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PSYCHROMETRY CHART PSYCHROMETRY CHART 1 & HEAT LOAD1 & HEAT LOAD

RAMLI MOHD. YUSOFFRAMLI MOHD. YUSOFF

JURUTERA MEKANIKALJURUTERA MEKANIKAL

CKM, IPJKR MALAYSIACKM, IPJKR MALAYSIA

RAMLI MOHD. YUSOFFRAMLI MOHD. YUSOFF

JURUTERA MEKANIKALJURUTERA MEKANIKAL

CKM, IPJKR MALAYSIACKM, IPJKR MALAYSIA

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DEFINITION - DEFINITION - PSYCHROMETRICS isPSYCHROMETRICS is

the science that deals with physical laws governing the behaviour of AIR-WATER mixtures.

The measurement of the heat and water vapour properties of air.

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FACTORS INFLUENCING FACTORS INFLUENCING COMFORTCOMFORT

1. TEMPERATURE2. HUMIDITY3. AIR MOTION4. PURITY OF AIR

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AIR AND PROPERTIESAIR AND PROPERTIES

DRY AIR CONSISTS OF ;

NITROGEN (77%) +

OXYGEN (23%) +

OTHER GASES +

WATER VAPOUR (small in quantities but significant to air-cond)

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PROPERTIES OF DRY AIR PROPERTIES OF DRY AIR AND ITS RELATION TO AND ITS RELATION TO PSYCHROMETRIC CHARTPSYCHROMETRIC CHART

• DRY BULB (db) TEMPERATUREDRY BULB (db) TEMPERATURE

• WET BULB (wb)TEMPERATUREWET BULB (wb)TEMPERATURE

• DEWPOINT (dp)TEMPERATUREDEWPOINT (dp)TEMPERATURE

• RELATIVE HUMIDITY (rh)RELATIVE HUMIDITY (rh)

• SPECIFIC HUMIDITY (HUMIDITY SPECIFIC HUMIDITY (HUMIDITY RATIO)RATIO)

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DRY BULB TEMPERATUREDRY BULB TEMPERATURE

• (db) is the temperature that is (db) is the temperature that is measured using the standard measured using the standard thermometerthermometer

• db is represented as vertical lines on db is represented as vertical lines on the chart the chart

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DB

Dry Bulb

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WET BULB TEMPERATUREWET BULB TEMPERATURE

• Temperature associated with the Temperature associated with the moisture content of the air.moisture content of the air.

• Taken by surrounding the thermometer Taken by surrounding the thermometer with a wet wick and measuring the with a wet wick and measuring the reading as the water evaporatesreading as the water evaporates

• WB line slant from the lower right WB line slant from the lower right towards the upper left hand corner. towards the upper left hand corner.

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DBWB

Dry Bulb

Wet

Bulb

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QUESTION?QUESTION?

TANDAKAN SUHU UDARA BERIKUT DIATAS GAMBARAJAH PSYCHROMETRY ANDA

92DB , 80WB

95DB , 83WB

75DB, 64WB

72DB, 60WB

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DEW POINT (DP) DEW POINT (DP)

• DP corresponds to the dry bulb (or wet bulb) DP corresponds to the dry bulb (or wet bulb) temperature at which air becomes completely temperature at which air becomes completely saturated.saturated.

• When moist air is cooled, it cannot hold the same When moist air is cooled, it cannot hold the same amount of moisture. At some point, the moisture will amount of moisture. At some point, the moisture will condense out of the air onto any nearby surface.condense out of the air onto any nearby surface.

• DP is read along the saturation line (100% rh)DP is read along the saturation line (100% rh)

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DBWB, DP

Wet

Bulb, Dew

Point

Dry Bulb

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QUESTION 2?QUESTION 2?

APAKAH TITIK SUHU EMBUN (DEW POINT) BAGI SUHU BERIKUT?

92DB , 80WB

95DB , 83WB

75DB, 64WB

72DB, 60WB

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RELATIVE HUMIDITYRELATIVE HUMIDITY

• Ratio of the actual water vapour pressure of the air to Ratio of the actual water vapour pressure of the air to the saturated water vapour pressure of the air at the the saturated water vapour pressure of the air at the same temperature .same temperature .

• If the air is holding all the moisture it can for a specific If the air is holding all the moisture it can for a specific set of conditions, then it is said to be 100% rh.set of conditions, then it is said to be 100% rh.

• The amount of moisture the air can it hold increases as The amount of moisture the air can it hold increases as the dry bulb temp. increases.the dry bulb temp. increases.

• RH line curve from the lower left hand portion up and RH line curve from the lower left hand portion up and to the right to the right

PSYCHRO1 15Dry Bulb

Wet

Bulb, Dew

Point

DBWB, DP

RH

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QUESTION 3?QUESTION 3?

APAKAH RELATIVE HUMIDITY (RH) BAGI UDARA SUHU-SUHU BERIKUT?

92DB , 80WB

95DB , 83WB

75DB, 64WB

72DB, 60WB

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SPECIFIC HUMIDITYSPECIFIC HUMIDITY

• Is the amount of water vapour, by weight, Is the amount of water vapour, by weight, in the air.in the air.

• Represented as horizontal lines on the Represented as horizontal lines on the chart and is normally given in “grains” of chart and is normally given in “grains” of moisture per pound of dry airmoisture per pound of dry air. .

PSYCHRO1 18Dry Bulb

Wet

Bulb, Dew

Point

DBWB, DP

RH

Sp.

Hum

idit

y

Sp. Humidity

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QUESTION 4?QUESTION 4?

APAKAH KANDUNGAN MOISTURE (MOISTURE CONTENT GRAIN/POUND) BAGI UDARA DI SUHU-SUHU BERIKUT?

92DB , 80WB

95DB , 83WB

75DB, 64WB

72DB, 60WB

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