An experimental investigation of a small-scale air-heated humidification-dehumidification (HDH) desalination system with bubble-column humidification and dehumidification units was conducted. The study addressed the performance of the multistage air-heated bubble-column HDH system, which has limited coverage in the literature, by operating two bubble-column humidifiers in series for the air humidification process with air reheating. The effect of operating parameters such as airflow rate, air temperature, and saline water levels in both humidifiers on the performance metrics of the system were investigated. The product distillate rate, energy consumption, gain output ratio (GOR), and specific energy consumption (SEC) are the main indicators of performance for the proposed desalination system. Response surface methodology (RSM) was applied to the current system using the design of experiment (DoE) for the prediction of variables that greatly affect productivity and energy input. The airflow rate, air temperature, and water level of the second humidifier have a favourable effect on the distillate rate and GOR of the system. In contrast, the effect of the water level inside the first humidifier is insignificant. Furthermore, the RSM optimization approach was used to obtain the optimum distillate productivity. An optimized distillate rate of 0.45 L/h and a GOR of 0.4 are achieved at 1.5 SCFM (standard cubic feet per minute) of airflow rate, and 6.5 cm of water level in the second humidifier with 140°C air inlet temperature. The numerical optimization reveals the optimal operating parameters, that correspond to maximum distillate production of 0.3 L/h with minimum input energy of 0.71 kW, to be 139°C air temperature, 1.13 SCFM of airflow rate, 6.5 cm and 3 cm water levels of second and first humidifier, respectively.

RESUMO A Gérbera (Gerbera jamesonii Bolus ex Hook. F.; Asteraceae) é uma das plantas ornamentais economicamente mais importantes devido ao seu valor estético. No presente estudo, estabelecemos um método de micropropagação para a produção em larga escala de material de plantio de qualidade de gérbera ‘Pink Melody’. Oitenta e seis por cento dos explantes do capítulo produziram brotos adventícios (15,44 ± 0,34 brotos por capítulo) em meio Murashige e Skoogs (MS) contendo 2 mg L-1 de 6-benzilaminopurina (BAP) após seis semanas de incubação. A maior taxa de multiplicação de brotos (17 brotos por explante) foi obtida em meio MS suplementado com BAP e meta-Topolina (cada um a 2 mg L-1) após oito semanas. Os micro-brotações foram enraizados com sucesso (91,35%) em meio MS de meia força contendo 2 mg L-1 de ácido indol-3-butírico (AIB) em quatro semanas. As plântulas micropropagadas foram aclimatadas com uma taxa de sobrevivência de 97,5% e produziram flores sem aberrações morfológicas visíveis.

ABSTRACT Gerbera (Gerbera jamesonii Bolus ex Hook. F.; Asteraceae), is one of the most economically important ornamental plants due to its aesthetic value. In the present study, we established a micropropagation method for the large-scale production of quality planting material of gerbera ‘Pink Melody’. Eighty-six percent of the capitulum explants produced adventitious shoots (15.44 ± 0.34 shoots per capitulum) on Murashige and Skoogs (MS) medium containing 2 mg L−1 6-benzylaminopurine (BAP) after six weeks of incubation. The highest shoot multiplication rate (17 shoots per explant) was obtained on MS medium supplemented with BAP and meta-Topolin (each at 2 mg L−1) after eight weeks. The micro-shoots were successfully rooted (91.35%) on half-strength MS medium containing 2 mg L−1 indole-3-butyric acid (IBA) within four weeks. The micropropagated plantlets were acclimatized with a 97.5% survival rate and produced flowers with no visible morphological aberrations.