![]() the humidity ratio is approximately 65 grains h2o/lb dry_air.the relative humidity is approximately 50%.The state of air with dry bulb temperature 75 oF and wet bulb temperature 62.5 oF can be visualized in the psychrometric chart as indicated below. the relative humidity is approximately 49%Įxample - the State of Air in the Psychrometric Chart.If the dry bulb temperature of air is 18 oC and the web bulb temperature is 12 oC - then the difference between them is 6 oC. Dry and Wet Bulb Temperatures chart Example - Relative Humidity Dry and Wet Bulb Temperatures - SI Units T db - T wbĭownload and print Air - Relative Humidity vs. The table below can be used to estimate the relative humidity of air if dry and wet bulb temperatures are known. Relative Humidity - Temperature in Celsius the humidity ratio is approximately 0.0057 kg h2o/kg dry_air.the relative humidity is approximately 42%.If the dry bulb temperature of air is 19 oC and the web bulb temperature is 12 oC - then the state of air can be visualized in the Mollier diagram as indicated below. Example - The State of Air in the Mollier Diagram Relative humidity can be estimated from the tables below or alternatively from a psyhrometric or a Mollier diagram. Sufficient air movement can be achieved with a sling thermometer or similar. Note that continuously air flow around the thermometer is important to evaporate water from the wet clothing and achieve a correct wet bulb temperature. Wet Bulb Temperature - T wb - can be measured with a standard thermometer with some wet clothing, cotton or similar, around the bulb. If any two properties of air at a condition are known, then rest of the psychrometric properties can be determined by plotting that condition of air on psychrometric chart, represented by point.Air humidity can be estimated by measuringĭry Bulb Temperature - T db - can be measured with a simple thermometer as shown above. 2 clearly indicates the way of finding out every psychrometry property for any point plotted reading the psychrometric chart. We can find out all the psychrometric properties by reading the actual psychrometric chart having values. 2, where a point plotted on psychrometric chart is encircled. Generally, these lines are drawn with values 10%, 20%, 30%, up to 100%. They are curved lines parallel to saturation curve. The values of enthalpy are given on the scale provided above the saturation curve. These lines are uniformly spaced, parallel and also coinciding with the wet bulb temperature lines. Vertical lines uniformly spaced and drawn parallel to Y-axis on the chart are called as dry bulb temperature lines.Įnthalpy (total heat) lines are inclined straight lines (diagonal lines). The various lines or curves marked on the chart are discussed below. 1 shows the general construction of the psychrometric chart. Psychrometric chart provides solution to many practical problems dealing with air.The use of psychrometric chart permits the graphical analysis of psychrometric data and processes.Psychrometric chart is probably the most valuable single tool available to the air conditioning engineer or design technician.Psychrometric chart overcomes this difficulty and eliminates lot of calculations. Computation of psychrometric properties of air-water vapour mixture using mathematical solutions is tedious and time consuming, and even the use of tables is a slow process because of the necessity of interpolation.Psychrometric chart is very useful for finding out the properties of air, which are required in the field of air conditioning. ![]() Role or Advantages of psychrometric Chart In a psychrometric chart, dry bulb temperature is taken as abscissa (X-axis) and specific humidity (i.e. The psychrometric chart is normal y drawn for standard atmospheric pressure of 750 mm of Hg. Psychrometric chart is a graphical representation of the various psychrometric properties of moist air.
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