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Dapeng, While BESTEST (and ASHRAE Standard 140 - which is identical to BESTEST) try hard to be very clear about what assumptions you should make in each of the test cases, there is still a lot of room for interpretation. Some years ago, we ran TRNSYS 16.1 through those test cases as well and found that you can make quite legitimate interpretations of the standard and come out with quite a variety of results. I would recommend you have a look at a couple papers that we wrote about the effort: "Converging on a Recommended Set of Interpretations and Assumptions in Applying Standard Tests to Energy Analysis Tools" "Experiences with and Interpretations of Standard Test Methods of Building Energy Analysis Tools" both are available at http://www.tess-inc.com/pubs. If my recollection is correct, we were within the range on the 600 cases. If anything, the annual cooling that modern versions of TRNSYS predict is on the low end of the range and is sometimes below the range. It is worth keeping in mind that the "acceptable range" of results does not come from an analytical solution. It comes from the results generated by a bunch of software tools and TRNSYS (version 13!) is one of them. Other software developers have mentioned to me recently that building science and cooling load algorithms have advanced since the 1980s and that more recent algorithms do predict lower cooling loads than did the older algorithms. This is not reflected in the BESTEST or Standard140 results; those ranges are still set by the older versions of the tools. Best, David On 11/14/2011 21:14, Dapeng Li wrote:
-- *************************** 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 |