Klima Alfa offers ENVIRONMENTAL test chambers that are used to simulate an environment or combination of environments under laboratory

controlled conditions that duplicate or exaggerate the effects found

in actual service. They assist the engineer and scientist in exploring

the effects of equipment and in developing equipment for resistance

to the many environmental forces.

The acceptance of and demand for environmental simulation

facilities result from the following factors: (1) parallel and reproducible

tests can be made, (2) equipment being tested can usually

be observed and analyzed during testing, and (3) supporting equipment

requirements are reduced to a minimum. Field testing and

product development costs are reduced, lead time required for completion

of product development is shortened, and most desirable

reliability features can be incorporated in the original manufacture

of the product.

Klima Alfa  Environmental test chambers are used not only to determine the

performance of mechanical and electrical equipment, but for certain

tests on personnel as well. Personnel testing includes (1) checking

protective equipment and clothing, (2) altitude and space procedures

indoctrination, and (3) studying physiological and psychological

effects.

Temperature Chambers. These are used for (1) temperature

soaks at high and low extremes, (2) temperature shock testing in

which the part is subjected to rapid high and low temperature

cycling, and (3) programmed cycling in which the parts are

subjected to repetitive expansion and contraction stresses and

breathing.

Humidity Chambers. These may involve simply exposing the

equipment to a constant humidity level, or cycling, wherein the temperature

and relative humidity are varied. Cycle testing induces

breathing and condensation within the parts tested. Subcooling may

also be used to produce icing conditions.

COOLING SYSTEMS

Temperature reduction in test chambers are accomplished by

both mechanical refrigeration systems and the use of expendable

refrigerants. Both methods are used directly or in conjunction

with secondary heat transfer fluids.

Mechanical Refrigeration

Mechanical refrigeration system uses vapour compression with a working medium as refrigerant.The system includes a compressor condenser expansion valve and an evaporator to complete the cycle.

Expendable Refrigerants

Expendable refrigerants, such as dry ice, liquid carbon dioxide,

liquid nitrogen, liquid helium are used for producing low temperatures in environmental chambers.

Sublimation of dry ice within the chamber, chilling brine for

circulation through heat exchangers, or direct expansion of the liquids

within the test space are common expendable refrigerant methods.

Liquid nitrogen, liquid helium, and other cryogenic liquids

work particularly well below the temperature range of mechanical

refrigeration systems.

The advantages of expendable refrigerants in environmental test

equipment are reduced initial cost, basic simplicity, reduced weight

and size of the chamber, and the ability to produce very rapid pulldown

rates to low temperatures. Disadvantages include higher operating

costs, the need for a reliable source of expendable refrigerants,

the potential personnel hazard resulting from the absence of oxygen

when the air is displaced in the test space, and the possible detrimental

effect of submerging the tested product in the gas or liquid of

an expendable refrigerant which is expanded directly into the test

space.

HEATING SYSTEMS for Environmental chambers

Electric heat is most commonly used in environmental chambers.

Prime or extended surface, tubular, or strip heaters are suitable

for circulating airstream systems. This method is a

conduction or convection type of heating used to duplicate conditions

in storage, in transportation, and when a protective housing is

provided around equipment. With proper precautions, open

nichrome, strip, or coil wire heaters is used; they offer the

advantages of a rapid response because of their low thermal mass.

All types of electric heaters require proper insulation and protection

against moisture. Generally speaking, temperature test chambers

(dry-bulb control) may use open wire resistance heaters,

although condensation at low temperatures may produce excessive

moisture and corrosion on the heaters.