Cooling performance

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Check Cooling Performance

Create a name for this routine for future reference.  For example, “April 2018 routine check”.

Pre-cooling information – plate coolers

Select the type of plate cooler.  The list contains four of the most common types of plate coolers (or plate heat exchangers) found in Australian dairies.  If unsure, use the diagram below as a guide to determining which type is present.

M series plate coolers are older in design and generally have lower cooling capabilities.  They are typically found in older dairies and/or dairies with fewer than 20 milking units.  Small diameter (25, 32, or 38 mm) milk and coolant transport pipes is a characteristic of M series plate coolers.  They can be configured as a single or double bank.

Industrial plate coolers are much larger in size (physical dimensions) than M series plate coolers.  They have greater cooling capacities, more efficient, and are typically found in larger dairies.  The milk and coolant transport pipes are 50 mm in diameter, a distiguishable characteristic.   They can be configured as a single or double bank.

To tell a single bank from a double bank plate cooler simply count the total number of pipes entering/exiting the plate cooler.  A single bank will have 4 pipes (milk in/out, coolant in/out) and a double bank will have 6 pipes (milk in/out, coolant 1 in/out,  coolant 2 in/out).

Single bank plate coolers are characterised by having four pipes

Double bank plate coolers are characterised by having six pipes

Measuring temperatures to assess plate cooler performance

Temperature measurements should be taken during milking and at the same time. It is useful to take readings over a couple of milkings so you can get an idea of the ‘average’ temperature reading for both water and milk.

If using an ordinary dairy or AI thermometer – you will need to collect a sample of fluid at a convenient point and measure its temperature. Alternatively there may be adhesive strip thermometers fitted that measure the temperature through the wall of the metal water/coolant inlet and milk outlet pipes.
Temperature strips provide an easy way of taking measurements


Measurements for single bank plate coolers:  Measure the temperature of water in (at source or through pipe wall) and milk out (at vat or through the pipe wall). Record your readings.

Measurements for double bank plate coolers: Measure the efficiency of the first bank by turning off the water/coolant supply to the second bank of the plate cooler prior to making these measurements as per instructions for the single bank plate coolers above.  Allow a few minutes to elapse before taking the temperature measurements.

To measure the efficiency of the second bank you need to leave the first bank of the plate cooler running. Then measure the temperature of coolant in (at source or through the pipe wall) and milk out (at vat or through pipe wall).  Allow a few minutes to elapse before taking the temperature measurements.

Record the measurements taken and make notes of any atypical operation or situations.

How plate coolers work

Pre-cooling information – cooling towers

There are generally two types of cooling towers: natural draft and induced draft.  Natural draft cooling towers are simple, often “home-made” and have small cooling capabilities (suited to very small dairies).  Induced draft cooling towers are commercial products that use fans to improve performance and coooling capabilities.

Examples of cooling towers

The measurement of water temperatures within the cooling tower holding tank/sump can be used to determine how effectively the cooling tower is operating. Two measurements are required; one just before starting, and the other immediately after the cooling tower has ceased routine operation.  As cooling tower performance is greatly affected by temperature and relative humidity, recourding the average ambient air temperature during cooling tower operation is essential as this will be used as a reference for assessing performance.   Cooling towers perform poorly when relative humidity is high, so taking multiple measurements over a number of days is preferable.

Record the measurements taken and make notes of any atypical operation or situations.

Measurements for bulk milk tanks

Ensure equipment is turned off and safety precautions are in place when inspecting equipment involving moving parts.

  1. Select how many vats are to be assessed in this test.
  2. For each vat record the motor size (in kilowatts, kW) of each compressor, and the number of compressors.
  3. Record the capacity of each vat being tested.
  4. Select the type of cooling system used.

Performing the test

This test is best done by starting with an empty vat, i.e. the first milking after the milk has been picked up and repeating the measurements over a few days.

Note the time that you turn on the vat to start coolling.

Measure the temperature of the milk entering the vat. This is usually the same as the temperature of the milk leaving the plate cooler (see instructions above). If there is already milk in the vat, ensure you measure the temperature of the milk entering the vat (not the temperature of the already cooled milk).

Then record the time that the vat refrigeration shuts off after cooling the milk, and the temperature that the milk is cooled to. Finally, estimate the volume of milk cooled at that milking by vat gauge, dipstick or from the factory slip. Record these figures in the sections provided.

Make notes of any atypical operation or situations.