In an industrial bottling plant, the glass bottles must be washed, dried, and co

Question

In an industrial bottling plant, the glass bottles must be washed, dried, and cooled before going to the filling department. The plant operates at atmospheric pressure at a capacity of 1000 bottles/hr. During washing process the bottles retain 0.1kg H2O/kg glass and enters the drier at 25C. Determine the heat load on the dryer if the dry bottles leave at 100C. Each bottle weighs 0.5 kg. Assume the heat capacity over the temperature of operation is 0.18 kcal/kg.K for glass and 1.00 kcal/kg.K for water.

Explanation / Answer

N = 1000 bottles/h

Ratio = 0.1 kg water / 1 kg glass

Ti = 25°C

Cpglass = 0.18 kcal / gC = 0.753 J/gC

Cpw = 1  kcal / gC = 4.184 J/gC

Assume it is evaporating at 100°C:

Vaporization = = 2264.76 J/g

bottle mass = 0.5 kg of glass...

Assume a basis of 1 hour

so

Ntota = 1000 botles

mass of bottle = 0.5*1000 = 500 kg of glass

mass of water = 0.1 kg of water / kg of glass* 500 kg glass = 50 kg of water

Qglass = m*C*(Tf-Ti) = 500*0.753 (100-25) = 28237.5 kJ (per hour)

Qwater = m*C*(Tf-Ti) + m*Hvap = 50*4.184 * (100-25) + 50*2264.76 = 128928 kJ ( per hour )

total = 28237.5 +128928 = 157165.5 kJ (per hour)

1 h = 3600 s

Q duty = 157165.5 / 3600 = 43.6570 kW

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