DriSteem Vaporstream Especificaciones descargar pdf (Pagina 61)

P a g e 5 6 • D R I - S T E E M D e s i g n G u i d e

D R I - S T E E M D e s i g n G u i d e • P a g e 5 7

Drip-free dispersion is possible

HVAC engineers often express concerns about steam condensation

on internal duct elements when specifying humidification

systems. And these concerns are valid, for if severe enough, water

accumulation from condensation can leak through ducts to cause

damage below. This is an immediate — and easily noticeable

— problem. A less visible and potentially more harmful situation

is condensation causing standing water on duct floors. A warm air

handling system containing moist dust is an ideal breeding ground

for microorganisms.

But these harmful situations do not need to occur. Understanding

the factors that affect absorption, and selecting and maintaining

the proper equipment, will eliminate moisture problems caused by

humidification.

Factors that affect absorption

Absorption is affected primarily by three things:

1. Duct or AHU temperature. Cool air absorbs less than warm air

and requires a longer absorption distance.

When equal amounts of steam are introduced into equivalent

ducts but with different air temperatures, the lower temperature

systems of 50 °F to 55 °F (10 °C to 13 °C) are more challenging

to ensure absorption than systems with higher temperatures.

2. ∆ RH (the difference between entering and leaving RH). The

more vapor that needs to be dispersed into the airstream, the

longer the absorption distance.

Generally speaking, the higher the relative humidity that must

be produced in the airstream the more challenging the task. The

desired room or space RH enters into this discussion as well.

3. Mixing of air and steam. Uneven airflow, non-uniform mixing

of steam with air, and the number of steam discharge points on

a dispersion assembly affect absorption distance. Also important

is the percentage of the airstream covered by the dispersion

assembly (see Figure 58-1).

Placement in airstream critical

Absorption or nonwetting distance is the dimension downstream

from the leaving side of the steam dispersion assembly to the

point where wetting will not occur, although wisps of steam may

H o w t o d e s i g n f o r p r o p e r

h u m i d i f i c a t i o n s t e a m a b s o r p t i o n

Multiple tubes increase

air and steam mixing

A bank of closely spaced multiple dispersion

tubes is far superior to a single duct tube.

In the example shown on the next page,

the absorption distance of 48"(1.2 m) can

be reduced to less than 6" (15 cm) by

adding dispersion tubes and a condensate

header. With multiple tubes, steam is

more evenly distributed into the airstream.

This causes a rapid homogenization of

the steam/air mixture, which results in a

faster re-evaporation or second change

of state. Adding a condensate header

allows increased capacity. DRI-STEEM has

a variety of steam dispersion devices that

accommodate absorption requirements

ranging from the simplest application to the

most difficult.

Determine the absorption distance

Use the graphs in our catalogs or use

DRI-CALC to calculate absorption distances

by product for your particular application.

These published absorption distances are

guaranteed so that you can be confident of

complete absorption.

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 83 84

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DriSteem Vaporstream Especificaciones Pagina 61

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