jbomba
27-09-2009, 05:32 AM
Ok im having a few dramas calculating airchange load. Product load & defrost load. Here is what i have so far. Im calculating over 24 hours.
The room is loaded with 1500kg of product per day
The storage temp is -35
Temp of product entering the room is 35 degrees
The specific heat of the product above freezing is 3.182kj
The specific heat of the product below freezing is 1.717kj
The freezing temp is is -1.17
The latent heat of fusion is 233.48kj
there are 6 x 20 minute defrosts per day with the heater elements totaling 10Kw
Ineed to allow for 2 complete air changes
here is what i have so far
Airchange Load = IRVxACFxenergyxusage/time
IRV -LxWxH = 15x10x5 = 750m3
Now i have not been given an ACF(or is that 2^ )
Energy - 60%R.H, - 35 degrees storage =0.1045
Usage Factor - im assuming it is 1
1 hour = 3600 seconds x 24 = 86400 seconds
So i have gone :
IRVxACFxEnergyxUsage/time
750m3 x (2?) x 0.1045 x 1/86400= 1.814236111Kw
Now for defrost load
10Kw x 2/24=0.83Kw
Now for the product Load
Q=m x cp x deltaT
m=1500kg
cp=3.182 - Above freezing
1.717 - below freezing
delta T - 35+1.17=36.17 - Delta T above freezing
-35--1.17=33.83 Delta T below freezing
Pull down time 24hours =86400 seconds
so 1500kg x 3.182 x 36.17=172.639/86400=1.998Kw
1500kg x 1.717 x 33.83=87.129/86400=1.008Kw
1.998 + 1.008=3.006Kw
how do i work out the latent heat?
Thanks for your help here guys. I cant be to far off can i?
The room is loaded with 1500kg of product per day
The storage temp is -35
Temp of product entering the room is 35 degrees
The specific heat of the product above freezing is 3.182kj
The specific heat of the product below freezing is 1.717kj
The freezing temp is is -1.17
The latent heat of fusion is 233.48kj
there are 6 x 20 minute defrosts per day with the heater elements totaling 10Kw
Ineed to allow for 2 complete air changes
here is what i have so far
Airchange Load = IRVxACFxenergyxusage/time
IRV -LxWxH = 15x10x5 = 750m3
Now i have not been given an ACF(or is that 2^ )
Energy - 60%R.H, - 35 degrees storage =0.1045
Usage Factor - im assuming it is 1
1 hour = 3600 seconds x 24 = 86400 seconds
So i have gone :
IRVxACFxEnergyxUsage/time
750m3 x (2?) x 0.1045 x 1/86400= 1.814236111Kw
Now for defrost load
10Kw x 2/24=0.83Kw
Now for the product Load
Q=m x cp x deltaT
m=1500kg
cp=3.182 - Above freezing
1.717 - below freezing
delta T - 35+1.17=36.17 - Delta T above freezing
-35--1.17=33.83 Delta T below freezing
Pull down time 24hours =86400 seconds
so 1500kg x 3.182 x 36.17=172.639/86400=1.998Kw
1500kg x 1.717 x 33.83=87.129/86400=1.008Kw
1.998 + 1.008=3.006Kw
how do i work out the latent heat?
Thanks for your help here guys. I cant be to far off can i?