Exhaust&natural gas absorption chiller

2.1 Working principle
In our daily life, as we all know that, we will feel cool if dripping some alcohol on the skin, that’s because the evaporation will absorb heat from our skin. Not only alcohol, all other kinds liquid will absorb surrounding heat while evaporation. And the lower the atmospheric pressure, the lower the evaporation temperature. For example, the water boiling temp is 100℃ under 1 atmosphere of pressure, but If the atmospheric pressure drops to 0.00891, the water boiling temp becomes to 5℃.That’s why under vacuum conditions, water can vaporize at very low temp.
That is the basic working principle of a LiBr absorption chiller. Water(refrigerant) vaporizes in the high-vacuum absorber and absorbs heat from the water which is to be cooled. The refrigerant vapor is then absorbed by the LiBr solution(absorbent) and circulated by pumps. The process repeats.
2.2 Flow diagram
The working principle of the chiller is shown as Figure 2-1. The diluted solution from the absorber, pumped by the solution pump, passes the low-temp heat exchanger(LTHE) and high-temp heat exchanger(HTHE), then enters the high-temp generator(HTG), where it is boiled by the high-temp flue gas and natural gas to generate high-pressure, high-temp refrigerant vapor. The diluted solution turns into intermediate solution.
The intermediate solution flows via HTHE into the low-temp generator(LTG), where it is heated by the refrigerant vapor from HTG to generate refrigerant vapor. The intermediate solution becomes concentrated solution.
The high-pressure, high-temp refrigerant vapor generated by HTG, after heating the intermediate solution in LTG, condenses into refrigerant water. The water, after being throttled, together with the refrigerant vapor generated in LTG, enter the condenser and be cooled by the cooling water and turns into refrigerant water.
The refrigerant water generated in the condenser passes a U-pipe and flows into the evaporator. Part of the refrigerant water vaporizes due to the very low pressure in the evaporator, while the majority of it is driven by the refrigerant pump and sprayed on the evaporator tube bundle. The refrigerant water sprayed on the tube bundle then absorbs the heat from the water flowing in the tube bundle and vaporizes.
The concentrated solution from LTG flows via LTHE into the absorber and is sprayed on the tube bundle. Then, after being cooled by the water flowing in the tube bundle, the concentrated solution absorbs the refrigerant vapor from the evaporator and becomes diluted solution. In this way, the concentrated solution continuously absorbs the refrigerant vapor generated in the evaporator, keeping the evaporation process continuing. In the meantime, the diluted solution is transmitted by the solution pump to HTG, where it is boiled and concentrated again. Thus a cooling cycle is completed and the cycle repeats.

Fig. 2-1 Process Flow Diagram

2.3 Main Components and Functions
1. Generator
HTG Function: Boils the solution with the high-temp flue gas or heat from the burner to generate the primary refrigerant vapour which will enter LTG and concentrate the solution into intermediate solution which will flow to HTHE.
LTG Function: Concentrates the intermediate solution into concentrated solution with the primary refrigerant vapour, which becomes refrigerant water, which in turn creates the secondary refrigerant vapour.

2. Condenser
Condenser Function: Condenses the secondary refrigerant vapour from LTG into water and cools down the primary refrigerant water from HTG, with heat being taken away by the cooling water.

3. Evaporator
Evaporator Function: By evaporating the refrigerant water, absorbs heat from the water flowing through the air conditioning system.

4. Absorber
Absorber Function: The concentrated solution absorbs the refrigerant vapour from the evaporator, with the heat being taken away by the cooling water.

5. Heat Exchanger
High temp. Heat Exchanger Function: Recovers heat from intermediated solution from HTG.
Low temp. Heat Exchanger Function: Recovers heat from concentrated solution from LTG.

6. Automatic Air Purge System
System Function: The air purge system is ready to pump out the non-condensable air in the heat pump and maintain a high vacuum condition. During operation, the diluted solution flows at a high rate to produce a local low pressure zone around the ejector nozzle. Thus the non-condensable air is pumped out of the heat pump. The system operates simultaneously with the heat pump. While the heat pump is working, the automatic system helps maintain a high vacuum inside and ensure system performance and a maximized service life.
The air purge system is a system composed of the ejector, cooler, oil trap, air cylinder and valve.

7. Solution Pump
The solution pump is used to deliver the LiBr solution and secure the normal flow of liquid working mediums inside the heat pump.
The solution pump is a wholly-enclosed, canned centrifugal pump featuring zero liquid leakage, low noise, high explosion-proof performance, minimal maintenance and a long service life.

8. Refrigerant Pump
The refrigerant pump is used to deliver refrigerant water and ensure the normal spray of refrigerant water on the evaporator.
The refrigerant pump is a wholly-enclosed, canned centrifugal pump featuring zero liquid leakage, low noise, high explosion-proof performance, minimal maintenance and a long service life.

9. Vacuum Pump
The vacuum pump is used for vacuum purging at the start-up stage and air purging at the operation stage.
The vacuum pump features a rotary vane wheel. The button to its performance is vacuum oil management. The prevention of oil emulsification has an obviously positive impact on air purging performance and helps lengthen the service life.

10. Electric Cabinet
As the control center of the LiBr heat pump, the electrical cabinet houses the main controls and electrical components.