Apparaturs Dew Point Temperature

[Timothi]

Dear Experts,

I have the following data for heat load calc using excel sheet.

Outside DB = 38 Deg C
Outside WB = 30.8 Deg C
Outside RH = 60%

Inside Room conditions = 23.5 Deg C, 55% RH
Room Total sensible heat = 10000 BTU/HR
Room Total latent heat = 1800 BTU/HR

There is no mixing of return air with outside air.


How to find the apparatus dew point temperature (ADP)?




Thanks in Advance

Sharing knowledge is the best way to learn

 

[Drazen]

you need mollier diagram for that.

draw your points (outside conditions, room conditions) and draw vertical line through room state point.

adp will be at intersection of your vertical line and saturation line.

if you use american psychrometric chart, the process is the same, but you are drawing horizontal instead of vertical line.

 

[317069]

ASHRAE would help you to solve your homework

 

[willard3]

Learn to read a psychometric chart. The information is there.

 

[getitdone91]

Rather than bicker about the question, some individuals may find it useful to turn it into a real discussion. For this process, using a psychrometric chart, I would:
1) Find points for indoor and outdoor conditions
2) Find SHR and draw sloped line to determine the coil discharge conditions.
3) Draw line from outdoor conditions through coil discharge condition line that will intersect the ADP.

For this particular application, assuming 100% OA (as stated), with no energy recovery, the cooling process is pretty darn close to not being possible....

 

[317069]

This site is not to help lazy students to not learn their courses or books, we advise them to read and learn, why do you thing he is asking about ADP if it is not a homework and he does not want to spend sometime to upgrade himself and learn, we eventually working for his benefit, also I think there is something wrong in your explanation and we may need to read ASHRAE again together

 

[willard3]

If this person is an Engineer as he says, he will have to learn to read a psychrometric chart. Now is a good time to start

 

[BronYrAur]

You guys are brutal - I love it!

Without doing someone's homework for them, please help me dust the cobwebs out of my brain on one issue. How do you know the coil discharge temperature unless you know what the bypass factor is? You can determine the SHR line easy enough and take that from the room condition back to the saturation line. But don't you need to know the coil bypass factor in order to know where the cooling process line intersects the SHR line? I suppose if an air flow had been given, the required discharge temperature could be calculated, but no air flow was given in the original question.

Is enough information given in the original question to determine the ADP?

 

[Timothi]

Anyways, thanks for all your replies (regardless of the content). Finally I got it done.

Sharing knowledge is the best way to learn

 

[ChasBean1]

I wish I had time to be on this more often. The ADP is the lowest dew point allowed by the cooling device based on surface temperature. If I have 38°F water, my coolest coil temperature might be 38°F (ADP) but my leaving bulk air stream temperature might be 53°F. The ADP is important because it defines the lowest dew point leaving air temp.

 

[BronYrAur]

So back to my question, don't we either need to know the CFM or the coil bypass in order to determine the ADP? Otherwise, how do you know the discharge temperature? Once the discharge temp is known, a line can be drawn from entering air condition, through the discharge temp point on the SHR line until it hits the saturation curve. That is the ADP.

So again, the thing I can't get past is how do you know the coil discharge temperature based on the information given in the original post?