Abstract. Using models and algorithms presented in the first part of the article, a spatio-temporal distribution of the step response of a floor heater was determined. The results have been presented in the form of heating curves and temperature profiles of the heater in the selected time moments. The computations results were verified through comparing them with the solution obtained with the use of a commercial program -NISA. Additionally, the distribution of the average time constant of thermal processes occurring in the heater was determined. The analysis of the use of a graphics processing unit in numerical computations based on the conjugate gradient method was done. It was proved that the use of a graphics processing unit is profitable in the case of solving linear systems of equations with dense coefficient matrices. In the case of a sparse matrix, the speed-up depends on the number of its non-zero elements.Key words: air floor heating, step response computation, parallel computations, GPGPU.
Computational program parameters, material properties of the model, computing platformThe construction of the analyzed model of the heater was described in the first part of this paper ( Fig. 2 in [1], where L = 0.15 m). In order to conduct the discrete approximation of the model, an appropriate fragment of the floor slab was covered with a finite difference mesh of an identical step along x, y axes which equal ∆x = ∆y = 2.34375 · 10 −3 m. The mesh has 65×97 nodes. However, the number of nodes taken into consideration (and thus the number of unknown quantities of the obtained system of equations) is smaller and equals to 4289. As 2016 nodes, which are placed in the crosssection of the duct of the given temperature T H , should be omitted. The step response was determined with the assumed time step ∆t = 2 s and the N = 27000 number of steps. As a result, the considered time interval equals to 54 000 s (15 hours from letting the hot air into the ducts).Denotations of material properties were explained in the first part of the article (chapter 2 in [1]). The following set of data was assumed:Computations were done with the use of a personal computer equipped with an Intel Core 2 Quad CPU Q9650 3.00 GHz processor, RAM memory of 4 GB and a 64-bit Windows 7 Professional operating system. A Gigabyte Nvidia GeForce GTX480 graphics card equipped with 480 streaming processors, and 1536 MB of GDDR5 memory were installed in the computer. It also contained the CUDA parallel computing environment [2,3]
Step responses and their computational verificationThe computations of the step response were done according to the algorithm described in the first part of the article [1]. The obtained curves can be presented in a graph for selected points of the analyzed model of a floor heater. Characteristic points (A-J) were marked in Fig. 1, and the obtained graphs of the step response are presented in Fig. 2. Fig. 1. Analyzed fragment of the heater with the characteristic points and adiabats *