Diffusion‐driven desalination using waste heat in air streams

Abstract

SUMMARYRecently a diffusion-driven desalination (DDD) process has been described as a method for distilling mineralized water. Extensive studies have already examined the performance of the process using waste heat in water streams. This work focuses on the performance of the diffusion tower (evaporator) using waste heat in air streams. Both experimental and parametric investigations are included. It is observed that the evaporation process is very inefficient when heated air and ambient water are input to the diffusion tower. In contrast, efficient evaporation is achieved when both heated air and heated water are input to the diffusion tower. An industrial application is considered where a waste heat air stream at 828C is available and a recuperative heat exchanger is used to heat the feed water. It is found that the optimum operating conditions include an air mass flux of 1:5 kg m À2 s À1 ; an air to feed water mass flow ratio of 10 in the diffusion tower and a fresh water to air mass flow ratio of 2 in the direct contact condenser. At these operating conditions, a fresh water production efficiency of 0.22 and a specific energy consumption of 0:0012 kW h kg À1 can be achieved. The analytical model used to analyze the performance of the DDD process agrees well with the experimental measurements.

In situ chemo‐polymerized polypyrrole‐coated filter paper for high‐efficient solar vapor generation

“…Among them, the solar still (solar steam generation device) is one of the most effective methods to alleviate Yuliang Zhang and Shengjia Cao contributed equally to the work water shortage. [11][12][13][14][15] A high efficiency solar steam generation device, combining photothermal conversion materials and substrate materials, should consist of the following features: a hydrophilic and mesoporous structure providing enough water with superior stability and nontoxic, a heat blocker (supporting material) with low thermal conductivity, and a light absorber with a high light absorption capability. 9,16,17 Among them, high efficiency photothermal materials that can absorb the light and convert it to heat are the key to maximize the rate of the solar water desalination.…”

“…[2][3][4] Although solar energy is a promising source of energy, the low efficiency of solar-to-steam conversion has greatly hampered the practical application of solar energy, such as solar evaporation and water desalination, because of the large amount of optical and systemic heat loss in conventional distillation processes. [11][12][13][14][15] A high efficiency solar steam generation device, combining photothermal conversion materials and substrate materials, should consist of the following features: a hydrophilic and mesoporous structure providing enough water with superior stability and nontoxic, a heat blocker (supporting material) with low thermal conductivity, and a light absorber with a high light absorption capability. 10 There are various solar-driven desalination methods such as solar still, multiple-effect distillation, and multistage flash.…”

Experimental study of the specific energy consumption for brackish water desalination by reverse osmosis

“…Thermal desalination processes are technologies alternative to RO. For brackish water desalination they may demonstrate SEC of 1.2 kWh m − 3 11 and 1.5–2.0 kWh m − 3 for thermal vapor compression and 7–10 kWh m − 3 for mechanical vapor compression 12.…”