“I was looking for a new cooling sys- tem that would be reliable and offer the redundancy to enable it to continue run- ning even with a pump failure,” Burton said. “I also wanted a system that would provide not just the capacity to cool all of our furnaces and equipment running at the same time, but that would have the additional capacity to support anticipated future growth.”
Te next step in the overall cooling
system design is to make adjustments for the desired incoming water temperature from the tower to the process, the outgo- ing water temperature from the process to the tower and the climatic data for the foundry location.
Cooling Towers Te three basic types of cooling tow-
ers are evaporative, dry air and hybrid (adiabatic wetted dry air coolers). Evaporative cooling towers use water
sprays and fans to reduce the temperature of the hot water returning from the fur- nace. Tey offer the advantage of being highly efficient at removing heat, even during the summer months in warm climates. Evaporative cooling towers are available as large capacity units and, when configured as vertical cross-flow units, require a relatively small footprint. Dry air cooling towers use only air
flow supplied by fans to reduce the tem- perature of the water. Tey are effective when air temperature is cool but might not function properly during the sum- mer months in warm climates. In those cases, trim coolers, essentially added heat exchangers using city water supplies, might be needed to supplement the dry air cooling units. Dry air cooling installa- tions require a relatively larger footprint than comparable evaporative cooling systems because air flow is less efficient for cooling than evaporation. Hybrid units operate as dry air coolers
during the cooler months and incorpo- rate a water spray used only as needed during the hottest summer months. Essentially, evaporative cooling support is built into the hybrid unit. So hybrid cooling towers operate with equal effec- tiveness in hot weather and cold weather, offer a simplified design and reduce city water consumption. Because of the large cooling capac- ity needed, the warm summers typical
34 | MODERN CASTING February 2014
in southern Georgia and the limited space available for installation, Chassix required an evaporative cooling tower for its new system. Te selected unit is a ver- tical cross flow cooling tower with two 75 HP fans, able to cool 5,500 gallons per minute (GPM) from 115F to 85F. While the cooling tower’s job is to
reduce the temperature of the heated water coming from the furnace, water returning to the furnace that is too cold will cause its own problems. Tat’s because water that is close to or below
the prevailing wet bulb temperature, typically about 75F or less, will produce condensation on the furnace coil that can lead to electrical arcing. Such arcing can result in serious coil damage. To address this problem, most induction furnace cooling systems incorporate automatic cold water diversion valves. When the automatic controls detect that the tem- perature of the water leaving the furnace is too cold, the water is diverted from the cooling tower and flows directly back into the furnace. Tis continues until the
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