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Wyświetlanie 1-3 z 3
Tytuł:
Determination of transient fluid temperature using the inverse method
Autorzy:
Jaremkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/240590.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
temperature measurement
transient conditions
uncertainty analysis
pomiar temperatury
warunki przejściowe
analiza niepewności
Opis:
This paper proposes an inverse method to obtain accurate measurements of the transient temperature of fluid. A method for unit step and linear rise of temperature is presented. For this purpose, the thermometer housing is modelled as a full cylindrical element (with no inner hole), divided into four control volumes. Using the control volume method, the heat balance equations can be written for each of the nodes for each of the control volumes. Thus, for a known temperature in the middle of the cylindrical element, the distribution of temperature in three nodes and heat flux at the outer surface were obtained. For a known value of the heat transfer coefficient the temperature of the fluid can be calculated using the boundary condition. Additionally, results of experimental research are presented. The research was carried out during the start-up of an experimental installation, which comprises: a steam generator unit, an installation for boiler feed water treatment, a tray-type deaerator, a blow down flashvessel for heat recovery, a steam pressure reduction station, a boiler control system and a steam header made of martensitic high alloy P91 steel. Based on temperature measurements made in the steam header using the inverse method, accurate measurements of the transient temperature of the steam were obtained. The results of the calculations are compared with the real temperature of the steam, which can be determined for a known pressure and enthalpy.
Źródło:
Archives of Thermodynamics; 2014, 35, 1; 61-76
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reduction of dynamic error in measurements of transient fluid temperature
Autorzy:
Jaremkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/240052.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
analiza niepewności
model pierwszego obiektu
pomiar temperatury
stała czasowa
warunki przejściowe
first-order model
temperature measurement
time constant
transient conditions
uncertainty analysis
Opis:
Under steady-state conditions when fluid temperature is constant, temperature measurement can be accomplished with high degree of accuracy owing to the absence of damping and time lag. However, when fluid temperature varies rapidly, for example, during start-up, appreciable differences occur between the actual and measured fluid temperature. These differences occur because it takes time for heat to transfer through the heavy thermometer pocket to the thermocouple. In this paper, a method for determinig transient fluid temperature based on the first-order thermometer model is presented. Fluid temperature is determined using a thermometer, which is suddenly immersed into boiling water. Next, the time constant is defined as a function of fluid velocity for four sheated thermocouples with different diameters. To demonstrate the applicability of the presented method to actual data where air velocity varies, the temperature of air is estimated based on measurements carried out by three thermocouples with different outer diameters. Lastly, the time constant is presented as a function of fluid velocity and outer diameter of thermocouple.
Źródło:
Archives of Thermodynamics; 2011, 32, 4; 55-66
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The analysis of thermocouple time constants as a function of fluid velocity
Autorzy:
Majdak, M.
Jaremkiewicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/114056.pdf
Data publikacji:
2016
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
time constant
thermocouple
transient temperature measurement
experimental analysis
Opis:
In steady-state conditions when the fluid temperature is constant, there is no damping and time lag so the temperature measurement can be performed with a high accuracy. But when the fluid temperature is varying rapidly as during the start-up, quite appreciable differences occur between the exact and measured temperature because of the time required for the transfer of heat to the thermocouple placed inside a thermometer pocket. The temperature of the fluid is one of the key parameters affecting the proper operation of thermodynamic cycles, so the precise determination of its value is very important. The speed of the response of control systems to a temperature change is closely related to the time constant of the used thermocouples. The paper presents a significant impact of fluid velocity changes (in this case air) on the value of time constants of thermometers. For this purpose, the experimental study was carried out using sheathed thermometers with different diameters and hot junctions. The time constants determined for various thermometers are compared.
Źródło:
Measurement Automation Monitoring; 2016, 62, 9; 284-287
2450-2855
Pojawia się w:
Measurement Automation Monitoring
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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