Effect of storage medium on thermal properties of packed beds

Aly, S.L.; El-Sharkawy, A.I.

doi:10.1016/0890-4332(90)90201-t

Cited by 44 publications

(8 citation statements)

References 8 publications

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“…They reported that an increase in particle diameter reduces pressure drop, increases Nusselt number and hence the heat transfer. Aly and El-Sharkawy [5] studied the effects of storage material properties on the thermal behaviour of packed beds during charging. They concluded that the type of the storage material and their physical properties are the two important parameters affecting the design of solid packed bed.…”

Section: Introductionmentioning

confidence: 99%

Performance improvement studies in a solar greenhouse drier using sensible heat storage materials

Ayyappan¹,

Mayilsamy²,

Sreenarayanan³

2015

Heat Mass Transfer

103

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heat is stored when the material changes phase from solid to a liquid. Thermo-chemical storage is a technique, which involves chemical reactions.Sensible heat storage is the most simple and inexpensive way of energy storage system although there are few advantages of phase change energy storage over sensible heat storage, but the technological and economical aspects make sensible heat storage superior. Packed beds represent the most suitable storage units for air-based solar system. A packed bed storage system consists of loosely packed solid material through which the heat transport fluid is circulated. Heated fluid (usually air) flows from solar collectors into a bed of graded particles from top to bottom in which thermal energy is transferred during the charging phase.Solids have been reported as widely used storage materials on low temperature range. Energy can be stored up to 800 °C in sand, cast iron, steel, aluminium, aluminium oxide, magnesium oxide and granite. Metals have good conductive characteristics and thus require only a small heat transfer area. Sand and rocks on the other hand, need a relatively large heat transfer area. Solar greenhouse driers can be used very effectively for crop drying. Many studies have been conducted by the researchers in different regions of the world with different climatic conditions for the drying of fruits, vegetables, cereals, grains, oil seeds, spices, fish etc. using solar greenhouse dryer. Thermal energy storage either sensible or latent heat are required to improve the utility and performance of the solar greenhouse dryers. Many studies have been conducted by the researchers using various sensible heat storage materials like water tanks, gravel beds, ground, sand, concrete etc. where energy is stored in the form of sensible heat. Hasnain [1] reported that solid materials such as rocks, metals, concrete, sand and brick can be used for low as well as Abstract Experiments were conducted in a natural convection solar greenhouse dryer using different sensible heat storage materials (concrete, sand and rock-bed) in order to study their thermal performance. For both sand and rockbed, 4″ thickness was found to be optimum as it provides better drying environment both during day and night. The dryer reduced the moisture content of coconuts from 52 (w.b.) to 7 % (w.b.) using concrete as heat storage material in 78 h saving 55 % of drying time compared to open sun drying which takes 174 h for reducing the moisture content to the same level. The sand took 66 h saving 62 % of drying time whereas rock-bed took only 53 h thereby saving 69 % of drying time compared to open sun drying. The efficiency of the dryer was found to be 9.5, 11 and 11.65 % using concrete, sand and rock-bed respectively.

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Section: Introductionmentioning

confidence: 99%

Performance improvement studies in a solar greenhouse drier using sensible heat storage materials

Ayyappan¹,

Mayilsamy²,

Sreenarayanan³

2015

Heat Mass Transfer

103

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“…For a fixed volume bed, the increase of the storage material density increases considerably the storage capacity, as well as the rate of charging the system [12]. This is because a high density contributes in the improvement of the thermal capacity ( ρ ×C p ), which has the most pronounced effect on the amount of the energy stored in the packed bed.…”

Section: Densitymentioning

confidence: 99%

“…In this perspective, a parametric study conducted by Aly and El-sharkawy [12] about the effect of the thermophysical properties on the packed bed performance, showed that the higher are the specific heat capacity and density, the higher will be the amount of energy stored in the system as well as the rate of charging. Besides, a high thermal conductivity is required to enhance the thermal dynamic of the system, as when this property increases it improves considerably the rate of charging as well as increases the amount of energy stored for a specific charging period [12]. Furthermore, thermomechanical and chemical stability of the storage material are also required, since the rock should survive thermal cycling without disintegration or chemical decomposition.…”

Section: Introductionmentioning

confidence: 98%

Thermophysical and chemical analysis of gneiss rock as low cost candidate material for thermal energy storage in concentrated solar power plants

Jemmal

Zari

Maâroufi

2016

Solar Energy Materials and Solar Cells

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“…There have been a lot of numerical and experimental studies carried out to evaluate the thermal behaviour of packed bed latent heat thermal energy storage (PBTES) system. Aly and El‐Sharkawy 8 developed the transient two‐phase numerical model to obtain the temperature variations in air and in the solid medium of the packed bed. The influence of storage material properties was investigated on the thermal performance of packed bed during the charging period.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of a packed bed latent heat thermal energy storage with cylindrical‐shaped encapsulation

Kumar

Saha

2021

Int J Energy Res

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Summary In this work, a numerical model of a vertical cylindrical packed bed latent heat thermal energy storage (PBTES) system filled with cylindrical‐shaped encapsulations is developed. Two energy equations with a non‐equilibrium heat transfer model are employed to analyze the transient variation of heat transfer fluid (HTF) and encapsulated phase change material (PCM) considering the filler material as a porous medium. An enthalpy‐porosity technique is used to model the melting and solidification of PCM inside the capsule. The effects of the shape of the encapsulation, the aspect ratio of cylindrical encapsulation, the porosity of the storage system, HTF flow rate and encapsulation material are studied using the validated numerical model. For the same volume of encapsulation, the heat transfer rate and the thermal efficiency are found to be higher for the spherical encapsulation as compared to the cylindrical encapsulation. The thermal efficiency and the heat transfer rate of the storage system increase with the increase in the aspect ratio of the encapsulated PCM cylinder. With an increasing flow rate of HTF through the packed bed, the heat transfer rate and thermal efficiency improve. The PBTES with higher thermal conductive encapsulation material is more efficient and has a higher HTF temperature at the outlet during the discharging operations. The stabilization factor (SF) is introduced to assess the stabilization performance of the PBTES. The SF is lowest for the cylindrical encapsulation of aspect ratio of 4/3, the porosity of bed of 0.33 and the lowest HTF flow rate of 7.05 L/min considered in this study.

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Effect of storage medium on thermal properties of packed beds

Cited by 44 publications

References 8 publications

Performance improvement studies in a solar greenhouse drier using sensible heat storage materials

Performance improvement studies in a solar greenhouse drier using sensible heat storage materials

Thermophysical and chemical analysis of gneiss rock as low cost candidate material for thermal energy storage in concentrated solar power plants

Performance analysis of a packed bed latent heat thermal energy storage with cylindrical‐shaped encapsulation

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