4BE3 U6 C5 Obj 1 EMH
84 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

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.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

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

    More Like This

    Quiz de Fundamentos de Refrigeración
    19 questions

    Quiz de Fundamentos de Refrigeración

    OutstandingMoonstone avatar
    OutstandingMoonstone
    Closed Loop Systems in HVAC
    19 questions

    Closed Loop HVAC System Quiz and Flashcards

    Reusl avatar
    Reusl
    Glycol in Closed Loop Systems
    10 questions

    Glycol in Closed Loop Systems

    Reusl avatar
    Reusl
    Heat Transfer Quiz
    10 questions

    Heat Transfer Quiz

    EndearingVerism avatar
    EndearingVerism
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser