Chillers & Refridgerant Cycle Flashcards
What are chillers used for ?
Cool water in a chilled water system for us by HVAC equipment to cool rooms & equipment
What are stages of the refrigeration cycle?
Compression,condensation,expansion,and evaporation
What are corresponding components of chiller ?
Compressor,condenser,expansion valve(flash economizer),and cooler
What is compressor surge?
Reversal of refrigerant flow from the condenser to the cooler
What causes compressor surge ?
High differential press. between cooler & condenser
How is compressor surge prevented ?
Hot gas bypass valve and line routed from compressor discharge to cooler, which raises cooler press.
What is refrigerant stacking ?
Collection of refrigerant in the condenser rather than it moving back to cooler
What causes refrigerant stacking ?
Low d/p between condenser and cooler
How is refrigerant stacking prevented ?
Essential chillers have refrigerant head pressure control valve that throttles condenser cooling water flow , which raises or lowers condenser Press.
What is the purpose of the compressors inlet guide vanes ?
Control capacity of the chillers to control cooling of chilled water
What parameter is used to control the inlet Guide Vanes?
Chilled water leaving the cooler, going to HVAC loads
Whats the powers supply voltage to chillers compressor?
4.16kv
How many stages is the compressor ?
2 stages
What enters the second stage of the compressor ?
Flash gas from gas chamber in the Flash Economizer
What cools the compressor ?
Liquid refrigerant from sump of the bottom of condenser
What maintains the flow of the refrigerant ?
The D/P between the condenser and cooler
What lubricates the compressor bearings?
Oil pumped through cooler and filter to bearings
What controls the oil temp. When chiller is shutdown ?
Heaters in the oil sump
Why is the oil maintained heated ?
Minimize absorption of refrigerant by oil
What function does chillers condenser perform ?
Transfer heat from refrigerant to cooling water system
What is the function of the thermal economizer?
Subcool liquid refrigerant to increase efficiency (bottom of condenser)
Where does liquid refrigerant from thermal economizer go?
Into the Flash Gas Chamber in Flash Economizer, via High Side Float Valve
What is purpose of Flash Economizer ?
Provides intermediate pressure barrier between condenser and cooler
Regulates flow of refrigerant
What is the function of High Side Float ?
Serves as refrigerant level control for condenser, also maintaining level in thermal Economizer (bottom condenser)
What causes the liquid refrigerant to flash to a vapor in Flash Gas Chamber?
Expanded volume of chamber drops pressure
What is the purpose of the chillers cooler?
Transfer heat from chilled water to refrigerant
What is purpose of chillers pump down unit ?
Transfer to and from storage tanks, used for maintenance
