ECO-POWER
Heat exchangers are designed to heat (or cool) one material from another. However, over
the last 150 years or so, a wide variety of types and designs have emerged, meaning that
finding the most suitable type of heat exchanger for your
application is not always simple. Matt Hale, international sales & marketing director, HRS Heat
Exchangers, guides you through the main types of heat
exchanger produced by HRS and what applications each is best suited to
H
eat exchangers can play a key role in anaerobic digestion (AD) and other energy applications.
All but the most basic heat exchangers are created to a bespoke brief, designed to take into account the material/s being heated or cooled, the heating or cooling medium, the amount of product being processed, product velocity, risk of fouling and a host of other factors. However, over the years, some standard design types have emerged, and understanding the differences between these can make the specification process less of a mystery.
KEY CONSIDERATIONS Our industrial heat exchangers are suitable for a range of environmental, energy and chemical applications, including digester heating, biogas dehumidification and digestate processing. The first consideration should be the nature of
the material being processed, in particular its viscosity and whether it contains particles. The simpler and less viscous the material being processed, the simpler the heat exchanger can be. As materials become thicker, or contain
suspended particles or large solids, then heat exchange becomes more difficult, and more sophisticated designs are required to provide the necessary performance. Starting with simple multi tube designs, the range moves through double tubes – where viscosity is higher or solids are present – and scraped surface designs for the most challenging applications.
MAIN HEAT EXCHANGER TYPES Most heat transfer applications will require the use of corrugated tube heat exchangers. These offer a number of benefits over smooth tube designs – in particular, heat transfer and energy efficiency are increased (making them better for high-capacity heating or cooling). Fouling is also minimised meaning that units can be more compact and economical, and cleaning and servicing requirements are reduced. For the most challenging applications (such as
30 HOW DO YOU
CHOOSE THE RIGHT HEAT EXCHANGER?
materials with high fouling potential, or where certain product characteristics are required), scraped surface heat exchangers are used. Depending on whether the product needs gentle handling or increased mixing, HRS offers rotating and reciprocating designs.
CORRUGATED TUBE HEAT EXCHANGERS HRS offers two types of corrugated tube heat exchangers for anaerobic digestion: • Double tube heat exchangers • Multitube heat exchangers Double tube heat exchangers consist of a tube
within a tube and are among the most versatile corrugated tube heat exchangers. The HRS DTI Series is a true counter current heat exchanger for industrial use and is ideal for thicker solutions and light sludges. The HRS DTR Series is based on the DTI but has been adapted for direct energy recovery (product vs product), in particular in sludges with low viscosity. The tube is removable for easier and faster cleaning, reducing operational downtime when processing high fouling products such as sludge heating/cooling and pasteurisation, digester heating and sludge-to-sludge heat recovery. Multitube heat exchangers are the simplest
design and carry the product in more than one interior tube, while the service fluid flows through the surrounding shell. The HRS K Series is a complete stainless-steel shell and tube heat exchanger designed for general applications
ENERGY & SUSTAINABILITY SOLUTIONS - Winter 2023
featuring low- to medium-viscosity materials. Specifically designed for exhaust gas cooling and
thermal recovery applications, the HRS G Series passes the exhaust gases through the interior tubes while the service fluid flows through the surrounding shell. The G Series is for heat recovery from cogeneration exhaust gases, boiler exhaust gases, industrial exhaust and flue gases.
SCRAPED SURFACE HEAT EXCHANGERS Scraped surface heat exchangers (SSHEs) are the preferred choice for difficult heat transfer applications; for example, those with high viscosities and where fouling can become a problem. The patented Unicus Series is based on a
traditional shell and tube heat exchanger, but with scraping elements inside each tube. The reciprocating movement of the scrapers mix the fluid whilst cleaning the heat exchange surface. This keeps heat transfer high and reduces downtime. The Unicus Series is ideal for the evaporation of digestate and sludges. Wherever you require heat transfer in your AD
or energy application, whether heating digesters, cleaning biogas or pasteurising digestate, HRS has the ideal heat exchanger for you, and the expert staff to help you find it.
HRS Heat Exchangers
www.hrs-heatexchangers.com
www.essmag.co.uk
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