In this study, a numerical simulation has been conducted in order to evaluate the thermal hydraulic performance of a turbulent single-phase flow inside an enhanced tube equipped with a square-cut twisted tape (STT) insert. The classical twisted tape (CTT) insert was also investigated for comparison. The k-ε renormalized group turbulence model has been utilized as the turbulent model. Various twist ratios (y/W) of 2.7, 4.5, and 6.5 were investigated for the Reynolds number range of 8000–18,000, with water as the working fluid. The numerical results indicated that, in comparison with the plain tube (PT), the tube equipped with the STT with the twist ratios of 2.7, 4.5, and 6.5 led to an increase in the values of the Nusselt number and friction factor in the inner tube by 45.4–80.7% and 2.0–3.3 times, respectively; in addition, the highest thermal performance of 1.23 has been obtained. The results further indicated that the tube equipped with the CTT of the same twist ratios improved the Nusselt number and friction factor in the inner tube by 40.3–74.4% and 1.7–3.0 times, respectively, in comparison with the PT; further, the maximum thermal performance of 1.18 was achieved.

This study aimed to enhance distilled water production by employing conventional single-slope solar distillers with continuous seawater input. Three solar absorbers—i.e., a flat absorber, an absorber with 10 fins, and an absorber with 15 fins—were designed and examined experimentally. The seawater entered the distillers continuously due to gravity. Moreover, the seawater level inside the distillers was kept constant by using a floating ball valve. The overall size of each distiller was fixed at 1136 mm × 936 mm × 574 mm. The performance of the distillers was analyzed and discussed. The average yields of the flat absorber, the absorber with 10 fins, and the absorber with 15 fins were 1.185 L/d, 1.264 L/d, and 1.404 L/d, respectively. The results of the absorber with 15 fins were about 18.5% higher than those of the flat absorber. The experimental results were compared with the established correlations. This new design with increased water yield provides an effective approach for harvesting sunlight in remote tropical regions for small-scale solar desalination.

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An experimental study was performed to determine the effect of the number of evaporators on the water production and coefficient of performance of an air-water harvester. Water was obtained on the evaporator walls in free convection and condensation heat transfer modes. The evaporator dimension was 480 mm × 285 mm × 6.25 mm, and it was made of copper pipes. The evaporators were installed in a parallel arrangement in an open box (top and bottom open) with a size of 500 mm × 500 mm × 500 mm. The refrigerant R134a was used as the working fluid. The experiments were performed at a low pressure of 40 psi and a high pressure of 180 psi. In the outside evaporator walls, air flowed naturally and part of the water vapour in the air condensed. Three evaporator variations were tested: Case A (one evaporator), Case B (two evaporators), and Case C (three evaporators). Each evaporator contained 25 copper pipes and the length of each pipe was 285 mm. The maximum water production and the evaporator efficiency attained were 0.51 L a day and 13 % respectively. The COP of the machine was ranging from 5.2 to 13.3. Increasing the evaporator number elevated the water production.