Milk chiller problem, pl help me

[muna]

Dear friends,

pl help me to find out the problem

we have installed 20tr glycol chiller with ammonia systems for chilling 10,000ltr/hr milk by alfa laval PHE.

we designed for chilling milk from 8 degree to 6 degree celcious(i.e 6degree drop)

but practically we give input milk is 6degree only
but we getting output milk temp is 3.5degr to 4 degree only(i.e is 2.5 degree drop only)
we gave the coolant side glycol temp is -5.5 degree to -6 degree
but we didn't get at least 5 degree drop

the milk chiller heat transfer area is 3.84m^2

pl anybody help me
whether the designed system is correct or not?

?????????

u can send ur idea to my mail box
munakp@gmail.com

im very much thankful to you,

[NoNickName]

And the leaving glycol temperature is?

[muna]

And the leaving glycol temperature is?

it is -2*c only

[muna]

it is -2*c only

we designed for chilling milk from 8 degree to 2 (not 6 degree as i mentioned) i.e 6degree drop

[NoNickName]

Milk is approximately heavy as water (1.032 for raw milk).

On the warm side:
20TR = 70kW
70kW with a volume flow of 10000ltr/h gives a dt = 6°C therefore the leaving milk temperature is 2°C, but the wall temperature is -0.91 for a leaving glycol temperature of -1°C, very close to freezing temperature of milk (-0.55).

In my opinion, the heat exchange in your case is limited by formation of frosted milk on the plates.

[mad fridgie]

Milk is approximately heavy as water (1.032 for raw milk).

On the warm side:
20TR = 70kW
70kW with a volume flow of 10000ltr/h gives a dt = 6°C therefore the leaving milk temperature is 2°C, but the wall temperature is -0.91 for a leaving glycol temperature of -1°C, very close to freezing temperature of milk (-0.55).

In my opinion, the heat exchange in your case is limited by formation of frosted milk on the plates.

great minds think alike

[muna]

yes , u are absolutly correct dear, one time we did CIP cleanning with dismandling plates, we seems that there were some milk freezed pieces,
so we put a automatic temp control actuator valve, it never allowed to freeze the milk, if once touching 2*C it ll stop the glycol flow,

so tel me what is the input parameter must to cool the 10000ltr/hr milk @6*c input(i need glycol in temp and suface area of pHE)

[muna]

great minds think alike

thank you so much mad Fridge for your valuable words & advice , pl give me the comple design,

Thnx in advence

[NoNickName]

I think you should not cool the milk at a temperature below 4°C.

[muna]

I think you should not cool the milk at a temperature below 4°C.

hmm, now im getting outlet milk @ 2*C for 6000ltr/hr, but i need same temp for 10,000ltr/hr

[NoNickName]

Increase the surface of exchange

[monkey spanners]

it never allowed to freeze the milk, if once touching 2*C it ll stop the glycol flow

Which fluid are you measuring to get 2C ?

If its the milk that might be you problem as the outlet temp won't tell you if there is ice on the plates, (ice will act as an insulator so the milk will be touching ice at 0C and not a stainless steel plate at -6C)

The only glycol chiller system i have seen ran at around -3C and controlled the flow of glycol into the plate cooler based on the temperature of the glycol coming out, the colder the outlet temp the less glycol flow.

I have installed some ice builder systems that have supplied chilled water at 0C to a two stage plate heatexchanger with mains water to the first stage and our milk outlet temperature was around 2.5C, this was direct from the milking parlour so the milk was at cow body temp, so i'm not sure you necessarily need such a low starting glycol temp.

The other thing i would ask is are all the plates in the correct way in the plate heat exchanger?

[chemi-cool]

The two Glycol system I maintain from time to time have milk feeding pumps with speed controlled by the milk outlet temp.
The Glycol feeding temp is -0.5°C to -2.5°C.

Increase the surface of exchange

Thats the right thing to do.