Environmental Systems Environmental Systems And And

IntegrationIntegration

Roger CoatesRoger Coates

Basic Basic PrinciplesPrinciples

0 10 20 30 40 Altitude, thousands of feet

Am

bient temperature ºF

100

80

60

20

0

-20

- 40

- 60

- 80

-100

- 120

Hot Day

Standard Day

Cold Day

• Dry-Bulb Temperature

• Wet-Bulb Temperature

• Dew-Point Temperature

Air temperature registered by an ordinary thermometer

Air temperature registered by a thermometer when its bulb is covered by a wet wick and exposed to a current of rapidly moving air

The temperature to which air must be reduced in order to cause condensation of any of its vapour

• Specific Humidity

• Absolute Humidity

• Relative Humidity

The ratio of the weight of water vapour to the weight of dry air in the mixture, expressed as either pounds or grains of moisture per pound of dry air.

The weight of water vapour oer unit volume of air, expressed as either pounds or grains of moisture per cubic foot.

The ratio of the partial pressure of the water vapour in the mixture to the saturate partial pressure at the dry bulb temperature, expressed as a percentage.

TemperatureIs the property which determines the direction if of flow of heat between the object and its surroundings

100º - 0º

212º - 32º

=

ºC

ºF - 32º

100º

180º=

5

9

ºC - 0º

ºF - 32º =

ºcentigrade = 5/9 * ( ºfahrenheit - 32)

ºfahrenheit = 9/5 * ºcentigrade + 32

Simple Thermocouple Unit

Ice BathIndicator

Copper

Constantan

TransferTransfer ofof HeatHeat 

Heat, is a form of energy.

Energy can neither be created nor destroyed.

It can be transformed, or moved from one place or one material to another.

This energy continues to exist regardless of its form or location.

Heat will flow from an object having a certain level of energy into an object having a lower level.

Any material that allows this transfer easily is said to be a conductor of heat.

Any material that blocks or impedes the transfer is called an insulator.

Units of HeatUnits of Heat

Units of HeatUnits of Heat

Addition of ONE Btu of heat

Heat Heat TransferTransfer

Convection

Is the circular motion of a material medium carrying heat energy from place to place , such as hot water steam or heated air.

Heat Heat TransferTransfer

ConductionThe transfer of heat energy from particle to particle within a substance

Heat Heat TransferTransferRadiation

Energy travels outward from a body in the form of wave motion.

The amount of energy which is radiated is a function of the temperature

Specific HeatSpecific Heat

The heat energy (Btu’s) required to raise the temperature of one pound of a substance one degree (F).

The heat energy (Calories) required to raise the temperature of one Kg of a substance one degree. (C)

Imperial Units

Metric Units

Substance Specific Heat

Water 1.0

Ice 0.50

Alcohol 0.59

Aluminium 0.22

Copper 0.093

Iron 0.11

Silver 0.056

Lead 0.031

Platinum 0.032

Mercury 0.033

Sensible HeatSensible Heat

Latent HeatLatent Heat

Heat applied to a cake of ice adds latent heat, causing the ice to change in state from a solid to a liquid.

The liquid remains at the same 0ºC temperature as the ice.

If heat is now applied to the 0ºC liquid, the liquid absorbs sensible heat, rising in temperature to 100ºC without changing in state.

Continued application of heat after the liquid reaches 100C adds latent heat causing a change in state from a liquid to a vapour. The temperature of the vapour remains at 100ºC

VapourisationVapourisation

Heat of FusionHeat of Fusion

Heat of Heat of VapourisationVapourisation

PressurePressure

Effect of Pressure Effect of Pressure on Change of Stateon Change of State

HumidityHumidity

HumidityHumidity

HumidityHumidity