The performance of absorption chillers is extremely
dependent upon the entering hot water temperature and flow rate. Where
water temperatures are over 250°F, as little as 1.2- 1.5 gallons per
minute of hot water can produce one ton of cooling. For example, a 120 gpm
waste heat stream at 250°F can probably produce 80-100 tons of cooling.
However, the same size stream at 200°F may produce only half as much
cooling. Additionally, the absorption equipment must be derated for lower
hot water supply temperatures. For example, a chiller that can produce a
nominal 560 tons with 250°F hot water will produce about 534 tons with
240°F, 430 tons with 220°F, and only 375 tons with 210°F hot water. This
deration of capacity seriously impacts the economics as the first cost per
ton rapidly increases. Remember also that absorption chillers fired with
hot water will only reduce that water temperature ~ 30-50°F for return to
the heat source. This tends to limit the viability waste heat recovery.