Mixed, forced and free convection heat transfer at the greenhouse cover

Papadakis, G.; Frangoudakis, A.; Kyritsis, S.

doi:10.1016/0021-8634(92)80037-s

Cited by 60 publications

(27 citation statements)

References 22 publications

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“…Concerning the heat transfer between the cover and the outside air, the convection could range from natural through mixed to forced, depending on temperature difference and wind speed. However, most of the time it was in the region of mixed convection, which is agreement with Kittas (1986), Papadakis et al (1992) and Navas (1996). The flux was mainly turbulent (Gr ≥ 10 8 and Re ≥ 10 5 ).…”

Section: Modification Of Crop Ventilation and Heat Transfer Coefficisupporting

confidence: 88%

“…The Nusselt number is a function of the Grashof (Gr) and Prandtl (Pr) numbers if convection is free and of the Reynolds (Re) and Prandtl numbers if it is forced (Monteith, 1973). However, in greenhouses most of the convection heat exchange is due to mixed convection with both processes involved (Stanghellini, 1987;Papadakis et al, 1992). In this case Stanghellini (1987Stanghellini ( , 1993 suggested that Nu m was a function of the Grashof and Reynolds numbers.…”

Section: Modification Of Crop Ventilation and Heat Transfer Coefficimentioning

confidence: 99%

See 1 more Smart Citation

Greenhouses climate modelling. Tests, adaptation and validation of a dynamic climate model

Baptista¹,

Bailey²,

Meneses³

et al. 1970

Span. j. agric. res.

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Most greenhouse climate models are specific for a particular combination of greenhouse type, crop, region and weather conditions. Models are formulated and validated for those conditions and it is not easy to directly extrapolate them to other, different conditions. In order to use them the coefficients need to be calibrated by experimental work, followed by validation of the adapted model. The main purpose of this work was the application of a formal dynamic climate model, defined and validated for heated greenhouses in continental regions of Spain, to non heated greenhouses in a mild winter region at the coast of Portugal. The original model was tested, adapted and validated so it simulated the microclimate inside unheated greenhouses. The methodology used enabled the problems to be identified, the model to be modified in a systematic way and then re-run to determine the improved performance. The new model includes new properties for some boundary components and sub-models for ventilation and stomatal resistance applicable to this greenhouse-crop system and new expressions for the convection heat transfer coefficients. In the validation process predicted and measured variables were compared graphically to show trends in the data and by using statistical parameters to characterise model performance. The model was validated with data representing different weather, ventilation operation and tomato crop conditions. Good agreement between predicted and measured data was obtained. It has been proved that this model can be used to estimate the greenhouse climate conditions, based on the weather conditions and on the greenhouse-crop system characteristics.Additional key words: convection heat transfer coefficients, nocturnal ventilation, unheated greenhouses. Resumen Modelado del clima de los invernaderos. Experimentación, adaptación y validación de un modelo climático dinámicoLa mayor parte de los modelos climáticos de invernaderos son formulados y verificados para aquellas condiciones concretas en que fueron definidos, como son el tipo de invernadero, el cultivo y las características climáticas. Para aplicarlos en condiciones distintas, los coeficientes de los modelos deben ser calibrados, proceso seguido de la correspondiente validación del modelo adaptado. El objetivo principal del presente trabajo fue la aplicación de un modelo climático dinámico formal, definido y validado para invernaderos calefactados del interior de España con clima continental, a invernaderos no calefactados de la costa de Portugal con clima templado. La metodología empleada en este estudio permitió identificar los problemas del proceso de adaptación, modificando el modelo de una forma sistemática, para después determinar su comportamiento mejorado. El nuevo modelo climático incluye nuevas propiedades para algunos componentes de contorno, nuevos submodelos para la ventilación y la resistencia estomática del sistema invernadero-cultivo, y nuevas expresiones para los coeficientes de transferencia convectiva de calor. Para el proceso d...

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Section: Modification Of Crop Ventilation and Heat Transfer Coefficisupporting

confidence: 88%

Section: Modification Of Crop Ventilation and Heat Transfer Coefficimentioning

confidence: 99%

Greenhouses climate modelling. Tests, adaptation and validation of a dynamic climate model

Baptista¹,

Bailey²,

Meneses³

et al. 1970

Span. j. agric. res.

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“…In many situations, the heat transfer is by mixed convection due to the equal importance of the external pressure field and buoyancy effects (Hieber, 1973;Papadakis et al, 1992;Lamrani et al, 2001).…”

Section: Fundamental Calculation Of Convection Heat Transfermentioning

confidence: 96%

PA—Precision Agriculture

Roy¹,

Boulard²,

Kittas³

et al. 2002

Biosystems Engineering

132

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“…Mengikuti sebagian besar pola rumus empiris dalam penelitian sebelumnya oleh Bot (1983), Garzoli dan Blackwell (1981), Kittas (1986), dan Papadakis et al (1992), koefisien konveksi pada pipa pendingin dan air didalamnya (h a ): Tabel 1. Ikhtisar persamaan yang digunakan dalam perpindahan panas konveksi paksa.…”

Section: Analisis Pindah Panasunclassified

Analysis of Heat Transfer in Cooling Pipe for Root Zone Cooling System

Araswati

Suhardiyanto

Solahudin

2017

JTEP

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Jurnal Keteknikan Pertanian (JTEP) terakreditasi berdasarkan SK Dirjen Penguatan Riset dan Pengembangan Kementerian Ristek Dikti Nomor I/E/KPT/2015 tanggal 21 September 2015. Selain itu, JTEP juga telah terdaftar pada Crossref dan telah memiliki Digital Object Identifier (DOI) dan telah terindeks pada ISJD, IPI, Google Scholar dan DOAJ. Mulai edisi ini redaksi memandang perlu untuk meningkatkan nomor penerbitan dari dua menjadi tiga kali setahun yaitu bulan April, Agustus dan Desember berisi 12 naskah untuk setiap nomornya. Hal ini dimaksudkan untuk mengurangi masa tunggu dengan tidak menurunkan kualitas naskah yang dipublikasikan. Jurnal berkala ilmiah ini berkiprah dalam pengembangan ilmu keteknikan untuk pertanian tropika dan lingkungan hayati. Jurnal ini diterbitkan dua kali setahun baik dalam edisi cetak maupun edisi online. Penulis makalah tidak dibatasi pada anggota PERTETA tetapi terbuka bagi masyarakat umum. Lingkup makalah, antara lain: teknik sumberdaya lahan dan air, alat dan mesin budidaya pertanian, lingkungan dan bangunan pertanian, energi alternatif dan elektrifikasi, ergonomika dan elektronika pertanian, teknik pengolahan pangan dan hasil pertanian, manajemen dan sistem informasi pertanian. Makalah dikelompokkan dalam invited paper yang menyajikan isu aktual nasional dan internasional, review perkembangan penelitian, atau penerapan ilmu dan teknologi, technical paper hasil penelitian, penerapan, atau diseminasi, serta research methodology berkaitan pengembangan modul, metode, prosedur, program aplikasi, dan lain sebagainya. Penulisan naskah harus mengikuti panduan penulisan seperti tercantum pada website dan naskah dikirim secara elektronik (online submission) melalui

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Mixed, forced and free convection heat transfer at the greenhouse cover

Cited by 60 publications

References 22 publications

Greenhouses climate modelling. Tests, adaptation and validation of a dynamic climate model

Greenhouses climate modelling. Tests, adaptation and validation of a dynamic climate model

PA—Precision Agriculture

Analysis of Heat Transfer in Cooling Pipe for Root Zone Cooling System

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