Chickens with an average mass of 2.2 kg and average specific heat of 3.54 kJ/kg*

Question

Chickens with an average mass of 2.2 kg and average specific heat of 3.54 kJ/kg*C are to be cooled by chilled water that enters a continuous-flow-type immersion chiller at 0.5 C. Chickens are dropped into a the chiller at a uniform temperature of 15 C at a rate of 500 chickens per hour and taken out. The chiller gains heat from the surroundings at a rate of 200 kJ/h. Determine (a) the rate of heat removal from the chickens in kW, and (b) the mass flow rate of water, in kg/s, if the temperature rise of water is not to exceed 2 C.

Explanation / Answer

Mass flow rate of chicken mchicken= 2.2*500 = 1100 kg/hr = 1100/(60*60) kg/s = 0.305 kg/s

(a) Rate of heat removal from chicken, Q = mchicken* Cp_chicken* (T)chicken

So, Q = 0.305*3.54*(15-2) = 14.06 kW.

(b)Heat addition from surroundings = 200 kJ/hr = 200/(60*60) kJ/s = 0.055 kW

Assume Cp for water = 4.186 kJ/kg C

Heat transfer from chicken + Heat addition from surroundings = Heat addition to water

So, 14.06 + 0.055 = (mCp T)water = m * 4.186 * (2-0.5)

This gives m = 2.25 kg/s = 8093 kg/hr.

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