Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric...

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Using the Psychrometric Chart Problem Statement The air in a room has a drybulb temperature of 80 o F and a wetbulb temperature of 65 o F. Assuming a pressure of 14.7 psia, use the ps ychrometric chart to determine: 1. The specific humidity. 2. The relative humidity. 3. The dew point temperature.

Transcript of Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric...

Page 1: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Using the Psychrometric Chart

Problem StatementThe air in a room has a dry‐bulb temperature of 80oF and a wet‐bulb temperature of 65oF.  Assuming a pressure of 14.7 psia, use the psychrometric chart to determine:p , p y

1. The specific humidity.

2. The relative humidity.

3. The dew point temperature.

Page 2: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Given: TDB = 80oF;  TWB = 65oF; p = 14.7 psia

To Find: a)  ω;  b)  φ; c)  TDP

Solution:

Locate the properties TDB = 80oF and TWB= 65oF on the psychrometric chart.

Page 3: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Psychrometric chart with TDB = 80oF and TWB = 65oF indicated80 F and TWB = 65 F indicated.

Page 4: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Solution (cont’d):

Draw a vertical line from TDB = 80oF which crosses the TWB  = 65oF diagonal line.

Th i t ti f th t li i di tThe intersection of these two lines indicates the state of the atmospheric air.

Page 5: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Psychrometric chart with lines drawn inPsychrometric chart with lines drawn in.

Page 6: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Solution (cont’d):

To determine ω, draw a horizontal line from the “state point” to the right and read the humidity ratio .

⎞⎛ i tlb⎟⎟⎠

⎞⎜⎜⎝

⎛=

airdrylbmmoisturelbm,

,010.0ω

Page 7: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Psychrometric chart with ω indicatedPsychrometric chart with ω indicated.

Page 8: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Solution (cont’d):

To determine Ф, note the curved line (indicated in green) that passes through the state point.

Ф = 45%

Page 9: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Psychrometric chart with green linePsychrometric chart with green line.

Page 10: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Solution (cont’d):

The dew point temperature is defined as the temperature at which condensation commences from the atmospheric air.  The TDP state point will have the same ω as the atmospheric air state point but the Ф willatmospheric air state point, but the Ф will be 100%

Page 11: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Solution (cont’d):

D h i t l li f th t h iDraw a horizontal line from the atmospheric air state point to the “Saturation temperature oF” line TDP = 57 5oFtemperature  F  line.  TDP  57.5 F.

Page 12: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Psychrometric chart with horizontal line toPsychrometric chart with horizontal line to the saturation temperature line.

Page 13: Using the Psychrometric Chart worksheets/Module 4/psychrometric chart.pdfUsing the Psychrometric Chart Problem Statement The air in a oroom has a dry‐bulb temperature of 80 F and

Summary:

ω = 0.010Φ = 45%T 57 5oFTDP = 57.5oF