A multipurpose desalination, cooling, and air-conditioning system powered by waste heat recovery from submarine diesel exhaust fumes and cooling water

The role of cooling and air-conditioning systems in submarines is assessed as indispensable, and a reliable water supply is essential for both crew and equipment. At the same time, the large amounts of high-temperature exhaust fumes discharged from submarine engines provide an excellent opportunity to recover and apply this waste energy in required applications. This paper introduces a novel multipurpose desalination, cooling, and air-conditioning system to recover waste heat from both the exhaust fumes and the cooling water of submarine engines. The whole system is mathematically modelled and analysed based on the actual thermo-physical parameters of the engine\u27s exhaust fumes. The analysis indicates that at cooling water flow rate of 0.25 kg/s and diesel exhaust mass ratio (X) of 0.25, the mass flux through the membrane in the desalination unit reaches 8.3 kg/m2h. Whereas for the same cooling water flow rate, the mass flux increases by 2 kg/m2h as X increases from 0.25 to 0.3. The results also show that a 160 kW cooling power is only achievable when X varies between 0.8 and 0.95 and the refrigerant mass flow rate is in the range of 0.27 kg/s to 0.34 kg/s

Integration of heat pipe solar water heating systems with different residential households: An energy, environmental, and economic evaluation

This study presents a detailed methodology for evaluating the energy, environmental, and economic contributions of heat pipe solar water heating (HPSWH) systems in various households. The hot water consumption patterns of Perth residents in Australia in one, two, and four-occupant houses are extracted in hourly basis throughout a year. The annual performance of the system is evaluated based on parameters such as saved energy, solar fraction, avoided CO2 emission, saved money, and payback period. Moreover, an experimental rig is designed, manufactured, and tested. The results show that the contribution of the solar system in meeting the hot water demand is around 99% in summer, while this contribution drops to 36–51% in winter. Almost 387–1146.8 kg of CO2 emissions can be avoided annually in Perth if HPSWH systems are integrated with the conventional heating systems. In addition, it is shown that the HPSWH system has its most economic justification in households with higher number of occupants. Moreover, the payback period is much lower for houses with conventional electric water heating systems compared to houses with LPG systems

A novel solar-driven direct contact membrane-based water desalination system

This study proposes a novel integrated solar membrane-based desalination system. The system includes vacuum glass tubes to increase absorbed solar energy and to decrease heat loss, heat pipes to transfer the absorbed energy efficiently, and a tubular direct contact membrane distillation module to use the absorbed energy more effectively. To improve the freshwater production rate and overall efficiency of the proposed system, a cooling unit was also added to the permeate loop of the desalination unit. The performance of the system was experimentally investigated without (Case I) and with (Case II) the cooling unit in summer and without the cooling unit in winter (Case III) under climatic conditions of Perth, Western Australia. The experimental results indicated that except a few minutes in the morning, the heat pipe solar system was able to provide all the required thermal energy for the desalination system. The maximum thermal efficiency of the solar system in summer reached ~78% and its exergy efficiency fluctuated between 4 and 5% for a noticeable amount of time from 10:30 AM to 3 PM. Moreover, the maximum freshwater production rate were 2.78, 3.81, and 2.1 L/m2h in Cases I, II, and III, respectively. The overall efficiency of the system improved from 46.6% in Case I to 61.8% in Case II showing the technical effectiveness of implementing the cooling unit in the permeate flow loop of the system. In addition, the daily averaged specific energy consumption in Cases I, II, and III were 407, 377, and 450 kWh/m3, respectively

Improving urban run-off quality using iron oxide nanoparticles with magnetic field

Run-off from road surfaces is a major source of pollution in the environment. The aim of this study was to investigate the efficiency of nano iron oxide under a magnetic field to improve urban run-off quality. Experiments were conducted in a 50mm diameter column made of Plexiglass in which 20 cm deep stainless steel wool was used as the medium bed. A pair of magnets, each with 0.7 T magnetic charge density, was installed around the column. The particle size of the iron oxide was determined by X-ray diffraction (XRD) analysis. Atomic absorption spectroscopy, spectrophotometer, turbidimeter, and pH meter were used to measure heavy metals, nitrate and phosphate, turbidity and pH, respectively. Results from XRD analysis revealed that the average nanoparticle size was 32 nm. The average removal efficiency for turbidity, Pb, Zn, Cd, and phosphate were 41.5, 93.9, 96.2, 88.4, and 87.4%, respectively. However, nitrate was not removed from the column tests. The results of this study showed that nano iron oxide in the presence of magnetic field has the potential to improve urban run-off quality. However, for further reduction of turbidity and nitrate removal other options should be considered

Performance analysis of a thermal-driven tubular direct contact membrane distillation system

This paper examines the performance of a thermal-driven tubular direct contact membrane distillation (DCMD) system theoretically and experimentally. A multi-step mathematical model was developed to predict the freshwater productivity of the tubular DCMD module applicable for both small and large-scale applications by considering the changes in the operational variables along the membrane’s length. The proposed model was verified by building an experimental rig which was tested under different operational conditions. The results showed that keeping the mass flow rates in the hot and cold channels either near the end or beyond the transition range of the flows results in higher water production. In addition, heating up the feed stream is more efficient for enhancing water productivity than using the same amount of energy to cool the permeate stream down. Finally, the effects of operational and physical factors on the freshwater productivity were identified and discussed

Immobilization of magnetite nanoparticles for the removal of arsenic and antimony from contaminated water

Magnetite (Fe3 O4) nanoparticles were synthesized and immobilized in a synthetic resin poly-methyl methacrylate (PMMA). The Fe3 O4 nanoparticle-PMMA composites were studied for their efficiencies of removing dissolved arsenic (As) and antimony (Sb). The effects of major environmental and operating parameters on the removal of As and Sb were investigated in batch experiments. Singular and competitive adsorption of As and Sb onto the composites were studied. The results demonstrated the capability of the Fe3 O4-PMMA composites for removing dissolved metalloids

Small scale desalination technologies: A comprehensive review

In recent decades, problems related to fresh water has become a very important issue for humans. Small-scale desalination (SSD) systems, besides large-scale desalination (LSD) systems, fulfil an important role in meeting freshwater demand by eliminating the cost of transmission and have the advantage of treating water on-site. In this study, for the first time, a comprehensive review of previous studies has been carried out on SSD systems (less than 25 m3/d water production). These systems are powered using renewable, non-renewable or hybrid sources of energy, incorporating different treatment technologies such as: reverse osmosis (RO); electro dialysis (ED); capacitive deionization (CDI); membrane desalination (MD); humidification–dehumidification processes (HDH); multi-effect desalination (MED); and hybrid technologies, including a combination of RO-UF, RO-ED and RO-MED. The advantages and drawbacks of the systems that operate using fossil fuels and renewable energy (RE) systems have been studied, considering membrane, evaporation and salinity features. Among these, solar-based desalination systems are the most popular. Accordingly, numerous studies on RO, ED, MD, HDH and MED technologies for solar-SSD systems have been compared in terms of their freshwater productivity, energy consumption and cost of produced water. Attention has also been paid to SSD systems powered via wind, geothermal, tidal and hybrid energies. It has been determined that the RO system holds the largest market share in both non-renewable (25 %) and renewable energy (40 %) systems. In addition, a comparison of low-cost SSD and LSD systems shows that SSD systems are economically competitive with LSD systems. The outlook for the future shows that the use of SSD systems powered using non-renewable energy is likely to decrease, except in areas where energy costs are very low. In addition, the use of solar-SSD systems is likely to increase, where systems that operate solely on wind or geothermal energy will be replaced by hybrid renewable energy systems

Urban runoff treatment using nano-sized iron oxide coated sand with and without magnetic field applying

Increase of impervious surfaces in urban area followed with increases in runoff volume and peak flow, leads to increase in urban storm water pollution. The polluted runoff has many adverse impacts on human life and environment. For that reason, the aim of this study was to investigate the efficiency of nano iron oxide coated sand with and without magnetic field in treatment of urban runoff. In present work, synthetic urban runoff was treated in continuous separate columns system which was filled with nano iron oxide coated sand with and without magnetic field. Several experimental parameters such as heavy metals, turbidity, pH, nitrate and phosphate were controlled for investigate of system efficiency. The prepared column materials were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDXA) instruments. SEM and EDXA analyses proved that the sand has been coated with nano iron oxide (Fe3O4) successfully. The results of SEM and EDXA instruments well demonstrate the formation of nano iron oxide (Fe3O4) on sand particle. Removal efficiency without magnetic field for turbidity; Pb, Zn, Cd and PO4 were observed to be 90.8%, 73.3%, 75.8%, 85.6% and 67.5%, respectively. When magnetic field was applied, the removal efficiency for turbidity, Pb, Zn, Cd and PO4 was increased to 95.7%, 89.5%, 79.9%, 91.5% and 75.6% respectively. In addition, it was observed that coated sand and magnetic field was not able to remove NO3 ions. Statistical analyses of data indicated that there was a significant difference between removals of pollutants in two tested columns. Results of this study well demonstrate the efficiency of nanosized iron oxide-coated sand in treatment of urban runoff quality; upon 75% of pollutants could be removed. In addition, in the case of magnetic field system efficiency can be improved significantly

Thermal performance of an evacuated tube heat pipe solar water heating system in cold season

This study evaluates the performance of a heat pipe solar water heating system to meet a real residential hot water consumption pattern theoretically and experimentally under non-ideal climatic conditions during a cold day in Perth, Western Australia. A mathematical model was developed and used to calculate the optimum number of glass tubes of the heat pipe solar collector. Based on the obtained data, an experimental rig with 25 glass tubes was designed, built, and tested as the temperature changes after 25 tubes reached the insignificant value of 0.6%. The results showed that hot water extraction had significant impact on the thermal performance of solar water heating system by increasing the amount of the absorbed energy and overall efficiency and decreasing exergy destruction. This indicates the importance of considering hot water consumption pattern in design and analysis of these systems. Auxiliary heating element was a necessary component of the system and played an important role mainly at the beginning of the operation in early morning (operation time of 19 min) and partly during the cloudy and overcast periods (operation time of 8 min). Two empirical equations relating the thermal and exergetic efficiencies of the heat pipe solar collector to the operational and environmental parameters were proposed. Comparison of the theoretical and experimental outlet temperature of the collector showed very good agreement with the maximum absolute and standard errors being 5.6% and 1.77%, respectively

Socio-hydrological modelling to assess reliability of an urban water system under formal-informal supply dynamics

Increasing water scarcity in developing world cities combined with poor performance of water supply systems has led to an increasing reliance on informal water supply systems. Although the availability of informal supply provides a coping mechanism that enables water consumers to be resilient to failures in water supply, the longer-term effects on formal water supply systems (FWSS) are uncertain, with a potential reduction of tariff recovery (RT), and in turn a service provider’s financial sustainability. This motivates an analysis of the coevolving dynamics and feedbacks involved in water systems where formal and informal components co-exist. Investigating Hyderabad, Pakistan as a case study, a dynamic socio-hydrologic system model is built, comprised of a formal system’s water and fund balance, consumer behaviour and infrastructure conditions. Simulations are executed on a monthly basis at a household level and for a 100-year period (2007–2107) using data available from years 2007–2017. Demand shift to informal is observed to be weakly associated with lower recovery rates, with household income as a major predictor. The FWSS’s financial balance, predominantly driven by infrastructure condition, appears to be less sensitive to recovery of a tariff to generate sufficient revenue