Flashcards
Final Exam Questions
Flashcards do conjunto (40)
- 1What are three criteria that determine the cross-sectional area of a duct?The cross-sectional area of a duct is determined by the required ACH, the necessary CFM, Friction-Loss, and available Fan-Power. (notes) (481)
- 2How does pressure-loss impact the design of duct-work system.Key areas of pressure loss, within duct work, include air filters, cooling and heating coils, ductwork and fittings, terminal devices and delivery devices. Ductwork losses are most amenable to reduction through integrated architectural and engineering design.
High velocity airflow and long or convoluted duct work will increases friction loss. Ductwork should be kept reasonably short by selecting good fan room locations, and space and volume constraints that result from poor planning should not force the use of too small ducts that result in high velocity airflow. - 3What are three issues that proper air mixing addresses?Prevents stagnant air, ensures temperature and humidity equivalence and occupant comfort.
- 4What is a plenum?Air-cavity, supply and return, low noise, high volume of air, better mixing
- 5Give two reasons why a convector, radiator, and/or supply diffusers is typically placed near a window?Placement near windows (convectors) (1) prevents condensation on glass, (2) raises temperature of glass to incite mixing in the space.
- 6Describe the components and stages of a VAV system.Controls temperature of space by varying 1. the volumes of supply air rather than the supply air temperature
2. Based on use-interior zones of large buildings typically only require cooling because of occupant and lighting loads
3. Perimeter zones can have vary loads depending on season and exposure. - 7How does the ACH rate change in the following ventilation system typesMixed-Flow Ventilation: The ACH rate is about 3-8 ACH (air changes per hour)
Laminar Flow Ventilation: Air flows across the room at a rate of about 14-32 ACH
Displacement Ventilation: 0.05 - 1 ACH - 8Describe the purpose and function of a “fan” roomActs as an indoor air quality mitigation component and protects HVAC equipment
- 9What is the difference between a boiler and a furnace?449 and 441
- 10What mediums do we use to transfer heat inside buildings?440. Page 440: An air-to-air heat exchanger (whereby heat in exhaust air is transferred to incoming fresh air, heat pump, A heat-transfer system may use electricity as a driving force or be self-powered. Heat pumps and air-to-air heat exchangers are both commonly found in high-performance building
- 11What are the advantages/disadvantages of moving heat through a duct?481
- 12What is the difference between a shaft and a chase?A shaft is a fire-rated code required enclosure used in HVAC if you penetrate more than two stories.
A chase encloses the ductwork in heights that don't require a shaft. - 13How can the choice of heating system affect the shaft size?air heating systems need bigger shafts because they have ductwork which take up more room.
Water systems use piping, so the shaft can be smaller - 14What is the difference between a radiator and a convector?Radiators superheat water under pressure until it becomes steam, heats through infrared radiation, circulates through convection, has a higher operating temperature, and is slower to raise the overall temp of a space.
Convectors - circulates air through convection, heats through convection, lower operating temperature and faster to raise ambient temperature. - 15What is the primary difference between the method through which water is circulated in a hydronic vs. a steam heating system?steam heating - apply energy that changes the state of water.
Uses condensation and evaporation cycle to move medium
Hydronic - uses water as the heat transfer medium.
-Does not change phase of water - 16A refrigerator is a type of air-to-air heat pump.true
- 17Describe the basic principle that governs how heat is transferred in Conduction vs. RadiationRadiation: transferred through thermal radiation on the electromagnetic spectrum
Convection: Transferred through the flow of a fluid caused by a difference in density as a result of temperature flux - 18What causes convection flow in air?Convection is flow or movement of a fluid (air, water, etc) caused by the difference in density as a relationship to temperature flux 110
- 19Convection is a form of heating.True, Other forms of heating are conduction and radiation (notes)pg. 110 (Also convection, conduction, radiation, evaporation)
- 20How do the thermal loads of small buildings differ from those of large buildings?Smaller buildings are skin loaded, which means the climate dictates whether heating or cooling is the main design concern.
Larger thermal loads in buildings due to greater floor area, more mechanical equipment, more people and more lights. (p.497) - 21Climatic condition determines whether an Evaporative Cooling System is appropriate?Does not use a mechanical compressor to chill water
Evaporative cycle utilizes ambient air
Requires a low-humidity environment to operate efficiently (pg 342) - 22What is the advantage of using an Air-Water system for Cooling?P 546
-Uses only enough air to reach required IAQ, about 10% less than the airflow needed in all-air systems
-Reduced demand for distribution volume (piping is smaller than ductwork) - 23What is the role of refrigerant in a Vapor-Compression Cooling system?uses refrigerant as the medium which absorbs and removes heat
Removes heat from space to be cooled and rejects heat elsewhere (455) - 24What are the two principle differences between a Vapor-Compression and an Absorption Refrigeration system?The Absorption Cooling uses combustion and heat and also has two chambers, one high and one low pressure. The pressure does not change the phase of the medium.
455 - 25Draw and Label a diagram that explains the components and stages of a Vapor-Compression refrigeration system.456
- 26Why do Air-Handlers often include a re-heat stage?-energy savings
-it increases capacity and efficiency (asked Emmy) Isn’t this part of the process where it is more efficient to reheat the air after it is cooled? - 27What is a Chiller?A chiller is a machine that removes heat from a liquid via a vapor compression or absorption refrigeration cycle. This liquid can then be circulated through a heat exchange to cool equipment, or another process stream (such as air or process water)
- 28A steam turbine chiller is a form of vapor-compression refrigerator.TRUE because on page 456 a “steam-driven turbine” is mentioned which is under the Vapor Compression Refrigeration section
- 29What does HVAC stand for?Heating, ventilation and air conditioning
Heating is a process whereby the temperature of something is increased. Ventilation is a
process that moves or circulates air. AC refers to cooling. Page 421 - 30How are Cooling Towers utilized in Large-Scale HVAC systems?Dry Cooling Towers: heat is transferred through a surface that separates medium from ambient air - “air cooled” heat exchanger - uses convective heat transfer - surface to fluid (air)
Wet Cooling Tower (open circuit): Use the evaporation of water (Endothermic) to remove energy from system. Working fluid and evaporation fluid are often the same
Fluid Cooling Tower (closed-circuit): Use the Evaporation of water (Endothermic) to remove energy from system. Working fluid and evaporation fluid are kept separate (prevent contamination) - 31What is the difference between a Split and Package HVAC system?A single package air-air heat pump moves heat between an outdoor air stream and an indoor air stream; although kept separate, both streams pass through a single enclosure assembly.
A split system air-air heat pump moves heat via a refrigerant loop between the outdoor unit and the indoor unit. This is a system with both outdoor and indoor components. ( q pg 466) - 32What is a heat pump?464
- 33What does One-Ton of cooling measure?A TON is used as a measure for refrigeration--describes heat extraction capacity of refrigeration and air conditioning equipment.
Defined as a rate of transfer= melting 1 short ton of pure ice @ 0 degrees C in 24 hours - 34Why is the Enthalpy of Air-Conditioning greater than Sensible Cooling?????
- 35In which circumstances is the process of evapotranspiration utilized in the control of storm water management? At the Building-Scale? At the Site-Scale?989?
- 36Describe the purpose and function of a dry-well.A drywell is an underground structure that disposes of unwanted water, most commonly surface runoff and stormwater, and in some cases greywater. It is a covered, porous-walled chamber that allows water to slowly soak into the ground (that is, percolate), dissipating into the groundwater.
- 37What is a soil-stack? How does it work?the pipe that takes all the waste water from the upstairs plumbing system of a building
944 - 38What is the purpose and function of a plumbing trap?A plumbing fixture which traps debris that has drained from the sink and prevents it from forming a clog deep within the plumbing system, and to stops sewer gases from passing into the home. 933
- 39What are two easy ways to distinguish between supply and return plumbing??
- 40Draw and label a diagram of a storm-water management solution for a single-level home with a pitched roof.815
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- 300 Arch FlashCards sobre Final Exam Questions, criado por Justine Bradley em 17-05-2017.
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