Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers
The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Di...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-10-01
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| Series: | Membranes |
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| Online Access: | https://www.mdpi.com/2077-0375/12/11/1029 |
| _version_ | 1827646148427382784 |
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| author | Nunzio Cancilla Alessandro Tamburini Antonino Tarantino Salvatore Visconti Michele Ciofalo |
| author_facet | Nunzio Cancilla Alessandro Tamburini Antonino Tarantino Salvatore Visconti Michele Ciofalo |
| author_sort | Nunzio Cancilla |
| collection | DOAJ |
| description | The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height <i>H</i> ≈ 1 cm, Δ<i>T</i> ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels. |
| first_indexed | 2024-03-09T18:51:57Z |
| format | Article |
| id | doaj.art-7cd1c37f35f8416498ff9f49de0b3391 |
| institution | Directory Open Access Journal |
| issn | 2077-0375 |
| language | English |
| last_indexed | 2024-03-09T18:51:57Z |
| publishDate | 2022-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Membranes |
| spelling | doaj.art-7cd1c37f35f8416498ff9f49de0b33912023-11-24T05:47:58ZengMDPI AGMembranes2077-03752022-10-011211102910.3390/membranes12111029Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel SpacersNunzio Cancilla0Alessandro Tamburini1Antonino Tarantino2Salvatore Visconti3Michele Ciofalo4Dipartimento di Ingegneria, Università di Palermo, Viale delle Scienze Ed. 6, 90128 Palermo, ItalyDipartimento di Ingegneria, Università di Palermo, Viale delle Scienze Ed. 6, 90128 Palermo, ItalyDipartimento di Ingegneria, Università di Palermo, Viale delle Scienze Ed. 6, 90128 Palermo, ItalyDipartimento di Ingegneria, Università di Palermo, Viale delle Scienze Ed. 6, 90128 Palermo, ItalyDipartimento di Ingegneria, Università di Palermo, Viale delle Scienze Ed. 6, 90128 Palermo, ItalyThe results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height <i>H</i> ≈ 1 cm, Δ<i>T</i> ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels.https://www.mdpi.com/2077-0375/12/11/1029membrane distillationheat transferpressure dropspacer-filled channelspheres spacerthermochromic liquid crystals |
| spellingShingle | Nunzio Cancilla Alessandro Tamburini Antonino Tarantino Salvatore Visconti Michele Ciofalo Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers Membranes membrane distillation heat transfer pressure drop spacer-filled channel spheres spacer thermochromic liquid crystals |
| title | Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers |
| title_full | Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers |
| title_fullStr | Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers |
| title_full_unstemmed | Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers |
| title_short | Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers |
| title_sort | friction and heat transfer in membrane distillation channels an experimental study on conventional and novel spacers |
| topic | membrane distillation heat transfer pressure drop spacer-filled channel spheres spacer thermochromic liquid crystals |
| url | https://www.mdpi.com/2077-0375/12/11/1029 |
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