Research About The Determination Method Of HVAC Outdoor Design Conditions

The outdoor design conditions are the basis of HVAC system design. Generally, thedetermination method of HVAC outdoor design conditions can be divided into threeissues: period of record, not-guaranteed rate statistical methods and meteorologicalelement. With the analysis about those three issues, our research aims to obtain amore rational determination method of HVAC outdoor design conditions.The standard deviation analysis and optimal climate normal were used to obtain theoptimal period of record of outdoor design conditions. Firstly, minimal period ofrecord and the corresponding optimal average k were determined respectively, thenwith the comparison of the minimal period of record and the optimal average k, theoptimal period of record of outdoor design conditions were obtained, and the methodof uniformity analysis of the distribution of those “x hour events” and comparison ofthe size of “x” was proposed to verify the superiority of the optimal period of record.The case analysis of Tianjin station show that the heating design temperature,air-conditioning design dry-bulb temperature of winter and summer is13,10and15years respectively, the air-conditioning design wet-bulb temperature is14years. Withuniformity analysis of the distribution of those “x hour events” and comparison of thesize of “x”, superiority of the period of record was verified.A TRNSYS indoor temperature calculation model was established to analyze thenot-guaranteed rate statistical method of the heating design temperature, and casestudy of Tianjin show that the indoor “not-guaranteed rate” of the “not-guaranteed5days per year” heating design temperature is just “not-guaranteed5.3hours per year”.Based on the cause of the not-guaranteed rate difference between indoor and outdoor,the comparison of the indoor “not-guaranteed rate” when solar irradiance was takeninto account or not was adopted, so necessity of the corresponding solar irradiancewas analyzed. By the analysis of building thermal process, the outdoor heatingeffective temperature was proposed and verified.When solar irradiance is not taken into account, the not-guaranteed rate differencebetween indoor and outdoor is caused just by the build ing thermal property, with thecomparison of the difference between indoor and outdoor “not-guaranteed” hourswhen the mean duration of meteorological variables is different, the suitable mean duration of meteorological variables of heating design temperature was analyzed, andfound the most suitable mean duration of meteorological variables of heating designtemperature is the non-overlapping two days.