A revised radiant time series method (RTSM) to calculate the cooling load for pipe-embedded radiant systems

Abstract

Cooling load calculation can significantly affect the first cost, energy consumption, and performance of air-conditioning systems. Current peak cooling load calculation theories and methods are developed based on all-air systems, which remove the room heat gains through purely convective heat transfer. Studies found that they are not suitable for radiant systems that remove room heat gains through both radiation and convection, especially for the integrated operation of radiant terminal and dedicated outdoor air system (DOAS). This study proposed a revised radiant time series method (RTSM) to calculate the cooling load for radiant systems. The method assumes the heat transfer rate of the radiant terminal as a negative “heat gain” and uses radiant time series factors to calculate the cooling load for DOAS. From the results of an example room, we find that the proposed RTSM has good accuracy compared to the heat balance method (HBM), while it slightly underestimates/overestimates the cooling load for radiant terminal/DOAS. Besides, a parametric simulation with 34,992 cases considering nine impact factors was performed. We find that compared to HBM, the relative errors of the peak cooling loads for the majority of the cases are within ± 10%, and the peak load occurring time differences are very minor, which are within the accuracy range of engineering applications. In summary, the revised RTSM was developed to offer a rigorous cooling load calculation approach for radiant systems, yet does not require complicated iterative calculations. Moreover, though originated from HBM, it has additional advantage of quantifying the cooling load converted from different heat gains separately, which is preferred in engineering applications.