On farm milk pre-cooling

2007-08-07 14:27
charriau
Sales manager

Cooling and pre-cooling of the milk in the farm : actual situation

First of all it is necessary to understand how the cooling of the milk is made. It is in fact a transfer of calories which takes place due to a temperature difference between the milk and the cooling liquid (water for example). In practice, milk pre-cooling occurs between final unit and tank. During the milking, milk is extracted from the jar of the milk machine by a centrifugal pomp working in cycle. These cycles are driven by a level detector located in the room of milk. Being added to the already existent system, the pre-coolant must be able to fit to the characteristics of every milk farm.

Let us take the example of a farm producing 1000 litres of milk per 1 hour, and equipped with a milk pump with a flow of 10000 litres in hour in-50 kPa. It is necessary to know that the pump works in cycles. The time of pumping is only a tenth of the complete time of the milking, it is 6 minutes in our example. It means that it performs 100 cycles of about 10-litres (according to regulating), that is 2,78 litres in a second (during every phase of pumping from 3 till 4 seconds).

The transfer of calories (the exchange) is made according to precise laws of physics. This exchange is maximum when both fluids are in movement, but as soon as one of the fluids becomes stationary (the milk for example), thermal strats settle immediately. It causes a very important increase of coefficient R (1), and exchange falls to about 90 - 95 %. This phenomenon can be determined every day, in a milk tank for example, when agitation is stopped. Therefore the milk must be in movement on the evaporator to be correctly cooled down. Since the milk pomp works in cycles, we can note that in 54 minutes, the milk becomes stationary and therefore exchange becomes less efficient. It is for this reason that the most part of the existent systems of pre-cooling (plates or tubular) stop water when the milk pomp is stopped. Therefore we must to note that in this example, we have really only 6 minutes to cool down 1000 litres of milk.

We also know that we need from two to three litres of water (2) to pre-cool down a litre of milk. So, for a milk pomp of a 10000-litre debit, the instantaneous debit of water must be between 20000 and 30000 litres, but only during 6 minutes (that is from 6 to 9 litres in a second). Not many farms have installation of water that can provide such instantaneous debit of water.
So, from these conclusions, we had to conceive a pre-cooler that would be able to work on every farm, what ever the milk quantity, flow of the installed milk pomp and water flow.


(1) Coefficient of thermal resistance.
(2) In the example of 1000 litres by milking, it is also necessary to provide the stocking of the water used for pre-cooling, it is  2000 - 3000 litres of capacity according to the report  - from 2 to 3 litres of water by litre of milk.

Dernière modification par charriau (2013-02-13 18:52)

2007-10-30 15:57
charriau
Sales manager

A ten times more efficient cooling with the TEM-DY

After this report, and aware that technical solutions were available; we explored a wide spectrum of concrete possibilities.

Our objective was to achieve a maximum performance of exchange without corrupting the quality of the milk or unsettling the functioning of the installation of milking of working that it is for the milking or washing, and with the capacity to answer favorably to important debit of milk. It is in effect there that energy savings to be accomplished will be biggest in absolute value and that the request of instantaneous electrical potency is the most important.

Let us keep our example 1000 litters in one hour with only 6 minutes to assure pre-cooling (that is 1/10th of time because the pomp works by cycles). In that case, the necessary instantaneous debit of water is from 20 to 30 m3 (6 - 9 litters / s). It proves to be impossible to set up such installation in the great majority of farms if we like to cool down the milk significantly.

Our target is to cool down actively the milk during all time of milking that is one hour in our example. It is a continuous cooling, it increase from 6 minutes to 60 minutes; we multiply the cooling time by 10. Besides, the amount water will pass from 6 to 9 litres / seconds to an uninterrupted debit from 0,6 to about 0,9 litres / seconds (it becomes more realistic). So the instantaneous water flow is divided by 10, and it works with existing farm water pipes (diam 20).  It restricts the complete investment of the farmer which wants to achieve a maximum performance.

In milk cooling tanks, the milk (on open air) is put in movement for the duration of cooling with the aid of an agitator. With this in mind, we opted for a little appropriated circulator* (about 100 Watts), which puts the milk in movement in the exchanger for the duration of a cycle 30 - 40 seconds (here the milk is protected from air). This implement is very simple and has the ability to multiply the duration of exchange by 10 if we stay in chosen example (1000 litres in hour). It is easy to imagine that performances are not comparable with what exists this day. We are going to be able to answer favorably to the big production of milk and even have the possibility of undertaking an immediate cooling of the milk from an ice bank system. Besides, it becomes easy to get weaker potency. It is even more true for the big capacity tanks which are equipped with several compressors.


* patented product

P.S: In the chosen example of 1000 litres by milking, it is also necessary to store the water used for cooling. That is 2000 litres - 3000 litres of capacity according to the report from 2 to 3 litres of water by litre of milk.

Dernière modification par charriau (2007-11-13 15:46)

2007-10-30 16:15
charriau
Sales manager

CHARRIAU created a new tubular cross flow heat exchanger whose one of the applications is the pre-cooling of milk on the farm. This new system is made of stainless steel tubes (AISI 304) with a length of 2,5; 3,5 or 6,5 m adapted to the parlour size, in standard dimensions. This type of assembly requires little height, which avoids to modify the structure of the room. Moreover its modularity can adapt the overall length of the exchanger depending on the milk flow of each farm and obtain the best ratio performance/costs.

Thanks to its design, the flexible exchanger tube offers a great flexibility of adaptation and assembly. Delivered in kit, its installation is easy to realize, either by technicians experts in milking equipment.

On a sanitary level, visits and controls of the equipments can be made whenever it is required. The  connexions respect the sanitary standards recommended by competent organizations such as EHEDG ASEPT SAS for Europe and 3A sanitary standards for the USA. The precooler is located in the milk line between the milking machine and the milk cooling tank so the cleaning is made by the washing system of the milking machine and its drainage is automatic (thanks to the gravity). The simple design of the exchanger tube, brings the  best economic solution.

Using the exchanger tube for the milk pre-cooling allows to :

-  improve the milk quality on a bacteriological level by stabilizing milk immediately. The raw material of milk is preserved, because deteriorations are minimized with major reductions in the lipolysis, thermal shocks, damping caused by the wall of the milk cooling tank. It makes it possible to preserve or to find SAVOUR - FLAVOUR - TEXTURE in cheeses with raw milk. It is a way to respond to the demands of informed consumers.

- obtain a tepid source of water. The adduction water used with the pre-cooling (that is to say between 1,7 litre and 2,5 litres per litre of pre-cooled milk) is directed automatically and stored for the watering of cows or to other use; during winter time, this water gains several degrees and is extremely appreciated by the animals.

- make important energy savings, the electricity consumption of the milk cooling tank is reduced at least by 50%. Moreover, being less requested, the longevity of the tank will increased.

images/produits/tem-class-pre-refroidissement05.jpg

The physico-chemical characteristics of milk are well preserved, even for a milk of great bacteriological quality.

1 - The microbial proliferation (psychrotrophes, leucocytes, etc...) slows down very quickly.
2 - The milk already cooled by previous other milking in the tank is less warmed (very important).
3 - Reduction of the thermal shock of hot milk with cold milk (which involves membranes cracking, dilatation-contraction).
4 - In the exchanger, hot milk is not in contact with the ambient air of the room.
5 - The hot milk is not affected by the agitation of the tank (foam, lipolysis).
6 - In the exchanger, milk is static : no lipolysis, poor emulsions, reduction of the mechanical agitation time (milk is less hot so less fragile).
7 - Protects and consolidates the membranes of the fatty globules (by reducing their dilation).
8 - The quality of milk is better thanks to the reinforcement of the fatty globules, by an instantaneous pre-cooling and even an instantaneous complete cooling with an ice bank tank or  a  frozen water power station (optimal solution).
9 - The milk circulation is carried out without filter and risk of obstructions.
10 - The connexions for the circuit milk respect the most rigorous sanitary rules (EHEDG in Europe, 3A in the USA).
11 - The milking machine do the cleaning without being modified.
12 - For milk and water, the exchanger evacuate by itself and drains automatically. So it does not fear freezing.
13 - This system, due to its adaptation to the milk flow of each farms, does not impose thermal regulation of the flow of cooling water. The volume of milk stored in the exchanger, the heat-transferring surface and the time of the exchange of the calories are maximum.
14 - The water warmed by milk is very appreciated by animals, especially in winter. No water loss.
15 - In case of power failure the milk is still pre-cooled.
16 - Profit of production per cow on 1 year : 120 litre minimum especially in winter.
17 - Electricity savings = 50% minimum and more in certain areas.
18 - Suppression of the damping of milk (source of contamination).
19 - Help with the delayed starting of the tank (1st milking mainly).
20 - Help at the beginnings and ends of lactation (goats and ewe).
21 - Essential for the dairy plants in emergent countries.
22 - It offers the best ratio performance/price.


Take a look at the TEM-Class

Dernière modification par charriau (2011-10-06 14:45)

2012-11-19 17:36
charriau
Sales manager
A comparison of milk pre coolers available on the french market.

Test "GIE lait viande" published in PLM