Srbislav B. Genić

Supply water temperature regulation problems in district heating network with both direct and indirect connection

General form of equations for hot water temperature in house installation and district heating system according to the outside temperature are well known. The influence of heat exchanger type and its fouling on heat output in DH system is experimentally determined. When both direct and indirect connections are applied to the same district heating network, certain exploitation problems have been noticed due to real behavior of heat exchangers. Two technical possibilities are discussed in order to overcome problems.

The influence of heat exchanger performances on the design of indirect geothermal heating system

Geothermal water can be used for heating objects both by direct or indirect systems. Indirect heating system with supplementary heat source is analyzed in this paper, and mathematical model that includes heat transfer in heat exchangers, heat emitting units and heat losses of object is established. Useful diagrams are also given to illustrate mathematical model.

Froth Porosity and Clear Liquid Height in Trayed Columns

The paper deals with some of the results obtained during experimental research of fluid dynamic behavior of cascade columns. The three most commonly used types of trays (tunnel, sieve, and valve) occupied our attention and 595 experimental runs were performed on a 314 mm inside diameter column with an air-water system. Analysis of measured values of froth porosity has confirmed that Azbels equation should be used, despite its theoretical origin. For clear liquid height, a new correlation was established, because statistical parameters of equations taken from literature were not satisfactory. Both equations were tested on experimental data obtained on two rectangular columns, showing good statistical parameters.

Number of Trays in Gas–Liquid Columns in Case of Intensive Entrainment: Broadening of the Kremser Equation

Abstract The paper deals with the tray efficiency estimation in the presence of entrainment, using one-parametric diffusion model for the column as a whole. The case of mass transfer in the trayed column accompanied by intensive entrainment of liquid is analysed, when both equilibrium and ‘dry working regime’ operating lines are straight. Using proposed algorithm it is possible to determine the number of actual trays in the column based on the inlet and outlet concentrations in one phase, inlet concentration in the other phase and the characteristics of mass transfer at trays. The obtained equations present the broadening of well-known Kremser equations.

Results of experimental research on parameters that determine stable operating limits of ceramic burner with packed bed of uniform spheres for combustion of low calorific gaseous fuels

The research presented in this paper focuses on parameters that determine stable operating limits of porous burner. The experimental research was carried out on laboratory installation consisting of ceramic cylinder filled with packed bed of Al2O3 spheres. Gaseous fuel is prepared by mixing the compressed natural gas (CNG) and nitrogen (N2) in defined ratio, depending on set heating value of the inlet gaseous fuel. Experimental program included combustion of low calorific gaseous fuel (7.5 to 15 MJ/m3) within porous burner, where inlet power ranged between 2 and 4 kW. Total number of experimental sets in experimental study was 16, where seven of them were considered as stable. Results of experimental research are presented and discussed within this paper.

Calculation of the Heat Transfer Coefficient for Laminar Flow in Pipes in Practical Engineering Applications

ABSTRACT Paper presents an analysis of existing correlations for laminar liquid flow and heat transfer in tubes based on the published theoretical research and experimental data. Considering the relatively large deviation of existing correlations from the experimental data, the novel correlation for laminar heat transfer in tubes is proposed. The new correlation covers large range of tube diameters ranging from micro-scale level 125.4 µm to conventional diameter 20.8 mm, Graetz numbers up to 6500 and fluid to wall viscosity ratio 0.0048–11.7. Correlation ratio of the newly proposed relationship for a total number of 390 experimental runs is 96.6% and standard deviation is 16.2%. Moreover, correlation covers both the hydraulically and thermally undeveloped and developed flows and all cases of boundary conditions that can be met in industrial applications.