Absorption chiller sets are very different to vapour compression chiller sets
and as such some of the functions, features and technologies are explained
in this sheet.

Worldwide concern over global warming issues and environmental impact on
the way we carry out our everyday lives has dictated that an alternative approach to air conditioning is required. Absorption cooling offers this.

The single biggest difference is the omission of a compressor on an absorption chiller.

BROAD absorption chillers use a heat source as the energy input medium. This results in minimal electrical consumption with an absorption chiller. The only energy source a BROAD absorption chiller cannot use is electricity.

When a liquid absorbs heat from its surroundings, it evaporates. The classic example of this phenomenon involves alcohol. When you spread alcohol on your hand, your hand will feel cold.

The alcohol is absorbing heat from your hand and evaporating into the air. This example is emblematic of the absorption process that occurs in absorption cooling. Water evaporates at 100deg C under normal atmospheric pressure (760 mmHg), but under vacuum conditions, water can evaporate at very low temperatures. By creating a vacuum (6 mmHg) within absorption chiller systems, water is evaporated at temperatures as low as 40C.

That water, in the form of water vapour, then migrates from the evaporator to the absorber where a lithium bromide solution (a very strong absorbent of water) absorbs the surrounding vapour, continuously maintaining the low pressure vacuum condition in the evaporator/absorber vessel. All absorption chillers are designed as per the theory that the water within the chiller system will take away the heat of the water flowing through the air conditioning system as it evaporates under vacuum conditions. The concentrated lithium bromide solution absorbs the water vapour.

The now diluted solution is pumped back to the high and low temperature generators (HTG and LTG) where a heat source is added to re-vaporise the water separating it from the lithium bromide solution. The concentrated LiBr solution returns to the absorber and the water vapour migrates to the condenser where it becomes pure distilled refrigerant water..

BROAD absorption chillers have the ability of using a wide range of heat sources to initiate and produce chilled water. The lithium bromide solution is heated in the generator in a similar fashion to water being boiled in boiler. Traditional burners can be used, using natural gas, LPG or oil, alternatively a waste heat stream from a process will also heat the solution effectively. Waste heat streams can vary from hot water, steam or exhaust from an engine, industrial process, exhaust from incineration or steam from a condensed gas generator.

There is also the ability to use solar energy from solar collectors. The various kinds of energy streams appropriate for BROAD absorption chillers is remarkable and just about any energy input will drive the machines with the exception of electricity.

BROAD absorption chillers can be used in exactly the same way that a traditional vapour compression chiller is used. Where there is an air conditioning or refrigeration requirement a BROAD absorption should be considered. For comfort cooling BROAD absorption chillers can produce 70C chilled and for refrigeration processes temperatures as low as 30C can be achieved.

The chilled water can then be used in any of the normal ways, cooling coils in air handling units, serving chilled water fan coil units, chilled beams amongst some examples. Capacity for BROAD absorption chillers range from as low as 16kW right up to 23,260kW with very good incremental increases to ensure accurate load matching.

BROAD absorption chillers have the ability of using a wide range of heat sources to initiate and produce chilled water. The lithium bromide solution is heated in the generator in a similar fashion to water being boiled in boiler. Traditional burners can be used, using natural gas, LPG or oil, alternatively a waste heat stream from a process will also heat the solution effectively. Waste heat streams can vary from hot water, steam or exhaust from an engine, industrial process, exhaust from incineration or steam from a condensed gas generator.

There is also the ability to use solar energy from solar collectors. The various kinds of energy streams appropriate for BROAD absorption chillers is remarkable and just about any energy input will drive the machines with the exception of electricity.

In the past absorption chillers were critised for being unreliable, unstable and lacking the ability to perform at part and low loads. BROAD have revolutionised this and have invested heavily to make the BROAD absorption chiller the most reliable amongst its competition. Absorption cooling in general has moved forward a huge amount and BROAD has lead this trend.

BROAD absorption chillers now incorporate fully automatic purging meaning cooling capacity reduction and internal corrosion are things of the past; this feature is a standard offer and not a cost option unlike what other manufacturers put forward. Crystallization was also a historic problem for absorption cooling because the solution used in the process (LIBr) is salt based, BROAD absorption chillers now feature a self diagnostic and dynamic de-crystallization procedure which is carried out under normal circumstances whilst the chiller is operational without any need fro intervention by an operator or maintenance person.

BROAD acknowledges that purchasing a chiller is a large commitment and the customer needs the confidence that their investment will perform to its maximum ability for the duration of its working life. BROAD absorption chillers do not suffer any detrimental effects when working at part load and can be operate as low as 5% of the full cooling capacity.

BROAD have a continual goal to improve the efficiency of their absorption chillers and manufacture machines with the best coefficient of performance (COP) in their class. To achieve this BROAD has adopted plate heat exchanger technology, parallel flow operation which reduces start up time and energy, incorporated speed control on the small pumps which serve the absorber and refrigerant circuit, intelligent PLC control which constantly monitors all chiller parameters and adjusts accordingly to ensure the operation is as efficient as possible. Developed and patented two pass spraying on the evaporator tubes. The PLC also has the ability to signal condenser water pump and cooling tower fan to maximise efficiency and reduce energy on the condenser water side.

These features result in lowest operating cost which gives faster paybacks and good return on investment.

BROAD are very proud that their absorption chillers cause far less impact on the environment in comparison to traditional vapour compression. This is achieved by using non ozone depleting refrigerant to cool the evaporator tubes and producing significantly less harmful green house gases. Typically, a gas fired BROAD absorption chiller will produce 30% less CO2, an indirect fired absorption chiller will use 75-90% less and chiller using solar energy will produce up to 95% less. BROAD is reducing investment globally in power generation and is committed to research and development in ecological sustainable technologies for the HVAC industry.

BROAD are the only manufacturer in the world who can provide a complete and reliable solar air conditioning system. This is an area that BROAD is focusing major efforts on with respect to improvement and refinement. In the past fifteen years BROAD products have reduced construction and investment in power stations around the world

Contrary to common belief BROAD absorption chillers are extremely low maintenance, latest cutting edge technology such as auto purging, auto decrystallization, electronic maintenance and service records ensure this. Older technology absorption chillers relied on manual purging which required a maintenance technician to purge the chiller with a vacuum pump weekly to remove non condensable gases, non condensable gases occur naturally during the absorption process, if too many are allowed to develop this can reduce cooling capacity and in extreme cases lead to corrosion internally. BROAD absorption chillers use in line falling head pressure and the hydraulics of the process to remove non condensable gases without any need for operator intervention.

Crystallization takes place in absorption chillers because the LIBr solution is similar in make up to common table salt, at low temperatures and when the concentration of the solution is high there is a risk of crystallization which reduces cooling capacity and can if left without remedial action end in internal pipework becoming blocked. BROAD absorption chillers incorporate a patented auto decrystallization procedure; the highly sophisticated intelligent control system monitors temperatures throughout the chiller and if temperatures indicate that crystallization may occur the chiller takes proactive action to avoid this. This is also done automatically without the need for an operator.

There are a very few moving parts within an absorption chiller and therefore maintenance is limited to visual inspections monthly and minor maintenance quarterly or half yearly depending on operational hours. BROAD absorption chillers come with a twelve month warranty which includes first year maintenance; Energy Conservation Systems can provide full maintenance cover beyond this and are available for all technical and maintenance back up. Every BROAD absorption chiller comes with a tool box which includes approximately four years worth of consumable spare parts. Additional spares are readily available from Energy Conservation Systems.

BROAD absorption chillers are widely used throughout the world, customers such as US Department of Energy, Madrid Airport, various global health departments, hotel chains such as Holiday Inn, department stores such as Bloomingdales to name just a few. BROAD absorption chillers are used as lead chillers because of their reliability and are exceptional value for money.

BROAD absorption chillers are not only packed with reliability and energy saving technologies, they also come with excellent no cost options such as exterior hot and cold surface insulation; all other manufacturers charge this as an optional extra. BROAD absorption chillers include the most sophisticated and innovative programmable logic controller (ICS) with a 40cm touch screen which displays clear graphical images and allows the user to navigate easily through straight forward and self explanatory service menus. Functional areas in the controller are password locked to avoid accidental input. Only authorised staff need to know the password. The touch screen can be located up to 30 metres from the chiller if required. All chillers come with an impressive tool box that includes routine spare parts to cover the chiller for up to fours years’ maintenance.

BROAD absorption chillers are programmed to control your cooling tower fan, pump, water renewal system and chilled water system should your require it. Other manufacturers charge for this facility, if you do not want to use these functions there is no problem, there are simply made inactive at commissioning stage. We would recommend taking full use of these valuable signals as they will ensure that your BROAD absorption chiller controls parameters effectively thus saving maximum energy.

Every single BROAD absorption chiller is fully load tested at full and part load before they leave the factory, this guarantees that the correct cooling capacity is achieved and that no problems are found when the chiller arrives on the jobsite. In fact every BROAD absorption chiller is commissioned twice, giving the customer confidence that they are receiving exactly what they have paid for. All Broad absorption chillers can be internet monitored; this provides that extra bit of reassurance that your chiller is cared for every step of the way.

BROAD absorption chillers are monitored free of charge in the first year as long as they are connected to telephone line, after this there is a minimal annual fee.

LiBr is made up of non-toxic white crystal particles. It is stable and odorless with a salty taste at room temperature. Its chemical characteristics are the same as table salt (NaCI). It is degenerative, non-volatile and decomposable in the atmosphere but soluble in water. If allowed to mix with oxygen for long periods it will cause corrosion to metal surfaces, this was a problem for older technology absorption chillers.

BROAD absorption chillers use the auto purge procedure to maintain the vacuum inside the chiller at all times, this avoids oxygen ever leaking into the chiller. Maintaining a very good vacuum in an absorption chiller is one of the most important objectives to ensure a long service life.

Typically the economic life is similar to a traditional vapour compression, depending on use a BROAD absorption chiller should last around 20 to 25 years.

If maintenance is performed to a very high standard the chiller may operate satisfactorily for years beyond this prediction, this is line with guidance from the AIRAH technical handbook “Economic Life of Equipment”.