Closed circuit cooling towers provide evaporative cooling for a lot of types of methods, and the specific utility will largely decide which BAC Closed Circuit Cooling Tower is greatest suited for a venture. Comparability Table Specialised assistance is obtainable through your local BAC Representative.
Closed circuit cooling towers function in a fashion much like open cooling towers, except that the heat load to be rejected is transferred from the process fluid (the fluid being cooled) to the ambient air by means of a heat change coil. The coil serves to isolate the method fluid from the outside air, holding it clean and contaminate free in a closed loop. This creates two separate fluid circuits: (1) an external circuit, by which spray water circulates over the coil and mixes with the outside air, and (2) an inner circuit, wherein the method fluid circulates inside the coil. During operation, heat is transferred from the internal circuit, by way of the coil to the spray water, after which to the environment as a portion of the water evaporates.
BAC manufactures two sorts of closed circuit cooling towers: combined circulate and counterflow.
Mixed circulation is the use of both a heat alternate coil and fill for heat transfer in a closed circuit cooling tower. The addition of fill to the standard closed circuit cooling tower design reduces evaporation within the coil part, decreasing the potential for scaling and fouling. BAC’s mixed circulate closed circuit cooling towers make the most of parallel flow of air and spray water over the coil, and crossflow air/water circulate by the fill.
In parallel flow, air and water flow over the coil in the identical path. The method fluid travels from the bottom to the top of the coil, increasing effectivity by bringing the coldest spray water and air in touch with the process fluid at its coldest temperature.
In the fill of BAC’s mixed movement closed circuit cooling towers, air and water interact in a crossflow configuration: water flows vertically down the fill as air flows horizontally across it.
Combined Move: Parallel Circulate of Air and Water Over the coil
Mixed Circulation: Crossflow Configuration Over the Fill
In a counterflow closed circuit cooling tower design, the move of the air is in the opposite direction of the spray water. In BAC’s counterflow closed circuit cooling towers, air travels vertically up by way of the unit while the spray water travels vertically down over the coil. The process fluid flows from high to bottom through the coil and is in thermal counterflow to the air.
The circulate of air by way of most manufacturing unit assembled closed circuit cooling towers is offered by one or more mechanically pushed followers. The fan(s) may be axial or centrifugal, every type having its own distinct advantages.
Axial fan models require roughly half the fan motor horsepower of comparably sized centrifugal fan models, offering significant lifecycle price financial savings.
Centrifugal fan items are able to overcoming reasonable quantities of exterior static strain (0.5 12.7mm of H2O, making them suitable for both indoor and outdoor installations. Centrifugal followers are also inherently quieter than axial fans, though the difference is minimal and may typically be overcome via the appliance of non-obligatory low sound fans and/or sound attenuation on axial fan models.
Fans may be utilized in an induced draft or a pressured draft configuration. The rotating air handling components of induced draft equipment are mounted in the highest deck of the unit, minimizing the impact of fan noise on near-by neighbors and offering most protection from fan icing if units operate in sub-freezing circumstances. The use of corrosion resistant supplies ensures long life and minimizes upkeep necessities for the air dealing with parts.
Rotating air handling parts are positioned on the air intake face at the base of compelled draft towers, facilitating easy access for routine maintenance and service. Additionally, locating these components within the dry entering air stream extends component life by isolating them from the saturated discharge air.
Product capacities are called out when it comes to a stream fee at 95ºF/85ºF/78ºF. This refers back to the move charge of water that the unit can cool from a 95ºF (35.0ºC) entering water temperature to an 85ºF (29.4ºC) leaving water temperature at a 78ºF (25.6ºC) getting into wet-bulb temperature. BAC gives choice software to evaluate the performance of a closed circuit cooling tower at any circumstances.
All capacities proven are for a single cell; multiple cell units could be applied to attain bigger capacities.
All BAC Closed Circuit Cooling Towers are capable of withstanding getting into fluid temperatures as excessive as 180ºF (eighty two.2ºC), and the HXV is able to withstanding even greater temperatures due to the added dry coil expertise.
Advantages of Closed Circuit Cooling Towers
Figure 1: Chiller Loop with a Cooling Tower
Open cooling towers expose process cooling water to the environment, sometimes as part of a chiller system loop. Open towers use an efficient, easy, and economical design. All components in an open system have to be suitable with the oxygen launched via the cooling tower.
Determine 2: Chiller Loop with a Closed Circuit Cooling Tower
Closed circuit cooling towers completely isolate the method cooling fluid from the ambiance. That is achieved by combining the heat rejection gear with a heat exchanger in a closed circuit tower. A closed loop system protects the quality of the method fluid, reduces system maintenance, and gives operational flexibility at a barely increased preliminary cost.
When deciding which system is finest for an utility, several factors must be thought of.
If an utility should produce full capability throughout the year, maintaining a clear, dependable system loop is vital. Isolating the process fluid in a closed loop system prevents airborne contaminants from coming into and fouling the system. Sustaining optimum performance in an open loop system will require regular upkeep to assure comparable effectivity. Excessive efficiency chillers and heat exchangers depend on clean course of water to operate properly and are significantly impacted by even small amounts of fouling.
The preliminary equipment cost of an open loop system will likely be less than a comparably sized closed loop system, because the open system does not embody the intermediate heat exchanger part. Nonetheless, the upper first price of a closed loop system might be paid back throughout years of operation by way of the next savings:
Since the method fluid of a closed loop system is totally isolated from the setting, routine maintenance is simply required on the heat rejection equipment itself. The need to shut down the system periodically to clean the heat exchanger is dramatically decreased, if not totally eliminated. Providing clean process fluid to the system will lengthen the life of different elements in the system (condenser bundles, compressors, and so forth.).
Sustaining proper course of fluid high quality in a system could involve several steps, similar to chemical treatment, filtration tools and the addition of clean make-up water. A closed circuit cooling tower can provide the next advantages over an open cooling tower:
Closed circuit towers permit for the next modes of operation not attainable with open towers:
Closed Circuit Tower vs. Open Tower / Heat Exchanger
Figure 3: Chiller Loop With Cooling Tower/Heat Exchanger Combination
Sometimes, an open cooling tower is paired with a heat exchanger to capture some of the benefits of closed loop cooling. Selecting closed circuit cooling towers over this open tower/heat exchanger mixture should still be a better choice for the following causes:
These guidelines present some basic information to help decide whether or not a closed circuit cooling tower is best suited for a selected application than an open tower, with or and not using a heat exchanger. For extra help with a venture, please contact your native BAC Representative.