Human Comfort & Mechanical System Fundamentals

A (sf) = area of bldg assembly
C (Btu/hr-sf-°F) = conductance
e (hr-sf-°F/Btu) = emittance
Eᵗ (Btu/hr-sf) = total solar radiation
hₒ (Btu/hr-sf-°F) = coefficient of heat transfer
k (Btu/hr-sf-°F) = thermal conductivity (1" of thickness)

U (Btu/hr-sf-F) = coefficient of heat transmission
V (ft3/min) = volumetric airflow rate
a = absorbance
ε = thermal emissivity

1) human comfort is based on:
2) the body's heat production is measured in metabolic mets, what is a "met?"
3) one met =

1) what are the main 3 ways the body loses heat?
2) convection is:
3) when/how does the body lose heat thru convection?

1) when does heat loss thru evaporation occur?
2) what is radiation?
3) when does the body lose heat thru radiation?
4) what is conduction?

1) on avg, a gen comfortable air temp range is btwn:
2) a tolerable range is btwn:
3) IMC & IBC req any space for human occ. provide:
4) what is "effective temperature?"

1) what is dry-bulb temperature?
2) what is wet-bulb temp?
3) in dry air, moisture evaporates rapidly & causes wet-bulb temp to read as:
4) in moist air, a wet-bulb temp reads as:
5) what new technology measures relative humidity?

1) what is relative humidity?
2) comfortable relative humidity range:
3) tolerable range:
4) when humidity goes up like in the summer, why does someone feel hotter than temp indicates?

1) air movement tends to increase (__) & (__) thru convection
2) wind speeds from (__) to (__) are acceptable for cooling w/ annoying drafts

1) if surface temp around body is colder than skin temp, the body:
2) if the surface temp is warmer:
3) rate of radiation depends on:
4) what is the "viewed angle?"
5) ^ Ex person next to fireplace feels warm because:

1) the "emissivity" of an obj. is it's ability to:
2) the "emittance" of an obj, is the:
3) what type of objects have low vs high emissivity?

1) what is "mean radiant temp" (MRT)?
2) MRT is important comfort factor in winter & cold rms b/c as air temps decrease:
3) what is a globe thermometer?

1) what is operative temperature?
2) human comfort std.'s are based on wearing clothes, so to quantify effects the unit "clo" was developed which =
3) where are 2 types of ventilation req.'s designed for?

1) when natural ventilation is used, IMC & IBC req area that can be opened to outdoors be = to:
2) when rm is ventilated thru adjoining rm:
3) when mech ventilation is used, rate of supply air into rm must be:

1) w/ mech ventilation, amt of OSA brought in depends on:
2) "comfort charts" show the relationships btwn:
3) chart shows as humidity increases, to prvd same amt of comfort at lower humidity levels, air temp must:
4) if temp drops blw recommended levels, what is needed to maintain comfort?

1) what is a "psychrometric chart?"
2) what is psychrometry?
3) this chart is used to make calcs for determining:

1) can hot or cold air hold more moisture?
2) on chart, the 100% relative humidity line is also known as:
3) what is "enthalpy?"

1) what is enthalpy line on chart used for?
2) what is sensible heat?
3) what is latent heat?
4) what is humidity ratio?

1) what climate only do evaporative coolers (aka swamp coolers) work?
2) external loads that cause heat loss:
3) external loads causing heat gain:
4) internal loads causing heat gain:

1) conduction is transfer of heat thru:
2) convection is transfer of heat thru:
3) conduction is transfer of heat thru:
4) in order to determine the size of a heating system for a bldg:
5) how is heat lost in a bldg?

1) a mat.'s "thermal conductivity" (k), is the rate heat passes thru:
2) "conductance" (C) is the ^ same property when:
3) "resistance" (R) of a mat. is the # of hrs needed for:
4) total conductance & total resistance are related, equation is:

1) when bldg assembly consists of more than one mat., value to calc heat loss is:

1) amt of heat loss thru 1 unit of area of bldg mat. is dependent on the coefficient of heat transmission of mat. & temp differential btwn inside & out
- for entire area of one mat. type, value is multiplied by total area to get total heat loss "q"

1) how is the value of ΔT (change in temp) found?
2) heat loss calcs & psychrometric charts are used to avoid condensation on:

1) b/c of warmer inside temps, to avoid water vapor from inside bldg permeating the const. & condensing on surfaces like wood sheathing & causing damage to it or reducing effectiveness of insulation, what can be done?
2) what is a "thermal gradient?"

1) heat loss thru infiltration is calculated w/ equation:

*infiltration greatly affects energy use so codes req. use of air barriers to min. it

1) heat gain thru bldg envelope can be calc'd like heat loss w/ equation q = U A ΔT
except that:
2) design equivalent temp diff. (DETD) accts for:

1) an alt to DETD is "sol-air temp" which is a value for:
2) in heat gain calcs, sol-air temp can be used in place of:
3) the sol-air temp calculation is:

SOL-AIR TEMP EQUATION
Tₒ is outdoor dry-bulb temp
"a" is surface's absorbance for solar radiation (light colors typ 0.45 & dark typ 0.90)
Eᵗ is total solar radiation incident on surface in Btu/hr-sf

1) heat gain thru glazing is calc'd by:
2) "design cooling load factor" (DCLF) accts for:
3) occupants of a bldg produce which two kinds of heat?

1) sensible heat gain from occupants is about (__) Btu/hr
2) total sensible heat is estimated by:
3) 1W (watt) = 3.41 Btu/hr so heat gains from lighting can be calc'd by multiplying:

1) why must latent heat be acct'd for in calc-ing heat gains?
2) in heat gain calcs latent heat is calc'd separately or % of total sensible heat which is based on:

1) why is using bldg mat.'s w/ a high mass an effective passive method to mitigate effects of heat gain via solar radiation & air temp?
2) how do you calc sensible heat gain thru infiltration?

1) if a bldg is mech ventilated, vol of air brought into bldg is multiplied by:

*see definitions P16-12

1) "coefficient of heat transmission" (U) - overall rate of heat flow thru any combo of mat.'s, is the reciprocal of the sum of all the resistances in the bldg assembly
2) "conductance" (C) - # of Btu/hr that pass thru 1sf of same mat. of given thickness when temp differential is 1F

6) "latent heat" - heat that causes a change of state of a substance, like heat req'd to change water to steam (amt of heat req'd to change state of a substance is much greater than heat req'd to raise temp of a substance {sensible heat})

9) "specific heat" - # of Btu's req'd to raise the temp of a specific mat by 1F - it's a measure of a mat.'s capacity to store heat as compared w/ the storage capacity of water