Whenever we plan to use any technical product in our environment, we make the decision to purchase it based on the assessment of its features, which can usually be divided into two groups. The first are those that are easy to describe by parameters such as shape, size, weight, colour, etc. In other words, these are purely “physical” parameters. The second type of parameter is those that focus on functional features. As a rule, they are described as a series of technical parameters expressed in appropriate units, which describe how our product will function under certain UNCHANGEABLE working conditions (read on to understand why we wrote the word “UNCHANGEABLE” in capitals). We often refer to these particular parameters as a common and very apt term – “performance”.

Heat recovery components… what do we really sell?

For the industry of heat recovery systems, technical parameters which we call “performance” constitute the most important information package about a given type of Counterflow Recuperator or Rotary Heat Wheel. We are aware, that our clients are usually producers of Air Handling Units or Rooftops. When designing their products, they take into account the minimum efficiency of the heat recovery section, which on the one hand is dictated by appropriate legal regulations, and on the other – by the strong competition that surrounds them. Usually, they decide to fit a certain model of the heat recovery system for a certain size of the Air Handling Units, which will perform at the minimum required efficiency within the assumed airflow rate. For our Clients, reliable performance information of our heat recovery systems is the key to designing high efficient air handling units, capable to recover the heat with efficiencies not worst than dictated by legal regulations or standards. So, getting reliable performance information of our products is crucial for our clients to achieve their success. Also, it shows, that the performance of our heat recovery systems is the core value of our products. And this is what we actually sell.

What makes the performance calculation so complex?

It turns out that describing the heat recovery performance of a Counterflow Recuperator or Rotary Heat Wheel is not as simple as in the case of a TV or mobile phone. For such products, the performance remains unchanging regardless of the working conditions. The brightness of the TV screen remains the same at any air temperature or humidity in the room. The computing performance of the mobile’s CPU or its’ screen resolution is a fixed value, which can be simply listed on the technical specification consisting of a few pages only, together with all remaining parameters.

For the heat recovery systems, the performance which strongly depends on the actual working conditions needs to be computed individually for each application case. Taking into account, that performance depends on the mutual proportion of both airflow rates (supply, return), and the temperature and humidity of each of the airstreams – the number of combinations of these parameters would be millions. Little too much to fit on a few pages of printable technical specifications.

So, the only way to give our clients reliable performance reports of our heat recovery systems at any combination of airflow, temperature and humidity is to engage cutting-edge computing technologies – and in fact… IT.

 All models, all sizes in one… the swiss rotors.dll

Having in mind the need to provide our business partners with detailed information on the performance of the heat recovery systems we produce, and at the same time being aware of the impossibility of making them available in the form of printable tables or charts, the only logical solution seems to be to create and provide an IT tool, that allows determining the operating parameters of any type, model or size of recuperators or regenerators we manufacture at any working conditions.

The first thing that comes to mind is the selection program, formerly widely available on CD-ROM, today as a service based on a web browser. Of course, such a tool exists and is available on our website under the name Energy Recovery Selection Software. Its friendly interface allows us to quickly determine the performance of the selected model of any heat recovery system or our portfolio. Therefore, whenever we need to calculate the performance of a single or few heat recovery units, the online tool we provide is all you need.

However, for our main business partners – manufacturers of air handling units, which have to make hundreds to even thousands of calculations a day, the online service with a friendly interface turn to be far from useful. For our clients who need to calculate the performance of our products as a part of the air handling unit – the only appropriate solution is to provide a dynamic calculator that can be implemented with their selection tool. A calculator that deliberately doesn’t have its own user interface, and why, if the results of the calculations are to appear as part of the parameters of our client’s product – the air handler.

Dynamic-link library

What we are talking about is the Dynamic-Link Library (or DLL for short) – a shared library in a form of one single file, which contains implementations of various programs – in our case entire heat recovery calculation algorithm. The DLL is not considered as a standalone program, however, it can be used as a part of other applications.

The Swiss Rotors DLL is, on the one hand, a dynamic catalogue of all the heat recovery solutions we offer – Counterflow Recuperators, both in AL or HIPS Rotary Heat Wheels of any type, wave height, thickness or the size of the wheel itself. On the other hand – our DLL is a super-efficient performance calculator for each of these catalogued models.

How does the swiss rotors dll work?

Same like any type of calculator, the Swiss Rotors DLL needs some input information, like the type of heat recovery system to calculate, both supply and return airflow rates, parameters of both airstreams any other auxiliary data. As a result of the calculation, we have precise information about its performance, like air temperature gain on the supply side, recovery capacity, efficiency and air pressure drop. This precise data is listed as output variables and may be used as input data for further calculations of the entire air handling unit.

How to implement the swiss rotors dll to the ahu selection tool?

Needless to say, the application of the DLL to be a part of the AHU selection tool is a job for IT engineers. What they have to do can be somehow compared to “implant surgery”, where the DLL file is implanted into the complex structure of the AHU selection tool. These “IT surgeons” are fully supported by Swiss Rotor who has written a special, highly detailed manual (this time a few pages printable PDF document), where all input and output variables are clearly listed and parametrized.

Why the accuracy of the calculations is crucial?

Let’s imagine a quite simple supply and return air handling unit with a Rotary Heat Wheel, in which the heater raises the air from the temperature gained on the heat recovery section up to the temperature required by the assumptions of the ventilation system design. And now, let’s imagine, that the air temperature gained on the heat wheel on the supply side is actually lower than the one calculated and listed by the DLL. It’s easy to figure, that the air handling unit (and the entire ventilation system handled by it) will suffer from insufficient heating capacity. The situation would be similar for work in summer, where too optimistic parameters of air cooling in the heat recovery section could cause erroneous assumptions as to the cooling capacity of the used chiller or VRF. Underestimated air pressure drop of the heat recovery system passed to the fan working point algorithm would cause wrong selection of the fan size or its capacity.

And now, let’s imagine that all above listed bad scenarios occur at the same time: overestimated heat recovery in winter and summer + underestimated air pressure drops. Result: totally wrong design of the Air Handling Unit, insufficiency of heating and cooling capacity of the entire ventilation system together with insufficient airflow rates both on supply and return.

How do we guarantee the high accuracy of the performance calculations?

This is probably not a properly asked question. The actual question would be: Who guarantees that the Swiss Rotors DLL is capable of making precise calculations of the performance of the offered heat recovery systems? The answer is The EUROVENT CERTIFICATION for the MEAR market and AHRI CERTIFICATION for the US market– an independent third-party certification body that keeps our Swiss Rotos DLL under constant surveillance.