FEATURE HEAT TRANSFER CHOOSE CORRUGATED TUBES OVER SMOOTH TUBES
There are a variety of tubular heat exchangers on the market, but for many applications corrugated tubes continue to be preferred over smooth ones. Matt Hale, international sales & marketing director of HRS Heat Exchangers, explains why…
W
hile plate heat exchangers are still commonly used for simple viscous
fluids such as water, milk and some thin oils, for most other applications tubular heat exchangers are the preferred choice. There are many different types of tubular heat exchanger available (such as annular space, double tube and multitube), but the biggest influence on efficiency is the type of tube used, rather than the configuration – corrugated tubes are more efficient at transferring heat than smooth ones and have a number of other benefits. When a fluid passes through a tube,
several things affect the way it moves, such as pressure, the nature of the fluid (how viscous it is), and the design of the tube wall. In a smooth tube, fluids often follow a smooth path in which the particles which make up the fluid do not interfere with each other. This is known as laminar flow. However, where smooth flow is disrupted, tiny whirlpool regions form in
transfer by 10 per cent compared to a smooth tube, then the unit can be made 10 per cent shorter than an equivalent smooth-tube while delivering the same performance. The increased thermal efficiency – which can be up to three- times that of a smooth tube heat exchanger – also means that less space is required to achieve the same level of heat transfer. Depending on application, a corrugated tube heat exchanger can therefore be up to half the size of its smooth tube equivalent. This is why HRS’ heat exchangers are commonly specified for installations where space is restricted. Not only does preventing the formation of a
boundary layer in the tube
the fluid and turbulence occurs. Unsurprisingly, this is known as turbulent flow. Turbulence makes tubular heat
exchangers more efficient by preventing viscous (thick) materials sticking to the wall of the tube, where they can act as insulation and prevent efficient heat transfer (known as a boundary layer). It also prevents materials in suspension from dropping out of the carrier fluid and having a similar effect. Because a corrugated tube has an
increased heat transfer rate compared to a smooth tube of the same length, the heat exchanger can be made smaller. For example, if corrugations increase the heat
One advantage of corrugated tubes is that they prevent viscous fluids and suspensions from forming an insulating boundary layer on the tube surface
increase the thermal efficiency of the heat exchanger, it also reduces the downtime needed to keep removing it. Therefore, the operational run times between cleaning cycles are longer with corrugated tubes than smooth ones, further increasing the overall efficiency of the process. For some types of viscous material, a
Corrugated tube heat exchangers have been used to replace spiral units at a water treatment works (below)
SWITCH TO THERMAL FLUID CUTS ENERGY COSTS BY A SIXTH
Babcock Wanson’s TPC 400B Thermal Fluid Heater has been installed into Freedom Brewery’s Abbots Bromley site in Staffordshire as part of its Wort Boiler system. Together with other updates to the process, this has resulted in reducing the overall energy costs per litre brewed by more than 80%. Whilst thermal fluid heaters are used extensively in many industries, the brewery sector has traditionally
used steam as the heating method of choice. With the upsurge of micro breweries, this is slowly changing as, unlike steam boilers, thermal fluid heating systems are compact, easy to use and offer substantial savings in total energy and maintenance costs. Freedom Brewery’s commitment to reducing its environmental impact, also prompted the move from steam to thermal fluid heating. The TPC 400B is a fully automatic coil type, multi-pass thermal fluid heater complete with integrated
burner, control system and safety devices. It provides optimal distribution of the heat, high fluid velocity in the exchange tubes and continuous flow monitoring to ensure long thermal fluid and system life. At Freedom Brewery the thermal fluid circulates through the external Wort Boiler which, due to the use
of thermal fluid, does not require rating as a pressure vessel. Once at temperature, the wort thermosyphons through the heat exchanger without the need to use a copper casting pump, ensuring simple operation and reducing site electrical costs. A precise heat transfer to the process is achieved through an integrated control system to enable Freedom to achieve quality products whilst reducing fuel costs. Commenting on the decision to move away from steam, Andrew Taylor, director at Freedom Brewery,
said: “We chose thermal fluid because it was more cost-effective to install and run, has a smaller space requirement than steam and provides a greener solution.” Taylor is also impressed with the reduction in energy costs. He said: “Our energy costs per litre brewed are now a sixth than they were before!” Babcock Wanson
corrugated tube provides sufficient turbulence to prevent the need for mechanical agitation, such as in a scraped- surface or screw-driven heat exchanger. With no moving parts, a corrugated tube is easier to clean and maintain, and may be more reliable, than a scraped-surface heat exchanger, although this is not always the case in every application. When taken together, the benefits of
corrugated tubes are significant. So much so that at HRS Heat Exchangers, we don’t used smooth tubes in our non-scraped tubular heat exchangers. The increased heat transfer efficiency, particularly at higher flow rates, means that less heat transfer area is required, so we can produce shorter, more compact designs which are also cheaper to manufacture.
www.babcock-wanson.co.uk
HRS Heat Exchangers
www.hrs-heatexchangers.com
38 APRIL 2019 | PROCESS & CONTROL
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
