Direct fired LiBr absorption chiller (heater) is a type of refrigeration (heating) equipment powered by natural gas, coal gas, biogas, fuel oil etc. LiBr aqueous solution is used as the circulating working fluid, in which the LiBr solution is used as the absorbent and water is the refrigerant. The chiller primarily comprises of the HTG, LTG, condenser, evaporator, absorber, high-temp heat exchanger, low-temp heat exchanger, auto purge device, burner, vacuum pump and canned pumps.

WORKING PRINCIPLE

Refrigeration Cycle

The refrigeration principle of this direct fired absorption chiller (heater) is shown in Figure 1. The heating and cooling switch valve F5 is opened, and F6-F10 are closed. The diluted solution from absorber is transported by the LTG solution pump , and heated by the low-temp heat exchanger and then enters the LTG. In the LTG ,the diluted solution is heated and boiled by the flowing high-pressure and high-temp refrigerant vapor from HTG and the solution is concentrated into an intermediate solution.

Most of the intermediate solution is transported by the HTG solution pump into HTG, after heated by the high-temp heat exchanger. In HTG, the fuel combustion releases heat to heat the LiBr solution to generate high-pressure, high-temp refrigerant vapor, and the solution is further concentrated into concentrated solution.

In the LTG, the high-pressure, high-temp refrigerant vapor from the HTG heats the dilute solution in the LTG and condenses into refrigerant water, which enters the condenser together with the refrigerant vapor generated in the LTG through throttling and depressurization, and then cooled into the refrigerant water corresponding to the condensing pressure by the cooling water in the condenser.

The refrigerant water in the condenser enters the evaporator after being throttled by the U-type tube, and then delivered by the refrigerant pump, sprayed on the evaporator tube cluster, absorbing the heat of the chilled water and evaporating, and then the temperature of the chilled water in the tubes drops, so as to achieve the purpose of refrigeration.
After part of intermediate solution from the LTG mixed with the concentrated solution from the HTG, it flows through the low-temp heat exchanger and enters the absorber, sprays on the absorber tube cluster, and is cooled by the cooling water, and absorbs the refrigerant vapor from the evaporator at the same time and then becomes the diluted solution. The LiBr solution diluted by absorbing the refrigerant vapor in the evaporator is transported into the generator for heating and concentration by the generator pump, which completes a refrigeration cycle. The process is repeated by direct fired absorption chiller so that the evaporator can continuously produce low-temp chilled water for air conditioning or production process.

Heating Cycle

The heating process of the direct fired absorption chiller (heater) is shown in Figure 2, the heating and cooling switch valves F5, F13, F14 are closed, F6-F10 are opened, the cooling water circuit and the refrigerant water circuit stop running, and the chilled water circuit is converted to a domestic hot water circuit. The Absorber, condenser, LTG, high-temp heat exchanger, low-temp heat exchanger stop working. The diluted solution in absorber is delivered to HTG and concentrated through the solution pump. The generated refrigerant vapor enters the evaporator through the tube and valve F7, condenses on the evaporator tube cluster, and heats the domestic hot water. The condensed refrigerant water enters the absorber from the evaporator water tray through valve F9. The concentrated solution in HTG enters the absorber through valve F8, and is mixed with the refrigerant water in absorber becoming diluted solution. The diluted solution is delivered back to HTG by solution pump and heated. The aforesaid cycle by direct fired absorption chiller occurs repeatedly to form a continuous heating process.