Heat recovery characteristics of membrane distillation

Abstract

A simulation model, using a mass transfer coefficient which has as its driving force a humidity difference and a heat transfer coefficient which has as its driving force an enthalpy difference, is developed for investigating the operating characteristics of membrane distillation. Optimum conditions are calculated by the model and the calculated results are proved by actual experiments. Simulated results show that the higher the feed input temperature and the cooling water input temperature, the smaller are the recycling rate, membrane area, and heat energy. For a system which has a 0.216‐m2 membrane and heat exchange area, optimum conditions of feed input and cooling water input temperature and recycling rate are 90 °C, 50 °C, and 18.5 kg/h, respectively. Furthermore, an actual experiment was performed and its permeate rate and heat input were 1 kg/h and 0.21 kW h. From the work, the latent heat recovery is seen as about 66 percent and the simulation model reliability is verified. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(3): 135–150, 1996

Fouling and wetting in the membrane distillation driven wastewater reclamation process – A review

“…[145]. The effect of varying feed flow rate (14,17,30,42, and 57 mL/s) was investigated for 18.5 ppm methylene blue dye containing wastewater by vacuum membrane distillation using a PP membrane at 50°C feed temperature [57]. At Reynolds number < 5000, significant flux increase was observed with the increase in the flow rate, mainly due to the prevention of the pore blocking by the dye molecules as well as reduced temperature and concentration polarization effect due to enhanced heat and mass transfer [57].…”

“…Due to reduced sensitivity to concentration polarization and the much high driving force resulting from a temperature difference, MD can operate at high salinities on the feed side [10]. MD demonstrates several distinct advantages such as: a 100% theoretical non-volatile salt rejection, a lower required operating temperature as compared to conventional thermal desalination processes, the ability to utilize low-grade thermal energy, a lower operating hydrostatic pressure, and less stringent mechanical property requirements for the membranes used when compared to conventional pressure-driven membrane processes such as reverse osmosis (RO) [8,9,19,[11][12][13][14][15][16][17][18]. MD has the potential to provide sustainable water recovery when heat sources (low-grade or renewable) and waste-heat from industrial processes are readily available [20,21].…”

Nanocarbon-Immobilized Membranes for Separation of Tetrahydrofuran from Water via Membrane Distillation

“…MD has numerous benefits over traditional distillation such as low operating temperatures and capital investment, and it can be combined with other membrane processes such as ultrafiltration (UF), PV, and RO . Furthermore, the heat required in MD can be obtained from alternate energy sources, such as solar energy , or microwave energy , to make it more energy efficient. While MD has been extensively studied for water desalination, very few studies have reported the applications related to solvent recovery and have been limited to ethanol and isopropyl alcohol (IPA). ,− …”

Experimental and numerical investigation of a new hollow fiber-based multi-effect vacuum membrane distillation design

“…Lee and Kim developed and validated a systematic hollow fiber VMD model, which quantified that approximately two-thirds of the input energy goes towards the enthalpy of vaporization [8]. Therefore, having a multi-effect design, where subsequent effect(s) can usefully condense the permeate vapor from previous effect(s), can result in a significant improvement in the specific energy consumption, as was also found by Kurokawa and Sawa [9]. The functional principle of the multi-effect system is that there is continuous heating of the feed water at the given effect during the evaporation process (i.e., the mass transfer process) using the latent heat of the permeate vapor from the previous effect.…”