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Performance of an Integrated Solar-Greenhouse Photovoltaic Ventilated Dryer with Clay-CaCl2 Energy Storage Desiccants for Tomato Drying
Susan Andrew Mbacho,
Thomas Thoruwa,
Nickson Kipngetich Lang’at,
Elias Ako
Issue:
Volume 9, Issue 2, June 2021
Pages:
19-29
Received:
28 March 2021
Accepted:
19 April 2021
Published:
29 April 2021
Abstract: The use of solar energy in drying of perishable crops such as tomatoes is a good alternative to the problem of post-harvest processing in tropical eastern African countries. A review of the literature revealed that most of the solar crop drying systems developed during the last five decades have small loading capacity and cannot operate during the night. Therefore, an integrated solar greenhouse dryer system [SGDS] with Clay-CaCl2 desiccant energy storage system was designed and tested. Such SGDS have the advantage over other solar systems of high loading capacity and structural simplicity. In addition, they have relatively good thermal crop drying performance compared to most solar dryers. However, their main limitation, like most solar dryers, is their inability to dry at night. Therefore, to enhance night-time drying capacity, a prototype SGDS integrated with a low-cost Clay-CaCl2 desiccant energy storage system was designed, fabricated, and tested. The drying performance of this prototype was evaluated using loads of fresh tomatoes during October – December 2019 at Nairobi, Kenya. The dryer was able to dry fresh tomatoes from 93.9% (mcwb) to 8.3% (mcwb) within 27hours with solar greenhouse drying efficiency of 23% during daytime and desiccant drying efficiency of 19.9% during nighttime. The drying rate for the two-day light drying was 0.985kg/h and 0.875kg/h respectively and that in night drying using desiccants was 0.34kg/h. Based on these results, it was concluded that prototype solar greenhouse dryer with Clay-CaCl₂ energy storage has great potential for drying perishable produce such as tomatoes in tropical countries.
Abstract: The use of solar energy in drying of perishable crops such as tomatoes is a good alternative to the problem of post-harvest processing in tropical eastern African countries. A review of the literature revealed that most of the solar crop drying systems developed during the last five decades have small loading capacity and cannot operate during the ...
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Numerical and Experimental Studies on Heat Transfer Enhancement in a Circular Tube Inserted with Twisted Tape Inserts
Haoxu Liu,
Guowei Zheng,
Changzhong Man,
Ke Jiang,
Xiaogang Lv
Issue:
Volume 9, Issue 2, June 2021
Pages:
30-40
Received:
15 April 2021
Published:
24 May 2021
Abstract: Numerical simulations and experiments are carried out in this paper to research about characteristics of heat transfer, frictional resistance and comprehensive performance of turbulent water flow (3000 < Re < 10,000) in a circular tube with twisted tape inserts. A new type of twisted tape is proposed and it shows excellent performance on heat transfer enhancement. Effects of three parameters including twist ratio (p/w=3, 4, 5), geometrical structure of alternation of clockwise and counterclockwise, existence of semicircular cuts are researched in simulations. The results show that lower twist ratio and the geometrical structure of alternation of clockwise and counterclockwise can enhance heat transfer while the existence of semicircular cuts can significantly reduce flow resistance. Experiments are conducted to validate the actual effect of the twisted tapes and the experimental results are basically consistent with the simulation results. Nusselt number and friction factor with the new type of twisted tape inserts are respectively 1.66-2.42 times and 4.36-4.97 times to that of plain tube while the maximum value of PEC (performance evaluation criteria) reaches 1.42 in experiments. The results of simulations and experiments indicate that the new type of twisted tape has a distinct advantage on heat transfer enhancement. Verification between simulations and experiments are carried out. The result shows that all deviations of corresponding values between simulations and experiments are within 15%, which reflects that the numerical predications are basically in agreement with the experiment results. Finally, a comparative analysis was carried out with the new type of twisted tape in this paper and the different twisted tapes in the previous research. The new type of twisted tape proposed in this paper has higher Nusselt number and friction coefficient.
Abstract: Numerical simulations and experiments are carried out in this paper to research about characteristics of heat transfer, frictional resistance and comprehensive performance of turbulent water flow (3000 ...
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Research on Fracture Initiation Pressure in Deviated Well of WCH9 Block
Siyu Xie,
Yongquan Hu,
Xiaojin Wan,
Shaowei Wu,
Liming Cheng,
Hui Yuan
Issue:
Volume 9, Issue 2, June 2021
Pages:
41-47
Received:
22 April 2021
Published:
24 May 2021
Abstract: Highly-deviated well are applied for effectively developing WCH9 gas field with deep buried and low permeability, and the payzone are candidates for hydraulic fracturing by evaluation of gas reservoir. Therefore, fracture initiation pressure is a key parameter for design of hydraulic fracturing treatment. Firstly, a series of experiments were completed by core sample from target formation, Young's modulus is about 13GPa and Poisson's ratio is 0.286 at a confining pressure of 40MPa, horizontal principal stress is 78 MPa and 63 MPa, and in-situ stress profiles were interpreted by logging data. Then, the formation rock is regarded as isotropic linear elastic material, thus total stresses distribution on the deviated wellbore wall was determined by stress superposition principle, in which in-situ stress redistribution around the deviated wellbore, fluid pressure acted on the borehole wall and filtration stress are taken into account when fracturing fluid was injected into wellbore. Further, prediction model of fracture initiation pressure was established by applying criterion of maximum tensile stress and effective stress transformation. Lastly, according to the borehole trajectory, in-situ stress and other parameters from payzone of WCH9 block, fracturing initiation pressure varied with Deviation angle and azimuth angle were computed by numerical simulation method, these results provide a basis for optimization design of hydraulic fracturing technology parameters.
Abstract: Highly-deviated well are applied for effectively developing WCH9 gas field with deep buried and low permeability, and the payzone are candidates for hydraulic fracturing by evaluation of gas reservoir. Therefore, fracture initiation pressure is a key parameter for design of hydraulic fracturing treatment. Firstly, a series of experiments were compl...
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Dynamic Thermal Study of a Building Insulated with Local Biosource Materials and Analysis of Consumption
Guy Clarence Semassou,
Jean-Louis Comlan Fannou,
Edmond Claude Vodounnou,
Mèdéhou Elogni Segbotangni,
Kouamy Victorin Chegnimonhan
Issue:
Volume 9, Issue 2, June 2021
Pages:
48-59
Received:
13 May 2021
Accepted:
28 May 2021
Published:
7 June 2021
Abstract: The quality of infrastructure, including buildings, is an indicator of a country's development status. However, it must be noted that these buildings entail high energy costs and also contribute to the global greenhouse effect. The building sector is therefore a crucial issue in terms of adapting to climate change because it is at the heart of a dual energy and environmental problem. To address this challenge, energy efficiency policies are increasingly being adopted worldwide, with the aim of improving the energy performance of buildings. In the present work, the thermo-physical properties of four types of materials, namely: "cement and roast fibre" composite, "cement and rice husk" composite, "agglomerate" and "cement and bar soil" composite, were exploited to implement thermal simulations under TRNSYS environment. The aim was to determine the thermal contributions of the walls built with these materials and those allowing a better comfort in the building by estimating and comparing the energy needs of the proposed variants with those of the reference building. The study showed that the walls made of "cement and rice husks" composite and "cement and roast tree fibres" composite allow to reduce respectively by 20% and 11%, the cooling needs linked to air conditioning for the living room, and respectively by 32% and 27% for the bedroom, compared to the reference building made of agglomerate (with a thickness e= 0.15 m). For the walls made of "cement and earth bar", the cooling requirement increased by 31% for the living room and decreased by 5% for the bedroom, compared to the "chipboard" reference building. Furthermore, the TEWI evaluation showed that the "cement and rice husk" and "cement and roast fibre" composites have a lower environmental impact.
Abstract: The quality of infrastructure, including buildings, is an indicator of a country's development status. However, it must be noted that these buildings entail high energy costs and also contribute to the global greenhouse effect. The building sector is therefore a crucial issue in terms of adapting to climate change because it is at the heart of a du...
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