![]() ![]() The purpose of ASHRAE Research Project RP-754 was to find the outdoor design occurrences of extreme dew-point temperature and the corresponding mean coincident dry-bulb temperature for a large number of locations in North America. Software was also developed so users could extract the design values, cumulative frequencies, and DB/DP, DB/WB, DB/H, and DB/WS coincident matrices for 1444 locations from a = , However, the new design dew-point values indicate the potential for significantly more extreme dehumidification design conditions than would be found by using the old extreme dry-bulb temperature with mean coincident wet-bulb temperature. A comparison with the previous design values indicated that the new dry-bulb and wet-bulb design conditions are slightly less extreme than the values previously published. The data were analyzed to produce annual frequency-of-occurrence design dry-bulb (DB), wet-bulb (WB), and dew-point (DP) temperatures with mean coincident values at the design conditions. Months that had sufficient data were then used in the analysis. The data went through quality checking and short-term linear interpolation filling processes. Twelve years of data were used for the other locations. Thirty-three years of hourly weather data were used for approximately half of the US and all of the Canadian locations. Design conditions were determined for 509 US, 134 Canadian, 339 European, 293 Asian, and 169 other worldwide locations. The procedure is specifed on page 18.27, Section 6.3, with conduction forced into the classical form of q=UAdT on page 18.28.This paper describes the process used to revise the design weather data tables in the 1997 ASHRAE Handbook-Fundamentals. The implications of this are that the RTS method is assuming steady state, regardless if steady state has or can actually be achieved. This assumption is the basis for the RTS derivation from the HB method". Thus, the heat gain for a particular component at a particular hour is the same as 24 h prior, which is the same as 48 h prior, etc. The Radiant Time Series (RTS) Method is a simplified version of the Heat Balance Method.26 states "The RTS method is suitable for peak design load calculations, but it should not be used for annual energy simulations because of its inherent limiting assumptions." The handbook later states "Design cooling loads are based on the assumption of steadyperiodic conditions (i.e., the design day’s weather, occupancy, and heat gain conditions are identical to those for preceding days such that the loads repeat on an identical 24 h cyclical basis). ![]()
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