Milk chiller problem

[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 pratically 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 coolent side glycol temp is -5.5 degree to -6 degree
but we didn't get atleast 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 (munakp@gmail.com)

im verymuch thankful to you,

[nike123]

There is no need to post your question in multiple threads.



we designed for chilling milk from 8 degree to 6 degree celcious(i.e 6degree drop) From 8 to 6 is 2 degree drop.
If it is 6 degree drop than, if 8°C at enter mean that on exit will be 2°C.
Which is your case?

What is PHE model#?
What is measured glycol flow rate? What glycol type is inside and what concentration.
What is measured milk flow rate? Is it 10m^3/hr?
20 TR should be sufficent to cool 20% propilene glycol 5°C if flow is about 12000l/h
__________________

[Gary]

What are the input and output temperatures on the glycol side of the PHE?

[muna]

thank you nike,

Sorry for the multi post, I am new to this RE, so i didn't read the rules im verysorry
we designed for chilling milk from 8 degree to 2degree celcious(i.e 6degree drop)
M10 not Exact,

Glycol flow rate is 27360 Ltr/hrMilk flow rate is 10,000 LTR/hr

[muna]

Glycol input is -6*c
output is -2 *c

[nike123]

thank you nike,

M10 not Exact,

Glycol flow rate is 27360 Ltr/hrMilk flow rate is 10,000 LTR/hr

Are you sure that you have counter-flow of milk/glycol in PHE. Check connections and flow directions. It must be counter-flow.

What is glycol concentration and type?

[muna]

Are you sure that you have counter-flow of milk/glycol in PHE. Check connections and flow directions. It must be counter-flow.

What is glycol concentration and type?
yes you are correct it is counter flow only, glycol and water concentration is about 30%

[nike123]

Glycol flow rate is 27360 Ltr/hrMilk flow rate is 10,000 LTR/hr

Is that measured flow with measuring device?

With that flow rate you stated above and temperature diference of 4K (-6--2) that qlycol is taking from HE about 40TR which is not possible.
So something is wrong. Either flow rate or measured temperatures.

[muna]

Is that measured flow with measuring device?

With that flow rate you stated above and temperature diference of 4K (-6--2) that qlycol is taking from evaporator about 40TR which is not possible.
So something is wrong. Either flow rate or measured temperatures.
milk side we get measure by milk silo scale and pumping time
but
glycol we took pump designed output for 14mtr head i.e is 7.6ltr/sec
our assumption the glycol flo rate not less than 20,000ltr/hr

so guide me, what i have to do?

[Gary]

Is that measured flow with measuring device?

With that flow rate you stated above and temperature diference of 4K (-6--2) that qlycol is taking from HE about 40TR which is not possible.
So something is wrong. Either flow rate or measured temperatures.

Or all of the above.

[nike123]

milk side we get measure by milk silo scale and pumping time
but
glycol we took pump designed output for 14mtr head i.e is 7.6ltr/sec
our assumption the glycol flo rate not less than 20,000ltr/hr

so guide me, what i have to do?

With what instrument you are measuring temperature?

Adjust flow (reduce) until you get 5K temperature difference at glycol side. That will give you maximum heat transfer to you PHE. Than check milk side.

[muna]

With what instrument you are measuring temperature?

Adjust flow (reduce) until you get 5K temperature difference at glycol side. That will give you maximum heat transfer to you PHE. Than check milk side.
thanks a lot, your reply makes me thinking in depth,
we are using digital temp indiacator as wel as analog thermo meter with 0.5 *c error

you mean 5k, how much *c ?? we need minimum 5*celcious in milk side

[nike123]

thanks a lot, your reply makes me thinking in depth,
we are using digital temp indiacator as wel as analog thermo meter with 0.5 *c error

you mean 5k, how much *c ?? we need minimum 5*celcious in milk side

What kind of temperature measuring device. (IC, surface probe, Pt100 Pt1000, K-type etc..)?
It should be measured with Pt1000 probe which is in copper sleeve inside glycol pipe or with some very accurate surface probe at some distance of HE (about 25-50 cm from HE). Or with this kit:
http://www.yellowjacket.com/images/products/ElctrncInstrmnts/69104_lg_SuperheatKit_case.jpg

5K (upper case) means 5 Kelvin
Kelvin is same as Centigrade degree when it is used as temperature difference unit. And, according to SI unit system, it is preferable unit to use when there is temperature difference in game.

[mad fridgie]

Glycol is to cold, or milk velocity is to low.
Is the milk flow consistant?

[nike123]

If you want that your PHE is at maximum exchange capacity, than you need introduce concept of thermal length.
That mean if you want temperature drop on milk side of 6K, than you also need temperature drop on glycol side of 6K. You do that by changing flow of glycol to get same "thermal length".

Edit: Ignore this since I forgot to care about frost.

[muna]

Glycol is to cold, or milk velocity is to low.
Is the milk flow consistant?
hmm, yes milk flow rate is consistant,but now we can't cool the 10000ltr/hr milk with is PHE, bcoz ifigive 10000ltr as a inputmilk i could get only 1 to 2 *c drop, so i adjust the flow rate of milk which for 4*c drop

[mad fridgie]

hmm, yes milk flow rate is consistant,but now we can't cool the 10000ltr/hr milk with is PHE, bcoz ifigive 10000ltr as a inputmilk i could get only 1 to 2 *c drop, so i adjust the flow rate of milk which for 4*c drop
Install, 3 port valve, supply full flow of glycol at a higher temperature!

[muna]

Install, 3 port valve, supply full flow of glycol at a higher temperature!
ya alredy it has been installed, and gave it to full force full open in glycol side @-6*C and as well as 10,000ltr/hr of milk @ 6*C as input, but milk output is only 2*C drop(i.e 4*)
so pl give the correct parameter for chilling the milk 6*C to 2*C,
so im greatful to uuu

[mad fridgie]

ya alredy it has been installed, and gave it to full force full open in glycol side @-6*C and as well as 10,000ltr/hr of milk @ 6*C as input, but milk output is only 2*C drop(i.e 4*)
so pl give the correct parameter for chilling the milk 6*C to 2*C,
so im greatful to uuu
Glycol is to cold, full force say at -2C not -6C

[nike123]

With that surface of PHE and flow rates you presented you could only go with -4°C glycol at inlet and 1°C at outlet (13,2 m^3/h) if you wish that 10000l/h milk is cooled from 8°C to 2°C (1K approach).

http://i55.tinypic.com/169iz2p.jpg

If you increase surface to 5,9m^2 than you could go with -2°C glycol at inlet and 1°C (22m^3/h)at outlet if you wish that 10000l/h milk is cooled from 8°C to 2°C (1K approach).

http://i56.tinypic.com/30vojuo.jpg

[Gary]

Everyone seems to be in agreement that -6C is too cold. The glycol should not be colder than -4C.