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ET 426

FEATURES:
- Examination of different capacity control methods
- Open compressor with variable speed
- Adjustable cooling load via heater
- Controlled defrosting with temperature specification

DESCRIPTION

Technical Description

The efficient control of the capacity and temperature in refrigeration systems is an important topic in refrigeration engineering. With ET 426 different methods of capacity control can be investigated. For this purpose a refrigeration circuit with two refrigeration chambers is available in which a cooling load is generated using an adjustable heater. Fans in both refrigeration chambers ensure an even temperature distribution.

In the first refrigeration chamber a thermostat with solenoid valve and an evaporation pressure controller control the pressure of the refrigerant in the evaporator and thereby the temperature.

Sensors record the temperature in the second refrigeration chamber and the temperature of the refrigerant upstream and downstream of the evaporator. A refrigeration controller processes the signals from the sensors. Via a solenoid valve the refrigeration controller changes the refrigerant flow in the evaporator and controls thereby the temperature in the second refrigeration chamber. The temperatures at which the fans and a defrost heater are switched on or off are also set at the refrigeration controller. In addition the refrigeration capacity of the overall refrigeration circuit can be adjusted via the speed of the compressor. There also is the option to adjust the refrigeration capacity at a capacity controller in the compressor bypass.

Both refrigeration chambers feature a window to be able to monitor the fan operation and formation of ice. Manometers enable the easy reading of pressures at the relevant points.

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


Learning Objectives / Experiments

- key devices for changing the refrigeration capacity
  * thermostat
  * evaporation pressure controller
  * refrigeration controller
  * capacity controller
  * compressor with variable speed
- operation of a refrigeration controller with specification of temperatures for
  * controlling the refrigeration capacity
  * switching the defrost heater on and off
  * switching the fans on and off

FEATURES

Technical Description

The efficient control of the capacity and temperature in refrigeration systems is an important topic in refrigeration engineering. With ET 426 different methods of capacity control can be investigated. For this purpose a refrigeration circuit with two refrigeration chambers is available in which a cooling load is generated using an adjustable heater. Fans in both refrigeration chambers ensure an even temperature distribution.

In the first refrigeration chamber a thermostat with solenoid valve and an evaporation pressure controller control the pressure of the refrigerant in the evaporator and thereby the temperature.

Sensors record the temperature in the second refrigeration chamber and the temperature of the refrigerant upstream and downstream of the evaporator. A refrigeration controller processes the signals from the sensors. Via a solenoid valve the refrigeration controller changes the refrigerant flow in the evaporator and controls thereby the temperature in the second refrigeration chamber. The temperatures at which the fans and a defrost heater are switched on or off are also set at the refrigeration controller. In addition the refrigeration capacity of the overall refrigeration circuit can be adjusted via the speed of the compressor. There also is the option to adjust the refrigeration capacity at a capacity controller in the compressor bypass.

Both refrigeration chambers feature a window to be able to monitor the fan operation and formation of ice. Manometers enable the easy reading of pressures at the relevant points.

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


Learning Objectives / Experiments

- key devices for changing the refrigeration capacity
  * thermostat
  * evaporation pressure controller
  * refrigeration controller
  * capacity controller
  * compressor with variable speed
- operation of a refrigeration controller with specification of temperatures for
  * controlling the refrigeration capacity
  * switching the defrost heater on and off
  * switching the fans on and off

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