HOW MUCH THIS HOW MUCH THIS DIRT COST YOU? DIRT COST YOU? Fouling Factor Fouling Factor Chad Venkat, Legionella Solutions Chad Venkat, Legionella Solutions
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HOW MUCH THIS HOW MUCH THIS DIRT COST YOU?DIRT COST YOU?
Fouling FactorFouling Factor
Chad Venkat, Legionella SolutionsChad Venkat, Legionella Solutions
Fouling FactorWhere Do These Particles Come From?
A typical 200 TR cooling tower the cascading water "scrubs" airborne contaminants from the atmosphere and carries 600 pounds of particulate matter from airborne dust and make- up water supply into the heat exchanger.
REF: CLIVE BROADBENT, ASHRAE REPORT 1992 & ASHRAE HAND BOOK 1996
Fouling FactorWhere Do These Particles Come From?
In addition, the system itself produces particles. These include corrosion products, mineral precipitates [e.g. iron oxides, hardness slats], microbiological colonies, aggregates of organic chemicals and many others.
Fouling FactorWhere Do These Particles Come From?Contamination by dissolved and particulate material leaking from the process side of heat exchange equipment adds to the process by precipitating insoluble chemical products, providing nutrients for accelerated biological growth, and accelerating corrosion and the formation of corrosion products.
Fouling FactorWhere Do These Particles Come From?
The particulates in cooling tower, when bound together by precipitation of scale-forming minerals, result in a greatly increased volume of scale and layer thickness.
Fouling FactorContaminants In Condenser Cost You Money?
These layers decrease heat transfer efficiency, reduce flow rate across heat exchange surfaces and encourages corrosion, resulting in addition fouling.
Slower flow allows more particles to settle, amplifying the problem and further reducing efficiency.
Typical Cooling Loop
Different Types Of WaterHARD WATER: The sudden changes in surface temperature causes dissolved solids [soluble] to lose their solubility. The resulting mineral ions become crystals. These crystals form a scale on the heat exchange surface. This is fouling.
DIRTY WATER: This is the non-soluble particulate in the water. Solids in suspension can also be caused by chemical reactions that occur in the treatment of a water system when soluble are chemically converted into insoluble and become suspended solids. These tend to circulate through the system or settle out where solid have settled out or are low velocity areas in the piping system.
Different Types Of Water1. Precipitation / Crystallization - dissolved inorganic
salts with inverse solubility characteristics. 2. Particulate / Sedimentation - suspended solids,
insoluble corrosion products, sand, silt. 3. Chemical Reaction - common in petroleum
refining and polymer production. 4. Corrosion - material reacts with fluid to form
corrosion products, which attach to the heat transfer surface to form nucleation sites.
5. Biological - initially micro-fouling, usually followed by macro-fouling.
Flow ProfileTurbulent high velocity flow helps to keep solids in suspension. Systems that are run at widely varying loads will havehighly varying flow rates & velocities.
Fouling FactorHOW DOES THIS A DIRTY WATER EFFECT A HEAT TRANSFER SYSTEM:
The Fouling layer inhibits heat transfer across heat-exchanger surfaces. The Foul Factor [ft2°F/BTU] is a quantitative indicator of heat exchange efficiency.
It represents the area of Chiller surface required to transfer a BTU of heat per unit of time.
The lower the number, the more BTUs a given wall area will transfer and therefore the more transfer a BTU of heat per unit of time. As a Foul layer thickens, the Foul Factor increases and heat transfer efficiency is decreased.
Currently, Condensers in water-cooled systems are designed to run efficiently at a foul factor of 0.00025 [per ARI Standards 550-98]
Fouling Factor
CONDENSER FOULING AFFECTS:1. COP BY 5% TO 15%2. REFRIGERATION CAPACITY BY 5% TO 20%3. SCT BY 5% TO 15%4. SDT BY 5% TO 10%
REF: ASHRAE JOURNAL NOVEMBER 2000 & FIELD TESTING
Typical Dirty System• Fouling is the formation of a deposit on the heat transfer
surfaces in a heating / cooling systems. • To put it simply, think of it like the buildup of grease in a
kitchen sink's trap. Keep pouring grease down the drain and soon you'll have a clog. Likewise, as the mineral ion scale builds up in a heat exchanger, water restriction and attendant problems occur.
INDEPENDENT STUDYA STUDY COMPLETED BY DREXEL UNIVERSITY
Under extreme fouling conditions shows that the foul factor increased from 0 at initial state until it reached the asymptotic level of .00024 without any water treatment.
Likewise, as the mineral ion scale builds up in a heat exchanger,water restriction and attendant problems occur. Energy required was reduced from the asymptotic level from 29% to 19% or approximately 33% by using filtration only.
POWER SAVINGSENERGY SAVINGS CALCULATIONSA layer of foul or scale measuring 1 ÷ 1000 inch thick can reduce heat transferto increase energy costs by as much as 10 %.
The formula listed below can be used to calculate the energy cost per year for an air-conditioning system:
AC TR X KW ÷ TR X Load factor X Hours of Operation per Year X Cost/KwhFor Example: 400 TR X 0.65 Kw/TR X 0.7 load factor X 2500 operating hours X0.07/Kwh = US $ 31,850 Energy Cost for One year.
From the above example, considering the same 400 TR chiller operating 2500hours a year at US $ 0.07/Kwh with a foul layer of 1 ÷ 1000 inch thick will resultin US $ 3,185 increased energy costs per year. This is a 10 % increase!
POWER INCREASE
Each .0001 increase in fouling results in 1.1% increase in power.New chillers are designed to operate with a fouling factor of.00025 [ASHRAE]
0
44.00.048.00433.00.036.00322.00.024.00211.00.012.0015.50.006.00051.10.001.0001
00Power IncreaseScale ThicknessClean
0
44.00.048.00433.00.036.00322.00.024.00211.00.012.0015.50.006.00051.10.001.0001
00Power IncreaseScale ThicknessClean
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
DUPONT CASE STUDY
2525%% 25%25%
COPCOPREFRIGERATIONREFRIGERATION
CAPACITYCAPACITY HEATHEAT EXCHANGER LIFEEXCHANGER LIFE
DISCHARGEDISCHARGE TEMPERATURETEMPERATURE
SIDE STREAM FILTRATIONSIDE STREAM FILTRATION
ENERGYENERGY CONSUMPTIONCONSUMPTION
10%10% 1010%%
Saving Your MoneySaving Your Moneywww.hysave.com.auwww.hysave.com.au
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