net refrigeration capacity

[ahmadfitri]

hello, i am new in this area. can i know how to calculate the net refrigeration capacity of Chilled water system(air Cooled).
data is 3.3m3/hr nominal flow rate,water outlet temp 20C, ambient temp 32C,
hopefully some one can help me. Slide 8 .O {color:black; font-size:149%;} a:link {color:#CCCCFF !important;} a:active {color:#3333CC !important;} a:visited {color:#B2B2B2 !important;}

[amitsaxena]

Dear U calculate like this

Your flow is =3.3m3/hr= 3300Liters/hr
=0.92liters/ sec= 0.94kgs/sec

Cooling required = 0.94*4.2*12= 47 Kwatts

[ahmadfitri]

why u choose temp diff. 12? if i not mistaken the ambient temp temp is at condenser@Qh and the the water outlet is at evaporator @Ql

[ahmadfitri]

Here i attach the drawing.Please help me!!!!!!!!!!1:confused:

[Sandro Baptista]

To do the calculation there is need of more information. For instead you said that the water difference temperature is between 4 and 8 K. If we consider a 4 K and 3,3 m3/h it would be about 15 kW but if it is with 8 K with would be about 30 kW. BUT...the real capacity could not be one of this values because it also depends on:

- Air temperature which affects the condensing pressure. Higher condensation pressure less capacity;

- Chilled water temperature inlet which affects the suction pressure. Higher water temperature » higher suction pressure » higher capacity

The capacity it would be a result of these parameters and other which would make so that the refrigeration unit would give specific capacity at an equilibrium point.

If you measure accurately the water flow and the water temperature difference (inlet-outlet) then we can get the capacity. If it is glycol or a brine it would be a difference on the calculation beacuse the density and the specific heat woul be differente from the water.

[nike123]

Q=m*c*(t2-t1)

Q=capacity
m=mass
c=specific heat capacity
t2-t1= temperature difference of media entering and leaving heat exchanger

You need to know only one information more:
water entering temperature.
Mass is, as Amitsaxena alredy calculated, 0,94kg/s
Specific heat of water is 4.1813 kJ/kg K

[ahmadfitri]

Thank you very much for all. but the problem is no water temp inlet.From only that data they given me the net refrigeration value 24.4KW and i need to prove that value. the power consumption (with pump)3bar is 11.1KW.

[amitsaxena]

Dear Can, you provide all the information, you have as its very difficult to make out what is water inlet conditions.

Thanks
Amit