NCEES 2008 practice test #536 (HVAC)

[goodal]

In the following problem, they did not use the water weight as given by ASHRAE to calc the latent load using the latent heat of fusion. they just used the total weight of the pork.

#536:

In a refrigerated warehouse, 10000 lb of whole lean ham is brought in at 40F cooled to 28F, frozen and cooled to 0F. The refrigeration required to do this in btu x 10^3 is.....

The six minute solutions used the water weight instead of the whole weight to get Ql. Which way is correct?

 

[HVACstevie]

Forget the six minute solution way. Use the meat tables in ASHREA. This is the method used in the NCEES practice exam.

 

[goodal]

Forget the six minute solution way. Use the meat tables in ASHREA. This is the method used in the NCEES practice exam.

Thanks but.... by using the entire weight of the meat, arent they assuming that the entire 10000lbm of meat is equal to 10000lbm of water that has to under go fusion vs if they used the water weight % in ASHRAE refrigeration (like 6 minute solutions)?

 

[Agg97]

Thanks but.... by using the entire weight of the meat, arent they assuming that the entire 10000lbm of meat is equal to 10000lbm of water that has to under go fusion vs if they used the water weight % in ASHRAE refrigeration (like 6 minute solutions)?

If I remember correctly about those 2 problems, one of them stated to assume that only ~80% of the meat was water weight. After that, you were simply using m*c*dT for water for the reduced water weight, with the c for water being used. The other one used the C values found in the ASHRAE Refrigeration handbook. Maybe I'm not remembering correctly???

 

[djshortsleeve]

ASHRAEs numbers include average factors.

My question is, which ASHRAE book includes this?

 

[goodal]

ASHRAEs numbers include average factors.
My question is, which ASHRAE book includes this?

ASHRAE refrigeration. i dont have the book here or i would give you the page number. its in one of the tables talking about food properties.

In an effort to truly understand this problem... Neither of the responses really helped. Either you acount for the water weight when you calc the latent load or you dont. It was done one way in 6 minute and another in NCEES. It makes sense in my head to use the water weight when multiplying by the latent heat of fusion, but if thats not what NCEES is going to use i want to do it their way.