Glossaire technique
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Source: Kältetechnik (Band 1), Klimatechnik
Auteur Hans-Jürgen Ullrich.
Commercialisation par Fa. COOL, Silvia Schröder, www.cool-schroeder.de
Glossaire technique
Ammonia :
Ammonia (NH3) has been used until today in industrial installations with capacities ranging from 100 kW to 5000 kW. Its main application areas are large cold stores, slaughterhouses, dairies, breweries and sport centres. Due to the ban of CFCs in new installations, the application range of ammonia will shift to smaller capacities. A completely new technology, which combines direct expansion with expansion valves and smaller charge permits the construction compact brine and water chillers down to a capacity of about 10 kW. Semi-hermetic compressors with aluminium winding are also being tested. However, due to its toxicity, ammonia cannot be used in all applications, as is the case for fluorinated refrigerants.
- Refrigeration > Refrigerants
Induction a/c unit :
The primary air volume flow prepared in the air conditioner corresponds to the minimum outside air part and remains constant throughout the year. The plants are designed mainly as high speed plants. The induction ratio between primary and secondary air is between 4 and 2. The air humidity in the room has to be controlled by the primary air - by dehumidifying it in summer and humidifying it in winter. The state of the primary air is held constant throughout the year and is between 13 °C and 16 °C and 85 to 95% ( near to the dew point) The secondary air flow , the circulating air in the room, is prepared by the induction device. No exhaust air is returned to the air conditioning central point. It is direct escaping air.
- A/C > A/C installations > Air/Water installations
Automatic expansion valve :
The automatic control valve controls the refrigerant mass flow to the evaporator depending on the suction pressure and maintains the latter at a constant level independently from the temperatures in the installation. Therefore, it is also called a constant pressure expansion valve. Automatic control valves cannot be used in refrigeration units controlled by pressostats, as they maintain the pressure at a constant level.
- Refrigeration > Control and measuring > Refrigerant flow meters
Automatic control valve :
The automatic control valve controls the refrigerant mass flow to the evaporator depending on the suction pressure and maintains the latter at a constant level independently from the temperatures in the installation. Therefore, it is also called a constant pressure expansion valve. Automatic control valves cannot be used in refrigeration units controlled by pressostats, as they maintain the pressure at a constant level.
- Refrigeration > Control and measuring > Refrigerant flow meters
Axial fans :
In axial fans the air flows through the impeller in the direction of the rotation axis. An axial fan consists of housing or just a duct ("wall ring"), the impeller (hub with blades) and the drive. The effect of the axial impeller is on the principle of the aerodynamics of a wing in a flow of air. As in aeronautics, the propulsive force defines the function of a wing. When exiting the impeller the air undergoes a twist caused by the impeller which continues when the air enters the ducting. As this twist is eliminated by friction it is to be seen as a loss. Using fixed vanes before or after the impeller, a part of this twist energy can be converted into pressure energy thus reducing the loss. Adjustable guide vanes make it possible to control the delivery flow. Depending on the design, axial fans are defined as propeller fans, wall or window fans, axial fans without guide wheels (for low pressures), axial fans with guide wheels (for high pressures) and opposed operation axial fans. In addition to doubling the delivery pressure, the last named are also very efficient as the twist is compensated for by the opposed operation.
- A/C > HVAC units
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