Advertising: 01622 699116 Editorial: 01354 461430
Paul Sands, of Stokvis Energy Systems, discusses how packaged plate heat exchangers and modulating boilers, when combined, present a very powerful package and provide solutions to the new Part L and EPBD requirements.
L
EDUCATIONAL FACILITIES BSEE Plate heat exchangers for educational premises
iverpool University has been taking its old calorifiers (which each store up to 3,000 litres of hot water) out of service as they reach the end of their service lives. Replacement is with plate heat exchangers, usually accompanied by a 300 - 500 litre buffer vessel, supplying hot water on demand.
A plate heat exchanger produces hot water at a reliable temperature on demand. The buffer vessel maintains a small supply for instant use and the system constantly recirculates the water through the system to prevent stagnation and cold-spots developing.
The university’s campus is served by a CHP district heating system, which is perfect for feeding into the Stokvis units. However, the university has around 300 separate buildings, ranging from laboratories to student accommodation.
Stokvis Econoplate packaged plate heat exchangers have been installed in five buildings, including the Mount Pleasant office building, the Sports & Fitness Centre, the Victoria Building, Harold Cohen Library and, most recently the kitchen of the Guild of Students.
Modulating boiler systems
Other educational establishments have recently installed packaged plate heat exchangers and modulating boiler systems. Each has a lot to offer in its own right and when combined these benefits are considerably enhanced – especially if they are packaged together in a compact, stand-alone structure.
Packaged plate heat exchangers are becoming increasingly popular because they solve a number of problems.
On their own, plate heat exchangers help to alleviate concerns about Legionnaire's Disease, using a series of vertically mounted, corrugated plates in a sandwich structure to quickly and efficiently transfer heat from the primary flow supplied by the boiler to the secondary flow serving the building. They provide a source of instant water without the need to store large quantities. And when packaged together with components, such as pumps, built-in time switches and flow and return connections, they offer a compact, space saving alternative to the traditional approach.
Thermal inertia
When used in conjunction with a single, large conventional boiler to serve the whole building, however, they are unlikely to realise their full energy saving potential. The intermittent demand for hot water from the building will result in the boiler cycling for shorter fired-up times compared to a boiler that is supplying a storage cylinder. Consequently, the boiler's thermal inertia comes into play.
The boiler's thermal inertia results from the heat required by its metal and water content before heat can be passed on to the system. As a result, a boiler could fire-up for 10 minutes to provide five minutes of heat.
In addition, conventional boilers are not efficient at part-load – and many conventional boilers spend much of their fire-up time attempting to match loads equivalent to 30% of their capacity. Attempts to match the load more accurately generally involve either modulating the boiler output or allowing a fixed output boiler to cycle with shorter fire-up times. Neither of these methods, however, is wholly successful.
Reducing the heat input of a burner, for example, takes no account of the secondary air introduced, which proportionally becomes higher as the rate is reduced, This excess secondary air results in higher percentages of flue losses, thus reducing the effective efficiency of the boiler.
In this respect, modular boilers in multiple boiler installations can use a variety of controlled firing sequences to more accurately match boiler output to load. Also, because smaller boilers with a lower thermal capacity are used, problems of thermal inertia are greatly reduced. In using a number of smaller output boilers to match loads, however, there may be problems with the number of controls and flues required. Therefore, higher output boilers capable of higher efficiencies at part load, yet with a nominally low thermal capacity have a great deal to offer.
It was with such considerations that the Stokvis Econoflame was developed. Available in outputs form 45kW to 1066kW, these units have a much higher heat exchanger surface area to output efficiency and a considerably higher heat exchanger surface area to output ratio when compared to conventional boilers of similar output.
The Econoflame premix boilers modulate on a frequency – inverter controlled fan and pressure – controlled gas valve giving step less modulation from as low as 17% up to 100% of output, which greatly boosts their efficiency when compared to a typical boiler set up. These two technologies – packaged plate heat exchangers and modulating boilers – represent significant innovations in heating technology.
stokvisboilers.com
Econoplate – comprehensive range of packaged plate heat exchangers
ECONOPLATE Plate Heat Exchangers
• Fully assembled package • Suits many industrial and commercial numerous applications
MADE IN THE UK
www.stokvisboilers.com VISIT OUR WEBSITE:
www.bsee.co.uk BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2016 27
• Various applications – hot water service, • Compact size
• Fast response to variable loads • Higher temperature drop • Low water content
heating, process, pressure breaks and plant protection
• Turbulent flow and even heat distribution • Various plate and gasket materials to suit
applications – hotels, schools, universities, hospitals and office blocks
THE CONSULTANTS AND CONTRACTORS CHOICE. For further information or to receive a technical guide tel: 0208 783 3050 or email:
info@stokvisboilers.com
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