How to choose the right heat exchanger
Your choice of heat exchanger depends on the nature of your product and process. On whether your product has high or low viscosity. On whether it contains particulates or fibres. On whether it contains starch or salt.
Factors like these all affect the complexity of your product, and thereby what type of heat exchanger will optimize your product quality and production process.
There are three main types of heat exchanger – plate, tubular and scraped. Each has different specifications and product suitability.
“Many different factors determine the type of heat exchanger that is best for your product,” says Inge Kristensson, Tetra Pak Application Specialist, Heat Transfer.
“Let’s say you’re a yoghurt manufacturer and you’re struggling with product quality that’s below expectations. The first question I’d ask is: ‘Is your heat exchanger designed for yoghurt?’ If the answer is ‘no’, that’s probably the cause of your quality issue.”
Another crucial factor is how much product you will produce and how much you will run the heat exchange module. Do you plan to run 100 litres per day, or 10,000 litres per hour? This will affect the size and type of heat exchanger that fits your specific needs.
Batch size matters
A producer running many small batches can often use a smaller heat exchanger focusing more on product losses than energy consumption. For large-scale production, the opposite is often the case, focusing on long running times and low energy consumption.
One word of advice is not to assume you know which heat exchanger is best for your product. There may be an alternative that can hit your sweet-spot better.
“Customers processing very viscous fluids sometimes ask for a tubular heat exchanger for the simple reason that there is a common belief that viscous fluids needs to be processed in tubes. In some cases I tell them that’s probably not the best idea, and that they should buy a plate heat exchanger instead – or a combination of plate and tube,” Kristensson says.
This is because compared with a tube, the high heat-transfer efficiency in the plate heat exchanger makes it easier to transfer heat from one side to the other. This is especially noticeable when processing viscous fluids.
Another crucial aspect is cost. Heat exchangers can be energy-intensive, and electricity costs are typically much higher over the lifetime of the equipment than the investment cost. Therefore it makes sense to find a heat exchanger that meets your product needs and is energy efficient at the same time.
Focusing on the total cost of ownership over the life of the heat exchanger, rather than the upfront investment cost, can save you a lot of money. Typically it pays to invest a little more in the hardware to reduce your total cost of ownership. It is wise to look beyond the current financial year and measure the total cost of running your heat exchanger over three to four years.
The payback on investing in an energy-efficient heat exchanger, rather than the cheapest model, is very quick – in many cases less than a year.
“If, like many producers nowadays, you have large capacity and long running hours, then it is definitely worth the money to have a higher initial investment cost but a lower total cost of ownership,” says Kristensson.
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