Alka Mihelić-Bogdanić

Specific wind energy as a function of mean speed

The most important parameter for the calculation of the specific wind energy is the duration for each wind speed separately. This paper includes the Rayleigh distribution and real variable efficiency depending on the mean wind speed in comparison with Betz limits and 100% efficiency. The calculation leads to the conclusion that the results are about four times higher with Betz efficiency and seven with 100% efficiency by selected wind speed.

Heat recovery in thermoplastics production

An energy optimization of production of a thermoplastic material, polyamid-6, i.e. nylon-6, using boiler flue gases heat recovery is presented. Energy and environmental studies show an increase of process efficiency simultaneously with a decrease of thermal pollution. If the feed water is heated with flue gases, the fuel consumption is reduced by about 13%, while the boiler outlet flue gases temperature decreases from 232°C to 55°C. Using an air preheater for combustion air preheating, 7.9% of the fuel will be saved, and at the same time, the atmospheric thermal pollution is diminished because the exhaust flue gases temperature becomes 62°C instead of 232°C. The combination of feed water and air preheating shows fuel savings of 13.6%, and the outlet flue gases temperature is reduced to 29.7°C.

Application of solar energy in drying processes

Abstract This paper presents the results of the study of three basic types of fossil fueled drying processes in comparison with the same processes using solar energy input based on solar data in Croatia. When using fossil fuel energy, savings could be approx. 27–29%. With solar energy input, the fossil fuel savings could be 14.6–100%, depending on the period of the year.

Solarized evaporation process

Abstract The minimization of fuel consumption in evaporation processes, could be achieved by using steam condensate heat recovery and also solar energy as a partial substitution for fossil fuels. In the presented article, the fuel savings methods in the one effect conventional and solarized processes are treated. The analysis includes the estimation of natural gas consumption, solar energy substitution and a summary of the savings for processes without and with condensate recovery. The reported results are obtained by calculations based on industrial plant data for NaNO 3 evaporation and measured irradiation for a selected location in Croatia

Solar Energy System and Waste Heat Recovery in Industrial Process

Publisher Summary This chapter deals with the solar energy system and waste heat recovery in industrial process. The main aim of this chapter is to describe and evaluate the probability of energy savings at steam pressing process in garment industry. Process input data assembled through process observing are used to establish process efficiency and energy conservation. The possibility of fuel savings using flue gases heat recovery and solar energy as partial substitution for fuel oil can lead to significant energy conservation. Returning boiler flue gases, with satisfying temperature of 204°C to the economizer, to preheat boiler feed water, about 9% fuel can be saved. At same time exhaust temperature lowers from 204°C to 45.9°C. If solar energy use is planning the appropriate meteorological data for selected location (Croatia, Zagreb to = 45,049) should be known. The yearly fuel oil consumption for pressing process in garment industry which becomes 2.03 × 106 kg can be reduced by 50.9% by using solar collector field of 20.8 × 103 m2 and flue gases heat recovery.

Heat recovery in polyester production: A case study

Energy savings in the synthetic fiber industry could be realized by using autoclave reactor condensate and boiler flue gas heat recovery. The non-cellulose (polyester) production process analysis shows that condensate returning from the reactor to the steam boiler raises inlet temperature, giving a reduced fuel requirement of about 8%. Also, boiler flue gas with a sufficiently high outlet temperature for boiler feed water and combustion air preheating results in further fuel savings. The process with an economizer saves up to 8.44%, and with a combustion air preheater, 6.25%.

Energy conservation using a recuperative drying process

Energy savings in drying processes might be achieved by using a dryer exhaust heat for ventilation and supply air preheating and also water or space heating. One of the various possibilities for heat conservation is the process with recuperation. Having analyzed one-stage and two-stage recuperative drying, it was established that the heat economy with the two-stage process is approximately twice as good. Compared with the process without heat recovery, the energy savings for the ventilation air heater is 41% and for the ventilation and supply air heaters is about 60%.

Generalized thermodynamic calculations for CHP generation

We describe the thermodynamic processes in a combined heat and power (CHP) unit. Our method involves three different pass-out flows. For specified thermodynamic conditions, we present equations relating the pass-out flow to the turbine work, process and supplied heat, and the thermal efficiency.

Impact of hybrid system in polyester production

Abstract This study represents the evaluation of energy efficiency improvement using combination of natural gas, solar energy and flue gases heat recovery in polyester production. The analyzed energy sources are used for dry saturated steam generation. The energy consumption for combined system on location (φ = 45°49′) with collector field of 23.23 × 103 m2, was investigated. The hybrid system was calculated for four variants: (1) solarized process without flue gases heat recovery, (2) solarized processes with heat contend in flue gases using economizer, (3) solarized processes with heat contend in flue gases using an air preheater and (4) solarized processes with heat contend in flue gases using economizer and air preheater. The best method among presented sources is solution using economizer and the air preheater with natural gas, solar energy and flue gases heat recovery. The natural gas consumption is reduced for 67.82% which indicates that this solution is the optimal one. At the same time the volume of exhaust flue gases is diminished from 4947.1 to 1430.4 /h while simultaneously decreasing outlet temperature of 172.85°. Together with considerable energy savings, this hybrid system is sustainable and environmentally acceptable.

Reducing Energy Supply In The Drying Process

ABSTRACT After a detailed analysis of original industrial drying (the most common form) as an energy intensive process, the possibilities for the reduction of fuel consumption are documented. This is done because, after conventional drying, where hot air is usually discharged into the atmosphere, there is great potential for heat saving via exhaust-to-supply air heat exchangers. Thus, the conventional process is compared with ones using recuperation and recirculation that increase drying efficiency. Reclaiming heat from the exhaust results in fuel savings of 28% in the recuperative drying process, and the fuel consumption is lowered by 24% in the proposed recirculative option. Improved efficiency is also evident from the calculations presented, with savings of about 51% for recuperation and about 49% for recirculation. With these options, energy-saving activities also result in improvements of the production process with respect to environmental impacts. From the presented calculations, it follows that th...