Heat to Cooling Absorption

Principle of absorption chillers

A solution of water (refrigerant) / lithium bromide (sorbent) is circulating in the chiller.

The basic property of an absorption chiller is that at one specific pressure and temperature corresponds to one value of solubility of a solution. Heated in the generator, the refrigerant vapour is released from the solution and flows to the condenser, where it is condensed, and then to the evaporator where it evaporates, removing heat from the chilled water. In the absorber, the remaining solution rich in lithium bromide absorbs refrigerant vapour.

The concentrated solution returns to a diluted state as refrigerant vapour is absorbed. Thereafter the solution is forced by a pump through the heat exchanger, collecting heat from the concentrate solution before returning to the generator for boiling again to repeat the cycle.

Three technologies of Absorption chillers

 

 

 

MEMENTO ABOUT ABSORPTION CHILLER

History:
1st absorption chiller
1st LiBr/H2O absorption chiller

1850
1970

Cooling capacity

From 5 kW to 12 MW

Example of high quality heat sources

Any suitable industrial waste streams (Exhaust, steam, hot water, etc.)
Any suitable combustible (Nat.gas, biogas, diesel, waste oil, wood pellets, etc.)

Typical applications

Industry, hospital, hotels, malls


For quick budgeting, please have a look at our Quick Budgeting Tool

Three technologies of absorption chillers

heatcool01

  • Refrigerant: Li-Br

Absorption: thermodynamic cycle using heat source in lieu of electricity
Refrigerant: Water (no CFC’s or freons)
Absorbent: Lithium bromide (type of salt)
Refrigeration effect: Evaporation under vacuum

  • Technical details

Compared with mechanical chillers, absorption plants have a low coefficient of  performance (COP =0.7 max). However, it only uses electricity for the pumps which  circulate the water in the different circuits (hot water, water to the cooling tower,  water to the solar collectors and chilled water) and a small pump to circulate the  lithium bromide solution in the chiller. For a 35 kW cooling load installation, we  estimate that the electric power needed is 21.8 kW using a conventional chiller and  only  5.5 kW with a plant which is using an absorption chiller.

Single-effect

Double-effect

Driving temperature
(Heat Medium circuit)

70-100°C
Low temperature: avoid crystallization and corrosion

130-160°C

COP at design conditions (approx.)

0.7

1.4

Collector technology

Evacuated tubes, Concentrating Solar Panels

High efficient evacuated tubes, Concentrating Solar Panels

 

The high adaptability of absorption chillers

Absorption is a widespread used technology. Indeed, this thermal driven technology can use any heat  (waste heat from industrial processes, gas, biogas, exhaust, etc.) to  be driven. Moreover, many products are available from low to high capacities (4.5 kW to some MW). Manufacturers are mainly from Asia (Japan, Korea, China, and India).

Example of applications

Presentation of a solar cooling plant with absorption chiller
Solar Cooling uses an absorption chiller instead of the conventional compression chiller. The two chillers are similar except for the method of raising the pressure of the refrigerant vapour. In a conventional chiller, a compressor is used to raise the pressure of the refrigerant whereas in an absorption chiller, heat is used. Consequently, a hot water storage tank is required. This tank is fed with energy produced by the solar circuit: the water is circulated from the bottom of the tank to the collectors before being reintroduced to the top of the tank.


Absorption chillers require three water circuits:

  • The heat medium water circuit provides heat to the generator of the chiller.
  • The cooling water circuit evacuates heat from the absorber and the condenser of the chiller.
  • The cooling water is cooled in the cooling tower before going back to the chiller.
  • The chilled water circuit releases heat to the evaporator of the chiller.


Trigeneration

This schematic below presents an exhaust fired absorption chiller in a tri-generation installation located in Austin, USA. Trigeneration is defined as the simultaneous production of cooling, heating and power in one process. This plant recovers nearly all of the "waste heat" produced by the gas turbine generating the electricity. The plant will simultaneously generate electricity to power buildings, then use the heat from the turbine to produce chilled water for air-conditioning and hot water. The Broad absorption chiller is run with the hot water coming from the gas turbine.



For more information, please consult the following case studies:

Case study - Absorption chiller installation in a Hotel
Case study – Waste heat utilisation on a deep frying facility

History

Absorption cycles have been used in air-conditioning applications for over 50 years. Ammonia-water absorption equipment was found to be well suited for large capacity industrial applications that required low temperatures for process cooling. In the late 1950s the first working double-effect lithium bromide – water absorption  equipment is currently used to produce chilled water for space cooling and can also be used to produce hot water for space heating and process heating.

In the 1960s the natural gas industry was very effective in promoting this alternative to electric-driven cooling. Absorption cooling and gas absorption chillers were costs, and better system performance. Counteracting this, innovations in compressors, electric motors, and controls increased the performance and decreased the cost of electric cooling systems. Additionally, and perhaps more importantly, the gas crunch of the seventies curtailed gas cooling promotion and forced prospective buyers to remain with conventional electric systems.

Since 1987 when the Montreal Protocol first came into existence many issues surrounding electric cooling including the use of CFC refrigerants and electric utility rates, have become increasingly complicated. Coincident with these electric cooling issues, gas costs have remained relatively stable while the technology itself has improved.

Since 1995 several factors have helped the absorption cooling market including: the opening of large natural gas equipment manufacturing plants in the United States, major developments in equipment financing and performance contracting. As of the end of 1997, two U.S. manufacturers were conducting research and development (R&D) programs aimed at producing triple-effect absorption chillers.

YAZAKI Developing Milestones: Developed its first Aroace absorption chillers in 1970,  Set-up the first mass production of small to medium sized absorption chillers,  YAZAKI designed the world’s first solar powered air conditioning system (1974),  YAZAKI starts production of the first Aroace water fired chillers WFC-400 and WFC-600 (4.5 & 7 kW capacity) (1977),  Started of production of the double effect absorption chiller/heater Aroace CH-DE series (70 & 105 kW) (1980),  YAZAKI launches its new AroaceWFC-SC 5 model, featuring 17.5 kW cooling capacity for the European market (2007)

BROAD Developing Milestones: First direct-fired non-electric chiller (DFA) manufactured in China (1992),  World's largest manufacturer and seller of non-electric chillers (since 1996),  World's only manufacturer remotely monitoring all chillers (since 1996), World's first exhaust-fired non-electric chiller (1999),  World's first multi-energy non-electric chiller (2001),  World's smallest non-electric chiller (2002) & largest central air conditioning (2003)und

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