Week 2: Hydronic heating Ch 3 & 4
If the material changes phase while absorbing heat, its temperature does not change. The heat absorbed in such a process is called ____ heat. Select one: a. latent b. sensible c. ambient d. radiant
A
The total liquid flow rate entering any portion of a fluid-filled (nonleaking) piping assembly will ____ the total flow rate exiting that assembly. Select one: a. always equal b. approximate c. might equal d. never equal
A
A ____ is a device for converting low-temperature heat into higher temperature heat. Select one: a. thermal converter b. heat pump c. radiating unit d. flue gasket
B
Although it is not a defined scientific term, it could be said that water is almost ____ times more "thermally concentrated" than air. Select one: a. 35 b. 3500 c. 3 d. 350
B
It is vital that the solar collectors and all exposed piping in a drain-back system be pitched a minimum of ____ toward the storage tank to allow complete drainage. Select one: a. 1/2 in./ft. b. 1/4 in./ft. c. 1/8 in./ft. d. 1/16 in./ft.
B
Most cast-iron sectional boilers are limited to use in ____ hydronic systems. Select one: a. "bare-bones" b. closed-loop c. packaged d. distributed
B
The heat absorbed or released by a material while it remains in a single phase is called ____ heat. Select one: a. ambient b. sensible c. latent d. radiant
B
A boiler operates at _____ efficiency only when it is being fired continuously under nonvarying conditions. Select one: a. manufacturer b. measurable c. steady-state d. DOE-certified
C
A flow restriction or stoppage in the ____ can lead to rapid formation of ice crystals on the cold heat exchanger surfaces separating the water and refrigerant. Select one: a. closed-loop b. water source c. evaporator d. storage tank
C
Hydronic system designers often need to know the ____ of heat transfer to or from a stream of water flowing through a device such as a heat source or heat emitter. Select one: a. exact volume b. thermal mass c. rate d. temperature
C
Incompressibility implies that liquids can exert tremendous pressure in any type of filled and closed container when they ____ due to heating. Select one: a. dissolve b. vaporize c. expand d. contract
C
The ____ pressure of a liquid is the minimum pressure that must be applied at the liquid's surface to prevent it from boiling. Select one: a. systemic b. surface c. vapor d. mean
C
The combination of metal and water weight gives cast-iron boilers the ability to absorb a significant amount of heat. Such boilers are said to have a high ____. Select one: a. size b. efficiency factor c. thermal mass d. life cycle
C
Analysis of combustion processes reveals that significant amounts of heat can be recaptured from the exhaust stream if the water vapor it contains can be ____. Select one: a. minimized b. replenished regularly c. expelled from the system d. condensed within the boiler
D
Boilers with low thermal mass tend to have ____ cycle efficiencies due to lesser amounts of heat remaining in the boiler following burner shutdown. Select one: a. unpredictable b. dependable c. lower d. higher
D
In solar anti-freeze based combisystems, the outside heat dump provides a way for the system to shed excess heat. It is activated if the temperature of the thermal storage tank reaches a ____ upper limit. Select one: a. local fire code b. manufacturer recommended c. DOE enforced d. user-set
D
One type of boiler design surrounds the combustion chamber with a water-filled heat exchanger. This arrangement is called a ____ boiler. Select one: a. condensation b. steam c. hydraulic d. wet-base
D
The amount of air that can exist in solution with water is strongly dependent on the water's temperature. As water is heated, its ability to hold air in solution ____. Select one: a. is viscosity dependent b. rapidly increases c. remains constant d. rapidly decreases
D
The viscosity of a fluid is an indicator of its resistance to ____. Select one: a. combining b. displacement c. heat d. flow
D
When a quantity of liquid water is put under pressure, there is ____ change in its volume. Select one: a. a significant b. a formulaic c. a corresponding d. very little
D
If the material changes phase while absorbing heat, its temperature will change Select one: True False
False
In full storage ETS systems, all energy used during the subsequent on-peak period is purchased and stored during the peak cycle. Select one: True False
False
It is not advisable to maintain water flow through the condenser whenever the heat pump is operating. Select one: True False
False
Many boilers currently used in North America were designed with the intent that flue gases would condense within the boiler. Select one: True False
False
The density of water is not dependent on temperature. Select one: True False
False
The heating capacity of the heat pump drops rapidly with increasing source water temperature. Select one: True False
False
The quantity of heat absorbed or released from the material is expressed as Btu/hr. Select one: True False
False
The rate of heat transfer into or out of the fluid stream in equations is expressed as Btu. Select one: True False
False
Condensing boilers are designed with large heat exchanger surfaces capable of extracting more heat from the exhaust gases compared to the heat exchangers in conventional boilers. Select one: True False
True
Conventional gas- and oil-fired boilers are currently used in the vast majority of residential and light commercial hydronic systems in North America. Select one: True False
True
If a cast-iron boiler is significantly oversized and experiences long off-times between firing cycles, much of the heat stored in the boiler's thermal mass can be carried up the flue by air currents passing through the combustion chamber. Select one: True False
True
It is often necessary to determine the quantity of heat stored in a given amount of material that undergoes a specific temperature change. An equation known as the sensible heat quantity equation, can be used for this purpose. Select one: True False
True
One of the most important properties of water relevant to its use in hydronic systems is specific heat. Select one: True False
True
The cast-iron sectional boiler is currently one of the most common boilers used in residential and light commercial buildings in North America. Select one: True False
True
The decision to use a wood-fueled boiler involves a time commitment much more demanding than for conventional heat sources operating on natural gas, propane, fuel oil, or electricity. Select one: True False
True
The difference in heat capacity of water versus that of air is the single greatest advantage of using water rather than air to convey heat. Select one: True False
True
The specific heat of water is high in comparison to other common materials. In fact, water has one of the highest specific heats of any known material. Select one: True False
True
The term "hydronic heat pump" always refers to a heat pump that delivers heat to a flowing stream of water. Select one: True False
True
The vapor pressure of a liquid is the minimum pressure that must be applied at the liquid's surface to prevent it from boiling. Select one: True False
True
When hydronic systems are first filled with water, dissolved air is present in the water throughout the system. Select one: True False
True
