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Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling
Thesis (PhD)--Stellenbosch University, 2017.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2017
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| _version_ | 1867613978205618176 |
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| access_status_str | Open Access |
| author | Getahun, Samuel Tenaw |
| author2 | Meyer, Chris J. |
| author_browse | Getahun, Samuel Tenaw Meyer, Chris J. |
| author_facet | Meyer, Chris J. Getahun, Samuel Tenaw |
| author_sort | Getahun, Samuel Tenaw |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2017. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/101078 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:43.650Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/101078 Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling Getahun, Samuel Tenaw Meyer, Chris J. Opara, Umezuruike Linus Stellenbosch University. Faculty of Engineering. Dept. Mechanical and Mechatronic Engineering. Refrigerated containers Refrigeration and refrigerating machinery Shipping -- Fruit Computational fluid dynamics UCTD Thesis (PhD)--Stellenbosch University, 2017. ENGLISH ABSTRACT: This dissertation addresses a number of topics that arise from the use of a refrigerated shipping containers (reefers) during transportation of fresh produce. The work contributes to (i) development of a computational fluid dynamics (CFD) model of a reefer packed with fresh produce, (ii) simultaneous estimation of produce quality and energy consumption to maintain product value and minimize wastage in the cold chain system. The work presented herein is concerned primarily with three topics: the airflow distribution in reefers (empty and packed), cooling operation of apple fruit, and energy use with respect to packaging designs and fan operation. Additionally, a chapter is presented that focuses on the impact of environmental conditions on the performance of fruit packed reefer during transportation. First, a numerical and experimental investigation of airflow and temperature distribution inside two types of empty reefers (T-bar floor and flat floor) used for fresh fruit handling was conducted to establish the fundamental characteristics of transport phenomena. Then, a CFD model of a fully loaded reefer was developed using porous medium approach. Fruit stacked pallets were modelled as porous media, in which volume average transport equations were employed, to avoid complex geometries inside packed pallet and minimize computational cost. Wind tunnel tests were used to obtain the pressure drop characteristics of palletized stack of apple fruit and the viscous and inertia coefficients in Darcy-Forchheimer equation. The detailed structure of the T-bar floor of the reefer and resistance-to-airflow of wooden pallets that were previously overlooked, were incorporated in the model. Airflow, pulp temperature and, energy consumption data obtained from a fully loaded, full-scale reefer were used to validate the model. The validated model was used to further investigate airflow distribution and fruit cooling performance of packaging designs used for handling apples and vertical airflow resistance or addition of bottom vent-holes. Energy consumption of reefers packed with apple fruit during shipping was examined experimentally and numerically using the validated model. The energy consumption of reefers packed with different apple packaging designs was evaluated with respect to seven-eighth cooling time, which confirmed the influence of ventilation area on energy use and the trade-off between the energy savings that can be achieved by employing packaging designs with low and high fruit packing density. In addition, the effect of evaporator fan on energy consumption was studied by simulating fruit packed reefers operating at low, medium, high and variable evaporator fan speeds. The study demonstrated significance of optimal fan speed operation on energy use of reefers packed with stacked load of fresh produce. Finally, the impact of climate on cooling performance and energy consumption of reefer during shipping was studied. The study showed an increase in fruit temperature and energy consumption due to heat conduction through the walls when the reefer operate in high temperature region. Overall, the CFD model developed predicted airflow, heat transfer and energy use with satisfactory accuracy. The model and research approach can be applied to a wide range of horticultural products and cold chains with slight modification. AFRIKAANSE OPSOMMING: In hierdie tesis word verskeie onderwerpe i.v.m. die gebruik van verkoelde skeepshouers gedurende die vervoer van vars produkte, behandel. Die navorsing dra by tot (i) ontwikkeling van ’n berekeningsvloeidinamika (BVD) model van ’n skeepshouer gepak met vars produkte, (ii) gelyktydige skatting van produk gehalte en energieverbruik om sodoende die waarde van die produk te behou en vermorsing van energie in die koue-ketting sisteem te verminder. Daar word veral op drie onderwerpe gefokus: die lugvloeiverspreiding in die skeepshouers (leeg en volgepak), die verkoeling van die appels, en die gebruik van energie deur die verkoelings- en waaierontwerpe. Daar is ook ’n hoofstuk wat fokus oor die impak van omgewingstoestande op die prestasie van vrugte verpak in die skeepshouer tydens vervoer. Daar is eerstens ’n numeriese en eksperimentele ondersoek gedoen na lugvloei en temperatuurverspreiding binne die twee tipes leë skeepshouers (T-vorm vloer en plat vloer) om die fundamentele kenmerke van die vervoerverskynsels te verstaan. Toe is ’n BVD model van ’n volle gelaaide skeepshouer met die gebruik van die poreuse medium benadering ontwikkel. Vrugte-verpakte houtpalette is gemodelleer as poreuse media, waarin gemiddelde volume vervoer vegelykings gebruik is om komplekse geometrie binne-in die gepakte houtpalet te vermy en om berekende koste tot die minimum te beperk. Windtonnel toetse is gebruik om die val-in-druk kenmerke van die gepakte appels en die taaiheids- en traagheidskoëffisiente van die Darcy-Forchheimer vergelyking te verkry. Die gedetailleerde struktuur van die T-vorm vloer van die skeepshouer en die weerstand tot lugvloei van houtpalette wat voorheen misgekyk is, word ook in die model geïnkorporeer. Die lugvloei, temperatuur van die vleisgedeelte van die vrugte, en die data oor energie-verbruik wat verkry is vanaf ’n volgelaaide, volskaal skeepshouer is gebruik om die model te valideer. Die gevalideerde model is gebruik om lugvloeiverspreiding en vrugte-verkoeling van verpakkingsontwerpe wat gebruik word vir die hantering van appels en die vertikale lugvloei weerstand of die byvoeging van ventilasie gaatjies verder te ondersoek. Die energieverbruik van skeepshouers gepak met appels is gedurende verskeping eksperimenteel en numeries met die gebruik van die gevalideerde model ondersoek. Die energieverbruik van skeepshouers met verskillende tipes appelverpakking is vir sewe-agstes verkoeling evalueer, wat die invloed van ventilasie area op energieverbruik en die kompromie met energiebesparing bevestig het, en verkry word deur die gebruik van verpakkingsontwerpe met lae-en hoë vrugte verpakkingsdigtheid. Verder is die effek van ’n verdampingswaaier op die energieverbruik bestudeer deur vrugteverpakte skeepshouers met waaiers wat teen lae- , middel- en hoë spoede loop, te simuleer. Die studie het die belangrikheid van optimale waaierspoed operasie op die energieverbruik van skeepshouers volgepak met vars produkte getoon. Laastens is die impak van klimaat op die verkoelingsdoeltreffendheid en die energieverbruik van skeepshouers tydens verskeping bestudeer. Daar is bevind dat die temperatuur van die vrugte asook die energieverbruik van die skeepshouer in streke met hoë temperature weens die geleiding van hitte deur die mure, verhoog. Oor die algemeen het die BVD model die lugvloei, hitte-oordrag en energieverbruik akkuraat voorspel. Hierdie model en navorsingsbenadering kan op ’n wye reeks tuinbou produkte en koue kettings, met klein aanpassings, toegepas word. Doctoral 2017-02-21T10:22:38Z 2017-03-29T12:05:42Z 2017-02-21T10:22:38Z 2017-03-29T12:05:42Z 2017-03 Thesis http://hdl.handle.net/10019.1/101078 en_ZA Stellenbosch University 218 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Refrigerated containers Refrigeration and refrigerating machinery Shipping -- Fruit Computational fluid dynamics UCTD Getahun, Samuel Tenaw Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title | Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title_full | Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title_fullStr | Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title_full_unstemmed | Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title_short | Investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh Fruit using computational fluid dynamics modelling |
| title_sort | investigating cooling performance and energy utilization of refrigerated shipping container packed with fresh fruit using computational fluid dynamics modelling |
| topic | Refrigerated containers Refrigeration and refrigerating machinery Shipping -- Fruit Computational fluid dynamics UCTD |
| url | http://hdl.handle.net/10019.1/101078 |
| work_keys_str_mv | AT getahunsamueltenaw investigatingcoolingperformanceandenergyutilizationofrefrigeratedshippingcontainerpackedwithfreshfruitusingcomputationalfluiddynamicsmodelling |