Lithium Bromide Absorption Unit

Suction end of a centrifugal compressor showing prerotation vanes

Basic absorption cycle

Fireman - Navy Firefighter, Fireman training manual
Page Navigation
184

An oil heater keeps the oil warm in the oil sump of the compressor during plant shutdown. If the oil is not kept heated, it absorbs large amounts of refrigerant. This results in excessive oil foaming when the unit is started. The heaters in most plants are connected so that they are automatically turned on when the compressor is off, and off when the compressor is on.. Figure 10-20 shows a centrifugal compressor air-conditioning unit. This particular plant has a 150-ton capacity and uses R-114 as the refrigerant. The gauges and controls for the plant are on the other side of the unit. Lithium Bromide Absorption Unit Water is used as a refrigerant in the lithium bromide absorption cycle. The absorption system differs from the compression-type refrigeration machines. The absorption cycle uses heat energy instead of mechanical energy to cause the change in conditions necessary for a complete refrigeration cycle. In other words, the compressor is replaced by steam heat. The following are the two principles that form the basis for the lithium bromide absorption refrigeration cycle: 1. Lithium bromide has the ability to absorb large quantities of water vapor. 2. When under a high vacuum, (vaporizes) at a low temperature and, absorbs heat. water boils in doing so, To understand the lithium bromide absorption cycle, follow along on figure 10-21 during as you read the following explanation. Notice that the EVAPORATOR and ABSORBER sections are in a common shell. The sections are separated by the refrigerant tray and baffles. This shell is under a high vacuum of about 29.8 in.Hg. Water boils at 35°F (1.7°C) at this pressure. (Note that this is only 3°F above the freezing point of water.) The refrigerant pump circulates the refrigerant (water) through the evaporator. The water is sprayed out over 88the chilled water tubes through a spray header. This causes the water to vaporize (or flash) more readily. As the water vaporizes around the chilled water tubes, it removes heat from the circulating chilled water. The water vapor is floating about in the evaporator/absorber shell. Now, the absorber comes into play. Lithium bromide solution is sprayed out from a spray header in the absorber. The absorber pump provides the driving head for the spray. As the lithium bromide solution is sprayed out, it absorbs the water vapor, which is in the shell from the evaporation process. As the lithium bromide absorbs more and more water vapor, its ability to absorb decreases. This is 47.217 Figure 10-20.-R-114 centrifugal air-conditioning plant. 10-22

Privacy Statement
Press Release
Contact