Emerson Fluid Chiller Anleitung zur Fehlerbehebung PDF herunterladen (Seite 14)

Thermal Expansion Valves

Emerson Climate Technologies

REFRIGERANT CODE NAMES

ARI Standard 750-2007 recommends the

following color coding of the TXVs:

R-12 White

R-22 Light Green

R-134a Light Blue

R-290 N/A

R-404A Orange

R-407A Lime Green

R-407C Medium Brown (Brown)

R-408A Medium Purple

R-409A Medium Brown (Tan)

R-410A Rose

R-502 Orchid

R-507A Blue Green (Teal)

R-744 N/A

As in liquid charges, the remote bulb can be lled

with the same refrigerant as the system refrigerant (pro-

ducing a gas charge). Or, it can be lled with a different

refrigerant, producing a gas cross-charge.

Adsorption Charges

The nal type of charge is adsorption. In adsorption,

solids hold large quantities of gas, not by taking them

into the body of the solid, as in absorption, but by gath-

ering them and holding them on the surface of the solid

without chemical reaction.

The vapor penetrates into the cracks and furrows of

the solid, allowing far greater capacity than possible with

absorption.

The advantage of an adsorption charge is that in a

xed volume, the quantity of vapor adsorbed varies with

the temperature and the system. So it can be used to

exert operating pressure as a function of temperature.

Typical adsorbents include: charcoal, silica gel, acti-

vated alumina.

Liquid charges have the following properties:

• Not subject to cross-ambient control loss

• Little or no superheat at start-up

• Superheat increase at lower evaporator temperatures

• Slow suction pressure pulldown after start-up

Liquid Cross-Charges

Liquid cross-charges means that the power element

contains a liquid refrigerant different from the system

refrigerant in which the TXV is used. The pressure tem-

perature curve of the charge crosses the curve of the

system refrigerant.

Liquid cross-charge advantages are:

• Moderately slow pull down

• Insensitive to cross-ambient conditions.

• Damped response to suction line temperature changes

(reduces tendency for TXV hunting)

• Superheat characteristics can be tailored for special

applications

Gas & Gas Cross-Charges

Using a gas charge in place of a liquid alters the

operational characteristics, because gas is compress-

ible. At some predetermined temperature, the gas in the

remote bulb becomes superheated, limiting the force it

exerts. This produces higher superheats at higher evap-

orator pressures and is labeled the Maximum Operating

Pressure (MOP) effect.

The MOP point temperature depends on how that

bulb was charged and where it will be used. All gas

charges are susceptible to cross-ambient control loss

when the power element is colder than the remote bulb.

They respond faster, but tend to hunt for the proper

operating level, so a ballast is often added to the remote

bulb to reduce that tendency.

What happens with an adsorption charge

Which Charge to Use?

Here are some typical examples of applications by

refrigerant charge:

Liquid Charge

Ice makers, pilots, liquid injection valves

Liquid Cross-Charges

Commercial refrigeration (low & medium temp.), ice

makers, transport refrigeration and air conditioning

Gas Charge

Air conditioning (including mobile), water chillers

Gas Cross-Charge

Heat pumps and air conditioning

MOP

Maximum Operating Pressure

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 71 72

Kommentare zu diesen Handbüchern

Keine Kommentare

Emerson Fluid Chiller Anleitung zur Fehlerbehebung Seite 14

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Nein Emerson Fluid Chiller