Evaporator TD for Bulk milk coolers

[tadipatrir]

Dear Members,

What is the TD used for bulk milk cooler evaporators. This evaporator is a plate type evaporator (stainless steel) in direct contact with milk.

Cheers!

[monkey spanners]

I'd say it depends a lot on how much milk is in the tank, how warm it is, how quick you want to cool it, the make of tank. Some uk ones will only cool 10% minimum per milking, others will cope with 5%. Another factor is how good the agitation of the milk is. you don't want to be evaporating much below 0c for long or you risk freezing the milk. Are you having a particular problem?

Jon

[tadipatrir]

Dear Monkey Spanners,

Thanks for your response. I am getting a TD of 9degC with milk at 4 degC and evaporating temp at -5degC. Because of high TD I am losing capacity of compressor and also possibility of milk frosting on evaporator is more as you mentioned.

Any suggestions??

[monkey spanners]

Is this a new system or an old one that has started to give problems?
I'd check the superheat, i'd check/set this with the milk around the temperature that you want it cooled to eg 3/4C. Even with 6/7c superheat it will be evaporating around -2/-3c as it reaches the set point. Check the tev phial for good contact on the suction pipe and for insulation.
Is the customer turning the tank on without enough milk in it? If they do it'll freeze and insulate the evaporator a bit, causing a lower suction pressure.
Other things i would check for 'slow to cool' are the water flow to the platecooler in the milk line (if fitted) many times i've been called out only to find he precooling is not working, and nothing is wrong with the tank. If they have two tanks, are they splitting the milking evenly between the two? Tanks in the uk are either four or two milking tanks so only designed for 25% and 50% filling respectivly per milking. Check how well the compressor is pumping i've known them to snap a conrod and only be running on one cylinder, not always obvious when the milk is nearly cool as the system is'nt work that hard then. Condenser nice and clean?

Jon

[suny]

Dear tadipatrir

Through my practical experience, the evaporative plate should be submerged with milk & proper agitation is a must. You can have a TD 6 to 7 deg to keep the milk at 4 deg C. I hope you should have calculated the capacity of the compressor to pull down with in 4 hours from the time of milking.

Suny

[tadipatrir]

Dear MS & Suny,

This is a new system with evaporator plate submerged and with good agitation with the help of an agitator. As it is a new sysytem condenser is also nice and clean and it is not at customer site but at our workshop.

As you doubted, superheat is more to the tune of 9 - 10 deg C. Probably I should reduce it by adjusting the setting.

Anything more....??

[monkey spanners]

Set up the superheat, its surprising how much differance it can make with these.
Check the milk temperature with a thermometer, sometimes the probe can be out of calibration on the tank and it is working ok, reading a higher temperature than it should.
What make of tank is it, just curious.

Jon

[tadipatrir]

Dear Monkey Spanners,

Sorry for delay in my response. It is a packo milk tank.

Regards,

[monkey spanners]

Hi Tadipatrir
I've fitted a few Packo milktanks for a local milking parlour agent and apart from the wiring diagrams i've found them to be one of the better makes on the market. Most of them have been the icebuilder models.

Cheers Jon