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12 Cards in this Set
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What is a buildings heating load? When does maximum heating load occur? 
It is a buildings maximum heat loss during the heating period. When the outside temp is lowest. 

What's is the general design tem p for HVAC? What is HVAC basically a practical application of? 
Anywhere between 21.1 to 22.2
Psychrometrics 

What is total resistance R? What are eqs for R? 
It is the total resistance to heat flow through the entire thickness of material.
R = 1 / C and k = R / L k is the conductivity, resistance per unit thickness of the material L is length or thickness. 

What is eq for heat transfer through walls, Windows, doors, and ceilings? What is U and how is it found? 
Qdot = U*A*(TiTo)
Overall heat transfer coefficient. U = 1/sum(R) = 1 / [1/hi + sum(L/k) + sum(1/C) + 1/ho]. 

What is ventilation? What is sensible heat? What is latent heat? What are eqs for both? Which is usually more significant? 
Ventilation is providing air and humidification to an occupied space.
Sensible heat is pure thermal energy that increases airs drybulb temp
Latent heat is moisture that increases airs humidity ratio.
Qs = mdot*cp*(TidTin)=Vdot*density*cp*(TidTin). Where Tin is dry bulb temp of air entering room
Ql = mdotwater*hfg = mdotair*∆w*hfg= Vdot*density*∆w*hfg
Sensible loads usually more significant and ventilation can be determined solely on that. However latent becomes more considerable if large moisture sources are present 

What is the sensible heat ratio? What is the latent factor? 
SHR = Qdotsensible / (Qdotsensible +Qdotlatent) LF = 1 / SHR 

What is the bypass factor? What is the lever rule i can use to find it? how do i find it graphically? 
It is the ratio of the bypassed air to the total AMT of air.
BF = (Tmix  Tcond) / (Troom  Tcond) Plot the two points on the psychrometric graph. The indoor design conditions (dry bulb and wet bulb temps) and the sat temp (ususlly of air leaving a/c) or dewpoint temp same thing. Then plot a line between the 2 pts. Then the BF will be the distance of the conditions of air entering the space to the Sat temp pt over the total length of the line plotted.


How do you use sensible heating ratio on psychrometrics chart? 
Use them protractor at the top to find the slope and then plot the line. 

What is saturation %? 
Another way to say relative humidity 

When a problem mentions air passing through a reheater and being raised sensibly what does that mean? 
If temp is being raised sensibly it is a represented by a horizontal line on the psychrometrics chart 

If I know the drybulb and wetbulb temps what can I find for air at those conditions on the psychrometric chart? 
v specific volume and w humidity ratio. 

If I am given wet bulb and dry bulb conditions for air for in and them have the relative humidity % of exit air what do I on the psychrometric chart to find exit conditions? If it's adiabatic (no heat applied) 
Basically from the pt that corresponds to given db and wb temps from a line up and to the left following constant enthalpy until it intersects with relative humidity line. 