Dry wet bulb ( Dry wet thermometer) The working principle of

Dry wet bulb ( 干和湿球温度计) Is a kind of measuring temperature, gas wet a device. It is composed of two same ordinary thermometer, one is used to measure the temperature, according to dry bulb thermometer. Another in ball encase with distilled water wet gauze, gauze bottom into distilled water, according to wet bulb. According to the dry bulb temperature and wet bulb temperature is measured, check & other; Wet air chart & throughout; , it is known that the state of air temperature, humidity, specific heat, enthalpy, specific volume, water vapor partial pressure, heat, sensible heat and latent heat, etc. Dry bulb, for example, 18 degrees, wet ball 15 degree, the difference of 3 degrees of longitudinal bar and the cross bars of wet ball 15 degrees 68 degrees is said the humidity of 68%. Through the measurement of value, contrasting wet air line graph can calculate air heating, cooling, humidifying and dehumidifying state changes. Psychrometer: as early as the 18th century human invented the psychrometer psychrometer accuracy also depends on two dry bulb and wet bulb thermometer itself precision; Moisture meter must be in state of ventilation: only the gauze water jacket, water quality, wind speeds are all meet certain requirements, to achieve the accuracy of the rules. The accuracy of the psychrometer only 5% 7% RH. Psychrometer principle: dry scouting dry wet thermometer head directly dew in the air, wet bulb temperature probe with wet gauze wrapped, the humidity measurement principle is that under a certain wind speed, wet bulb out at the wet gauze moisture evaporates away wet bulb probe on the quantity of heat, make the temperature lower than the ambient air temperature; And dry bulb thermometer to measure out the actual temperature of the ambient air is, at this point, the temperature difference between wet and dry ball and environment relative humidity has a corresponding relationship, but the relationship is nonlinear. Expressed in formula is quite complicated. Relations between the two will be influenced by many factors such as wind speed, the accuracy of the thermometer itself, atmospheric pressure, dry wet bulb ball bubble surface area size, gauze material and so on. Relative humidity = / water vapor partial pressure of saturated steam pressure ( Pressure, temperature, certain circumstances)