Cooling tower efficiency calculations cooling tower approach. Cooling tower efficiency is limited by the ambient wet bulb temperature. Range range is determined not by the cooling tower, but by the process it is serving. A discharge may be covered under this general permit if the discharge contains a small portion of cooling tower blowdown in addition to the nccw.
A basic understanding of the system water distribution shall be established in order to properly operate and maintain a cooling tower on a water efficient manner. Cooling tower basics calculation formulas cooling tower efficiency. Other factors, which we will see, must be stated along with flow rate m3hr. The water exits the cooling tower and is sent back to the exchangers or to other. Cooling tower blowdown is pumped to a firststage reaction tank. Cooling tower efficiency calculations along with approach, range, cycle of concentration.
Cooling tower blowdown the makeup water cooling tower blowdown water treatment presents several challenges due to the high salt concentrations and chemicals added in the cooling tower. Cooling tower makeup water calculation with example. The mass balance around a cooling tower as illustrated in the figure to the right is. Recovery and reuse of water from effluents of cooling tower. By using a blend of hard water and soft water, the cooling tower may still be able to run at higher cycles requiring less blowdown and makeup water. Calculation of effect of cycles of concentration on amount. Cooling tower efficiency calculation is described in this article. Blowdown is the difference between the set pressure and the reseating pressure of a safety or relief valve, expressed as a percentage of a set pressure or pounds per square inch. Based on above calculation, one can easily calculate the blow down needed to maintain the tds at any level. This process dilutes the system water mineral concentrations that steadily increase due to. To control the level of total dissolved solids tds within the boiler as water is boiled within the boiler and steam is produced, then the solids remain in the water and concentrate.
In ideal case the cold water temperature will be equal to the wet bulb temperature. Best management practice and guidance manual for cooling. Figure 4 illustrates these water system flow locations in generic terms. Drift is entrained water in the tower discharge vapors. The term induced draft denotes that air is drawn by fans through the flow of falling water and up and out of the cooling tower. In some large power plants, the cooling tower concentration cycles may be much higher. Shuichi chino, isamu sugiyama, jeffrey hollooway and deb mukhopadhyay, a new high efficiency r e verse. Thus, over time the level of total dissolved solids tds increases. Heat is removed by the tower primarily as the result of evaporation. Ides endtoend, integrated cooling tower blowdown water treatment solutions include highrecovery reverse osmosis solutions that reduce reject volumes and complete thermal zld solutions. Cooling tower efficiency calculations chemical engineering site. Concentration cycles in petroleum refinery cooling towers usually range from 3 to 7. Cooling tower wateris water circulated in an open system, such as the cooling tower and condenser of an airconditioning system or a turbine condenser.
Generally, after dosing of biocide blowdown is closed for 24 hours to make it more effective. When all the fresh water is evaporated solids are still in the tower the tower then refills. F drop in the temperature across the tower, and then an evaporation loss of 1. They reject process heat from the cooling water to atmosphere and keep the water cool. For example, new logic has a fullscale system installed at a gas production plant in the u. To control the cycle of concentration blow down or draw off is given. Cooling tower evaporative cooling system measurement. Contact fairfax water at 7036985800 to obtain both the cooling tower submeter and the cooling tower discharge blowdown meter. Noncontact cooling water nccw nccw includes once through cooling water for processes such as air compressors, welders, etc. Recirculating water is removed from the system by blowdown in order to control the water quality in the cooling tower system. Seawater cooling tower drift rate the drift rate for a new cooling tower equipped with best available drift eliminators would be 0. Our current blow down confirms the above calculation.
The cooling effect occurs because some of the water evaporates into a stream of air in contact with the water within the cooling tower. Guides and recommended procedures for water treatment. However, in a cooling tower circulating seawater, which has a dissolved solid content of about 35,000 ppm, the blowdown rate is typically maintained at about. Applying these values to formula 5, blowdown would be. If we start out with fresh water the tower has one cycle of concentration. Cooling tower plays a major role in chemical process industry. Technical reference for water conservation in cooling towers 1st edition. Cooling towers dissipate heat from recirculating water that is run through cool chillers, airconditioning equipment, or other process equipment. They are located in areas that are situated after the fill and water sprays and just before the area where the air exits the cooling tower see figures 6 and 8. Cooling towers work by evaporating a small portion of water, approximately 1. Noncontact cooling water or condensate and boiler water. Considering the cooling tower blowdown quality, discharge to surface water.
Handbook of pollution prevention and cleaner production best practices in the petroleum industry, 2009. Further evaporation causes these dissolved solids to come out of so. Process description the cooling tower is fed by clarified california aqueduct water. Any water source has various levels of dissolved and suspended solids. Let say we have cooling tower with the following data.
Cooling tower calculations cooling water treatment. Drift eliminators are also known as mist eliminators. Slug dosed chemicals like nonoxidising biocide calculated based on hold up volume of cooling tower. Drift loss draw off or blowdown as the cooling water circulates the cooling tower part of water evaporates thereby increasing the total dissolved solids in. Process leaks, windage, and drift are really just forms of uncontrolled blowdown. Hello, i am working as an intern for a company and i have been given a project for water conservation. The associated losses caused by blowdown, evaporation, drift, and system leaks must be accounted for by system makeup requirements. At these condi tions, the cooling tower rejects 15,000 btuih per nominal cooling tower ton. Cooling tower efficiency calculations cooling tower efficiency calculation is described in this article. Calculations 417 cooling tower blowdown equation by james mcdonald, pe, cwt originally published. Cooling tower bleedoffblowdown is the flushing of a portion of high mineral concentration cooling tower system water down the drain, while simultaneously replacing it with fresh water. The polishing ro concentrate stream is utilized as cooling tower makeup water see figure 1. Proper treatment of the water that circulates through the tower is a key element relative to the thermal efficiency. Cooling tower basics calculation formulas cooling tower.
Also, a heat balance plus experience shows that evaporation losses are 0. See figure 1 on page 3 for an illustration of the water being recirculated, added to, or lost from a cooling tower. As pure water is evaporated all of the solids are left behind so they concentrate in the cooling tower water. The historical derivation of this 15,000 btulh cooling tower ton, as compared to the 12,000 btuih evaporator ton, is based. My prime focus is on reducing the water consumption in the cooling tower. Cooling tower discharges present a potential problem to the treatment of sanitary sewer and sludge quality especially for the biosolids reuse facility.
Water efficiency management guide mechanical systems. Cooling tower evaporative cooling system measurement and verification protocol brian boyd and kate mcmordie stoughton pacific northwest national laboratory. Cooling water treatment manual, national association of corrosion engineers, houston, tx. Even if the assumed evaporation and drift rates were perfectly accurate, the calculated. I know that usually conductivity is the controlling factor but i would like to know if there is any design rule out there that relates the amount of makeup water to the amount of blowdown. Quick calculation of cooling tower blowdown and makeup quimusa quick calculation of cooling tower blowdown and makeup cooling tower blowdown is important to the utility balances for new plants, to the control of scaling in cooling equipment and to the operation of cooling towers. Does anyone have a rule of thumb about the amount of blowdown water from a cooling tower. Cooling tower fundamentals spx cooling technologies. Makeup water mu must be added to replace the evaporation. Cooling tower water treatment cycles of concentration. Department of energy idaho operations office idaho national engineering laboratory this is an informal report intended for use as a preliminaryor working document work supported by the u. Cooling tower blowdown equation by james mcdonald, pe, cwt originally published. Cstn july 2003 l et s take a look at how to calculate cooling tower blowdown. These maximize the overall recovery and minimize the volume for disposal.
Calculate boiler water blowdown flow yamatho supply. In this article explained about basic concepts of cooling tower, types of cooling towers, formula for cooling tower efficiency. Drift eliminators are installed to prevent water entrained in the air from leaving the system. Cooling towers how to calculate cycles, blowdown, evaporation, makeup 2 replies here are the governing relationships for the makeup flow rate, the evaporation and windage losses, the drawoff rate, and the concentration cycles in an evaporative cooling tower system. As this occurs, a small volume of water is evaporated, reducing the temperature of the water being circulated through the tower.
The blowdown rate will depend on the cycles of concentration required to. Calculate the amount of makeup water required for a cooling tower with following conditions. Technical reference for water conservation in cooling towers. A cooling tower discharge blowdown meter is required to ensure accurate flow measurement for sewer service billing per chapter 67. The calculation of cooling tower efficiency involves the range and approach of the cooling tower. An additional advantage of cooling blowdown is in helping to comply with local codes regulating the discharge of high temperature liquids into the sewer system. Jea, as the control authority, is required to regulate cooling tower discharges to the potw. For example, a cooling tower sized to cool 4540 m 3hr through a.