Abstract
In the time series response factors method, the weighting factors relating room air temperature deviation to space heat extraction are used to calculate heat extraction from cooling load. In dynamic cooling load computation method by the use of computers, heat extraction, preheating load, heat storage load and room air temperature deviation from set point can be computed by the weighting factors method in which eight terms of weighting factors and common ratio are used (WZ-WX (standard) Method). It is difficult in practice, however, to calculate cooling load by manual calculation using the same method because of a large amount of calculation process. In this report, therefore, the approximate calculation method of cooling load, in which only the first three terms of weighting factors and common ratio are used (WZ-WX (three terms approximation) Method), and the simple method, in which weighting factors and common ratio can be derived easily from graphs (Simple Calculation Methods I, II) are proposed for manual calculation. The graphs prepared for this purpose show the relationship between the ratio of total surface area of the room enclosure to the floor area and the weighting factors per unit floor area. These graphs are made using the weighting factors computed by WZ-WX (standard) Method for various types of room with different size of room space, different positions of outside walls, different values of weight of structure. In this report comparisons are made with regard to the values of weighting factors among WZ-WX (three terms approximation) Method, Simple Calculation Methods I, II and WZ-WX (standard) Method, investigation being made on room air temperature transfer function coefficients proposed by ASHRAE and theoretical consideration on the weighting factors method. The results obtained may be summarized as follows: (1) The values of heat extraction and room air temperature deviation at the starting time of air-conditioning when the values seem sufficiently converged, calculated by WZ-WX (three terms approximation) Method is compared with the values calculated by WZ-WX (standard) Method with the result that little difference is found between them. The Simple Calculation Methods, I, II are compared with WZ-WX (standard) Method by the same scheme as above and in consequence the difference between them is found by less than 5 per cent. (2) If the initial value of heat storage load is assumed to be 80 per cent of the cooling load that would occur at the same time under intermittent operation of ten hours a day, it is found that heat extraction and room air temperature deviation at the start time of air-conditioning after two days calculated by the three terms of weighting factors method are 5 per cent larger or smaller than the converged value at the same time calculated by WZ-WX (standard) Method. (3) Values of room air temperature transfer fanction coefficients proposed by ASHRAE are converted into values of weighting factors and compared with the weighting factors given by WZ-WX Method. As a result, it is found that the absolute values of the first and second terms of weighting factors are smaller and the absolute value of the third term is larger. This must be due to the difference in assumption for heat capacity of the room. (4) In WZ-WX Method, the effects of radiation interchange among the inside room surfaces are taken into consideration by the factors WX. The values of heat extraction calculated by the use of weighting factors, in which the effects of radiation interchange among the inside surfaces are considered in direct calculation turned out to be in good agreement with those by WZ-WX Method.
