Lesson 8 - Refrigeration Technology

The vapour compression cycle is at the heart of a mechanical refrigeration process.

You may not realise it, but your household refrigerator employs this cycle. In a large brewery, the process is still very similar, although the equipment is much larger.

Let’s review the ordinary vapour compression cycle that you learned about in the Refrigeration Theory and Cycle lesson. However, we will look at it slightly differently and begin with the compressor.

A compressor is used to take saturated vapour (that has returned from the point of use) and pressurise it. This causes the vapour to be superheated at the higher pressure.

A condenser then cools the vapour down, which condenses the vapour into a liquid. Depending on the operation of the condenser, the liquid can be subcooled.

The liquid is allowed to expand (this can be achieved using an expansion valve), which effectively takes it back to the same pressure as the vapour was to start with.

The liquid then evaporates in an evaporator to become vapour, absorbing heat and this is where the refrigeration takes place.

The above steps can be run as a continuous process. If you look at a simple refrigerator, it runs until the temperature reaches the setpoint, and then stops. However, in a big brewery, you have many processes running with many different heat loads. In this instance, the liquid refrigerant is often stored in a liquid receiver. This facilitates the use of the primary refrigerant to directly provide cooling in the brewery. If all the cooling in the brewery is carried out using a secondary refrigerant, the secondary refrigerant can sometimes act as the store of refrigeration, although a liquid receiver can also help with this.

Let’s look in more detail at the different components used in the process, starting with the compressor.