Herrmidifier Load Calculator User Manual

Page 17

L o a d C a l c u l a t i o n G u i d e

w w w. h e r r m i d i f i e r- h v a c . c o m

SECTION IV TYPES OF EQUIPMENT

There are basically three types of humidification equip-

ment: Atomizing, Evaporative and Steam. The type of hu-

midification equipment used for any application is extremely

important and should be carefully selected with regards to

the level of R.H. desired to be maintained, the amount of

moisture needed to be added, services available, use of the

area being humidified, feed water equality and energy ef-

ficiency. Following is an overview of each type of humidifica-

tion equipment.

Atomization

This type of humidification equipment uses either CEN-

TRIFUGAL or PNEUMATIC forces to break water up into a

fine mist which is discharged into the atmosphere where it

evaporates to the vapor state. This process is endothermic

and takes latent heat from the air to evaporate the mist. (1

000 BTUs are required to evaporate one pound of water.)

Because atomization takes only enough heat from the air

as is needed to evaporate the water, it is usually a very ef-

ficient process. Atomizing equipment must be able to deliver

tiny droplets of a consistent size over a relatively narrow size

range. No large droplets should fall before turning to the va-

por state as this may cause damaged goods, wet floors, etc.

This puts physical limitations on capacities that can be re-

alized and/or successfully applied in given situations under

known conditions.

Every droplet in the fine mist has the same chemical makeup

as the water supplied to the equipment. When the droplets

evaporate to the vapor state, minerals are left behind in the

form of a white powder-referred to as Mineral Fallout. Use of

softened water does NOT alleviate this problem because in

softening one mineral is simply being substituted for another.

Demineralizers and use of the Reverse Osmosis Process

will remove the minerals and prevent Mineral Fallout. This

Mineral Fallout is usually not a problem except that it is unde-

sirable in certain applications such as computer rooms and

hospitals. There are basically two types of atomizing equip-

ment: Centrifual and Pneumatic.

CENTRIFUGAL ATOMIZERS pump water from a reservoir

onto a rotating disc impeller. The centrifugal force created

throws the water against a breaker screen

to form tiny droplets. Some type of air moving method, usu-

ally air vanes, is needed to pick up the mist and convey it into

the air space to be humidified. This type of equipment works

well in the lower capacity ranges (a few pounds of water per

hour) both as free standing or installed in an air handling

system. Larger capacities run into droplet size problems. If

this type of equipment is used in a dirty atmosphere serious

clogging problems result and considerable maintenance is

required to keep its efficiency at a satisfactory level. Also,

since there is usually a reservoir and air movement through

the equipment, algae formation and drying minerals can

result in clogging and the need for frequent maintenance.

Water spray nozzles that do not use air are considered to

be centrifugal atomizers and are NOT suited for humidifying

since their droplet size is seldom small enough to prevent

wetting of floors and materials.

PNEUMATIC ATOMIZERS use air pressure to break up wa-

ter into a fine mist. A much smaller droplet size in the mist is

more readily attained with pneumatic atomizers