Romana Dobáková

APPLICATION OF DIMENSIONAL ANALYSIS IN HEAT LOSS DETERMINING IN DISTRICT HEATING SYSTEMS

Existing procedures for determining the heat loss in heat distribution use balance relations, or rather they are based on the theory of heat and mass transfer. Dimensional analysis enables a new point of view that demonstrated the functionality of heat loss from selected physical quantities that contribute to heat loss. The solution provides one complex criterion and four simplex criteria of similarity. Transforming these criteria of similarity leads to the formulation of the functional dependence of only two criteria, on the basis of which the amount of heat loss can be determined. The resulting criterial dependency is simple, and is calculated in this paper for a pipe one meter in longth. The mathematic model for demonstrating the heat loss is of universal validity, and applies to a wide range of piping used for hot water distribution. However, for each nominal diameter of piping it is necessary to take into account the mutual dependency of the dimensionless arguments p 5 on p 1 , the form of which is always different. In the paper, this dependency is demonstrated for two nominal diameters DN65 and DN125.

High-temperature processing and recovery of autocatalysts

V tem clanku avtorji predstavljajo rezultate eksperimentalnih raziskav termicnega postopka pridobivanja kovin platinske skupine (PGM, angl.: Platinum Group Metals) s taljenjem izrabljenih avtomobilskih katalizatorjev v 80 kVA plazemskem reaktorju z uporabo primernih talil in redukcijskega sredstva. Kot zbiralnik plemenitih kovin je bila med taljenjem uporabljena siva litina. Produkti taljenja so zlitina, inertna steklasta žlindra, sintezni plin in pepel. V zlitini je bilo pri taljenju katalizatorja na osnovi kordierita koncentriranih 99,27 % PGM, pri katalizatorjih s Cr/Ni trakom pa 99,00%. Pri taljenju kordieritnih katalizatorjev se je v žlindri izgubilo 0,34 % PGM, pri Cr/Ni katalizatorjih pa 0,26 %. Kemijska analiza pepela je potrdila, da poleg mehansko pridobljenih oksidov CaO, SiO2, MgO, Al2O3, le-ta vsebuje tudi kondenzirane pare Fe in PGM. V pepelu se je pri taljenju katalizatorja na osnovi kordierita nahajalo 0,40 % plemenitih kovin, pri katalizatorju s Cr/Ni trakom pa 0,74 %. Sintezni plin iz procesa taljenja je imel zelo nizko kurilno (kaloricno) vrednost (0,16 MJ m–3 oz. 0,24 MJ m–3).

Model of heat losses from underground heat distribution system

The paper describes the linear density of the heat flow using dimensional analysis in the case of underground, pre-insulated piping. The methodology makes it possible to determine the heat loss based on a simple criterial relationship. Heat losses in the piping system were also calculated using numerical simulation. The difference between the experimentally detected losses and the values obtained from the model is −3.6% to 6.4%. The results of the numerical simulation at an ambient temperature of 25°C differ from the experiment by −1.7%. At an ambient temperature of −10°C the difference is −4.0%.The paper describes the linear density of the heat flow using dimensional analysis in the case of underground, pre-insulated piping. The methodology makes it possible to determine the heat loss based on a simple criterial relationship. Heat losses in the piping system were also calculated using numerical simulation. The difference between the experimentally detected losses and the values obtained from the model is −3.6% to 6.4%. The results of the numerical simulation at an ambient temperature of 25°C differ from the experiment by −1.7%. At an ambient temperature of −10°C the difference is −4.0%.

Recycling of the Electronic Waste Applying the Plasma Reactor Technology

Abstract The following paper discusses a high-temperature gasification process and melting of electronic components and computer equipment using plasma reactor technology. It analyses the marginal conditions of batch processing, as well as the formation of solid products which result from the procedure of waste processing. Attention is also paid to the impact of the emerging products on the environment.