Browsing by Author "D.S. Venkateswarlu"

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Estimation of Dispenser Cathode Surface Temperature of a Practical Potted Heater Cathode Assembly
(1993) A. Sil; A. Chatterjee; D.S. Venkateswarlu
The heat transfer through the porous and/or infiltrated potted heater-cathode structure is simulated by a numerical model. The model includes heat conduction through the porous potting having isometric pore shape and uniform size (310 μm in alumina potting and 20 μm in tungsten cathode pellet), imperfect interface heat transfer effect and radiative boundaries. In addition to the transient state study, a steady-state analysis using the numerical model has also been done on a commercial Spectra-Mat cathode. The predicted results have been compared with the experimental measurements and are found to be in good agreement. © 1993 IEEE
Of heat capacity at homologous temperatures for metals showing h.c.p. ⇄ b.c.c. transformation
(Springer India, 1986) P. Ramachandrarao; D.S. Venkateswarlu; S. Lele
Some interesting aspects of the temperature dependence of the Planck's function φ and heat capacities of metals exhibiting the h.c.p. ⇄ b.c.c. transformation have been brought to light by the use of reduced temperature (T*) and Planck's function (-φ T*). It has been shown that tangents drawn to the -φ T* vs T* plots of these metals at any chosen value of T* intersect at a point whose coordinates are defined by the slope and intercept of φ vs entropy plots at any homologous temperature and the selected T* value. A generalized expression obtained for the temperature dependence of φ has been used to demonstrate that the heat capacity of these metals may be visualized to have structural and material components. © 1986 the Indian Academy of Sciences.
One dimensional large signal analysis for helix TWTs and multicavity klystrons
(Publ by IETE, 1994) E.V.R.Narasimha Rao; D.S. Venkateswarlu
A simple software has been developed to depict the 1-D nonlinear electron - rf wave interaction of a helix TWT using the well known disc model to work on a simple 8088 based PC system. The software has been extended to the large signal analysis of klystrons also by consideration that the interaction now is a spot interaction rather than a distributed interaction and the discs are followed in the field-free drift region. Typical results of the TWTs and multicavity klystrons, such as the Applegate diagrams, and some of the normalized parameters viz, rf voltage amplitude (A(y)) vs distance y (for a TWT), normalized fundamental rf current vs distance y (I1/I0 for the klystron) are presented. The PC simulated results (A(y) and I1/I0 for the TWT and klystron respectively) are in good agreement with those published in the literature.
Thermal analysis of a cathode: temperature distribution and warm-up time
(1990) Anjan Sil; N.K. Samria; D.S. Venkateswarlu
This paper gives a theoretical estimate of the cathode temperature distribution at the surface and the warm-up time. Several cases of practical interest have been studied from the thermodynamic considerations using the software specially developed for this application. The software is in two parts, viz., the steady-state analysis which gives the cathode surface temperatures and the transient analysis which yields the warm-up time. Temperature-dependent thermal conductivity, specific heat, density, and emissivity have been used in the transient analysis which improves the accuracy. Scaling laws for the determination of cathode surface temperature have been devised to cater for various sizes of cathodes used in industry. Not reported so far, our results show that a pancake-heater configuration has a better thermal response but a non-uniform cathode surface temperature profile whereas the conventional helical-heater configuration has a relatively poor thermal response but a more uniform temperature profile on the cathode. This aspect gets amplified and is very revealing at larger cathode dimensions. © 1990.