Please make sure that you solve it fully, not only equations. Do all steps and g
ID: 718247 • Letter: P
Question
Please make sure that you solve it fully, not only equations. Do all steps and get final answear. Do not skip any steps please. I did post last time but I didnt get right answear..So, please send 100% right answear with all steps and work. And also dont forget to put right unit. Please, It should be answered by an expert.
Q4. Pasteurization is a common practice in the production of milk and juices. A company processes 6000 litres of milk per day. The milk is pasteurised in a heat exchanger by raising the temperature of the milk from 5 °C to 80 °C. This heating process is carried out on a heat exchanger which has an overall heat transfer coefficient (U) of 40m2(85 marks) kJ a) Calculate the amount of heat required per hour to pasteurise 6000 litres of milk per day The heat capacity of milk is 3.77 k the density (p) of milk is 1,03/cm (12 marks) b) Calculate the temperature of the water leaving the heat exchanger if the heat exchanger uses water at 100 oC to heat up the milk and the mass flow rate of water used is 500 (12 marks) kg/h exchanger (11 marks)Explanation / Answer
Ans
Part a
Mass flow rate of milk = volumetric flow rate x density
= 6000 L/day x 1.03 x 1000 kg/m3 x 1day/24h x 1m3/1000L
= 257.5 kg/h
Amount of heat required
Q = mass flow of milk x Cp of milk x (Tm2 - Tm1)
= 257.5vkg/h x 3.77 kJ/kg-°C x (80 - 5) °C
= 72808.125 kJ/h
Part b
Energy balance
Heat absorbed by milk = Heat released by water
Q = mass flow rate of water x Cp of water x (Tw1 - Tw2)
72808.125 kJ/h = 500 kg/h x 4.184 kJ/kg-°C x (100 - Tw2)°C
34.8 = 100 - Tw2
Tw2 = 100 - 34.8 = 65.2 °C
Part c
For countercurrent flow
Milk pasteurized from 5 - - - - - > 80 C
Water outlet to inlet 65.2 <----- 100 C
LMTD = (65.2 - 5) - (100 - 80) / ln (60.2 / 20)
= 40.2 / 1.102
LMTD = 36.48 °C
Q = U x A x LMTD
72808.125 kJ/h = 40 kJ/hm2°C x A x 36.48 °C
A = 49.90 m2