Lesson 8 - Heat Exchangers
This lesson focuses on the two main heat exchangers found in breweries, namely plate heat exchangers and shell and tube heat exchangers. The lesson will examine the components, assembly, and operation of these exchangers. It will also discuss how to select and size a heat exchanger and the considerations for cleaning, maintaining, and operating heat exchangers in the brewing process.
Plate Heat Exchanger – Fluid Mechanics
We can now move on to the internal workings of a plate heat exchanger. We will look at how fluid flows inside the exchanger and how the design and positioning of key components can achieve the required flow configuration.
To help us understand the fluid flow in a plate heat exchanger, let’s begin by watching a video clip.
Take a moment to follow the link below and consider how the two fluids flow through the exchanger. Note, this is for illustrative purposes only and is not a recommendation or endorsement of the supplier’s product.
Notice how two of the distribution passages bring fluids into the exchanger and distribute them into the spaces between the plates. The other two passages collect fluids from the space between the plates and direct them out of the exchanger.
Notice also how some plates have product fluid while others have utility fluid flowing over them. In the previous section, we learned that it is due to the presence of or lack of gaskets that allows specific fluids to flow across specific plates. This is illustrated in the figures below.
Figure: Plates illustrating how gaskets are configured to determine fluid flow
The plate on the left-hand side has the gaskets configured so that fluid flowing in the top-left channel flows over the plate and leaves the heat exchanger through the bottom-left channel. The fluid flowing in the top-right channel is blocked and does not flow across this plate.
The plate on the right-hand side has the gasket configured the opposite way which allows fluid in the top right-hand channel to flow across the plate while blocking fluid from the top-left channel.
The heat exchanger is arranged so plates with these two configurations are alternated – on one side of the plate is the hot fluid and on the other side is the cold fluid. Heat is then transferred from the hot fluid to the cold fluid through the plates. Did you observe the alternating of hot and cold fluid in the video clip?
Flow direction
Watch the clip again where it shows fluid flow through a plate exchanger. What do you notice about the direction of the fluid flow?
Give yourself 5-10 mins to think about this and then click ‘Next’ and continue with this lesson.