PSYCHROMETRIC CHART
https://www.mesubjects.net/wpadmin/post.php?post=7875&action=edit Psychrometric Properties
https://www.mesubjects.net/wpadmin/post.php?post=3704&action=edit Q. Bank Psychrometry
https://www.mesubjects.net/wpadmin/post.php?post=3094&action=edit Q. Ans Psychrometr1
https://www.mesubjects.net/wpadmin/post.php?post=2884&action=edit Q. Ans. Psychrome 2
https://www.mesubjects.net/wpadmin/post.php?post=586&action=edit Q. Ans. Psych Chart
PSYCHROMETRIC CHART
This chart contain moist air properties. This chart decides the processes in
achieving comfortable conditions. It is quite easy to learn
Construction
Refer Fig. is a Psychrometric chart.

Dry bulb temperature is the abscissa (along xaxis) and specific humidity is the ordinate (along yaxis) at 1 atmospheric pressure. It contains the following lines:

Vertical lines for dry bulb temperature

Horizontal lines towards right for specific humidity

Horizontal lines towards left up to saturation curve for dew point temperature.

Relative humidity lines are curves. On the extreme left is 100 % relative humidity line. Then 90 % 80% and so on.

Constant enthalpy lines and wet bulb temperatures are slant (diagonal ) lines and coincide.

Constant volume lines are also slant lines but are having more slope than the enthalpy lines.

Wet bulb temperatures are available on the saturation curve (100 % RH).

dew point temperatures are available on the saturation curve (100 % RH

Enthalpy lines represent the enthalpy of moist air per kg of dry air.
Psychrometric properties

Dry bulb temperature, t_{db}

Wet bulb temperature, t_{wb}

Dew point temperature, t_{dp}

Specific humidity, w

Relative humidity, Ф

Enthalpy of moist air, h

Specific volume of moist air/kg of dry air
Utility of the psychrometric chart
When any two properties are known, then the remaining five are found.
Say dry bulb and wet bulb temperatures are given.
Draw a vertical line as per given dry bulb temperature. Move along the constant enthalpy line as per given wet bulb temperature. It will meet the dry bulb vertical line. Thus we get a point on the chart.
(i) To find the dew point temperature, move horizontally towards left till it meets the saturation line. Read the dew point temperature at this point.
(ii) to find the specific humidity, move horizontally towards right extreme and read the value on the vertical line.
(iii)To find the relative humidity, find the position of the point in between two relative humidity lines. Then interpolate the required value.
(iv) To find the enthalpy, locate the constant enthalpy line passing through the point. Read its value from the enthalpy values marked on the chart.
(v)To find the specific volume, locate the two specific volume lines in between which the point lies. Interpolate the value of specific volume at the point
Use of psychrometric chart
we can know the condition of air present in a room, veranda outside Or anywhere. Measure the dry and wet bulb temperatures using sling Psychrometer . With the help t_{db} and t_{wb}, first point can be located on the psychrometric chart. We know the comfortable conditions. Mark second point on the Psychrometric chart. Now to reach from first point to second point, move horizontal, vertical lines and along the saturated curve. These movements are psychrometric processes shown in Fig. below.
PSYCHROMETRIC PROCESSES

Sensible heating moving horizontally towards right of the point.

Sensible cooling moving horizontally towards left of the point.

Humidification moving vertically upwards of the point

Dehumidification moving vertically downwards of the point

Heating and humidification

Cooling and dehumidification

Cooling and humidification

Heating and dehumidification