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EASY What type of systems are associated with chilled water-cooling systems and hot water heating systems?

  • Open loop systems
  • Closed loop systems (correct)
  • Semi-closed systems
  • Semi-open systems

    • What is the purpose of a chiller in a closed loop system?

  • To purify the water
  • To heat the water
  • To circulate the water
  • To cool the water (correct)

    • What type of fluids are used in closed loop systems?

  • Refrigerant only
  • Water, glycol solutions, or salt brines (correct)
  • Steam only
  • Oil only

    • Why is corrosion less likely to occur in chillers compared to boilers or condensers?

    <p>Because chillers operate at lower temperatures</p> Signup and view all the answers

    What is the primary cause of corrosion in chillers?

    <p>Galvanic action</p> Signup and view all the answers

    What is a characteristic of closed loop systems?

    <p>They recirculate the working fluid with minimal make-up water</p> Signup and view all the answers

    What is a common issue in closed loop cooling and heating systems?

    <p>Water quality issues</p> Signup and view all the answers

    What type of corrosion occurs when dissimilar metals are in physical contact with each other and exposed to a fluid?

    <p>Galvanic corrosion</p> Signup and view all the answers

    Which of the following can accelerate corrosion in heat exchangers?

    <p>High fluid flow</p> Signup and view all the answers

    What is the purpose of adding chemicals to the cooling system?

    <p>To eliminate corrosion</p> Signup and view all the answers

    What type of corrosion occurs when one particular metal is preferentially attacked?

    <p>Selective leaching</p> Signup and view all the answers

    What is the benefit of sodium nitrite in cooling systems?

    <p>It forms a protective iron oxide surface film</p> Signup and view all the answers

    What is the purpose of installing heat exchangers in a specific way?

    <p>To make cleaning easier</p> Signup and view all the answers

    What happens when fluid flow is too low in heat exchangers?

    <p>Deposits form</p> Signup and view all the answers

    What is the purpose of periodic cleaning of heat exchangers?

    <p>To keep heat exchangers free of deposits</p> Signup and view all the answers

    What type of corrosion inhibitor is molybdate?

    <p>Mixed metallurgy corrosion inhibitor</p> Signup and view all the answers

    What is the estimated material cost of re-tubing a chiller?

    <p>25-30% of a new chiller</p> Signup and view all the answers

    What happens when a metal gives off ions in a galvanic cell?

    <p>It wastes away and fails</p> Signup and view all the answers

    What is the approximate cost to replace a chiller with a capacity of 850 tonnes?

    <p>$97 500</p> Signup and view all the answers

    What is a common problem in heat exchangers, especially if there is fluid leaking into the system?

    <p>Solids fouling</p> Signup and view all the answers

    What is the purpose of a bypass line with a filter in a closed cooling system?

    <p>To maintain a low level of suspended impurities</p> Signup and view all the answers

    What is the maximum percentage of make-up water that should be added to a closed loop system per day?

    <p>0.1%</p> Signup and view all the answers

    What is the result of water freezing in a closed cooling system?

    <p>It expands by 9%</p> Signup and view all the answers

    What is the purpose of freeze stats in chillers?

    <p>To prevent freezing</p> Signup and view all the answers

    What type of solution is used to prevent freeze-up in HVAC cooling coils?

    <p>Water and glycol</p> Signup and view all the answers

    What is the risk in hot water closed-loop systems?

    <p>Scale formation, deposition, fouling, and corrosion</p> Signup and view all the answers

    What is the risk of freezing in hot water heating systems?

    <p>In both vestibule heaters and air handling unit-heating coils</p> Signup and view all the answers

    What is the purpose of using glycol and water solutions in heating systems?

    <p>To prevent freezing</p> Signup and view all the answers

    MEDIUM What happens to the metal that gives off ions in a galvanic cell?

    <p>It wastes away and fails</p> Signup and view all the answers

    Why is it important to keep heat exchangers free of deposits?

    <p>To reduce corrosion</p> Signup and view all the answers

    What is the effect of high fluid flows in heat exchangers?

    <p>Erosion can occur at piping turns</p> Signup and view all the answers

    What is the purpose of adding sodium nitrite to cooling systems?

    <p>To reduce corrosion</p> Signup and view all the answers

    What type of corrosion occurs when one particular metal is preferentially attacked?

    <p>Selective leaching</p> Signup and view all the answers

    What is the benefit of using molybdate corrosion inhibitors in mixed metallurgy systems?

    <p>It provides the best corrosion protection</p> Signup and view all the answers

    Why is it important to install heat exchangers in a specific way?

    <p>To make cleaning easier</p> Signup and view all the answers

    What happens when fluid flow is too low in heat exchangers?

    <p>Sediments can drop out and deposit on metal surfaces</p> Signup and view all the answers

    What is the purpose of periodic cleaning of heat exchangers?

    <p>To reduce corrosion</p> Signup and view all the answers

    What is the effect of excessively high or low fluid flows on corrosion?

    <p>It accelerates corrosion</p> Signup and view all the answers

    What is the primary benefit of using a closed loop system in cooling and heating applications?

    <p>Reduce the risk of corrosion and scaling</p> Signup and view all the answers

    Which of the following is NOT a common issue in closed loop cooling and heating systems?

    <p>Electrical short circuits</p> Signup and view all the answers

    What is the primary cause of corrosion in chillers?

    <p>Galvanic action</p> Signup and view all the answers

    What is the purpose of a pump in a closed loop chilled water system?

    <p>To circulate the chilled water through the system</p> Signup and view all the answers

    What type of fluid is commonly used in closed loop heating systems?

    <p>Glycol solution</p> Signup and view all the answers

    What happens to the chilled water in a closed loop system after it absorbs heat from the process fluid?

    <p>It is circulated back to the chiller to reject the heat</p> Signup and view all the answers

    What is the purpose of the light blue lines in Figure 1?

    <p>To show the flow of chilled water</p> Signup and view all the answers

    What is a common issue in both closed loop cooling and heating systems?

    <p>Corrosion</p> Signup and view all the answers

    What is the primary method to prevent solids fouling in heat exchangers?

    <p>Using a slipstream filter</p> Signup and view all the answers

    What is the approximate cost of replacing a chiller with a capacity of 1750 tonnes?

    <p>$160 000</p> Signup and view all the answers

    What is the consequence of biological fouling in heat exchangers?

    <p>Decreased heat transfer efficiency and promotion of corrosion</p> Signup and view all the answers

    What is the purpose of adding dispersants in cooling systems?

    <p>To keep dead biological matter in suspension</p> Signup and view all the answers

    What is the risk of freezing in cooling systems that operate at higher temperatures?

    <p>High risk</p> Signup and view all the answers

    What is the purpose of using glycol and water solutions in HVAC cooling coils?

    <p>To prevent freezing</p> Signup and view all the answers

    What is the effect of water freezing in a closed cooling system?

    <p>It expands by about 9% and can rupture or damage pipes and equipment</p> Signup and view all the answers

    What is the purpose of freeze stats in chillers?

    <p>To protect the chiller evaporator coil from freezing damage</p> Signup and view all the answers

    What is the risk in hot water closed-loop systems?

    <p>Fouling and corrosion</p> Signup and view all the answers

    What is the maximum percentage of make-up water that should be added to a closed loop system per day?

    <p>0.1%</p> Signup and view all the answers

    HARD Why is galvanic corrosion more likely to occur in chillers?

    <p>Because chillers use dissimilar metals in contact with each other</p> Signup and view all the answers

    What is the primary benefit of using a closed loop system in cooling and heating applications?

    <p>To minimize make-up water</p> Signup and view all the answers

    What is the consequence of solids fouling in heat exchangers?

    <p>Reduced heat transfer efficiency</p> Signup and view all the answers

    Why is corrosion less likely to occur in chillers compared to boilers or condensers?

    <p>Because chillers operate at low temperatures</p> Signup and view all the answers

    What is the primary method to prevent scaling in heat exchangers?

    <p>Using a water softener</p> Signup and view all the answers

    What is the primary cause of biological fouling in heat exchangers?

    <p>Microbial growth</p> Signup and view all the answers

    What is the purpose of the pump in a closed loop chilled water system?

    <p>To circulate the water</p> Signup and view all the answers

    What is the consequence of high fluid flows in heat exchangers?

    <p>Erosion of the heat exchanger surface</p> Signup and view all the answers

    What is the primary mechanism by which sodium nitrite protects ferrous metals from corrosion?

    <p>By forming a protective iron oxide surface film</p> Signup and view all the answers

    What is the primary reason why molybdate is a more effective corrosion inhibitor than sodium nitrite in mixed metallurgy systems?

    <p>Because it provides better corrosion protection for copper and copper alloys</p> Signup and view all the answers

    What is the primary consequence of selective leaching in cooling systems?

    <p>Tube failure due to the preferential attack of one metal</p> Signup and view all the answers

    What is the primary reason why it is important to install heat exchangers in a specific way?

    <p>To make it easier to clean the heat exchanger</p> Signup and view all the answers

    What is the primary effect of high fluid flows on heat exchangers?

    <p>It strips protective chemical coatings from pipe and heat exchanger surfaces</p> Signup and view all the answers

    What is the primary benefit of using a closed loop system in cooling and heating applications?

    <p>It reduces the risk of corrosion</p> Signup and view all the answers

    What is the primary reason why scaling is a lesser concern in closed cooling systems compared to open cooling systems?

    <p>Because system losses and raw water make-up are minimal</p> Signup and view all the answers

    What is the primary reason why it is important to periodically check and adjust nitrite concentrations?

    <p>To ensure that the nitrite concentration is within the recommended range</p> Signup and view all the answers

    What is the primary consequence of biological growth within cooling systems?

    <p>It increases the formation of deposits</p> Signup and view all the answers

    What is the purpose of using a brine solution of water and calcium chloride or glycol in refrigeration systems that use closed cooling loops?

    <p>To prevent freezing</p> Signup and view all the answers

    What is the primary reason why molybdate is more effective at protecting brass than sodium nitrite?

    <p>Because it provides better corrosion protection for copper and copper alloys</p> Signup and view all the answers

    What is the estimated cost of re-tubing a chiller with a capacity of 2650 tonnes?

    <p>$65 000</p> Signup and view all the answers

    What is the primary consequence of galvanic corrosion in heat exchangers?

    <p>It leads to the failure of the heat exchanger</p> Signup and view all the answers

    What is the primary method to prevent solids fouling in heat exchangers?

    <p>Using a bypass line with a filter</p> Signup and view all the answers

    What is the consequence of not treating the make-up water in cooling systems that operate at higher temperatures?

    <p>Scaling</p> Signup and view all the answers

    What is the primary benefit of using a closed loop system in cooling and heating applications?

    <p>To minimize system losses and raw water make-up</p> Signup and view all the answers

    What is the purpose of adding biocides in cooling systems?

    <p>To remove biological fouling</p> Signup and view all the answers

    What is the risk associated with hot water closed-loop systems?

    <p>Scaling</p> Signup and view all the answers

    What is the purpose of using glycol and water solutions in heating systems?

    <p>To prevent freezing</p> Signup and view all the answers

    What is the consequence of not using demineralized, distilled, or reverse osmosis water in cooling systems that operate at higher temperatures?

    <p>Scaling</p> Signup and view all the answers

    Study Notes

    Closed Loop Systems

    • Closed loop systems are associated with chilled water-cooling systems, hot water heating systems, and internal combustion engine cooling systems.
    • These systems recirculate the working heat transfer fluid and use minimal amounts of make-up water.
    • The heat exchange fluids may be treated water, glycol solutions, or salt brines.

    Chillers

    • Chillers are heat exchangers that cool fluids.
    • The process fluid (chilled water or brine) is continuously circulated in a closed loop.
    • The chiller may use refrigerant or some other cold process fluid to chill the water.

    Water Quality Issues

    • Closed loop cooling and heating systems both suffer from water quality issues, including:
      • Corrosion
      • Solids fouling
      • Scaling
      • Biological fouling

    Corrosion

    • Corrosion can occur due to galvanic action, especially when dissimilar metals are in contact with each other and exposed to a fluid.
    • Corrosion can also occur wherever deposits form, making it important to keep heat exchangers free of deposits.
    • Corrosion inhibitors, such as sodium nitrite and molybdate, can be used to eliminate corrosion.
    • Sodium nitrite is an anodic corrosion inhibitor that forms a protective iron oxide surface film, but it is not effective for copper or copper alloys.
    • Molybdate inhibitors provide the best corrosion protection for systems of mixed metallurgy.

    Fouling

    • Solids fouling can occur due to fluid leaking into the system, corrosion, scaling, and biological growth.
    • Strainers or filters can be used to avoid fouling, and should be cleaned or replaced about once a year.
    • Bypass lines with filters can also be used to maintain a low level of suspended impurities.

    Scaling

    • Scaling can be an issue in closed cooling systems, especially at higher temperatures.
    • Make-up water should be demineralized, distilled, or reverse osmosis to prevent scaling.
    • Make-up water should never exceed 0.1% of the system capacity per day, or 2% of the system capacity per month.

    Biological Fouling

    • Biological fouling can occur if leaks occur, and can decrease heat transfer efficiency and promote corrosion.
    • Biocides and dispersants can be used to remove biofilms and prevent biological fouling.

    Freezing

    • Water can freeze if the refrigerated medium is below 0°C, which can cause damage to pipes, tubes, and equipment.
    • Chillers are equipped with freeze stats to prevent freezing damage.
    • Glycol solutions can be used to prevent freeze-up in HVAC cooling coils and refrigeration systems.

    Heating Systems

    • Hot water closed-loop systems are similar to those used for chilled water, but operate at higher temperatures, which can magnify the risks of scale formation, deposition, fouling, and corrosion.
    • The treatment and monitoring of these conditions is similar to those used for closed cooling systems.
    • Hot water heating systems may also be susceptible to freezing, especially in vestibule heaters and air handling unit-heating coils.

    Closed Loop Systems

    • Closed loop systems are associated with chilled water-cooling systems, hot water heating systems, and internal combustion engine cooling systems.
    • These systems recirculate the working heat transfer fluid and use minimal amounts of make-up water.
    • The heat exchange fluids may be treated water, glycol solutions, or salt brines.

    Chillers

    • Chillers are heat exchangers that cool fluids.
    • The process fluid (chilled water or brine) is continuously circulated in a closed loop.
    • The chiller may use refrigerant or some other cold process fluid to chill the water.

    Water Quality Issues

    • Closed loop cooling and heating systems both suffer from water quality issues, including:
      • Corrosion
      • Solids fouling
      • Scaling
      • Biological fouling

    Corrosion

    • Corrosion can occur due to galvanic action, especially when dissimilar metals are in contact with each other and exposed to a fluid.
    • Corrosion can also occur wherever deposits form, making it important to keep heat exchangers free of deposits.
    • Corrosion inhibitors, such as sodium nitrite and molybdate, can be used to eliminate corrosion.
    • Sodium nitrite is an anodic corrosion inhibitor that forms a protective iron oxide surface film, but it is not effective for copper or copper alloys.
    • Molybdate inhibitors provide the best corrosion protection for systems of mixed metallurgy.

    Fouling

    • Solids fouling can occur due to fluid leaking into the system, corrosion, scaling, and biological growth.
    • Strainers or filters can be used to avoid fouling, and should be cleaned or replaced about once a year.
    • Bypass lines with filters can also be used to maintain a low level of suspended impurities.

    Scaling

    • Scaling can be an issue in closed cooling systems, especially at higher temperatures.
    • Make-up water should be demineralized, distilled, or reverse osmosis to prevent scaling.
    • Make-up water should never exceed 0.1% of the system capacity per day, or 2% of the system capacity per month.

    Biological Fouling

    • Biological fouling can occur if leaks occur, and can decrease heat transfer efficiency and promote corrosion.
    • Biocides and dispersants can be used to remove biofilms and prevent biological fouling.

    Freezing

    • Water can freeze if the refrigerated medium is below 0°C, which can cause damage to pipes, tubes, and equipment.
    • Chillers are equipped with freeze stats to prevent freezing damage.
    • Glycol solutions can be used to prevent freeze-up in HVAC cooling coils and refrigeration systems.

    Heating Systems

    • Hot water closed-loop systems are similar to those used for chilled water, but operate at higher temperatures, which can magnify the risks of scale formation, deposition, fouling, and corrosion.
    • The treatment and monitoring of these conditions is similar to those used for closed cooling systems.
    • Hot water heating systems may also be susceptible to freezing, especially in vestibule heaters and air handling unit-heating coils.

    Closed Loop Systems

    • Closed loop systems are associated with chilled water-cooling systems, hot water heating systems, and internal combustion engine cooling systems.
    • These systems recirculate the working heat transfer fluid and use minimal amounts of make-up water.
    • The heat exchange fluids may be treated water, glycol solutions, or salt brines.

    Chillers

    • Chillers are heat exchangers that cool fluids.
    • The process fluid (chilled water or brine) is continuously circulated in a closed loop.
    • The chiller may use refrigerant or some other cold process fluid to chill the water.

    Water Quality Issues

    • Closed loop cooling and heating systems both suffer from water quality issues, including:
      • Corrosion
      • Solids fouling
      • Scaling
      • Biological fouling

    Corrosion

    • Corrosion can occur due to galvanic action, especially when dissimilar metals are in contact with each other and exposed to a fluid.
    • Corrosion can also occur wherever deposits form, making it important to keep heat exchangers free of deposits.
    • Corrosion inhibitors, such as sodium nitrite and molybdate, can be used to eliminate corrosion.
    • Sodium nitrite is an anodic corrosion inhibitor that forms a protective iron oxide surface film, but it is not effective for copper or copper alloys.
    • Molybdate inhibitors provide the best corrosion protection for systems of mixed metallurgy.

    Fouling

    • Solids fouling can occur due to fluid leaking into the system, corrosion, scaling, and biological growth.
    • Strainers or filters can be used to avoid fouling, and should be cleaned or replaced about once a year.
    • Bypass lines with filters can also be used to maintain a low level of suspended impurities.

    Scaling

    • Scaling can be an issue in closed cooling systems, especially at higher temperatures.
    • Make-up water should be demineralized, distilled, or reverse osmosis to prevent scaling.
    • Make-up water should never exceed 0.1% of the system capacity per day, or 2% of the system capacity per month.

    Biological Fouling

    • Biological fouling can occur if leaks occur, and can decrease heat transfer efficiency and promote corrosion.
    • Biocides and dispersants can be used to remove biofilms and prevent biological fouling.

    Freezing

    • Water can freeze if the refrigerated medium is below 0°C, which can cause damage to pipes, tubes, and equipment.
    • Chillers are equipped with freeze stats to prevent freezing damage.
    • Glycol solutions can be used to prevent freeze-up in HVAC cooling coils and refrigeration systems.

    Heating Systems

    • Hot water closed-loop systems are similar to those used for chilled water, but operate at higher temperatures, which can magnify the risks of scale formation, deposition, fouling, and corrosion.
    • The treatment and monitoring of these conditions is similar to those used for closed cooling systems.
    • Hot water heating systems may also be susceptible to freezing, especially in vestibule heaters and air handling unit-heating coils.

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    Description

    Learn about closed loop systems, commonly used in cooling and heating systems, which recirculate heat transfer fluids and minimize impurities.

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