Absorption Chiller

Hot Water Operated Absorption Chiller

Absorption chillers, as opposed to traditional chillers, utilize waste heat from other processes or equipment to drive a thermodynamic process that enables water to be cooled and distributed for HVAC requirements. Water is typically combined with either ammonia or lithium bromide in lieu of traditional refrigerants, with lithium bromide being the more popular choice since it is non-toxic.

Important factors to consider while building an absorption chiller

Because absorption chillers do not use electric compressors, they may offer considerable cooling capacity to a facility while not contributing to peak energy demand. The most important factor to consider when evaluating the application of such a chiller is that they do need a substantial and constant supply of waste heat to operate. Although industrial manufacturing facilities are the most apparent choices, other locations like as university campuses, bigger hospital complexes, or large hotels may frequently benefit significantly from adding an absorption chiller.

The advantages of using absorption chillers

The primary refrigerants used in absorption chillers do not contribute to global warming or ozone depletion. An absorption chiller may help the facility save money on energy, hot water, heating, and cooling. The absence of compressors in the machine reduces noise and vibration in the building, resulting in a peaceful atmosphere with excellent dependability.

An absorption chiller is powered almost completely by heat that would otherwise be wasted. It does not need electricity to produce chilled water and heat. It will not be necessary to provide nearly as much capacity in an emergency backup power system.

The Science of Absorption Chilled Water

Absorption Chiller Cooling Cycle (Source: Shuangliang)
Absorption Chiller Cooling Cycle (Source: Shuangliang)

An absorption chiller has a condenser, generator, evaporator, absorber, and heat exchanger. The absorber initially holds lithium bromide solution. It will be forced via the heat exchanger into the generator tank on the chiller’s top. The chiller’s generator will utilize heat from the sun or hot water, steam, and flue gas from other systems. Heat separates lithium bromide and water. Water steadily evaporates and rises to the condenser, while lithium bromide sinks.

The lithium bromide will return to the absorber through a conduit. The vapor will next travel via a  cooling coil in the condenser.  Following this, the vapor is condensed to the condenser bottom.

The  water is then sent to the evaporator, where it  remove heat out of the chilled water and becomes the vapor.

When water evaporates, it takes away the heat. The vapor is then absorbed by lithium bromide solution in the absorber. The mixture flows through the heat exchanger and return to the generator.

An absorption chiller produces chilled water with little energy input. It will continue to remove heat from the building throughout the heating and cooling cycle.

More about the working concept

Firstly, a mixture of lithium bromide and water in the absorber is pumped through the heat exchanger to the generator

In order to separate the mixture in the generator, heat source from hot water, steam or flue gas will change water to vapor leaving the lithium bromide behind. Then, the vapor will flow into the condenser.

The lithium bromide won’t be left as a waste. It will form as a liquid and sink to the bottom of the generator. After that, the lithium bromide liquid flows down to the absorber once more through the heat exchanger. This liquid will spray over the absorber, so it will absorb vapor in the absorber again.

Meanwhile, the vapor from the generator is condensing into a refrigerant in condenser . Because of that, it meets with a cooling coil, whose water from cooling tower flows inside to remove heat from the vapor.

Next, the refrigerant kept in a tray flow through a pipe to the evaporator. A fixed orifice controls the volume flow rate of refrigerant. Due to vacuum condition in the evaporator, the boiling temperature of water will be quite low.

Finally, the chilled water which carries all the unwanted heat from the building or any cooling process flows through the evaporator to extract the unwanted thermal energy by spraying refrigerant over the chilled water line a. Therefore, the chilled water temperature will be decreased from 12°C to 7°C and refrigerant vapor is moving to the absorber to be absorbed with absorbent agian.

Making the most of absorption chillers

While absorption chillers are superior to traditional cooling techniques in the areas we’ve previously discussed, appropriate and frequent maintenance is required for optimum operation. This is the only method to guarantee that the equipment lasts the whole 25 years. A chiller will perform flawlessly if personnel concentrate on the following areas of maintenance: controls, mechanical components, and heat transmission components. Here are a few examples of areas that need attention:

• Pump shaft seals- inspect for wear • Refrigerant leaks- the loss rate should not exceed 1%
• Heat transfer surfaces must be clean and free of sludge and scale.
• Heat exchanger tubes – cracking, pitting, and corrosion are not desired.
• Pump bearings – repair or cleaning may be required.

Choosing the Most Effective Absorption Chiller

Even if you follow all of the aforementioned maintenance methods, the equipment will degrade, and your maintenance expenses will rise. That might be the moment to update to a more contemporary, dependable, and efficient equipment. If the system is running at part load for extended periods of time, a chiller with excellent part load efficiency may be all that is required. It is also critical to properly size the chiller. A chiller that is too large for a given application would almost certainly run at a poor efficiency. If it is subjected to such pressures for a long period of time, it may develop severe issues. The chiller upgrade/selection process should be defined by a comprehensive study of operating requirements, facility type, and timeline.

Advantages of absorption chillers

Advantages of absorption chillers (Source: Shuangliang)

We mentioned it briefly at the beginning of this article. According to the definition of absorption chiller functioning and needs, the following are situations where the chillers would be preferred.

• Expensive electricity and cheap gasoline. Make sure the difference is significant enough.
• There is insufficient electrical power.
• There is waste heat available (for example from exhaust flow or hot water from engine jacket).
• The availability of sufficient hot water or low-grade waste steam.

It will also fit places where a peaceful atmosphere is a necessity — an absorption chiller is a silent, wear-free system owing to the absence of moving components — and requires little maintenance.

How to Install an Absorption Chiller

It is preferable to deal with a contractor that has expertise with complex systems such as absorption chillers. Experts can assist you in designing, building, and funding an absorption chiller system that makes financial sense for your business and has a solid, obvious route to generating a fair return on investment.