Mao, Chunliu (2016-05). Analysis of Building Peak Cooling Load Calculation Methods for Commercial Buildings in the United States. Doctoral Dissertation. Thesis uri icon

abstract

  • This study aims to provide valid comparisons of the peak cooling load methods that were published in the ASHRAE Handbook of Fundamentals, including the Heat Balance Method (HBM), the Radiant Time Series Method (RTSM), the Transfer Function Method (TFM), the Total Equivalent Temperature Difference/ Time Averaging Method (TETD/TA), and the Cooling Load Temperature Difference/Solar Cooling Load /Cooling Load Factor Method (CLTD/SCL/CLF), and propose a new procedure that could be adopted to update the SCL tables in the CLTD/SCL/CLF Method to make the results more accurate. To accomplish the peak cooling load method comparisons, three steps were taken. First, survey and phone interviews were performed on selected field professionals after an IRB approval was obtained. The results showed that the CLTD/SCL/CLF Method was the most popular method used by the HVAC design engineers in the field due to the reduced complexity of applying the method while still providing an acceptable cooling load prediction accuracy, compared to the other methods. Next, a base-case comparison analysis was performed using the published data provided with the ASHRAE RP-1117 report. The current study successfully reproduced the HBM results in the RP-1117 report. However, the RTSM cooling load calculation showed an over-prediction compared to the RTSM results in the report. In addition, analyses of the TFM, the TETD/TA Method and the CLTD/SCL/CLF Method were compared to the base-case cooling load. The comparisons showed the HBM provided the most accurate analysis compared to the measured data from the RP-1117 research project, and the RTSM performed the best among the simplified methods. The TFM estimated a value very close to the peak cooling load value compared to the RTSM. The CLTD/SCL/CLF Method behaved the worst among all methods. Finally, additional case studies were analyzed to further study the impact of fenestration area and glazing type on the peak cooling load. In these additional comparisons, the HBM was regarded as the baseline for comparison task. Beside the base case, fifteen additional cases were analyzed by assigning different window areas and glazing types. The results of the additional tests showed the RTSM performed well followed by the TFM. The TETD/TA Method behaved somewhere in between the TFM and CLTD/SCL/CLF Method. In a similar fashion as the base-case comparisons, the CLTD/SCL/CLF Method performed the worst among all methods. Based in part on the results of the survey and interview as well as the comparisons, updates to the SCL tables in the CLTD/SCL/CLF Method were developed that allowed the CLTD/SCL/CLF Method to be more accurate when compared to the HBM. The new updated SCL tables were calculated based on the SHGC fenestration heat gain model instead of the SC and DSA glass coefficients. Three examples were provided that showed the improved analysis with the updated SCL tables. All of the results showed an improved peak cooling load estimation.
  • This study aims to provide valid comparisons of the peak cooling load methods that were published in the ASHRAE Handbook of Fundamentals, including the Heat Balance Method (HBM), the Radiant Time Series Method (RTSM), the Transfer Function Method (TFM), the Total Equivalent Temperature Difference/ Time Averaging Method (TETD/TA), and the Cooling Load Temperature Difference/Solar Cooling Load /Cooling Load Factor Method (CLTD/SCL/CLF), and propose a new procedure that could be adopted to update the SCL tables in the CLTD/SCL/CLF Method to make the results more accurate.

    To accomplish the peak cooling load method comparisons, three steps were taken.

    First, survey and phone interviews were performed on selected field professionals after an IRB approval was obtained. The results showed that the CLTD/SCL/CLF Method was the most popular method used by the HVAC design engineers in the field due to the reduced complexity of applying the method while still providing an acceptable cooling load prediction accuracy, compared to the other methods.

    Next, a base-case comparison analysis was performed using the published data provided with the ASHRAE RP-1117 report. The current study successfully reproduced the HBM results in the RP-1117 report. However, the RTSM cooling load calculation showed an over-prediction compared to the RTSM results in the report. In addition, analyses of the TFM, the TETD/TA Method and the CLTD/SCL/CLF Method were compared to the base-case cooling load. The comparisons showed the HBM provided the most accurate analysis compared to the measured data from the RP-1117 research project, and the RTSM performed the best among the simplified methods. The TFM estimated a value very close to the peak cooling load value compared to the RTSM. The CLTD/SCL/CLF Method behaved the worst among all methods.

    Finally, additional case studies were analyzed to further study the impact of fenestration area and glazing type on the peak cooling load. In these additional comparisons, the HBM was regarded as the baseline for comparison task. Beside the base case, fifteen additional cases were analyzed by assigning different window areas and glazing types. The results of the additional tests showed the RTSM performed well followed by the TFM. The TETD/TA Method behaved somewhere in between the TFM and CLTD/SCL/CLF Method. In a similar fashion as the base-case comparisons, the CLTD/SCL/CLF Method performed the worst among all methods.

    Based in part on the results of the survey and interview as well as the comparisons, updates to the SCL tables in the CLTD/SCL/CLF Method were developed that allowed the CLTD/SCL/CLF Method to be more accurate when compared to the HBM. The new updated SCL tables were calculated based on the SHGC fenestration heat gain model instead of the SC and DSA glass coefficients. Three examples were provided that showed the improved analysis with the updated SCL tables. All of the results showed an improved peak cooling load estimation.

publication date

  • May 2016