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Compressible Flow
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
In this section, we discuss stagnation properties, in particular stagnation temperature and stagnation pressure. Stagnation temperature is the temperature attained in a flowing fluid by bringing the flow adiabatically to rest at a point. The kinetic energy of the flow is transformed entirely into enthalpy. A stagnation property is not to be confused with a static property, which is measured by an instrument moving at the local stream velocity. The two states that we are considering are the stagnation (or total) state and the static state. We can write the energy equation between these two states as ht=h+V22
Compressible Flow in Nozzles
Published in V. Babu, Fundamentals of Engineering Thermodynamics, 2019
As already mentioned, stagnation temperature and pressure are local quantities and so they can change from one point to another in the flow field. Changes in stagnation temperature can be achieved by the addition or removal of heat or work†. Heat addition increases the stagnation temperature, while removal of heat results in a decrease in stagnation temperature. Changes in stagnation pressure are brought about by work interaction or irreversibilities. Across a compressor where work is done on the flow, stagnation pressure increases while across a turbine where work is extracted from the fluid, stagnation pressure decreases. It is for this reason, that any loss of stagnation pressure in the flow is undesirable as it is tantamount to a loss of work. To see the effect of irreversibilities, we start with the last equality in Eqn. 15.15 and substitute for T2/T1 and P2/P1 as follows: T2T1=T2T0,2T0,2T0,1T0,1T1
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Published in L. I. Sedov, A. G. Volkovets, in Mechanics, 2018
Now we present general formulas for calculating integral characteristics of the flow. To calculate integral characteristics, one should know the distribution over the channel section of five independent parameters of state and gas motion, for example, pressure p, density p, and three components of the velocity vector v. In practice it is more convenient to perform direct measurement of T0, p0, p, and the two angles determining the velocity direction. The stagnation temperature T0 is measured by means of thermocouples; the total pressure p0, static pressure p, and velocity direction are measured by special nozzles and tubes.
Thermal modeling and analysis of novel twin-chamber community solar cooker as a replacement of biomass-based cooking
Published in International Journal of Green Energy, 2019
Stagnation temperature of plate, ambient air, glass cover, and utensil water were measured using J type thermocouples and digital temperature indicators of measuring range from 0 to 250°C and stem type mercury thermometers (0–200°C range, least count 2°C and Zeal make, UK). Average of the two values was used for calculations. Global solar radiation incident on the horizontal surface of TCCS cooker (W m−2) was measured using two solarimeters (range 0–1200 W m−2 having least count of 5 W m−2 make Central Electronics, India) and other one of MECO, Japan (range 0–2000 W m−2 and least count 1 W m−2). Average of the two values was used for calculations. Wind speed above the aperture of cooker was recorded using vane type digital anemometer (range 0–25 m s−1 and least count 0.1 m s−1).