Ashrae 55

Front 1

ASHRAE 55 Purpose

Back 1

Specify the combinations of indoor thermal environmental factors and personal factors that will be acceptable to a majority of the occupants.

Front 2

ASHRAE 55 Environmental Factors

Back 2

Temperature, Humidity, Air speed, Thermal radiation

Front 3

ASHRAE 55 Personal Factors

Back 3

Activity, Clothing

Front 4

ASHRAE 55 Scope

Back 4

Healthy adult at 0-10,000 feet, indoor spaces designed to be occupied at least 15 minutes.

Front 5

Adaptive Model

Back 5

A model relates indoor temp. ranges to outdoor weather conditions

Front 6

Clo

Back 6

A unit used to express thermal insulation provided by clothes.
1 clo = 0.155 m^2 °C/
W (0.88 ft^2·h·°F/Btu).

Front 7

Draft Rate

Back 7

Percent of people predicted to be dissatisfied due to draft.

Front 8

Humidity Ratio

Back 8

Ratio of the mass of water vapor to the mass of dry air.

Front 9

Relative Humidity

Back 9

Ratio of the partial pressure of the water vapor in the air to the saturation pressure of water vapor at the same temperature and the same total pressure.

Front 10

Clothing Insulation Icl

Back 10

The resistance to sensible heat transfer by clothes. Relates to whole body average.

Front 11

Insulation - garment Iclo

Back 11

Resistance to sensible heat transfer obtained from adding an individual garment over the nude body. Expressed in clo units.

Front 12

Met

Back 12

Energy generated inside the body due to metabolic activity, defined as
58.2 W/m2 or 18.4 Btu/h·ft2

Front 13

Energy produced per unit surface area by average seated person at rest.

Back 13

1 met
58.2 W/m2 or 18.4 Btu/h·ft2

Front 14

Average person surface area.

Back 14

1.8 m2 (19 ft2).

Front 15

Metabolic rate (M)

Back 15

The rate of transformation of chemical energy into heat and work by metabolic activities. In this standard, this rate is expressed in met units.

Front 16

Naturally conditioned spaces, occupant controlled

Back 16

Thermal conditions of the space are regulated primarily by the opening and closing of windows.

Front 17

neutrality, thermal

Back 17

The indoor thermal index value corresponding with a mean vote of neutral on the thermal sensation
scale.

Front 18

percent dissatisfied (PD)

Back 18

Percentage of people predicted to
be dissatisfied due to local discomfort.

Front 19

predicted mean vote (PMV)

Back 19

An index that predicts the mean
value of the votes of a large group of persons on the seven point thermal sensation scale.

Front 20

predicted percentage of dissatisfied (PPD)

Back 20

An index that establishes a quantitative prediction of the percentage of thermally
dissatisfied people determined from PMV.

Front 21

radiant temperature asymmetry

Back 21

The difference between the plane radiant temperature of the two opposite sides of a small plane element.

Front 22

response time (90%)

Back 22

Time for a sensor to reach 90% of the final value. about 2.3 times the "time constant"

Front 23

Thermal Sensation

Back 23

A subjective feeling graded as cool, warm, hot etc.

Front 24

Step Change

Back 24

An incremental change in a variable, by design or due to time interval between readings; typically, an incremental change in a control setpoint.

Front 25

Dewpoint temperature

Back 25

The Temp at which moist air becomes saturated.

Front 26

temperature, mean monthly outdoor air (ta(out) )

Back 26

Arithmetic average of the mean daily minimum and mean daily maximum outdoor (dry-bulb) temperatures for the month in question.

Front 27

temperature, mean radiant (tr )

Back 27

Uniform surface temperature of an imaginary black enclosure in which an occupant would exchange the same amount of radiant heat as in the actual nonuniform space

Front 28

temperature, operative (to )

Back 28

Uniform temp. of an imaginary black enclosure where an an occupant exchanges the same heat by radiation and convection as in the nonuniform environment.

Front 29

temperature, plane radiant (tpr)

Back 29

Uniform temperature of an enclosure in which the incident radiant flux on one side of a small plane element is the same as in the existing environment.

Front 30

Time Constant

Back 30

The time for a measuring sensor to reach 63% of the final value after a step change.

Front 31

turbulence intensity (Tu)

Back 31

Ratio of the St. Dev.of the air speed (SDv) to the mean air speed (v). Turbulence intensity may in percent. i.e., Tu = [SDv / va] · 100).

Front 32

Water Vapor Pressure

Back 32

The pressure that the water vapor
would exert if it alone occupied the volume occupied by the humid air at the same temperature.

Front 33

water vapor pressure, saturated dewpoint (psdp)

Back 33

The water vapor pressure at the saturation temperature corresponding to the reference pressure and without any liquid phase.

Front 34

Occupied Zone

Back 34

Space occupied by people, considered to be between the floor and 1.8 m (6 ft), more than 1.0 m (3.3 ft) from outside walls, AC equip. and 0.3 m (1 ft) from internal
walls.

Front 35

ASHRAE 55 General requirements

Back 35

Specify space, Consider activity and clothing, >15 min. occupancy, ID occupants, account for activity and clothing differences between occupants. ID those requirements not met for.