System Analaysis

[ivan25]

I'm a engineering student haveing few assignments to complet for System Analysis..
I have to design a cool room that has a total heat load of 5.0KW and is to be used to hold product at 6 c in a 30 c design ambient.
I have to " select the most suitable compressor set , remote air cooled condenser and forced or Induced deaft coolet to operate on R 22 at an evaporating temperature of 0 c and a condensing temperature of 40 c.

[Peter_1]

And what was your question exactly?

[nevgee]

....... I have to " select the most suitable .....

Then firstly you need to chose the manufacturer you intend to use for your various pieces of kit and then get some engineering /performance data from them.
Using their data you will be able to select your equipment and do a balance for optimum performance.

[ivan25]

What i want here to know how to calculate the capacity of the evaporator, compressor and the condenser...
I want to know the Td for calculating the evaporater...which is directly proportional to the capacity..
at a 6 c room temperature whot would be the saturated suction temperature..

[US Iceman]

product at 6 c - an evaporating temperature of 0 c = 6K temperature difference, so you have to find an evaporator with a 5 kW capacity at this temperature difference.

You have almost answered all of your questions youself. You just needed to put the parameters in the right order...

[TXiceman]

He is just trying to get someone else to do his assignment....not what the instructor had in mind, I'm sure.

Ken

[ivan25]

nope it isnt true ...that i want help to do my assignment...
i know it sound a bit silly,but the problem is there is limited information for me to calculate..
i will give u a similar problem with the right information,
a cool room at 3c & 85% Rh,on R404a , the required evaporator capacity is 10.5 kW. ok
the solution..
determine the necessary room Td to achive 85% Rh...
from the graph i have i got a Td of 3.5 kTd..
Calculate the required base capacity ie
base capacity = evaporator capacity/ Td
= 10500/3.5
= 3000w @1kTd.
Correction factor for the evaporator temperature
ie the S.S.T - Td
= 3 - 3.5
= -0.5 k
according to the table the capacity correction factor is 1.14
therefore the required bas capacity is
capacity correction factor * base capacity
= 1.14 * 3000
= 3420 w
I can now select for the manufacturer which evaporator is the closest one for the capacity calculated

in this problem i had Rh to find the Td...
and the evaporator capacity...
i know the solution is simple but i'm goin nuts... so i posted this question

[Peter_1]

You choose first your evaporator of 5 kW, 7 to 8 K DT (if no RH is demanded), then select a compressor which matches as close as possible 5 kW at te =0°C and tc=40°C, then add the power the compressors draws and add this to your capacity at the given conditions (+/-5 kW), let's say 6 .5 kW.
Then search for a condenser which can extract 6.5 kW at a DT of 10 K in an ambient of 30°C.

Use for all this correction factors for elevation (if any), other given capacities at other temperatures then you have here in you example (depends on the manufacturer), other liquid temperatures.. This is something you must find in your catalogues (spell checker says this is not a correct word. Is it?)

Select your TEV at 5 kW with te=0°C and tc=40°C.