Duplicating Freshwater Productivity of Adsorption Desalination System Using Aluminum Metal Filings

In this paper, improving the overall heat transfer coefficient by adding aluminum species to silica gel has been studied theoretically. An adsorption desalination system is proposed, and a lumped theoretical model conducted to investigate employing the metal additives within the adsorbent bed with and without a heat recovery between condenser and evaporator. A 30% of the total mass of the adsorbent bed contents was considered to be replaced by aluminum species. According to this, the overall heat transfer coefficient has been increased by 260%, which shows a good impact on the performance of the adsorption system. Daily water productivity was increased by 70% at the worst-case, reaching up to 17 m3/day/ton of silica gel without heat recovery. By employing heat recovery with the metal filing, the daily water productivity reached 42 m3/day/ton of silica gel which is four times the productivity of the classic silica gel-based adsorption desalination system.

Optimization procedure of a new type counter–flow heat exchanger

Plenty of studies exist in books and archival journals dealing with different types of heat exchangers. In the paper an analytical approach to evaluate the overall heat transfer coefficient of a new type heat exchanger is presented. Derived equations are applied to multi-objective optimization of a very large economizer of a recovery boiler, when the exchanger mass and size should be small but simultaneously heat transfer rate high.

Analysis of the effect of ultrasonic vibration on nanofluid as coolant in engine radiator

The paper discusses the combined methods of increasing heat transfer, effects of adding nanofluids and ultrasonic vibration in the radiator using radiator coolant (RC) as a base fluid. The aim of the study is to determine the effect of nanoparticles in fluids (nanofluid) and ultrasonic vibration on the overall heat transfer coefficient in the radiator. Aluminum oxide nanoparticles of 20–50 nm in size produced by Zhejiang Ultrafine powder & Chemical Co, Ltd China were used, and the volume concentration of the nanoparticles varied from 0.25 %, 0.30 % and 0.35 %. By adjusting the fluid flow temperature of the radiator from 60 °C to 80 °C, the fluid flow rate varies from 7 to 11 lpm. The results showed that the addition of nanoparticles and ultrasonic vibration to the radiator coolant increases the overall heat transfer coefficient by 62.7 % at a flow rate of 10 liter per minute and temperature of 80 °C for 0.30 % particles volume concentration compared to pure RC without vibration. The effect of ultrasonic vibration on pure radiator coolant without vibration increases the overall heat transfer coefficient by 9.8 % from 385.3 W/m2·°C to 423.3 W/m2·°C at a flow rate of 9 liter per minute at a temperature of 70 °C. The presence of particles in the cooling fluid improves the overall heat transfer coefficient due to the effect of ultrasonic vibrations, nanofluids with a volume concentration of 0.25 % and 0.30 % increased about 10.1 % and 15.7 %, respectively, compared to no vibration. While, the effect of nanoparticles on pure radiator coolant at 70 °C enhanced the overall heat transfer coefficient by about 39.6 % at a particle volume concentration of 0.35 % compared to RC, which is 390.4 W/m2·°C to 545.1 W/m2·°C at 70 °C at a flow rate of 10 liter per minute

Performance Analysis of a Solar Cooling System with Equal and Unequal Adsorption/Desorption Operating Time

In solar-thermal adsorption/desorption processes, it is not always possible to preserve equal operating times for the adsorption/desorption modes due to the fluctuating supply nature of the source which largely affects the system’s operating conditions. This paper seeks to examine the impact of adopting unequal adsorption/desorption times on the entire cooling performance of solar adsorption systems. A cooling system with silica gel–water as adsorbent-adsorbate pair has been built and tested under the climatic condition of Iraq. A mathematical model has been established to predict the system performance, and the results are successfully validated via the experimental findings. The results show that, the system can be operational at the unequal adsorption/desorption times. The performance of the system with equal time is almost twice that of the unequal one. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling system are also evaluated.

Definition and analysis of overall heat-transfer coefficient at the sections of “hot” export petroleum pipeline operating in northern winter conditions

Background. Receiving information on overall heat-transfer coefficient of pipeline pumping down the heat oil is required for resolving a number of process challenges: definition of specific cooling-off intensity of delivered petroleum, optimization of delivery processes, insulation efficiency assessment of pipeline sections etc. Aim. The actual values of the heat transfer coefficients are the most reliable basis for the implementation of optimization and technological calculations during thermohydraulic modeling and development of measures (a) to save energy during hot pumping and (b) to increase the reliability of the “hot” pipeline in order to exclude the possibility of its self-stopping and “freezing”. In the context of assessing the technological reliability of pumping, the determination and analysis of the total heat transfer coefficient for the sections of the oil pipeline were carried out and the capabilities of this methodological approach were demonstrated. Materials and methods. In the article, by the example of 266-kilometer long export pipeline (Ø 300 mm), functioning in «hot» delivery mode is presented the calculation process of defining the actual values of overall heat-transfer coefficient in route sections, and is done the analysis of this coefficient values, operation heating mode of the pipeline and their related factors of technological reliability of oil delivery process. Results. The difference in the values of the overall heat transfer coefficient at the sections of the pipeline is shown, which allows us to come to a practical conclusion about the different intensities of the thermal processes occurring in its different linear sections (aboveground, underground with intersection of marshy soils and rivers, with and without thermal insulation, operating in non-isothermal and isothermal modes). Conclusions. The proposed approach to determining the actual values of the total heat transfer coefficient for sections of the “hot” oil pipeline in combination with the analysis of the data obtained provides opportunities that are largely in demand from a methodological point of view and extremely important from a practical standpoint.

Performance Analysis of Shell and Tube Type Heat Exchanger Using Aluminium Oxide (Al2O3) Nano-Particle

Research in convective heat transfer using suspensions of nanometer sized solid particles in a base fluid started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. The very first part of the research work summarizes about the various thermo physical properties of Al2O3 Nanofluid. In evacuated tube solar water heating system nanofluids are used as primary fluid and DM water as secondary fluid in Shell and Tube Heat Exchanger. The experimental analysis of Shell and Tube heat exchanger integrated with Evacuated tube solar collector have been carried out with two types of primary fluids. Research study of shell and tube heat exchanger is focused on heat transfer enhancement by usage of nano fluids. Conventional heat transfer fluids have inherently low thermal conductivity that greatly limits the heat exchange efficiency. The result of analysis shows that average relative variation in LMTD and overall heat transfer coefficient is 24.56% and 52.0% respectively. The payback period of system is reduced by 0.4 years due to saving is in replacement cost of Evacuated Tube Collector. Keywords: ETC; Nanofluid; LMTD; Thermal Conductivity; Overall heat transfer coefficient

Parametric investigation of a chilled water district cooling unit using mono and hybrid nanofluids

This study presents a novel parametric investigation into the performance of a district cooling system using mono (Al2O3 and TiO2) and hybrid (Al2O3–TiO2) nanoparticles in the base fluids of water and ethylene–glycol water (EG-water) at a 20:80 ratio. The study analyses the effect of variables such as secondary fluid flow rate, evaporator and inlet temperatures, nanoparticle concentration, and air flowrate on the COP, total electrical energy consumption, and design of the district cooling unit. The analysis is performed with a thermal model developed and validated using operations data obtained from the McQuay chilled water HVAC unit operating in one of the facility plants at the Education City campus. The results of the study show that the use of nanofluids increased the overall heat transfer coefficient in the system by 6.6% when using Al2O3–TiO2/water nanofluids. The use of nanofluids in the evaporator also led to an average reduction of 23.3% in the total work input to the system and improved the COP of the system by 21.8%, 20.8% and 21.6% for Al2O3–TiO2/water, Al2O3/water, and TiO2/water nanofluids, respectively. Finally, an enhancement of 21.6% in COP was recorded for Al2O3–TiO2/EG-water nanofluids at a 5% nanoparticle volume concentration.