Aqua-Ammonia Absorption Technology

Natural gas-fired absorption air-conditioning systems, which were briefly
popular in the 1960’s, use ammonia as the refrigerant and water as the
absorbent.  In such systems, ammonia is boiled out of the water then condensed
in an outdoor coil.  The refrigerant is then expanded and evaporates in the
evaporator at low pressure, producing the cooling effect.  The ammonia is then
reabsorbed into the water.
           
Ammonia is a much more effective refrigerant than fluorocarbons in terms of
heat transfer and cycle thermodynamics.  In addition, ammonia has no ozone-depletion potential and no global-warming potential, and is not harmful to the atmosphere if released in the environment.  Ammonia/water absorption systems also have fewer moving parts than vapor-compression systems and exhibit long life.  In spite of this, in the past, these gas-fired systems have exhibited very low levels of efficiency.
           
Over the past two decades or so, many researchers have been trying to improve the efficiency of ammonia/water absorption systems, most notably by trying to capture and reuse the heat that is released when the ammonia is reabsorbed into the water.  This approach, described as generator-absorber heat exchange, or simply GAX, has been shown to raise efficiency levels dramatically, if implemented properly.
           
The new chiller/heat pump technology developed at Rocky Research also utilizes a GAX cycle, but the GAX aspect represents only one part of the solution to the performance limitations of the past.
           
Another important aspect of the design is the achievement of high-efficiency vapor separation.  Rocky Research’s generator has a special construction that allows high generated vapor purity despite having very low ammonia concentration liquid.  For example, on the hot end of the generator, the ammonia concentration in water which is used for absorption is in the range of 3 percent to 5 percent, while the vapor generated is Between 99.5 to 99.8 percent ammonia.  This performance is indicative of an extremely effective distillation process.
           
The absorber design includes a very unique heat-transfer surface enhancement that provides high heat transfer in conjunction with good surface wetting at part-load conditions, which makes it amenable to accepting variable-flow rates.

The combustion process includes a low-emission, variable-capacity burner, which is unlike other products on the market that are single-speed, on/off. 

Rocky Research’s aqua-ammonia absorption technology is unique in that it includes a true variable speed operation technology with the capability of load tracking.  The variable-capacity is made possible by a variable speed gas burner and by a new means of actively controlling the refrigerant.  Instead of employing a traditional orifice pack, which