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chapter 9
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Indicate whether the statement is true or false.
1. Repurposed propane tanks can be used in both open and closed hydronic systems.
a.
True
b.
False
2. Thermal expansion is not a design concern with unpressurized thermal storage tanks.
a.
True
b.
False
3. Stratification in a thermal storage tank provides more useful energy than an evenly-mixed tank at the same average
temperature.
a.
True
b.
False
4. Tankless water heaters have lower amperage requirements than tank-type electric water heaters.
a.
True
b.
False
5. Thermal storage prevents short cycling of the heat source.
a.
True
b.
False
Indicate the answer choice that best completes the statement or answers the question.
6. What type of piping is commonly used with multiple pressurized tank arrays to achieve equal flow through each tank?
a.
direct return
b.
asymmetrical return
c.
serial reverse return
d.
parallel reverse return
7. Which of these is an effect of flow through an internal heat exchanger coil?
a.
decrease in fluid density
b.
decrease in flow rate
c.
pressure increase
d.
head loss
8. Which factors affect the amount of heat held by a thermal storage tank?
a.
tank pressure rating and water exit temperature
b.
tank surface area and water inlet temperature
c.
tank volume and pressure rating
d.
tank volume and water temperature change
9. What is the recommended water flow direction when adding heat to an unpressurized thermal storage tank?
a.
Hot water enters at the bottom of the tank and flows upward.
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chapter 9
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b.
Hot water enters at the top of the tank and flows downward.
c.
Hot water enters at the center of the tank and flows upward.
d.
Hot water enters at the center of the tank and flows downward.
10. What is used to simultaneously supply heat from storage and supplemental heat from an auxiliary heat source?
a.
outdoor reset controller and diverter valve
b.
outdoor reset controller and differential temperature controller
c.
temperature sensing controller and diverter valve
d.
temperature sensing controller and differential temperature controller
11. Unpressurized thermal storage tanks have several advantages. What is NOT one of these?
a.
They eliminate the potential for biological growth in the tank.
b.
They do not need a separate expansion tank.
c.
They are less expensive than pressurized tanks.
d.
They are protected from overpressure conditions.
12. What effect does higher flow rate entering the tank have on the amount of mixing within the tank?
a.
It increases.
b.
It decreases.
c.
It remains the same.
d.
It depends on the temperature of the inlet fluid.
13. What are two factors that influence the rate of heat loss from a vertical cylindrical tank?
a.
average temperature of water in the tank and outer diameter of tank insulation
b.
piping arrangement and inlet water temperature
c.
average water temperature in the tank and size of heat exchanger
d.
piping arrangement and surface area of heat exchanger
14. Which of these is an advantage of a thermostatically controlled tankless electric water heater?
a.
It enables easy removal of the internal coil heat exchanger for cleaning.
b.
It has a large reserve of domestic water in the assembly that inhibits biological growth.
c.
It takes advantage of low initial temperatures when domestic water heating begins.
d.
It uses fewer valves than traditional pressurized tank thermal storage.
15. What determines the amount of usable heat from storage?
a.
average water temperature in the tank and lowest temperature at which the tank can supply heat to the load
b.
water temperature at the top of the tank and tank pressure rating
c.
minimum water temperature in the tank and the highest temperature at which the tank can supply heat to the
load
d.
amount of time between cycles of the heat source
16. What type of valve is used for thermal storage tanks that need to store either heated water or chilled water based on
the season of the year?
a.
check valve
b.
globe valve
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c.
4-way valve operated by 2-position motorized actuator
d.
2-way valve operated by 4-position motorized actuator
17. Which configuration allows heat to be transferred to the load as quickly as possible after the heat source turns on?
a.
2-pipe buffer tank configuration
b.
4-pipe buffer tank configuration
c.
6-pipe buffer tank configuration
d.
vertical flow jet configuration
18. What is typically used to counteract the mixing effects of a vertical flow jet?
a.
heat source stratifier
b.
reversing the flow direction
c.
internal flow diffuser
d.
increasing the inlet flow rate
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chapter 9
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Answer Key
