• Ramvir Singh

      Articles written in Pramana – Journal of Physics

    • Thermal conduction through porous and dispersed three-phase systems

      Ramvir Singh R S Beniwal R N Pande D R Chaudhary

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      A loose three-phase system made of metal, non-metal and air is considered resulting from small successive dispersions in effective continuous medium (ecm). The effective thermal conductivity of loose three-phase systems is estimated by extending theecm approach to multi-phase systems. The unsteady state line source (needle) method is employed to determine the effective thermal conductivity of some selected three-phase materials. The calculated and observed values show good agreement suggesting that the continuous medium approach can be applied to estimate effective thermal conductivity of multi-phase systems.

    • Heat conduction through moist soils at different temperatures

      Ashok K Singh Ramvir Singh D R Chaudhary

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      A numerical model has been described to estimate the effective thermal conductivity of moist soils, considering the effective continuous medium approximation and taking all possible interactions. Numerical solutions of the exact formulations are presented. Experimental measurements have been carried out for the thermal conductivity of dune sand at different moisture contents employing the method of unsteady state line source. The predicted and measured values show reasonable agreement.

    • Heat conduction and moisture migration in unsaturated soils under temperature gradients

      Ashok K Singh Ramvir Singh D R Chaudhary

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      An experimental study has been done to investigate the heat conduction and moisture distribution through the different layers of unsaturated soil. The soil is taken in the form of cylindrical columns in vertical and horizontal positions. The two ends of the cylindrical column were maintained at different constant temperature. The effective thermal conductivity was measured by dynamical method after achieving steady state. The distribution of moisture in the soil column was determined by gravimetric technique. The effective thermal conductivity (ETC) has also been predicted by temperature dependent model developed by Singhet al (1988). A close agreement has been found in experimental and predicted values of ETC.

    • Differential temperature sensors method for simultaneous determination of thermal conductivity and diffusivity

      L S Verma A K Shrotriya Ramvir Singh D R Chaudhary

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      An attempt has been made to minimize the sources of error involved in the transient probe method for thermal conductivity determination. Two sensors (thermocouples) are mounted parallel to the needle probe at known distances. This modification makes it a device for simultaneous conductivity and diffusivity determination. Thermal conductivity and diffusivity for glycerine, dune sand and mustard seed are determined by this method. Results obtained are compared with those obtained by a calibrated transient probe for conductivity and by a parallel wire method for diffusivity. Analysis of the results prove it to be a better instrument over the traditional ones. The technique can also be used as a direct reading device for conductivity and diffusivity measurements.

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