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ECS Final
ECS Final Exam Fall 2008
61
Architecture
Undergraduate 3
12/13/2008

Additional Architecture Flashcards

 


 

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Term
Single Zone System
Definition
Simplest form of air handling. Under 5000-15,000 SF

Advantages:
Centralizes control of temp. humidity, filtration, ventilation. Air distribution. Low first cost.

Disadvantages:
Poor control where loads differ btw. rooms. Cannot supply heating and cooling simulaneously.
Term
Variable Air Volume System
Definition
Volume of air is changed to meet varying zone loads. Temp is constant. Single zone AHU

advantages:
Low first cost, lower operation costs (relatively), High and low velocity

Disadvantages:
Cannot supply heating and cooling simultaneously, high velocity noise, poor control at low loads, supply volume variation over 20% can create drafts.
Term
Terminal Reheat System
Definition
Varying loads are compensated by adding heat within a terminal in the space. Single duct with air supply and temp. set to meet the needs of the space with the highest cooling loads.

Advantages:
good multi-zone control
low first cost, good flexability

Disadvantages:
high operating and maintenance cost
high velocity noise
Term
Multi-Zone system
Definition
Supplies constant volume to all spaces. Supply temp varies to meet demand. There is one heating and cooling coil, but separate dampers for each zone. Cooling and heating dampers work in parallel. Temps at both docks need to be set to meet maximum loads.

Advantages:
Good zone control. Agerage operating cost lowered by cutting off heating or cooling depending on the season.

Disadvantages:
high first cost, bulky ductwork, inherently inefficient, but better in real operation
lacks flexibility if space changes require modifying the HVAC system. Installed only in special instances w/ less than 12 zones.
Term
Dual Duct system
Definition
warm air duct and cold air duct supply air to mixing terminal, similar to multizone, but air is mixed at terminal box instead of by the AHU

Advantages:
Excellent control, optimum flexibility since heating and cooling ducts supplied throughout the building. High or low velocity.

Disadvantages:
High first cost, double duct work, cost of mixing boxes and controls. Inherently inefficient, high maintenance cost.
Term
By-pass provided at Zone or Room
Definition
"Neutral" air supplied through space to compensate varying loads. Multi-zone sometimes uses bypass distribution.

Advantages:
Average cost, less than dual duct, greater than varying air volume. can reduce duct sizes and costs. Better control than VAV. Lower operating cost
Term
Direct Expansion (DX) System
Definition
Also called direct refrigerant system. Located within or near the space. Heating is usually separate. Good for low temp. control spaces. Controls in smaller cheaper spaces are usually on/off/

Advantages:
decentralized mechanism
low first cost
low op. cost

disadvantages:
Noisy equip. in or near the space. DX unit evaporator must be within 60' of evaporator.
Term
Radial Duct Layout
Definition
used for first floor heating from basement, crawl space or slab on grade, but predominantly when the plan is similar in size to a small residence. The individual ducts are sized to supply air volumes needed at each space.
Term
Perimeter Loop
Definition
Used for first floor heating for slab on grade construction in colder climates. The perimeter loop keeps the slab edge warm. Usually residential but could be used for light commercial. Ducts sizing is more comlicated than with the radial cuct layout. Designed for constant pressure along hte perimeter loop.
Term
Extended Plenum
Definition
The trunk duct has continuous section dimension for the length of the plenum, which can't exceed 24'. Can be used in residential or small compace commercialzones. The static pressure decreases further from the AHU. Branch ducts are sized for air volume required at spaces. Simpler to design and construct that reducing trunk duct system, but harder to balance the air velocities at the outlets.
Term
Reducing Trunk Duct
Definition
This is the common approach for commerical buildings, where the ducts are designed first based on individual space loads. Each section of trunk duct between branches is then sized for the air volume that will pass through that section.
Term
design cooling Temperature
Definition
A temperature close to the most extreme expected for a location. Used to determine the design cooling Load
Term
Design cooling load
Definition
Determined by the Design cooling temp. maximum cooling load expected in a location.
Term
Demand charge
Definition
an additional charge for electric power psupplied by a utility company based on the peak electrical demand during a period. Design heating or cooling load- The total heat loss or gain from a house under the most severe winter conditions likely to occur.
Term
Sensible Heat
Definition
Heat that raises the body temperature.
Term
Dew Point
Definition
The temperature at which an air-water vapor mixture will become saturated and begin to yield drops of condensed water vapor (water)
Term
Discounted Payback
Definition
The time required for the cumulative net benefits derived from an investment to pay back the investment cost, taking into account inflation and the time value of money
Term
Energy Efficiency Ratio
Definition
The ratio of net cooling capacity in BTU/h to the total rate of electric input in watts under designated operation conditions.
Term
Efficiency, overall
Definition
The ratio of useful energy at the point of use to the thermal energy input for a designated time period, expressed in percent.
Term
Internal Rate of Return
Definition
The interest rate for which the total discounted benefits from an investment equal its total discounted costs.
Term
Coefficient of Performance
Definition
The ratio of the rate of net heat loss in BTU/h through a square foot of a wall or other building surface when the difference between the indoor and outdoor air temperature is 1F (U-1/R)
Term
Discounting
Definition
A technique for converting cash flows that occur over time to equivalent amounts at a common point in time- usually the present.
Term
Inflation Rate
Definition
A rise in the general price level (for al goods and services) resulting from a decline in the purchasing power of a dollar.
Term
Humidity Ratio
Definition
The weight of the actual water vapor in aa mixture per pount of dry air.
Term
heating System Performance Factor
Definition
The total heating output of a heat pump (in BTUs) during it's normal usage period for heating, divided by the total electric power input in watt-hours over the same period.
Term
Latent Heat
Definition
A term used to express the energy involved in a change of state.
Term
Seasonal Energy Efficiency Ratio
Definition
The total cooling of a central air conditioner in BTUs during it's normal usage period for cooling, divided by the total electric input in watt-hours over the same period
Term
Present Value
Definition
Past and future cash flows expressed in terms of current dollars by adjusting for inflation and any other factors that affect the time value of money.
Term
Salvage Value
Definition
The net sum to be realized fromt he disposal of an asset at the time of it's replacement, resale, or at the end of the study period.
Term
Marginal Costs
Definition
The incremental changes in costs associated with alternative investments.
Term
Life-Cycle Costs
Definition
The total of all relevant costs associated with an activity of project during the time it is analyzed. For buildings the Life-cycle costs include the costs of owning, operating and maintaining the building including energy costs.
Term
Ventillation Air
Definition
That portion of supply air which comes from outside plus any recirculated air that has been treated to maintain the desired quality of air within a designated space.
Term
Latent Heat
Definition
Term used to express the energy involved in a change of state.
Term
Time Horizon
Definition
A period of economic analysis over which time the costs and benefits of an investment are calculated.
Term
Enthalpy
Definition
The total heat in the mixture measured about 0F and including the latent heat of the water vapor
Term
annual Fuel Utilization Efficiency
Definition
The efficiency rating required by the federal government for rating gas or oil fired furnaces and boilers, based on average usage conditions including on/off cycling.
Term
cooling systems
Definition
Vapor compressor, Absorption Chiller, Dessicant cooling, Evaporative Cooling.
Term
Fiberboard Sheathign
Definition
Made from wood fibers, used as backing for surface for siding. Often asphalt impregnated to reduce the susceplibility to moisture degradation
-moisture absorption and degradation problems
-susceptible to mildew and rot
Term
polysterene- Styrofoam
Definition
Closed cell foam boards cut to length and width. Used for exterior sheathing of fiberboard. As an interior wall insulation must be covered w/ 1-1/2" or 5/8" gyp. bd. because it is combustible and out-gases toxic chemicals when burnt.
-no moisture degradation
-no mildew or rot
-dimensionally stable
-slight UV degradation, but R-value is stable
Term
Polystyrene- Bead board
Definition
heat and pressure treated to cause beads to adhere into molded shape, then cut to length and width
-Cheaper than Styrofoam
-more susceptible to vermin damage
Term
Polyurethane
Definition
Foamed into boards or directly into wall cavities. Pre-formed boards will have surface layers of low moisture permeability to reduce R-value degradation. Usually have aluminized foil surface for this purpose and add to rigidity. Often used in pre-fabricated metal building panels and inlulated doors.
-one of the highest R-values, but expensive
-Appreciable R-value degadation with exposure to air and UV light
-no mildew or rot
-not susceptible to vermin
-burns and gives off toxic gas
Term
Fiberglass blankets and batts
Definition
Made from melted glass, usually backed with craft or aluminized paper on one face
-fire proof
-not suscetible to mold or rot but will hold moisture that may rot adjacent mat.
-susceptible to vermin
-when used in horizontal applications will mat down over time.
Term
Mineral Wool blankets and batts
Definition
Made from melted rock instead of glass. Other than lower R-value, has many of the same attributes of spun fiberglass insulation.
more susceptible to vermin
Term
Fiberglass(loose fill)
Definition
can be blown in or hand placed. Has the same properties and thermal characterstics as in blanket/batt form. Lower listed R-values take into accoutnt he less uniform density that will result from the loose fill application method
Term
Vermiculite
Definition
Loose granual volcanic material compound. Over a period of 60 years 80% of the words supply of vermiculite has come form W.R. Grace & Co. in Libby, MT.
-very cheap
-fire proof
-not susceptible to mildew, rot, or insect problems
-no moisture degradation
-seggling can reduce R-value significantly and can create cold spots at the top of vall cavities where settling has occurred.
-asbestos tainted vermiculite in existing building spaces is a health hazard
Term
perlite
Definition
Loose granule mineral based insulator like vermiculite, but expanded and therefore lighter. Has many of the same properties as vermiculite but a higher R-value. Used as an additive for light weight concrete where the insulation properties are of greater importance than concrete strength
Term
cellulose fiber
Definition
made from recycled paper
-very cheap
-combustible and must be treated with fire retardant which presents quality control problems in the manufacturing process
-as with all fiber based products, susceptible to vermin
-Settling can be a problem
Term
blown insulation
Definition
Most loose fill insulations can also be blown into place
-fiberglass, mineral wool, vermiculite, perlite, cellulose
Term
urea formaldehyde
Definition
blown insulation in wall cavities for new constrction and retrofit applications. outgases formadehyde which is a health hazard to building occupants. It's use has been discontinued, but the product is still in place where it had been used with no national program for removal.
-relatively cheap
-fireproof
-chemically stable, but outgases formaldehyde
-no moisture or insect problems
-tends to bond with the wall
Term
Visible transmittance
Definition
The precent of incitent visible radiation transmitted by the glazing
Term
Solar transmittance
Definition
percent of incident total solar radation transmitted by the glazing
Term
Near-infared tranmittance
Definition
if solar radiation is assumed to be half light and half near-infared radiation
-approximated by doubling solar transmittance and subracting visible transmittance.
Term
Incident solar radiation
Definition
solar radiation that arrives at a given glazing at a certain time and date can still be described by the diagrammatic spectral distribution curve described earlier, with reductions in the power of certain wavelengths and perhaps even slight increases in teh power of other wavelengths.
Term
extinction coefficient
Definition
The rate at which glass absobs solar radiation
Term
refraction
Definition
bending of light passing through a medium
Term
angle of incidence
Definition
More radiation is reflected as angle of incidence is greater, measured w/ perpendicular angle = 0
Term
cut-off angle
Definition
Angle at which all incident light is relected (87)
Term
Spectral Selectivity
Definition
Glass admits most visible and near infared radiation, but not far-infared radiation creating the greenhouse effect. This is an example of this term.
Term
shading coefficient
Definition
Dimensionless ratio defined as the solar gain through a given fenestration compared to what the solar gain would have been through an unshaded opening the same size and orientation glazed with a standard single pane of 1/8" double strength clear window glass. Developed to provide a simple reference to a known product.
Term
cooling load factor
Definition
Sensible cooling load (Qrs)/Sensible heat gain(Qes)
Term
Cooling load calculation
Definition
Uses sun angle/ time of day charts
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