BU2 HVAC [page 11/23]

Cooling Tower

A device that passes the outside air over water to remove the systems heat from water.

Filter

A device used to separate solids such as dirt, dust and other particles from air

Damper

A device used to vary the volume of air passing through an air outlet, inlet or duct

Air conditioner

A device which provides air conditioning.

Thermostat

A device which responds to changes in temperature, directly or indirectly

Thermoelectric cooling

A direct current is passed through the circuit of a thermocouple then heat is given off at one junction and absorbed at the other

Heat

A form of energy that is transformed by temperature difference.

Condenser

A heat exchange device that rejects heat from the system absorbed by the evaporator

Condenser

A heat- exchange device in a refrigeration system; it consists of a vessel or arrangement of pipes or tubing in which refrigerant vapor is liquefied by the removal of heat

Compressor (Vapor pump)

A machine for drawing refrigerant from the evaporator at a relatively low pressure, compresses it and then discharges it to the condenser

Compressor

A machine for drawing refrigerant from the evaporator at a relatively low pressure, compresses it and then discharges it to the condenser.

Duct, Air conditioning Duct, Air Duct

A passageway usually fabricated of metal, fiberglass, concrete or cement and asbestos fibers; used to transfer air from one location to another.

Humidistat, Hygrostat

A regulatory device actuated by changes in humidity

Stamped Evaporator

A result of the first designs to create a larger pipe surface; two pieces of metal stamped with the impression of pipe passage through it. (Types of Evaporator)

lPLV (Integrated Part Load Value)

A single number figure of merit based on part-load EER or COP

Condensing Unit

A specific refrigerating machine combination for a given refrigerant

Cooling Tower

A structure, usually on the roof of the building over which water is circulated so as to cool it evaporatively in contact with air

Refrigerant

A substance which produces refrigerating effect by absorbing heat while expanding or evaporating

Freon

A synthetic chemical refrigerant

Centralized Type Air conditioning System-

A type of air conditioning system used for large installations with the use of ducts

Unit Air conditioner

A type of system used for small installation such as residences and small offices

Fan coil unit (FCU), Compressor

Air conditioning unit (direct expapsion method) is composed of the following:

Air Gleaning Equipment

Air may contain large quantities of dust, cinders,soot, smoke, fumes, pollen, dirt,bacteria and odor when breathed induces discomfort and disease. Contamination elements in the air are removed by filtration and air washing.

ACC fan, Condensing coil

Air-cooled Condenser (ACC) is composed of the following:

Air cooled condenser (ACC), Compressor

Air-cooled Condensing unit (ACCU) is composed of the following:

Air cooled condensing unit (ACCU) "Evaporator, Chilled water pipes

Air-cooled Water Chiller (ACWC) is composed of the following:

Desiccant

An absorber which could be liquid or solid that can remove water vapor from a material

Expansion Coil

An evaporator constructed with a pipe or tubing

Generator

Any device equipped with heating element used in the refrigerating system to increase the pressure of the refrigerant

Mechanical refrigeration

Based upon the alternate liquefying and evaporating of a volatile liquid refrigerant with a low boiling point

A type of air conditioning system used for large installation using ducts

Centralized Type Airconditioning System ( Types of Airconditioning Systems)

Air handling unit, Method of cooling, Source of heating such as boiler or furnace, Air distribution system, Control equipment

Centralized system elements:

Split Type Air conditioner

Composed of two separate sections, one installed inside the room while the other is mounted outside the building

air distribution

Correct __________ contributes much to an efficient air-conditioning system as does any single factor. An air conditioningsystem may deliver the required quantity of conditioned air and stillfail to give satisfactory room condition because of poor air distribution

Low velocity single duct system, High velocity dual duct system, Induction system, Hydronic system, Fan coil units

Delivery systems

Shell and tube heat exchanger, Direct expansion coils, Coils may also be submerged in the spray collecting tank

Direct cooling of water (methods used in cooling in an air conditioning system)

Air Conditioning Machinery

Equipment including any or all of the following: compressor, condenser, generator, evaporator, absorber, receiver, connecting pipe, air handling units, dehumidifier,humidifier and heat exchanger

Fan, Coil, Filterx

Fan coil unit is composed of the following:

COP (Coefficient of Performance)

For cooling- the ratio of the rate of heat removalto the rate of energy input For heating- the ratio of the rate of heat delivered to the rate of energy input

basement, on roof. or on intermediate floors,

For large, multi-storey buildings: (1) Place the centralized mechanical equipment in ___

Mechanical Equipment Room (MER)

For small or one storey buildings, place the equipment on roof or use _______ centrally located to minimize duct sizes, and placed along an outside wall for easy servicing and maintenance.

Cooling by absorption

Form of water chiller recently developed is the absorption machine

Sensible Heat

Heat in BTU absorbed by a substance in changing its temperature without changing its state

Heat Gains in Building

Heat lost during cold seasons must be made up by the heating system, in summer heat gained through conduction, convection and radiation must be removed by the air conditioning system

Heat transmitted through walls, roofs, floors, partitions. ceilings and glass owing to differences between indoor and outdoor temperature differences., Heat from solar radiation striking upon the exterior surfaces of walls and glass, absorbed by them and conducted through the interior., Heat carried in by infiltrating or ventilating outside air., Heat given off by occupants, Heat given off by lights, cooking devices, motors, fans and industrial processes within the conditioned space.

Heat may arise from any of the following: (Heat Gains in Building)

Convection

Heat transmission, either natural or forced (by means of fan or blower}, by currents resulting from differences in density due to temperature differences in the heated space.

By the use of recirculated water in contact with air neither air nor water being pre-heated., Pre-heating the air and mixing it with recirculated spray water., Pre-heating the spray water

Humidification of air by water sprays of the air washer is done inthree (3) ways:

Entry of outside air into the space to be conditioned;outside air affects both temperature and humidity level in the space to be conditioned

Infiltration and ventilation load (Cooling Load Calculation Factors)

Lights, occupants, equipment and the like

Internal loads (Cooling Load Calculation Factors)

Latent Heat of Vaporization

One where change is from liquid to gas

Latent Heat of Fusion

One where change is from liquid to solid state

A type of split type air conditioning unit

Package/ Cabinet Type Airconditioning System

Tempering Coils

Placed near the outdoor inlet and heats the air to about 35° Fso that the spray water willnot freeze.

Temperature of the surrounding air, Temperature of the surrounding surfaces,Relative humidity of air, Motion of air, Odors, Dust

Regulation of the following are considered essential for human comfort

Heat gained due to the heat energy incident on the surface and depends upon the characteristics of the surface

Solar load (Cooling Load Calculation Factors)

A type of air conditioning system composed of two separate sections, one installed inside the room (fan coil unit) while the other is mounted outside the building (air cooled condensing unit).

Split type Airconditioner ( Types of Airconditioning Systems)

Passing air through sprays of cold water, Passing air through a combination of cold water sprays and cooling coils, Passing air through refrigeration coils

Summer Air Conditioning Cooling and dehumidifying

Dry Bulb Temperature

Temperature of air- water vapor mixture as measured in the normal way with °Fthermometer

Wet Bulb Temperature

Temperature shown by a thermometer with a wetted bulb rotated rapidly in the air to cause evaporation of its moisture

Evaporator

That part of an airconditioning system in which refrigerant is vaporized thereby taking up heat and producing cooling.

Evaporator

That part of the refrigeration system in which refrigerant is vaporized, thereby taking up external heat and producing cooling.

Latent Heat

The amount of heat which is absorbed or evolved in changingthe state of the substance without changing its temperature

Heating and dehumidifying, Cooling and dehumidifying, Air motion, Air supply

The following standards have been found to provide satisfactory condition in spaces intended for human occupancy

Adiabatic Saturation

The introduction of water into an unsaturated air to increase humidity ratio but without transfer of heat to or from an outside source.

Ventilation

The process of supplying or removing air by natural method or mechanical means to or from any space

Radiation

The process of transmitting rays of heat through the air.

Enthalpy

The quantity of heat in BTU/ min. in a fluid or gas

AFUE (Annual Fuel Utilization Efficiency)

The ratio of annual fuel output energy to annual input energy

EER (Energy Efficiency Ratio)

The ratio of net equipment cooling capacity in BTU/ hr to the total rate of electric input in watts

Relative Humidity

The ratio of the weight of water vapor actually in humid air to the maximum possible weight of water vapor that the air could contain at the same temperature

Refrigeration and Air conditioning Standards (Mechanical regulations- NBC)

The temperature and humidity of air to be used for comfortable cooling shallbe maintained at 68-74 • F, effective temperature at an air movement from 4.57- 7.60 mpm withinthe living zone.

Dew Point

The temperature at which air- water vapor mixture will become saturated and begins to yield drops of condensed water

SEER (Seasonal Energy Efficiency Ratio)

The total cooling output of an airconditioner during its normal annual usage, in BTU/ hr, divided by the total energy input duringthe same period, in watt-hours.

Convection

The transfer of heat by motion of the particles of the heated substance

Conduction

The transfer of heat from one place of higher temperature to a place of lower temperature of the same body to another which it is in contact with. (Modes of Heat Transmission)

Ton of Refrigeration

The useful refrigerating effect equal to 211KJ/ min or 288,000 BTU/ 24 hrs or 12,000 BTU/ hr

Heat transferring from walls, doors, floors, ceilings, etc.

Thermal transmission loads (Cooling Load Calculation Factors)

Pre-heaters

These are used when it is desired to heat the air to wet bulb temperature such that it will become adiabatically saturated by passing through unheated spray of the water and emerged with a moisture content correspondingly to the required dew point.

Air Heaters

These include tempering coils, pre-heaters and re-heaters and generally consists of copper or aluminum tubes wound on the outside with a helical copper ribbon soldered in place,thus giving extended radiating surface.

Re-heaters

These serve to raise the temperature of the air leaving the washer to a degree necessary to maintain the temperature desired in the rooms of the building.

Single Duct, Variable Volume

This central station system supplies a single stream of either hot or cold at normal velocity. Capacity is adjusted to load by automatic volume control. Systems for exterior rooms would be zoned by exposure.

Finned Tube

This heat exchanger is quite efficient because the fins are in good contact with the pipe carrying the refrigerant. (Types of Evaporator)

Rotary type, Reciprocating type {commonly referred to as Piston type Compressor), Centrifugal type

Types of Compressors

Water-cooled condenser, Double pipe condenser, Shell and tube condenser, Shell and coil condenser

Types of Condensers

Air adjustment by opposed blade damper, Air adjustmentbysplitter damper, Air adjustment by conventional turns, Air adjustment by right angle turns with turning vanes

Types of air control

A self-contained unit which houses all the necessary air conditioning components such as the compressor, condenser and evaporator in the same cabinet.

Unitary/ Room Airconditioner ( Types of Airconditioning Systems)

Water Heaters

Water heaters are classified as open, those injected directly in to the water and closed, those which heat the water by heatexchangers from the steam supply.

Humidity

Water vapor within a confined space or environment

Humidity Ratio

Weight of water vapor in a mixture per pound of dry air

All- Air System

With this type of system, the air treating and refrigeration plants may be located some distance from the conditioned space in a central mechanical room. The central treating station not only cleans the air, but also heats or cools, humidifies or dehumidifies. Only the final cooling-heating medium (air) is brought into the conditioned space through ducts and distributed through outlets or mixing terminals.

All Water System

are those with fan coil unit types of room terminals to which may be connected one or more water circuits.The cooling medium (such as chilled water or brine) may be supplied from a remote source and circulated through the coils in the fans coil terminals which is located inthe conditioned space. These circuits may be either two-pipe or four-pipe distribution. Ventilation is obtained through an opening in the wall or from bleed-off from the interior zone system or by infiltration. Another variation, uses a unit ventilator.

Air Washers

are used for humidifying and for cleaning the air

Plenum duct system/ perimeter radial system, Extended plenum system, Reducing

extended plenum system, Perimeter loop system Types of supply duct systems

Air-conditioner

is another arrangement of the indoor portion of the unitary air-conditioner. The unit coupled with the air cooled condenser becomes a complete unitary air-conditioner . The unit is usually wall mounted.

Air-cooled water chiller

is another type of outdoor portion of a unitary air conditioner. The refrigerant inthe evaporator chills water that is then pumped to the coil in the fan coil untt. The fan and coil unit is the indoor portion of the unitary air conditioner.

Air Conditioning

is defined as the simultaneous control of air temperature. humidity, motion and purity of air in a confined space.

Air-cooled condenser

is designed to condense the hot refrigerant to a liquid by passing air over a condensing coil. The unit is generally placed outdoors, but can be located indoor if air intake and exhaust are extended to the outside.

Air-cooled condensing unit

is the complete outdoor portion of a split type air-conditioner. The unit coupled with a fan coilunit using refrigeration coilbecomes a complete split type air-conditioner. Units with centrifugal blowers are also available.

Air-Water System

the air apparatus and refrigeration plants are separate from the conditioned space; however, the cooling- heating of the conditioned space is affected is affected in only a small part by air brought from the central apparatus. The major part of room thermal load is balanced by warm or cooled water circulated either through a coil in an induction unit or through a radiant panel.