19 Questions
What is a characteristic of closed loop systems?
They recirculate the working heat transfer fluid
In closed loop systems, what can the heat exchange fluids be?
Treated water, glycol solutions, or salt brines
What is the purpose of a chiller in a closed loop system?
To cool the process fluid (chilled water or brine)
Which color represents the extent of the chilled water loop in Figure 1?
Light blue
What is the function of the closed loop heating system shown in Figure 2?
To provide heat
What is the common characteristic of closed loop systems regarding make-up water?
They use minimal amounts of make-up water
What is the purpose of using freeze stats in chillers?
To prevent the chiller evaporator coil from freezing damage
What is commonly used in refrigeration systems to prevent freeze-up?
Glycol solutions
Why are hot water closed-loop systems susceptible to scale formation and corrosion?
Because they operate at higher temperatures
What can cause vestibule heaters to freeze up?
Regular opening of doors
What accelerates corrosion in closed loop systems?
Excessively high fluid flows
Why are air handling unit-heating coils susceptible to freezing?
If the temperature drops below 0°C
Which inhibitor provides the best corrosion protection for systems of mixed metallurgy?
Molybdate
What is commonly used to fill heating systems for additional security against freezing?
Glycol and water solutions
What is the form of corrosion called when one particular metal is preferentially attacked in cooling systems?
Selective leaching
What risk is magnified in hot water heating systems as compared to chilled water systems?
Scale deposition and corrosion processes
How is solids fouling typically avoided in heat exchangers?
By using strainers or filters
When does scaling become a risk in closed cooling systems?
At high temperatures with impurities introduced from make-up water
What risk does freezing pose in closed loop systems?
Risk of corrosion
Study Notes
Closed Loop Systems Characteristics
- A characteristic of closed loop systems is that they recycle the same fluid repeatedly.
Heat Exchange Fluids
- In closed loop systems, the heat exchange fluids can be water, glycol, or brine.
Chiller Purpose
- The purpose of a chiller in a closed loop system is to cool the fluid.
Figure 1: Chilled Water Loop
- The color blue represents the extent of the chilled water loop in Figure 1.
Closed Loop Heating System
- The function of the closed loop heating system shown in Figure 2 is to provide heat.
Make-up Water
- A common characteristic of closed loop systems regarding make-up water is that they require minimal make-up water.
Freeze Stats
- The purpose of using freeze stats in chillers is to prevent freezing.
Refrigeration Systems
- Glycol is commonly used in refrigeration systems to prevent freeze-up.
Hot Water Closed-Loop Systems
- Hot water closed-loop systems are susceptible to scale formation and corrosion due to the high water temperature.
Vestibule Heaters
- Improper installation or inadequate air circulation can cause vestibule heaters to freeze up.
Corrosion
- Oxygen and high water temperature accelerate corrosion in closed loop systems.
Air Handling Unit-Heating Coils
- Air handling unit-heating coils are susceptible to freezing due to inadequate air circulation.
Corrosion Protection
- Molybdate-based inhibitors provide the best corrosion protection for systems of mixed metallurgy.
Freezing Protection
- Propylene glycol is commonly used to fill heating systems for additional security against freezing.
Form of Corrosion
- Selective corrosion is the form of corrosion where one particular metal is preferentially attacked in cooling systems.
Risk in Hot Water Heating Systems
- The risk of scaling is magnified in hot water heating systems as compared to chilled water systems.
Solids Fouling
- Solids fouling is typically avoided in heat exchangers by ensuring proper water treatment and filtration.
Scaling Risk
- Scaling becomes a risk in closed cooling systems when the water temperature is above 50°F (10°C).
Freezing Risk
- Freezing poses the risk of equipment damage and system failure in closed loop systems.
Learn about closed loop systems commonly used in heating, ventilation, and air conditioning (HVAC) systems. These systems recirculate a working heat transfer fluid, such as water, glycol solutions, or salt brines, and use minimal amounts of make-up water. The quiz covers the applications and characteristics of closed loop systems, including their association with chilled water-cooling systems, hot water heating systems, and internal combustion engine cooling systems.
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