Sanyo DE High temperature generator safety control, Expansion of safety operating zone

ENVIRONMENTALLY FRIENDLY TECHNOLOGY

High temperature generator safety control

SUPER ABSORPTION

The absorption cycle

When the temperature of the high temperature generator is higher					Together with the cooling water safety control and absorbent crystallization pro-
than a certain temperature level, the steam consumption is controlled to					tection control, the safety operating zone is broadened.
sustain safe operation.
Graph 8. Safety control chart
C)									100
generator(temp.highofTemperature°						Steam consumption ratio				ratio(%)consumptionSteam
									80
				Steam consumption
			control for 10 minutes
160									60
									40
150						Temperature of
									20
						high temperature generator
140									0
0	5	10		15	20	25	30	35

Time(minutes)

The absorption cooling cycle, like the compression refrigeration cycle, uti- lizes the latent heat of evaporation of a refrigerant to remove heat from the entering chilled water. The compression refrigeration system uses a chlorine based refrigerant and a compressor to transport the refrigerant vapor to be condensed in the condenser. The absorption system, however, uses water as the refrigerant and an absorbent to absorb the vaporized refrigerant. Heat is then applied to the solution to release the refrigerant vapor from the absor- bent. The refrigerant vapor is then condensed in the condenser.

The basic absorption cycle (see Figure 1) involves generator, condenser, evaporator and absorber with refrigerant (liquid) and lithium bromide as the working solutions. The generator utilizes a heat source (burner, steam or hot water) to vaporize the diluted lithium bromide solution. The water vapor that is released travels to the condenser where it is condensed back into a liquid, transferring the heat to the cooling tower water. Once condensed, the liquid refrigerant is distributed over the evaporator tubes, removing the heat from the chilled water and vaporizing the liquid refrigerant. The concentrated lithium bromide solution from the generator passes into the absorber, absorbs the refrigerant vapor solution from the evaporator and dilutes itself. The diluted lithium bromide solution is then pumped back to the generator where the cycle is started again.

Figure 1. Simplified absorption cycle

	Refrigerant vapor
	Condenser		Generator
Cooling	Liquid	Concentrated
water			Heat source
	refrigerant	solution

Cooling water

Chilled water

Evaporator Absorber

Absorbent pump

Expansion of safety operating zone

This ensures quick response to rapid changes and maintains stable operation.

Double effect type

The generator section is divided into a high temperature generator and a low temperature generator. The refrigerant vapor produced by the high tempera-

Figure 2. Double effect absorption cycle

Safety operating zone is between 19° C and 34° C of cooling water

temperature. (In case cooling inlet water temperature is 32° C)

Graph 9. Safety operating chart

100

ture generator is used to heat the LiBr solution in the low temperature gen- erator in which the pressure (hence the boiling point) is lower. Thus the heat of condensation is effectively utilized.

Refrigerant vapor

Condenser

Low temperature generator

Cooling water

Refrigerant vapor

Hight temperature generator

input(%)	80
	60
Maximum	40
	20
	0					(Variable from 20° C to 33° C)
		★--13	★--4	★	★+2

Cooling water inlet temperature(° C)

Liquid refrigerant

Evaporator

Chilled water

Intermediate solution

Concentrated solution

Absorber

Cooling water

Diluted solution

Absorbent pump

Heat source

Crystallization protection

As mentioned in the single effect type, the refrigerant vapor produced by the low temperature generator is sent to the condenser to become liquid refriger- ant. On the other hand, the refrigerant vapor produced by the high tempera-

Figure 3. Detail of generator

Refrigerant vapor to condenser

Microprocessor observes the absorbent concentration. Steam supply is stopped and the unit is recovered to the normal operation when the con- centration is over certain limit, to prevent the crystallization of absorbent.

Space saving by compact design

With the high performance heat transfer tubes, weight and size is re- duced by 10% of the previous C model.

ture generator turns to water as it releases heat to the intermediate LiBr solution. This happens inside the heat transfer tubes in the low temperature generator. The refrigerant vapor produced by both low and high temperature generators turns to refrigerant liquid and mixes in the condenser before re- turning to the evaporator.

Low temperature generator

Condensed refrigerant

Refrigerant vapor

High temperature generator

Heat source

Intermediate solution

Concentrated solution

Diluted solution

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