The Research On Applying Novel But Simple Methods For The Space Load Calculations In HVAC

The researches on space load calculations in HVAC have ever been ongoing actively at home and abroad. Recently a new method for performing design cooling load calculations, the Radiant Time Series Method(RTSM), has been developed. It is a method that is rigorous yet does not require the user to perform the iterative calculations required by the transfer function method(TFM). This new method can efficiently replaces all other simplified methods such as the transfer function method.Yet there are some difficulties in applying this novel but simple methods in China. First the periodic response factors of the building envelope should have been computed for calculating the space heat gains. Then the radiant time factors must be predetermined to convert the radiant portion of hourly heat gains to hourly cooling loads. For applying RTSM in our country, a novel method for calculating transient heat conduction through multilayer slabs, the frequency-domain regression method, is first used to efficiently and accurately compute the fundamental data including conduction transfer function, response factors and periodic response factors to calculate the transient heat conduction through typical walls and roofs in China, which has never been done in our country. With these data the hourly heat gains through building envelope can then be easily computed. And other kinds of heat gains can be calculated in the same way as that in TFM. In RTSM the convective portion of the space heat gains are directly converted to cooling loads. But the radiant portion is converted to hourly cooling loads by using radiant time factors. In order to get these factors, a procedure for calculating room transfer function coefficients from pre-determined room response factors is developed by combining the algorithm of "Least Square" with the theory of frequency response. And then the radiant time factors can be got to calculate the hourly cooling loads converted from the radiant portion of heat gains.In the end, a meeting room is used to illustrate the dynamic space load calculation process by applying RTSM with the data of our national weather conditions and dynamic thermal characteristics of our building envelope. This research will promote the application of RTSM in China.