainer. Solenoid valves enable the separate or parallel operation of the evaporators in the two chambers. The circuit is equipped with a capacity controller, a start-up controller and a combined pressures switch for the delivery and intake sides of the compressor. One heat exchanger each in the inlet of the two evaporators enables the supercooling of the refrigerant to be investigated for the efficiency of the process. The refrigeration capacity of the two individual chambers is controlled by a thermostat. The refrigeration chamber also features an evaporation pressure controller.

There are two defrosting methods for the freezing chamber: an electric defrost heater and a hot gas defrosting where hot refrigerant is fed directly from the compressor in the opposite direction through the evaporator.

The simulation of 12 different faults, such as e.g. faulty valves or  clogged pipes, is activated using a touch panel PC.

Relevant measured values are transmitted directly to the touch panel PC and analysed. The software enables e.g. the representation of the cycle in the log p-h diagram. 

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

Learning Objectives / Experiments

- familiarisation with the key devices for changing the refrigeration capacity
  * thermostat
  * capacity controller
  * start-up controller
  * evaporation pressure controller
  * condensation pressure controller
- fault finding in refrigeration system components
- effect of refrigerant supercooling
- familiarisation with defrosting methods
  * electric defrost heater
  * hot gas defrosting
- representation of the thermodynamic cycle in the log p-h diagram



[1] investigation of a refrigeration system with refrigeration and freezing chambers
[2] refrigeration circuit with compressor, condenser, capacity controller, start-up controller, combined pressure switch and 2 evaporators in insulated chambers
[3] each chamber with solenoid valve, thermostat, thermostatic expansion valve, fan and heat exchanger for refrigerant supercooling
[4] refrigeration chamber with evaporation pressure controller
[5] freezing chamber with electric defrost heater and hot gas defrosting
[6] separate or parallel operation of the chambers via solenoid valves
[7] simulation of 12 faults 
[8] touch panel PC for fault activation, data acquisition, evaluation and representation in the log p-h diagram
[9] refrigerant R404a

Technical Data

- refrigeration capacity: 2440W at -10/30°C
Condenser with fan
- volumetric air flow rate: 570m³/h
Evaporator transfer areas
- refrigeration chamber: 1,12m²
- freezing chamber: 1,88m²
Electric defrost heater: approx. 125W
Capacity controller: 0,2...6bar
Start-up controller: 0,2...6bar
Thermostat: 2x -25...15°C
Evaporation pressure controller: 0...5,5bar
Measuring ranges
- temperature: 6x -50...50°C; 5x 0...100°C
- pressure: 3x -1...12,5bar; 2x -1...24bar  
- flow rate: 2x 1.5...22,5L/h
- compressor power consumption: 0...5kW

Dimensions and Weight
LxWxH: 2420x780x1900mm
Weight: approx. 280kg Required for Operation 400V, 50Hz, 3 phases or 230V, 60Hz/CSA, 3 phases

Scope of Delivery

1 trainer
1 set of instructional material

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