Before designing an air conditioning system for a particular application, we must know the values of different psychrometric properties of air. Dry bulb temperature and wet bulb temperature are the two most important psychrometric properties of air.
Functions of psychrometer: Psychrometers are used to measure ‘Dry bulb temperature’ and ‘Wet bulb temperature’ of atmospheric air simultaneously.
Types of Psychrometers
Different types of psychrometers are,
- Sling psychrometer.
- Aspirated psychrometer.
- Commercial psychrometer.
- Hydrograph Recorder.
- Modified psychrometer.
- Relative Humidity Sensor.
Aspirated Psychrometer
An aspirated psychrometer is handled and used in the same way like sling psychrometer. An aspirated psychrometer consists of wet and dry bulb thermometers. The hand operated aspirator is provided to the wet bulb thermometer side. The aspirator is depressed at such a frequency that, there is no further depression in the wet bulb temperature.
Fig. 1: Aspirated psychrometer
Advantages of Aspirated Psychrometer
- Simple in construction.
- More accurate than sling psychrometer and hence, commonly used.
Commercial Psychrometer
Commercial Psychrometer consists of a small blower operated by 4.5 Volts D.C. motor. The blower is designed to create sufficient velocity across the wet bulb thermometer. By this way, the wet bulb temperature can be accurately measured. The arrangement for light is also incorporated in the instrument to facilitate the reading of thermometers.
Fig. 2: Commercial psychrometer