Abstract
A greater number of analysis and researches have been conducted over years to fully explain and exploit the phenomena on the mass transfer of latent thermal energy storage system on packed beds. The packed bed model is comprised of well filled spherical capsules, with most models utilizing the fundamental equation of Schumann except the PCM phenomena which is analyzed using the enthalpy formulae.
The model efficient utilization have provided the essence of testing its properties at the cryogenic temperatures of ambient 4k and above and several proves have indicated that only pressurized helium proves to be suitable for such zones. Great studies on enthalpy-flux methods and single blow transient system have provided the much analysis required. Though still greater weaknesses exist as there apparent discrepancy in the interpretation of the results due to the neglect of the axial and radial dispersion though, still a better experimental system have been developed at which gas flow can be utilized in step fashion in temperatures of about 4-300k. This apparatus operates on steady transfer, thermal uniformity, maximum particles contact between phases as well as the fluidizing medium, thereby enabling it to yield work efficiently (John and Stuard n.d).
Introduction
Packed beds are commonly utilized in biochemical and petrochemical industries as chambers of physical operations. Due to the great number of discrepancy their successful application relatively depends on accurate analysis of the whole process of both the endothermic and exothermic. The packed bed is commonly cylindrical in nature filled with suitable packing material as a respective of the application zone; the packing materials are usually designed uniformly across the cross-section of th4e column with constant pressure of the liquid or gas flowing at a specific rate. The fluidization purpose of the bed is majorly to provide maximum agitation of the phase contact of the solids and the fluids and the particles are to catalyze the reaction. In recent years amore developed catalyst regeneration reactors have been employed and this has been utilized in the petroleum, coal and gas adsorption operations.
Types of the fluidized packed beds
Understanding the fluid flow in packed bed is an important parameter for efficient production and most of the packing arrangements for the particles are always in rhombohedra and cubic to provide high surface area for highest and lowest bed contacts. For cold zones the fluidized beds should be placed to operate in high velocity, with minimum particles properties and increased bed diameter and distribution, in fluid state the velocity always exceeds the minimum fluidization velocity. Bubbling fluidization dynamics may also be utilized to achieve the intended results, these bubbles are majorly formed due to the instability of the gas solid fluidized bed. This makes the gas to form jets as it enters orifice of distribution this disrupts the flow to the region thereby resulting into psudofluid ending up emitting les energy in low temperate regions. However the intensity of the bubbling motion may increasingly becomes vigorous leading to increased amplitude in fluctuations in pressure thereby leading a transition to turbulence regime.
The other variety of packed bed that is also conventionally utilized is the spouted bed which posse’s inherent difference in the flow of structures, its annulus region is of higher compared to the sprout section by reaching maximum at the spout-annulus section and with higher particle diameter as these helps to increase its efficiency at velocity beyond minimum fluidization.
The operation of the packed bed at relatively low temperature
Measurement of the response of the bed to relatively low temperatures and the maximum gas flow requires relatively improved understanding of the heat transfer characteristics and fluid dynamics, this is only be achievable through detailed accurate experiments. The interdependent parameters such as the cross-sectional area, time, and gas and air velocity at different positions on the bed are necessary to account though not easy to achieve.
Fig showing the typical schematic cross-section of the packed bed
In order to maximize the potential of regenerators a prompt computation on the system is required and all the assumptions are to be taken into account. These includes that the tank is axial and incompressible , the temperature is invariant with the thermo physical properties and the ratio of the void to the volume of the packed bed is (14), as this will provide as opportunity to calculate the total energy balance operating on the elements(Felix, Solanki and Saini 2008 pg1767).
In case the latent heat is below the melting temperature range then;
H=CpsT+LpT(p=a2) As long as substantive experiment and analysis on the heat transfer on packed beds is carried out proper cautionary measures and accurate data tabulation using the above parameters should be of higher profile. A prompt channel scan should be accounted to ensure that they are all recognized by the instrument and proper data analysis is made to reduce the variations. Felix Regin A, Solanki SC, Saini JS. Heat transfer characteristics of thermalBibliography
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