capacity of refrigeration

[operator]

Help I'm hoping someone can help me out on this question. What is the capacity in tonnes of refrigeration of a system in which 1200 kg of the refrigerant are circulated per hour? The enthalpy of the vaporized refrigerant leaving the evaporator is 118 kj/kg and the enthalpy of the liquid refrigerant enetering the expansion valve is 64.66 kj/kg. I believe i have figured out the net refrigerating effect. It is done by subtracting the enthapy of liquid refrigerant enetering the expansion valve from enthapy of the vaporized refrigerant leaving the evaporator. That is 181 kj/kg-64.66 kj/kg = 116.34 kj/kg. The next step of the equation i'm not sure about. I know that the heat of fusion which is the amount of heat required to melt 1 kg of a substance, of ice is 334 kj. To melt 1000 kg of ice would require 334 x 1000= 334 000 kj. Therefore 1 tonne of refrigeration = 334 000 kj per hour. So do i multiply 1200 kg x 334 kj??? I did that and got 400 800 kj/24 hour. Final conversion to minutes gets me 278 kj/min. Is this right? can anyone help with this? Does anyone of anywhere else i can go for help?

[mbeychok]

Operator:

 

A metric ton (i.e., a tonne) of refrigeration is equivalent to the amount of heat required to melt a metric ton (i.e., 1000 kg) of ice in 24 hours. Thus, a tonne of refrigeration is equivalent to removing 334,000/24 = 13,917 kJ/hour ... not 334,000 kJ/hour.

 

Milt Beychok

(Visit me at http://www.air-dispersion.com)

[operator]

Right you are, sorry for not answering sooner . Thanks for letting me know. I think it might have been a typo on my part in the question. My question still stands though, do i multiply 1200 kg x 334? This gets me 400800 Kj/ per 24 hrs. If i divided by 24 I get 16700 Kj/hr or 278.33 Kj/min. Is this the correct answer? Thanks again.