EXAM TWO KEY
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2
Spring 2001 / Grondzik / 8 March 2001
Instructions: this exam is 1 hour and 15 minutes long. Write your name on the line above. The exam is exam is closed-book; you may refer to two index cards with your own notes -- but to no other materials. Read each question with care and answer all parts of multiple-part questions. Place all answers in the spaces provided and/or on the back of these sheets. You may circle or otherwise mark answers where appropriate. Provide complete, precise, and legible answers. The numbers in parentheses indicate the relative point value of each question. There are 100 total points on the exam.
# 1. (4)
A passive climate control system can generally be easily distinguished from an active system by several key characteristics. List two characteristics that will clearly set a passive system apart from an active system.
(a) a passive system uses no purchased energy
(b) elements in a passive system serve multiple purposes
also, a passive system is tightly integrated with overall building design
# 2. (3)
A heat source is a critical element in any heating system. In a passive heating system:
(a) the heat source is equally likely to be one of several readily available resources
(b) the heat source is almost universally going to be solar radiation
(c) the heat source might be combustion, electric resistance, a heat pump, or solar radiation
(d) no heat source is required -- since the system is by definition passive
# 3. (6)
Four "architectural" classifications or categories of passive heating systems are commonly accepted -- heat loss reduction approaches; direct gain approaches; indirect gain approaches; and isolated gain approaches.
(a) what characteristic makes heat loss reduction such a very different approach from the other three categories of passive heating systems?
heat loss reduction is a precursor approach to passive heating design -- it is the only one of the four approaches that provides no heating energy for a building; it simply (but importantly) reduces the need for heat
(b) what defining characteristic makes indirect gain systems so different from direct gain systems -- from an occupant=s perspective?
the physical separation of the solar collection function from the occupied spaces of a building (with the separation being provided by a masonry wall, water containers, or a roof)
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 2
# 4. (8)
Each of the following sketches illustrates a type of passive heating system. For each sketch, identify the type of system (direct gain, indirect gain, or isolated gain) and the name of the system (direct gain, Trombe wall, water wall, roof pond, or sunspace/greenhouse).
|Name: water wall
Type: indirect gain
|Name: Trombe wall
Type: indirect gain
Type: isolated gain
|Name: direct gain
Type: direct gain
# 5. (3)
A heat sink (or "cool" source) is a critical element of any cooling system. In a passive cooling system:
(a) the heat sink is equally likely to be one of several naturally available resources
(b) the heat sink is almost universally going to be solar radiation
(c) the heat sink might be mechanical, absorption, or evaporative
(d) no heat sink is required B since the system is by definition passive
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 3
# 6. (4)
Passive cooling systems are often classified or categorized using an architectural design focus. From an architectural design viewpoint, the four common classifications of passive cooling systems are:
(a) heat gain reduction
(b) direct loss
(c) indirect loss
(d) isolated loss
# 7. (4)
Passive cooling systems are also often classified or categorized using a thermodynamic focus. From the perspective of heat transfer, the four common classifications of passive cooling systems are:
(a) evaporative cooling
(b) conductive cooling
(c) convective cooling
(d) radiative cooling
# 8. (3)
Ultimately, the failure of the natural ventilation passive cooling system in the original School of Architecture building to work as intended was a result of:
(a) failure to consider the effect of relative humidity on occupant comfort
(b) failure of the solar chimneys to properly collect heat
(c) unusually hot weather in Tallahassee for the first 5 years the School was in operation
(d) a change in building code requirements regarding indoor air quality
# 9. (5)
The "greenhouse effect" is the reason that passive and active solar energy collection systems work. It is also the driving force behind global warming. Annotate the sketch below to clearly and fully describe how the greenhouse effect operates to heat the space depicted.
The "greenhouse effect" -- a process with specific steps -- is the heart of this question.
radiation from the sun passes
the glazing of the sunspace. The shortwave radiation
falls on the water tubes (or mass wall) and is absorbed.
The absorption of radiation heats up the water. As the
water becomes hotter than the surrounding air, the
absorber/storage element warms the surroundings
by convective and radiant heat exchange. Radiation
from the water tubes is longwave radiation, which is
generally reflected by the glazing (which also reduces
convective heat loss to the outside). Heat collected in
the sunspace is generally trapped there, which warms
the sunspace -- and then the adjacent building space.
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 4
# 10. (6)
Each of the following sketches illustrates a type of passive cooling system. Identify each sketch using the system names and types listed below. There are obviously more possible names/types than required.
|(a) direct loss, cross ventilation||(b) isolated loss, stack ventilation|
|(c) isolated loss, cool tube||(d) indirect loss, roof pond|
|(e) indirect loss, Trombe wall||(f) direct loss, desiccant cooling|
|1. (c) isolated loss, cool tube||2. (a) direct loss, cross ventilation|
|3. (d) indirect loss, roof pond||4. (e) indirect loss, Trombe wall|
# 11. (3)
An active heating system is comprised of four distinct sections (or elements). One of these elements is a means of control. Name the other three basic parts of an active heating system:
(a) a source of heat
(b) a means of heat distribution
(c) a means of heat delivery
# 12. (4)
A decision to utilize on-site combustion versus electric resistance in a heating system brings with it several architectural design ramifications or implications. Describe two serious design issues that would have to addressed if this decision were made.
(a) a need to provide for exhaust of combustion gasses from the building (flue, chimney, etc.)
(b) a potential need to store fuel on site
also, a need to provide outside air to location of combustion
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 5
# 13. (2)
Clearly describe the difference between a local heating system and a central heating system.
A local heating system serves a limited area of a building (often a single space) and the major system components are all located in that space (or immediately adjacent); whereas a central heating system serves multiple spaces in a building from a single source location.
# 14. (2)
Clearly describe the difference between a central heating system and a district heating system.
A central heating system serves multiple spaces in a building from a single source location; whereas a district heating system serves spaces in multiple buildings from a single source location.
# 15. (2)
What important architectural design advantage would result from a decision to use water to distribute heat in an active heating system instead of air?
The distribution components of the system will be substantially smaller and will require less coordination to integrate into the building.
# 16. (2)
What important architectural design advantage would result from a decision to use air to distribute heat in an active heating system instead of water?
The delivery of heat from an air system is substantially easier than from a water system, often requiring no space or volume within the conditioned spaces.
# 17. (9)
Match each of the functions listed below with the item of mechanical equipment (from the adjacent list) that would normally provide that specific function in a typical building.. Do NOT use connecting lines to answer -- use letters and numbers.
|(a) provide the force to circulate water in a piping system||= 9||(1) convector cabinet|
|(b) heat air in a residential central heating system||= 3||(2) fan|
|(c) clean air in a heating or cooling system||= 8||(3) furnace|
|(d) heat water in a central heating system||= 6||(4) duct|
|(e) serve as a container for the distribution of air||= 4||(5) diffuser|
|(f) serve as a delivery device in an air-based heating system||= 5||(6) boiler|
|(g) serve as a delivery device in an water-based heating system||= 1||(7) pipe|
|(h) serve as a container for the distribution of water||= 7||(8) filter|
|(i) provide the force to circulate air in a ductwork system||= 2||(9) pump|
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 6
# 18. (4)
Which of the illustrations below is of a vapor compression refrigeration system operating to cool and which is of a vapor compression system operating as a heat pump? Label the diagrams "cooling" and "heating."
Refrigerant leaving the compressor is hot -- if this refrigerant is directed indoors it will heat the space (heat pump; heating); if the hot refrigerant is first directed outdoors this dumping of heat is part of a space cooling process.
# 19. (3)
The adjacent illustration is of:
(a) an absorption chiller
(b) a mechanical chiller
(c) an evaporative cooler
(d) an stack inducer
# 20. (3)
The abbreviation (or acronym) "COP" stands for:
(a) cooling operating parameters
(b) coefficient of performance
(c) chloro-oxide-pentane (a greenhouse gas)
(d) control and occupancy phasing
# 21. (4)
The four primary components of a vapor compression refrigeration cycle are:
|(a) compressor||(b) condenser|
|(c) evaporator||(d) expansion valve|
ARC 3682 : ENVIRONMENTAL TECHNOLOGY 2 / EXAM TWO / page 7
# 22. (3)
A "ton" is used as a measure of:
(a) cooling capacity
(b) refrigerant weight
(c) equivalent environmental impact of a refrigeration system
(d) heating capacity of a given size pipe
# 23. (3)
A cooling or heating system "zone" is best described as:
(a) an area of a site with a defined microclimate
(b) a portion of a building requiring individual control
(c) a room in a building conditioned by a central cooling system
(d) the location in a building where central cooling equipment will be installed
It is reasonable to argue that the person on a design team BEST able to establish thermal zones for a building under design is the ARCHITECT -- and not the mechanical consultant. Provide a convincing (and accurate) argument in support of the contention that the architect should be the design professional who thermally zones a building:
Successful thermal zoning requires a good understanding of the timing of loads in one space relative to another space. This is driven by solar radiation patterns and occupancy patterns. The architect and mechanical consultant should both have a clear picture of solar patterns. The architect, however, should have a much better understanding of occupancy patterns -- having worked with the owner to understand the building's functions and usage. In addition, the architect should have a better sense of owner expectations and budget, which may temper a zoning layout based solely on BTUs. All-in-all, the architect has a clear edge (on the typical project).
Explain how the major functional components of an active heating (or cooling) system -- namely source, distribution, delivery, and control -- are handled in a PASSIVE system.
In a ACTIVE system specialized components are typically used to provide each of the four primary functions, thus it is usually easy to identify the components and their purpose. By definition, a PASSIVE system employs multi-use components that serve multiple functions. Isolating these functions is more difficult, but they still exist are are very important. The source in a passive system is typically external to the building and must be captured through appropriate design of building form, envelope, materials. Distribution and delivery in a passive system occur through natural convection, conduction, and radiation within/among the building interior elements (walls, floor, roof, air, etc.). Control in a passive system is usually of two types: gross control provided by the building design (overhangs, time lag) and finer control provided by the occupants adjusting curtains, window openings, movable insulation.
Last updated 20 March 2001