Gas turbine generators that experience high ambient air temperatures can benefit from evaporative cooling to improve turbine heat rate.
Is cooler air good for gas turbine generator efficiency?
Cooling ambient air can in fact have a positive effect on turbine generator output efficiency due to increased density of the air. For routinely warm climates, gains can be had by cooling the incoming air. By using evaporative cooling systems, the system heat rate can be improved while only causing a relatively small increase in inlet pressure drop. Certain large frame turbines can experience about 1.8% improvement for a temperature reduction from 30°C to 20°C (ref ASME Turbo Expo 2007).
Proper monitoring of wet and dry bulb temperatures will allow most operators to recognize changes in cooler system performance. However, best operation and reliability can be achieved with periodic inspections and by using high-quality evaporative cooling components for first install or for retrofit.
What are the components of an Evaporative Cooling setup?
Cooler Media – should be rigid and self-supporting. Materials such as resin impregnated cellulose or glass fiber that are chemically treated to resist degradation should be used. Treatments also yield efficient wetting and high evaporation rates. Cross fluted designs encourage water to stay at the front of the media pack, where dirt and minerals are most likely to collect. This also helps reduce water carry-over.
Distribution Pads – Distribution pads are used in conjunction with cooler media for lateral distribution of the water to the cooling media below. There, pads are 2” or 3” thick and are protected with a special edge treatment for long term performance and wear. Distribution pads are normally constructed with the same material as the cooler medium.
Drift Eliminator – The drift eliminator is made of an array of S-shaped passages. When air passes through the medium, water droplets impinge on the outside of each turn where they agglomerate and drain out of the front face. These droplets are large enough that they do not re-entrain in the air stream.
Downloadable Documents
Evaporative Cooler Media
Distribution Pads
Drift Eliminators
Our free Evaporative Cooling Preventative Maintenance Checklist for gas turbine users contains information and tips regarding On-Off cycling of pads, controlling scale and dirt, cleaning the sump and distribution system, minimizing nutrient contamination, and much more.
