4431 -- Effect of 1997 Handbook Summer Design Temperature Specifications on Enthalpy and Humidity Ratio PDF

The purpose of this paper is to provide a quantitative over-all description of the differences in humidity ratio and enthalpy that are associated with the new extreme weather specifications presented in the 1997 ASHRAE Handbook--Fundamentals as compared to the traditional weather data specification. Differences between the new specifications and the traditional specification are presented for the 0.4% annual frequency of occurrence data. The effect of population distribution and the 2.0% annual frequency of occurrence are examined. Both specifications result in an increase in the total enthalpy for most locations. For 85%-86% percent of locations, this increase was in the range of 0-4 Btu/lbm da (0-9.3 kJ/kg). For 11% of locations, the dew-point specification results in a lower enthalpy than the traditional dry-bulb specification. For 47% of all locations, the dew-point specification results in a humidity ratio more than 30 grains/lbm da (4.3 g/kg) higher than that of the dry-bulb specification.

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