René Pyszko

Heat output of the recuperator for preheating natural gas from a mobile container device

The paper describes the methodology for determination of the heat exchanger output for mobile container device designed to supply stationary stations with natural gas. Expansion of the gas in the device is considered in two stages. In the first stage from over-pressure of 22 MPa down to over-pressure of 0.4 MPa and then in the second stage to over-pressure of 2.2 kPa or 170 kPa. The overall temperature drop during gas throttling, which depends not only on the initial and final pressure but also on the temperature, was calculated by numerical integration of the Joule-Thomson differential coefficient. For the throttling temperature between 0 and 55 °C, the total temperature drop in the first stage varies between 53.8 and 67.4 K, and in the second stage then up to 2 K. The heat exchanger output was determined by an iterative process. Smooth supply of 600 m3 of natural gas per hour requires a heat exchanger with an output of approx. 26 kW. Gas combustion micro-turbine consumption is of the order of m3 of natu...

Monitoring and simulation of the unsteady states in continuous casting

Kontinuirno litje obsega termicne, mehanske in kemicne procese, ki tecejo v kompleksnem sistemu, ki vsebuje vrsto elementov, kot so: strjujoca se jeklena žila (gredica), kokila z oscilacijskim mehanizmom, izvlecni mehanizem, vodno hlajenje s podsistemom hladilnih sob, vec kontrolnih podsistemov itd. Zunanji opazovalec lahko vidi proces kot robusten in stabilen, toda v resnici imamo vrsto fluktuacij (nihanj) internih termicnih in mehanskih velicin in kakovosti produkta (nastajajoce konti lite gredice). Raziskave (casovno) nestabilnega obnasanja velicin, kot so: temperaturno polje strjujoce se konti gredice, debelina trdne skorje in metalurska dolžina, so avtorji prispevka izvajali z industrijskim diagnosticnim sistemom (DGS), dopolnjenim s specialno merilno opremo in termicnim numericnim modelom. V clanku avtorji predstavljajo izbrane rezultate analiz, opazovanja in simulacije nestandardni procesnih stanj. Prav tako predstavljajo metode dolocevanja robnih pogojev za numericni model. Diskusija obsega tudi t.i. Leidenfrostov fenomen in njegov vpliv na koeficient prenosa toplote med vodnim hlajenjem s sobami. Za natancno dolocitev vsakokratnih robnih pogojev obstajajo tehnicne omejitve. Zato so v postavljenem modelu uporabljene le zglajene vrednosti v realnem casu in prostoru. Poznavanje trenutnega stanja ves cas spreminjajocega stanja, je predpogoj za doseganje kvalitetne proizvodnje brez napak. Zato je primerno uporabljati termicni numericni model s tekocim (on-line) oz. neposrednim spremljanjem internega stanja na konti livni napravi. Predstavljeni rezultati so tesno povezani z realnimi procesnimi podatki.

Measurement of unsteady airflow velocity at nozzle outlet

The paper deals with a method of measuring and evaluating the cooling air flow velocity at the outlet of the flat nozzle for cooling a rolled steel product. The selected properties of the Prandtl and Pitot sensing tubes were measured and compared. A Pitot tube was used for operational measurements of unsteady dynamic pressure of the air flowing from nozzles to abtain the flow velocity. The article also discusses the effects of air temperature, pressure and relative air humidity on air density, as well as the influence of dynamic pressure filtering on the error of averaged velocity.

Monitoring of solidification in the continuous casting mold by temperature sensors

Defects of continuously cast strand, such as unevenness of shell thickness or cracks as well as unstable casting parameters result in changes of strand surface temperature which affect heat flux and temperature field in the mold wall. Methods based on the principle of measurement and mathematical processing of temperatures in the mold wall are used for the purposes of diagnostics of the shell formation process, prediction of surface and subsurface quality and breakout danger, adjustment of the casting axis or condition monitoring of the oscillating mechanism. Measured values of temperatures in the wall depend on the exact position of the sensor in the wall, especially in the normal direction to the mold working surface. Ensuring the accurate and constant distance between the sensor and the mold surface is technically demanding; therefore it is necessary to correct the measured temperatures mathematically. The article describes two methods for correcting the measured temperatures, based on physical and sta...