Tài liệu Research and simulation fluid dynamic in solar greenhouse dryer

VIETNAM NATIONAL UNIVERSITY ± HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY --------*------- DUONG HOANG PHI YEN RESEARCH AND SIMULATION FLUID DYNAMIC IN SOLAR GREENHOUSE DRYER Major: Chemical engineering Code: 8520301 MASTER THESIS HO CHI MINH CITY, January - 2022 THIS RESEARCH WAS CONDUCTED AT HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY ± VNU- HCM Supervisor: Dr. Tran Tan Viet Reviewer 1: Assoc. Prof. Dr. Nguyen Tuan Anh Reviewer 2: Assoc. Prof. Dr. Le Anh Kien The master thesis was defended at Ho Chi Minh city University of Technology, VNU-HCM, January 1st, 2022 (Online) The members of Assessment Committee including: 1. Assoc. Prof. Dr. Nguyen Quang Long - Chairman 2. Assoc. Prof. Dr. Nguyen Tuan Anh - Reviewer 1 3. Assoc. Prof. Dr. Le Anh Kien - Reviewer 2 4. Dr. Pham Thi Hong Phuong - Committee 5. Dr. Pham Hoang Huy Phuoc Loi - Secretary Confirmation of the Assessment Committee Chairman and the Head of Faculty after the thesis has been corrected (if any). Assessment Committee Chairman Assoc. Prof. Dr. Nguyen Quang Long Dean of Chemical Engineering Faculty Prof. Dr. Phan Thanh Son Nam I VIETNAM NATIONAL UNIVERSITY ± HCM SOCIALIST REPUBLIC OF VIETNAM HO CHI MINH CITY UNIVERSITY OF Independence - Freedom - Happiness TECHNOLOGY MASTER THESIS MISSIONS )XOO1DPH'821*+2$1*3+,<(16WXGHQW¶V,' Date of Birth: 01/01/1996 Place of Birth: Tra Vinh Major: Chemical engineering Code: 8520301 I. THESIS TITLE: RESEARCH AND SIMULATION FLUID DYNAMIC IN SOLAR GREENHOUSE DRYER MISSIONS AND CONTENTS: - Investigation of the impact of weather conditions on temperature and humidity distribution inside SGHD by changing a suitable grid by ANSYS Fluent. - Investigation of the influence of time on the temperature and humidity distribution inside the SGHD. II. DATE OF ASSIGNMENT: 22/02/2021 III. DATE OF COMPLETION: 05/12/2021 IV. SUPERVISORS: Dr. Tran Tan Viet +R&KL0LQKFLW\« SUPERVISORS HEAD OF DEPARTMENT Dr. Tran Tan Viet Assoc. Prof. Dr. Le Thi Kim Phung DEAN OF CHEMICAL ENGINEERING FACULTY Prof. Dr. Phan Thanh Son Nam II ACKNOWLEDGEMENT Each of us has a beautiful youth during my time at the Ho Chi Minh City University of Technology, where youth and enthusiasm are imprinted. This university is my home, where I can source knowledge to nurture my passion for learning. Also, it was the same place that gave me great friends, teachers, and unforgettable memories. First, I would like to express my gratitude and respect to my advisor Dr. Tran Tan Viet. Thank you for your support, guidance, and encouragement throughout writing my thesis. Thank you for creating the best environment for me to study and practice as a solid fulcrum when facing difficulties. Thank you for your teachings when I stumble to know that the past does not equal the future. Besides, I would like to extend this thanks to my friends. Thank you to my best friends (Tony, Bao, Nin, Luon, and Duong) who have always been with me throughout realizing my passion. Finally, my best sincere hank goes to my parents, who supported me with this project within the limited time frame. Ho Chi Minh City, 18th December 2021 Duong Hoang Phi Yen III ABSTRACT This study investigates the internal conditions of the solar greenhouse dryer with drying agricultural products. The operating conditions inside the solar greenhouse dryer were analyzed by ANSYS Fluent software using mathematical models. Additionally, the moist air outside changed according to the climatic conditions of the day. Specifically, moist air enters the dryer through two front doors and exits through three exhaust fans installed in the back, and the flow was considered unstable and tumultuous. Agricultural products inside the solar greenhouse dryer were modeled as a porous material, and the radiation was modeled according to the radiation model. The simulation results show the distribution of temperature and humidity inside the solar drying greenhouse by the influence of heat exchange, turbulent flow, and the process of removing moisture from the drying material to the outside. The simulation results show that indoor drying temperature ranges from 303.15 K to 323.1 K at each time from 7:00 AM to 6:00 PM. The drying house reached its highest temperature at 2:00 PM. Variations of relative humidity in GHSD are between 23.70% and 79.55%. The airflow velocity inside the drying house is almost independent of time and varies based on location. In addition, the numerical simulation for solar greenhouse dryer performance. The numerical simulations compared the meshing strategies for the dryer and showed the effects on both temperature distribution and relative humidity distribution of air inside the dryer. Unstructured meshes were used in the numerical simulation employing hexahedral meshing and tetrahedral meshing for mesh generation. The meshing strategies were evaluated through 2 sizes of cells, i.e., 0.1 m and 0.05m. The results indicated that the cell size has a stronger effect than the mesh type on the temperature profile and humidity of the air inside the dryer. Thus, the results gave the engineers more options to select the optimum meshing conditions and simulate the dryer. IV TÓM TҲT LuұQYăQÿm sӱ dөng phҫn mӅm mô phӓQJ$16<6)OXHQWÿӇ mô tҧ phân bӕ nhiӋWÿӝ, ÿӝ ҭm vj vұn tӕc cӫa dzng không kht ҭm bên trong nhj sҩ\1/07ÿһt tҥi tӍnh An Giang YjĈӗng Tháp vӟi tӯng mөc tiêu khác nhau (các thông sӕ khҧRViWWKD\ÿәi theo thӡi gian và sӵ ҧQKKѭӣng cӫDÿӝ FKLDOѭӟi). KӃt quҧ mô phӓng cho thҩy sӵ phân bӕ nhiӋt ÿӝ Yjÿӝ ҭm bên trong nhà kính sҩ\QăQJOѭӧng mһt trӡi do ҧQKKѭӣng cӫa quá trình WUDRÿәi nhiӋt, dòng chҧy rӕLYjTXiWUuQKWKRiWKѫLҭm tӯ vұt liӋu sҩy ra bên ngoài. KӃt quҧ mô phӓng cho thҩy nhiӋWÿӝ sҩ\WURQJQKjGDRÿӝng tӯ .ÿӃn 323,1 K tҥi mӛi thӡLÿLӇm tӯ 7 giӡ ViQJÿӃn 6 giӡ tӕi. Nhà sҩ\ÿҥt nhiӋWÿӝ cao nhҩt lúc 2 giӡ chiӅu. Sӵ WKD\ÿәi cӫDÿӝ ҭPWѭѫQJÿӕi trong nhà sҩy là tӯ ÿӃn 79,55%. Vұn tӕc luӗng gió bên trong nhà sҩy hҫXQKѭNK{QJSKө thuӝc vào thӡLJLDQYjWKD\ÿәi tùy theo vӏ trí. Ngoài ra, mô phӓng sӕ cho hiӋu suҩt cӫa thiӃt bӏ sҩy nhà kính bҵQJQăQJOѭӧng mһt trӡi. Bên cҥQKÿyNKҧo sát sӵ FKLDOѭӟi cho nhà sҩy và cho thҩ\FiFWiFÿӝng lên cҧ phân bӕ nhiӋWÿӝ và phân bӕ ÿӝ ҭPWѭѫQJÿӕi cӫa không khí bên trong. Các mҳWOѭӟi không có cҩXWU~Fÿѭӧc sӱ dөng trong mô phӓng sӕ sӱ dөQJFKLDOѭӟi lөc diӋQYjFKLDOѭӟi tӭ diӋn. Lӵa chӑQFKLDOѭӟi phù hӧSÿѭӧFÿiQKJLiWK{QJTXDNtFKWKѭӟc cӫa ô, tӭc là 0,1 m và 0,05m. KӃt quҧ chӍ ra rҵQJNtFKWKѭӟc ô có ҧQKKѭӣng mҥQKKѫQVRYӟi loҥLOѭӟLÿӃn nhiӋWÿӝ Yjÿӝ ҭm cӫa không khí bên trong máy sҩ\'RÿyNӃt quҧ ÿmWKӇ hiӋQÿѭӧc FiFÿLӅu kiӋQFKLDOѭӟi tӕLѭXYjP{SKӓng nhà sҩy. V DECLARATION I hereby declare that the thesis has been composed by myself and that the work has not to be submitted for any other degree or professional qualification. I confirm that the work submitted is my own, except where work formed part of jointly authored publications has been included. My contribution and those of the other authors to this work have been explicitly indicated below. Finally, I confirm that appropriate credit has been given within this thesis where reference has been made to the work of others. Part of the work presented in this thesis was my publication, which was previously published in Scientific Reports, Chemical Engineering Transaction, and the IOP conference journal. Chemical Engineering Transaction as ³Three-Dimetional of Simulation of The 6RODU*UHHQKRXVH'U\HU´DQGWKH,23FRQIHUHQFHMRXUQDODV³7KH,QIOXHQFHRI0HVKLQJ 6WUDWHJLHVRQ7KH1XPHULFDO6LPXODWLRQRI6RODU*UHHQKRXVH'U\HU´ The Author Duong Hoang Phi Yen VI TABLE OF CONTENTS MASTER THESIS MISSIONS ....................................................................................... I ACKNOWLEDGEMENT .............................................................................................. II ABSTRACT ..................................................................................................................III TÓM TҲT..................................................................................................................... IV DECLARATION ............................................................................................................ V TABLE OF CONTENTS ............................................................................................. VI LIST OF FIGURES ...................................................................................................... IX LIST OF TABLES ....................................................................................................... XI 1. PREFACE ....................................................................................................................1 1.1. Rationale ................................................................................................................1 1.2. Research aims and Objectives ...............................................................................3 1.3. Outline of thesis .....................................................................................................3 2. LITERATURE REVIEW ............................................................................................4 2.1. Solar drying process overview...............................................................................4 2.1.1. Solar drying ......................................................................................................4 2.1.2. Classification of drying methods using solar energy .......................................5 2.1.3. Various shapes of the SGHD ...........................................................................7 2.2. Introduction to computational fluid dynamic (CFD) simulation ...........................8 2.2.1. ANSYS Fluent .................................................................................................9 2.2.2. Working principle of ANSYS CFD .................................................................9 3. MATHEMATICAL MODELS .................................................................................12 3.1. Conservation equations [20] ................................................................................12 3.1.1. Mass conservation:.........................................................................................12 3.1.2. Momentum conservation ...............................................................................12 VII 3.1.3. Energy conservation.......................................................................................13 3.1.4. Heat and mass balances in SGHD: ................................................................14 3.2. Viscous Model [20] .............................................................................................18 3.2.1. Standard k-İPRGHO ........................................................................................18 3.2.2. Realizable k-İPRGHO ......................................................................................19 3.3. Species model [16] ..............................................................................................21 3.3.1. Mass diffusion in turbulent flow ....................................................................21 3.3.2. Treatment of Species Transport in the Energy Equation ...............................22 3.4. Radiation model [20] ...........................................................................................22 4. SIMULATION OF SOLAR GREENHOUSE DRYER ............................................24 4.1. Bench-scale of solar greenhouse dryer ................................................................24 4.1.1. Geometry ........................................................................................................24 4.1.2. Geometrical discretization [20]......................................................................25 4.1.3. Physical properties and boundary conditions ................................................26 4.1.4. Simulation method and the operating conditions ..........................................27 5. RESULTS AND DISCUSSION................................................................................29 5.1. Profile temperature and relative humidity inside the SGHD ...............................29 5.1.1. The distribution of temperature .....................................................................30 5.1.2. The distribution of relative humidity .............................................................33 5.2. The sensitive mesh ...............................................................................................35 5.3. Mesh quality ........................................................................................................38 5.3.1. Influence of number of cells on the simulated results ...................................41 5.3.2. Influent of mesh type on the simulated results ..............................................43 6. CONCLUSION .........................................................................................................48 LIST OF PUBLICATION .............................................................................................49 VIII REFERENCES ..............................................................................................................50 SHORT CURRICULUM VITAE .................................................................................52 IX LIST OF FIGURES Figure 1. Principle of heat collection of solar drying equipment [Héliantis: the principle] .........................................................................................................................................4 Figure 2. Classification of solar drying methods [9, 10] .................................................5 Figure 3. The structure of SGHD ....................................................................................6 Figure 4. The structure of SGHD using the indirect method [9] .....................................7 Figure 5. Various shapes of the SGHD [13] ...................................................................8 Figure 6. The fluid region of the pipe flow is discretized into a finite set of control volumes ..........................................................................................................................10 Figure 7. The whole process of CFD simulation stages [19] ........................................11 Figure 8. Distribution of some parameters in SGHD [21] ............................................15 Figure 9. The SGHD model designed by SpaceClaim ..................................................24 Figure 10. Simulation temperature profile inside the SGHD from 7:00 AM to 6:00 PM .......................................................................................................................................29 Figure 11. Experimental temperature inside the SGHD from 7:00 AM to 6:00 PM ....30 Figure 12:Temperature distribution of moist air in the volume (a) at various locations and (b) in the middle of the SGHD ...............................................................................31 Figure 13:Temperature distribution of moist air in the volume of the SGHD at various times : (a): 8:00 AM; (b): 10:00 AM; (c): 12:00 PM; (d): 1:00 PM; (e): 2:00 PM; and (f): 4:00 PM ...................................................................................................................32 Figure 14: Velocity vectors of the airflow inside the SGHD ........................................33 Figure 15:RH distribution of moist air in the volume of the SGHD at various time: (a): 8:00 AM; (b): 10:00 AM; (c): 12:00 PM; (d): 1:00 PM; (e): 2:00 PM; and (f): 4:00 PM .......................................................................................................................................34 Figure 16: RH distribution of moist air in the volume of the SGHD at various locations .......................................................................................................................................35 Figure 17. Mesh distribution of SGHD for different mesh grid types: (a) hexahedral mesh H01, (b) hexahedral mesh H005, (c) tetrahedral mesh T01, and (d) tetrahedral mesh T005 .....................................................................................................................38 X Figure 18. The orthogonal quality mesh (a) hexahedral mesh H01, (b) tetrahedral mesh T01, (c) hexahedral mesh H005 and (d) tetrahedral mesh T005. ..................................40 Figure 19. The skewness of mesh (a) hexahedral mesh H01, (b) tetrahedral mesh T01, (c) hexahedral mesh H005 and (d) tetrahedral mesh T005. ..........................................41 Figure 20. The skewness and orthogonal mesh quality (2015 ANSYS, Inc.) ...............41 Figure 21. Temperature distribution and velocity of air inside SGHD at 10 AM for different mesh grid sizes: (a) and (c): tetrahedral mesh T01, (b) and (d) tetrahedral mesh T005 ...............................................................................................................................43 Figure 22. Comparison of the average temperature profiles (a) and the maximum temperature profiles (b) computed using different tetrahedral meshes .........................43 Figure 23. Temperature distribution and the temperature volume rendering of air inside SGHD at 10 AM using hexahedral mesh type, (a) and (c): hexahedral mesh H01, (b) and (d): hexahedral mesh H005 ...........................................................................................45 Figure 24. Comparison of the average temperature profiles (a) and the maximum temperature profiles (b) computed using hexahedral mesh type T01 and tetrahedral mesh type H01 ........................................................................................................................45 Figure 25. Relative humidity distribution of air inside SGHD at 10 AM using tetrahedral mesh type T01 (a) and hexahedral mesh H01 (b). ........................................................46 Figure 26. Comparison of the relative humidity computed using hexahedral mesh type (H01) and tetrahedral mesh type (T01) .........................................................................47 XI LIST OF TABLES Table 1. The dimension of the SGHD ..........................................................................25 Table 2. Properties of the drying agent materials .........................................................26 Table 3. The properties of the solid material ................................................................26 Table 4. The boundary conditions of the SGHD ..........................................................27 Table 5. The operating condition of the SGHD ...........................................................28 Table 6. The type of mesh ............................................................................................36 1 1. PREFACE 1.1. 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Research aims and Objectives In this thesis, ANSYS Fluent is simulation software used to simulate the SGHD with 6mx8mx3.5m. This type of drying house has been placed in An Giang and Dong Thap province with two categories: Firstly, the primary objective of this work was to simulate the influence of time on the temperature and humidity distribution inside the SGHD. The daily meteorological aspects were considered in the simulation result, and the model was validated through experimental field solar drying data and representing an advance for the accurate prediction of the drying. This contributed to the design of a more efficient process. Secondly, this research simulates the impact of weather conditions on temperature and humidity distribution inside SGHD by changing a suitable grid by ANSYS Fluent. Two types of mesh, including tetrahedral and hexahedral meshing, were conducted in this research, and the number of cells generating a mesh is various values, dependent on the size of the cell. 1.3. Outline of thesis This work is split into 5 chapters: Firstly, A Preface and Literature review in Chapters 1 and 2 with the theoretical portion is discussed. Third, the mathematical models part of the thesis is described in Chapter 3. And then, the results and discussion in Chapter 4 and conclusions in Chapter 5. 4 2. LITERATURE REVIEW 2.1. Solar drying process overview 2.1.1. Solar drying The greenhouse effect can explain collecting heat from the sun of solar drying equipment. This is the accumulation of radiant energy of the sun under glass or a certain layer of gas according to the principle: "The monochromatic clarity of a glass or a layer RIJDVZLOOGHFUHDVHZKHQWKHZDYHOHQJWKȜRIWKHOLJKWLQFUHDVHVLQWKHPRUQLQJ´)LJXUH 1 illustrates the solar dryer's heat recovery principle. Figure 1. Principle of heat collection of solar drying equipment [Héliantis: the principle] 5 2.1.2. Classification of drying methods using solar energy Figure 2. Classification of solar drying methods [9, 10] 6 2.1.2.1. The direct drying method The structure of the forced convection solar drying equipment is shown in Figure 3. Figure 3. The structure of SGHD Part of the solar radiation reaching the dome will be reflected into the air, and the rest will pass into the interior of the chamber. On the other hand, part of the radiation is reflected from the material's surface. The surface of the material absorbs the rest. By absorbing solar radiation, the product temperature will rise, and it will begin to emit radiation of long wavelengths, and these waves cannot escape the environment outside the drying house due to the obstruction of the roof. As a result, the temperature of the product inside the chamber will become higher. In addition, the dome also has another function as insulation to reduce heat loss to the surrounding environment, facilitating the increase of the drying chamber temperature. However, losses due to convection and evaporation still occur inside the chamber. The moisture content is carried away by air entering the chamber from below and exiting through the opening in the drying house. The goal of a solar dryer is to provide the drying material with more heat than is available under ambient conditions, which should be sufficient to increase the vapor 7 pressure of the moisture in the dried material and significantly reduce the relative humidity of the drying air. Thus, increasing the moisture carrying capacity [2]. 2.1.2.2. The indirect drying method The indirect solar energy drying device has 02 parts: the heat collector and the drying chamber [3]. Products when drying will not be exposed to direct sunlight because they are placed in the drying chamber. If the hot air is led into the chamber by natural convection, it is called a natural convection solar drying device. If hot air is blown in, it is called forced convection. With a blower and ducting unit, the forced convection solar dryer can direct hot air to any location for multiple purposes. Forced airflow accelerates water vapor diffusion and shortens drying time [4]. The structure of the forced convection solar drying equipment is shown in Figure 4. Figure 4. The structure of SGHD using the indirect method [9] 2.1.3. Various shapes of the SGHD The structure of the solar drying house is one of the important factors determining the receipt of radiation from the sun through location and orientation. Several studies on the structure of the drying house show that the irregular shape receives higher solar radiation, and the Quonset shape reports the lowest solar radiation in the east-west direction. Besides, some irregular shaped drying houses will receive the highest amount