WATER usage and its disposal are demanding the attention of building owners and operators alike - the largest water authority in Australia, Sydney Water, has embarked on an ‘Every Drop Counts’ program with its primary goal to reduce water consumption by 17% over the next 10 years, in addition to the 18% already achieved since 1990.
Other states and cities around Australia are also taking count of their water reserves, with most imposing higher level water restrictions and inevitably increasing the costs to the end-user.
The inevitable question is: “Can the reality of shrinking water reserves and the continuing reduction of water usage mean that evaporative cooling, regardless of its energy efficient advantage, may become economically unviable?”
And the answer: “Absolutely not.”
High efficiency wet-dry hybrid evaporative condensers and fluid coolers developed by Baltimore Aircoil combine the advantages of both evaporative and air-cooled heat rejection devices resulting in much lower cooling temperatures than can be achieved with conventional air-cooled systems, with the added ability to provide water savings of up to 70%.
Two up
There are essentially two types of evaporative water-cooled systems used in condenser water loop systems: open cooling towers and closed circuit fluid coolers.
The most common system is the open cooling tower exposing cooling water to the atmosphere.
The second type of water-cooled system is the closed circuit fluid cooler that maintains cooling water in a closed loop that is not exposed to the atmosphere.
On the other hand, closed loop cooling systems offer a range of advantages.
The high efficiency chillers used in today’s cooling systems benefit from the use of clean water provided by a closed cooling water loop.
The fouling of chiller tubes is minimised with a closed condenser water loop and the chiller tubes do not need to be mechanically cleaned as often, which allows the cooling system to operate at maximum efficiency for longer periods.
Evaporative or combination
Some refrigeration plant owners resort to installing two separate pieces of equipment to save water and presumably operating costs.
The combination of an air-cooled and a water-cooled condenser has been the only viable method in gaining the benefits of both types of equipment.
Essentially, the air-cooled plant operates when ambient temperatures are low, and the water cooled plant supplements the refrigeration load during high wet-bulb and high ambient occurrences.
Hybrid versatility
New technology and enhanced engineering designs have resulted in the advent of hybrid condensers and hybrid closed circuit fluid coolers that combine the advantages of both air-cooled and evaporative heat rejection devices, which are lower in energy input and chemical consumption, are easier to maintain and provide maximum water savings.
Maximum water savings are achieved by providing three operating modes: dry, adiabatic and combined dry/wet.
At peak conditions in ‘dry/wet’ mode, a significant amount of heat is removed by sensible and evaporative heat transfer, hence reducing water consumption over conventional evaporative cooling.
As soon as the heat load and/or ambient conditions drop from peak design, water consumption is further reduced in the ‘adiabatic’ mode and is totally eliminated in the ‘dry’ mode of operation.
Depending on operating conditions, water savings of 70% can be achieved.
The combination of sensible, adiabatic, and evaporative heat transfer virtually eliminates plume which may occur with conventional evaporative cooling equipment.
Adding hybrid technology will only increase the popularity of evaporative cooling equipment in an operating environment that is striving for increased water and energy efficiencies.