Water-based Indoor Climate Systems, 2007
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GUIDELINES
GUIDELINES
GUIDELINES
Test methods for water-based indoor climate systems
Test standards are needed to be able to compare products from different suppliers. It is only then that product data will be of equal value, comparable and unambiguous.
The standards that have been applicable in Europe have been the Nordtest method NT VVS 078 "Ceiling Cooling Systems" and the so-called V Method in Swedish Association of Air Handling Industries V Publication 1996:1 (mainly in Sweden). At the same time in Germany, a DIN Standard has been drawn up for flat chilled ceilings, which is also used for passive chilled beams (chilled beams without supply air).
Nordtest and V Publication
The Nordtest and V methods are relatively similar. The V Method is a slightly revised version of the Nordtest method and was produced by the Swedish Testing and Research Institute and the then Swedish Association of Air Handling Industries (now: Svensk Ventilation, also called SwedVent) together with some suppliers from Sweden and Finland. The main difference between the two methods is at which water flow the products should be tested. In the Nordtest method, the water flow is fixed and related to the pipe diameter in the heat exchanger, i.e. all products are tested with the same water flow irrespective of the cooling capacity.
The purpose of the V Method was to allow products to be tested using an operating scenario that reflected true conditions and it was then chosen to steer towards the water flow that provides a temperature difference of two degrees through the heat exchanger. This means that if two products have a different cooling capacity, then they should be tested at different water flows.
The test room consists of two rooms, as in Figure 47, where heat is indirectly supplied to the inner test chamber via the floor and walls. The heating balances the supplied cooling capacity during the measurement sequence on the test object so that the test chamber’s temperature is constant.
DIN 4715
In the German DIN 4715, the test room is somewhat different, Figure 48. Here, the test chamber consists of an insulated room. Inside the test chamber, the test object’s cooling capacity is balanced by means of "dummies" (occupant simulators) that emit heat directly in the room.
EN Standards
As chilled beams are now starting to be used in other parts of Europe, work was started in 1996 to produce common European Test Standards. Since the start, Swegon has been an active party in this joint European effort that is now in the process of being finalised with three new Standards. Today, there is a new standard for flat chilled ceilings, EN 14240, one for passive chilled beams, EN 14518 as well as one draft (preliminary standard) for active chilled beams, prEN 15116. Both types of test rooms (Figure 47-48) can also be used from now on for testing chilled beams according to the new EN Standards.
At EuroVent, work is also in progress for the certification of chilled beams and this will probably be implemented sometime in 2007. The suppliers that participate in this work, among them: Swegon, will then refer to the new EN Standards for determining capacity data for cooling applications.
To consider
Regardless of whatever standard referred to, there is an underlying test method for producing product performance data. The new EN Standards are very similar to the old and the difference is first and foremost how the reference temperature in the test room is measured. Previously, it was calculated at a level of 1.1 metres above the floor whereas the new standards for chilled beams always refer to the “on coil” temperature, i.e. a temperature near the chilled beam. Previously it has been discussed whether chilled beams constitute a fully mixing air distribution system or if it is warmer up by the ceiling. When we use ”on coil” temperature as a reference, this discussion becomes uninteresting.
The product details for active chilled beams will probably remain unchanged. Passive chilled beams, based on natural convection, may on the other hand be affected since the testing is carried out without supply air and this causes a stratification in the test room. This stratification has previously not been taken into account.
Note that the test methods in question do not necessarily correspond with the operating scenarios that may come into question when designing an indoor climate system. In the standards, the cooling water system is designed for a two degrees temperature difference in the inlet and outlet pipework, while most such systems are designed for a three to four degree difference. To determine the correct cooling performance, the cooling capacity must therefore be recalculated for the appropriate cooling water flow. In Swegon documentation, all capacity data is based on a fixed water flow to make it possible to easily correct the preferred water flow. These correction curves are always available in connection to each product data specification. For reasons of simplicity, the Swegon ProSelect, BeamSelect and ProPipe calculation software is recommended for products with water cooling. This automatically corrects the cooling capacities to the relevant preferred water flow.
