Influence factors of the evaporation rate of a solar steam generation system: A numerical study

Abstract

Many efforts have been dedicated to improve the solar steam generation by using a bi-layer structure. In this paper, a two-dimensional mathematical model describing the water evaporation in a bi-layer structure is firstly established and then the finite element method is used to simulate the effects of different influence factors on the evaporation rate. Results turn out that: besides the high solar energy absorptivity of the first-layer, an optimum porosity of the second-layer porous material should be applied and the optimum porosity is about 0.45 in this work. This optimum porosity is determined by the balance between the positive effect of the lowering effective thermal conductivity of the second layer and the negative effect of the reduced vapor diffusivity in the second layer when the porosity is decreased. The influence of the thermal conductivity of the second-layer porous material is negligible because the effective thermal conductivity of the second layer is determined by the porosity while a larger porosity means more water in the second layer. The ambient air velocity could greatly enhance the evaporation rate, and the evaporation rate will decrease linearly with the increase of the air relative humidity. This study is expected to supply some information for developing a more effective bi-layer solar steam generation system.

Reduced Graphene Oxide Coated Hollow Polyester Fibers for Efficient Solar Steam Generation

“…The sample was irradiated by a solar simulator, and the temperature of the sample surface was recorded by an infrared camera. The solar steam performance of fibers was measured at the ambient temperature of ≈20 °C and a humidity condition of ≈12% . The weight change was monitored by electronic analytical balance.…”

“…The solar steam performance of fibers was measured at the ambient temperature of %20 C and a humidity condition of %12%. [49] The weight change was monitored by electronic analytical balance. www.advancedsciencenews.com www.entechnol.de…”

Systematic Study of the Effects of System Geometry and Ambient Conditions on Solar Steam Generation for Evaporation Optimization

“…[1,11,12] Of late, with a wide variety of new solar-absorber materials mushrooming, the solar desalination approach has begun to bear fruit. However, quite opposite to the common notion that the relative humidity (RH) affects ER, recent reports have confirmed that the solar evaporation is still able to maintain a high rate even when the RH greatly increases, [20,21] but understanding of how the evaporation can be sustained under such high humidity is still inadequate. [1,19] However, current studies often overlook the impacts from environment and the system itself.…”

“…Those neglectful factors, such as humidity that broadly changes with place and time, may be capable of manipulating the solar evaporation process. However, quite opposite to the common notion that the relative humidity (RH) affects ER, recent reports have confirmed that the solar evaporation is still able to maintain a high rate even when the RH greatly increases, [20,21] but understanding of how the evaporation can be sustained under such high humidity is still inadequate. [22] It is therefore more pressing to systematically study how the various system/ambient factors influence the evaporation process than to engineer a new solar absorber material, which sums up the motive of this work.This work shines light on the roles of relative humidity level of the ambience/system, waterlogged surface level, specific weight, carbonization thickness, and water salinity in influencing the water evaporation in a solar steam generation system, where microchanneled balsa wood was employed as an ideal research model for quantitative comparisons.…”

Solar vapor generation optimization of a carbon‐black/wood‐flour system with strength enhanced by polystyrene

“…50,51 Finally, the thermal insulation design in the improved system could almost limit all heat on the evaporation surface and thereby importantly reduce the heat losses. 52 Therefore, a relatively high evaporation efficiency has been achieved in this work.…”