Niek Dommerholt reports on a new development in the cooling or heating of various liquids or gases.
Whether to generate more profit or to be more energy efficient, increasingly customers are demanding that their existing plant, process and/or factory become more efficient.
It is not only governments that are making ever more stringent demands on industry, but consumers and individual employees are also demanding more awareness from companies.
There is a very clear call for companies to make their production processes more sustainable, more efficient and more energy efficient.
Bronswerk is willing and able to respond to this call. Therefore the company is investing time and money in the development of products and solutions to enable its customers to achieve their goals.
Here, Bronswerk would like to showcase its Flexplate heat exchanger, a sustainable and compact alternative to the conventional heat exchanger.
Similar to a plate heat exchanger, the Flexplate, consists of a series of stacked stainless steel plates welded together two by two along the outer edges, resulting in a kind of envelope. Advanced spot-welding processing of these two stacked plates makes it possible for the inside of these plates to be used for the liquid medium while the outside is used for the gas medium. Because these sets of stacked plates are very thin and close together, the heat transfer relative to the content is quite considerable, resulting in a compact installation.
A brand new development
The Flexplate is an entirely new development in the cooling or heating of various liquids or gases by means of air. Until this solution was created, liquid was often cooled by means of air using conventional heat exchanger tubes, consisting of the familiar finned tubes. Notwithstanding the advantages these finned pipes have (resistance to high pressure, for example), the Flexplate makes for a suitable – and in many cases, a superior – alternative.
The Flexplate, which largely resembles a plate heat exchanger, has many different applications, such as for condensers, evaporators, heaters and air cooling. Besides being a suitable alternative to conventional heat exchangers, the Flexplate will – depending on the process – also be suitable for other, and even new, applications. Potential uses for the solution include the following process conditions:
* Moist air from which the moisture condenses. Here the Flexplate doubles as a demister.
* Polluted air. Since the surface of the Flexplate is smooth, when combined with high air velocity there is little chance of dirt adhesion.
* High air temperatures. The Flexplate is made of stainless steel or Inconel, which makes it very suitable for high temperatures and is corrosion resistant too.
The example shown in the images here is Bronswerk’s Radiax compressor. In this set-up, following compression, air is then cooled by means of the Flexplates. The Radiax compressor is very efficient and, combined with the internal Flexplate cooling plates package, creates an extremely compact compressor.
Real-world case study
In the installation illustrated here, process air is cooled by water and is used in a plastics production plant. The biggest challenges for this design were the low pressure drop and limited installation space. The low pressure drop was necessary, as an existing fan had to be used. The reason for the installation space being limited was that the design was an extension of an existing process, meant to increase the efficiency of the entire process.
Additionally, it is essential for the air in this process to be dry after cooling and for it to remain below 10°C. Another requirement was for the installation to have a very long service life (sustainability) despite lots of moisture, which could cause corrosion. The illustration shows an outline sketch of this process. The air, which enters at 40°C, is cooled down to 10°C with a cross-counter flow of water. Since the water vapour in the air condenses through cooling, this water has to be drained off, so the plates serve as a demister as well as heat exchanger (condenser).
Owing to its compact design, it was possible to fit the unit (Flexplate in combination with built-in demister) into the available space. And owing to the requirement for a low pressure drop, the plate distance had to be correct (not as close to each other as in a plate heat exchanger), so that the pressure drop would remain limited yet capacity be maintained.
Condensing water vapour gives an enormous increase in the heat transfer coefficient, but only if the water droplets formed are able to flow away quickly. Due to the shape and vertical arrangement of the Flexplates, this is the case here.
The sustainability of this unit could be guaranteed on two distinct points. Because the installation is made entirely from stainless steel, it is corrosion resistant – guaranteeing long service life. In addition, owing to the low pressure drop, the existing fan could be used. In short, this unit complies with the sustainability requirements in all respects.
For more information at www.engineerlive.com/ipe
Niek Dommerholt is with Bronwerk Heat Transfer, Nijkerk, The Netherlands.