Unit 47 High-Pressure, LowPressure, and Absorption

The evaporator of a chiller can be used to absorb heat from ____.

• water

• a solution of water and polyethylene glycol

• the refrigerant

• both a and b

Two basic categories of chillers are the ____.

• compression cycle and absorption

• purge and absorption

• absorption and lithium bromide

• purge and lithium bromide

A benefit of operating a compressor unloaded is ____.

• reduced energy costs

• reduced compression ratios

• increased cooling

• both a and b

A reciprocating compressor with six cylinders, three banks of two cylinders each, can have its capacity reduced by unloading to ____% of full capacity.

• 33

• 50

• 66

• 25

Speeds up to rpm are used in centrifugal compressors.

• 15,000
• 20,000

• 25,000

• 30,000

A centrifugal compressor uses for capacity control.

• guide vanes
• block vanes

• guide blocks

• control vanes

7. Direct expansion evaporators have .

• expansion joints between sections of the evaporator

• an established superheat at the outlet of the evap
• subcooling at the outlet of the evaporator

The compressors used in low pressure chillers are the ____ type.

• reciprocating

• scroll

• screw

• centrifugal

When a chiller using a low-pressure refrigerant is operating, the low pressure side of the system ____.

• always shows a positive pressure

• is always in a vacuum

• contains a mixture of oil and air

• rejects oxygen and moisture

A purge unit ____.

• helps to provide subcooling in the condenser

• helps to provide superheat in the suction line

• relieves non-condensable gases from the system to the atmosphere

• provides capacity control