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Dear Yeo, Jean's responses are all quite accurate. I wanted to add a little bit to the discussion in the hopes that it might make your life a little easier. Some years ago, we participated in a research project in which we were looking at whether the performance of certain pieces of HVAC equipment can effectively be normalized. In other words you look at the COP and capacity of a device at a particular combination of inlet conditions and then divide the COP and the capacity by the rated COP and capacity for the device. Then you plot the normalized performance over the entire operation range of the equipment and you do the same for the same piece of equipment from other manufacturers and of other rated capacities. It turns out that some kinds of equipment (particularly single stage heat pumps and both air and water cooled chillers) normalize very well meaning that their normalized performance curves all look about the same. Unloading (part load ratio) curves can look a bit different but they begin to look similar again if you first sort them by compressor type (screw, rotary, etc.). Other pieces of equipment do not look the same at all if you normalize them (absorption chillers are a good example). The lesson in all this is that if you have a specific chiller, it is best to get the manufacturer's data for that chiller and to create a data file from it. If, however, you just need a generic chiller, you can use the default performance curves in the \Trnsys17\Tess Models\SampleCatalogData\ directory and set the rated capacity and COP parameters in the Type; you will be quite close in your performance estimates. One other note; make sure that the rated capacity and COP that you enter for parameters are at the same conditions to which the external data file is normalized. In other words, if the data file is normalized to a 5C oulet chilled water temperature and a 16C inlet cooling water temperature then make sure that the capacity and COP that you enter as the rated values are at those same conditions. Best, David On 2/15/2013 07:10, Jean Marais wrote:
Wow. You stated these questions so well that I can only think that you did so already knowing the answeres. -- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com |