Mechanical Eng.

Geothermal energy is one of the promising alternatives of power generation suitable for energy storage applications for load shifting operations. Cryogenic energy storage (CES) is an attractive option for energy storage driven by geothermal power. In this study, thermodynamic assessment of a cryogenic energy storage unit integrated to a single-flash geothermal power plant is performed and the effect of geothermal source temperature on the system performance is investigated. Initially, a resource that can supply geothermal water at 180 °C at a rate of 100 kg/s is considered. Power generated from the geothermal plant during off-peak hours is used to produce and store liquefied air. This liquefied air is used to generate power during peak hours using the heat of geothermal water. Our analysis indicates that the liquefaction unit consumes 4304 kW power in order to liquefy air for a 6-h charging period. In the discharge mode, the CES unit can produce a net power output of 12,049 kW for a 1-h operation. The flashing pressure is optimized at 255 kPa for which the total power output is 16,100 kW. The round-trip efficiency of the CES unit is determined to be 46.7% while the overall efficiency of the integrated system is 24.4%.

To get more out of geothermal power generation, integration of energy storage technologies to geothermal power plants could be used for base load peak shaving operations. Cryogenic energy storage is one the attractive options to store geothermal power during off-peak hours and produce power during peak hours. In this study, a new configuration consisting of a binary geothermal power plant, an air liquefaction unit, and a cryogenic organic Rankine cycle is considered and analyzed using the first and second laws of thermodynamics. A geothermal resource available at 180°C with a flow rate of 100 kg/s is used to power a binary cycle power plant with isopentane as the working fluid. Binary power plant produces 6253 kW power, which is used to liquefy air during a 6-h charging operation. During discharge operation, the liquefied air is pumped, and used as a heat sink for the cryogenic organic Rankine cycle with propane as the working fluid. The cryogenic organic Rankine cycle produces 1387 kW power. The liquid air after condensing operation is heated in the heaters with stored heat during charging operations and expanded in turbines for additional power generation. During the discharge operation, 10,660 kW power is produced by the combined cryogenic energy storage and cryogenic organic Rankine cycle unit while the total power generation is 16,920 kW. The cryogenic organic Rankine cycle system has a thermal efficiency of 35.3 % and a second law efficiency of 29.2 %. The storage system has a roundtrip efficiency of 28.4 % and a second law efficiency of 59.7 %. Six different working fluids are analyzed and compared for the cryogenic organic Rankine cycle. Effects of condensing temperature and compressor outlet pressure of the cryogenic organic Rankine cycle, and geothermal resource temperature on the system performance are investigated.

Geothermal energy is one of the promising alternatives of power generation suitable for energy storage applications for load shifting operations. Cryogenic energy storage (CES) is an attractive option for energy storage driven by geothermal power. In this study, thermodynamic assessment of a cryogenic energy storage unit integrated to a single-flash geothermal power plant is performed and the effect of geothermal source temperature on the system performance is investigated. Initially, a resource that can supply geothermal water at 180°C at a rate of 100 kg/s is considered. Power generated from the geothermal plant during off-peak hours is used to produce and store liquefied air. This liquefied air is used to generate power during peak hours using the heat of geothermal water. Our analysis indicates that the liquefaction unit consumes 4304 kW power in order to liquefy air for a 6-h charging period. In the discharge mode, the CES unit can produce a net power output of 12,049 kW for a 1-h operation. The flashing pressure is optimized at 255 kPa for which the total power output is 16,100 kW. The round-trip efficiency of the CES unit is determined to be 46.7% while the overall efficiency of the integrated system is 24.4%.

Despite the presence of a variety of studies dealing with the magnitude of particle Reynolds number, Re p defining transition from laminar to turbulent regime for flow through packed beds, the manner is still one of the unknowns. An approach based on the experimental data concerning upward airflow through fixed cylindrical packed beds is presented in this paper. The utilized packed beds had the following ranges of; sphericity, U, 0.55 6 U 6 1.00, packing material diameter to bed length ratio, D p /L, 0.04 6 D p /L 6 0.72, and bed porosity, e, 0.36 6 e 6 0.56. The test cases covered the ranges of particle Reynolds number, Re p 708 6 Re p 6 7772 and particle Froude number; Fr p 2.86 6 Fr p 6 10.39. The measurements of pressure drop through packed bed; DP Bed and superficial mean exit velocity; U are used to determine bed frictional effects in reference to the available literature on particle friction factors, f p. The magnitude of Re p defining transition is assumed to be 2000 with particular emphasis to the flow dynamics. The definitions of Bird et al. [R.B. Bird, W.E. Stewart, E.N. Lightfoot, Transport Phenomena, John Wiley and Sons, NY, 1960] are used to calculate f p. The calculated f p for the covered test cases are given as a function of pressure coefficient, DP* and Re p, Fr p , U, e, D p /L in the approximate ranges of laminar and turbulent flow for Re p < 2000 and Re p > 2000, respectively. The proposed separate equations of f p = f p (DP*, Re p , Fr p , U, e, D p /L) are satisfied for laminar and turbulent flows with corresponding average error margins of ±7.6% and ±18%. Furthermore ranges of transitional and fully rough flow through packed beds are estimated as 2000 6 Re p 6 4000 and Re p > 5000 with an analogy to the well-known Moody Chart in pipe flows.

An experimental study was conducted to determine the pressure drop characteristics of cylindrical packed beds through which turbulent pipe flow was passing. This study was planned to clarify the applicability of the well-known Ergun correlation proposed for beds composed with spherical particles on beds with nonspherical particles. The experimental packed beds were constructed by using two different irregular-shaped and one spherical-shaped packing materials for understanding the effects of particle shape or sphericity, particle size, bed porosity, and bed length to diameter ratio on the pressure drop. The beds were constructed by using zeolite, chickpea and glass bead materials to cover the particle sphericity range of 0.55 1.00. Systematic experiments and the data analysis procedure showed that the well-known Ergun correlation can be applied to all of the experimental beds composed with non-spherical and/or spherical particles with a maximum deviation of ±20%. This deviation can, however, be decreased to a negligible level of ±4% if some simple modifications, including the use of particle Reynolds number, Re p , a new form of particle friction factor, f * p , and some adopted empirical constants in the well-known Ergun correlation, are used.

An original model for thermodynamic analysis of a batch type fluidized bed dryer is proposed herein considering two separate systems comprised of drying air medium as a control volume and particles to be dried as a control mass. By means of the proposed model, energetic and exergetic analyses of a drying column of a batch type fluidized bed dryer are carried out as an original contribution to literature since there is no such like model in which the analyses are performed considering two separate systems. The energetic efficiencies evaluated by means of the proposed model using the data in literature are compared with those in literature and a good conformity is satisfied with an acceptable error margin of AE9%. A new correlation is also developed with a mean deviation of AE10% in order to evaluate the energetic efficiency for not only corn drying process but also drying processes of other particles at inlet air temperature of 50 C. Effects of air mass flow rate, mass of particle and ambient temperature on energetic and exergetic efficiencies are analyzed and some concluding remarks are highlighted for further studies.

This paper gives the hardware and software of a test rig with its experimental procedure, methodology and uncertainty analyses of measurements for batch type fluidized bed drying of corn and unshelled pistachio nut. The test rig is designed, constructed and operated for the analyses of drying performance of corn and unshelled pistachio nut in a batch type fluidized bed drying. The details of the test rig, the experimental procedure, the uncertainty analyses and the investigation of the effects of drying parameters on drying performance are the major scope of the paper. The accuracy of the experimental study herein is based on velocity, pressure, temperature and moisture measurements. Therefore it is vital and sensitive phenomenon for the determination of the uncertainties of the measurements before the current study as is the case with all other studies. The test rig is designed and constructed in accordance with literature review which is mentioned briefly in this paper. The basic terminology which is used in this study is also introduced herein. The overall uncertainties of velocity, pressure, temperature and moisture measurements are performed and found as 1.7%, 1.3%, 0.3% and 1.6%, respectively. Some pioneering studies related on conventional batch type fluidized bed dryers operated under atmospheric pressure are also tabulated as an original contribution to literature. Moreover, the effects of the particle mass, drying air temperature and drying air velocity on drying performance of the batch type fluidized bed dryer which is assisted with a conventional electrical heater unit are outlined without going into details in thermo-and fluid-dynamics of drying process.

An experimental study was conducted on the pressure drop characteristics of a variety of vertical packed beds in turbulent flow of air. The materials of different particle diameter, D p , with a range of sphericity Φ, 0.55 ≤ Φ ≤ 1.00 were used in random loose packing to produce beds of different lengths, L, with a range of porosity, ε, 0.36 ≤ ε ≤ 0.56. In the covered test cases the cross-sectional velocity distribution at the exit plane of the packed beds and the pressure drop ΔP Bed were measured in a particle Reynolds number range of Re p , 675 ≤ Re p ≤ 7772. The particular emphasis of the study was given to determine the influence of ε, Φ, D p , L, Re p on ΔP Bed. In this respect the measurements of ΔP Bed were compared with the well-known Ergun's Equation and the data were expressed in terms of correlations through introduced dimensionless parameters of pressure coefficient, ΔP ⁎ and exit Reynolds number Re exit. The proposed correlations of ΔP ⁎ = ΔP ⁎ (εRe p D p / L) and Re exit = Re exit (Re p D p / L) are found to be appropriate for the determination of ΔP Bed and mean exit velocity, U, respectively with an acceptable fit of experimental data in an error margin less than ± 20%. The methodology is presented in this paper as an alternative approach to the available literature on packed beds.

A batch type fluidized bed dryer is designed and constructed in order to investigate drying performance of a batch type fluidized bed drying process of corn and unshelled pistachio nut regarding to energetic and exergetic efficiencies. A series of experiments is carried out for the purpose in the covered range of 100 g≤ p m ≤300 g, 50 °C≤ T ≤75 °C, 6.87 m/s≤ m U ≤10.86 m/s and 47632≤ Re ≤75296. An increase in particle mass is found to cause an increase of drying time. On the other hand, an increase in drying air temperature and drying air velocity result in a decrease of drying time. The experimental results in terms of energetic and exergetic efficiencies are compared with the available ones in the literature by means of the previously proposed model of the authors. There is a good conformity between the present data and available data in the literature with a mean deviation of ±14% for energetic efficiency during drying process of corn. However, the deviation is raised to ±37% for energetic efficiency during drying process of unshelled pistachio nut, diverging from Eq. (9) which was previously proposed for corn drying. It can be deduced that both energetic and exergetic efficiencies are strongly dependent on air mass flow rate, particle mass and moisture content of particle to be dried and also ambient temperature.

Municipal solid waste (MSW) management has emerged as probably the most pressing issue many governments nowadays are facing. Traditionally, Waste-to-Energy(WtE) is mostly associated with incineration, but now, with the emergence of the bioeconomy, it embraces a broader definition comprising any processing technique that can generate electricity/heat or produce a waste-derived fuel. Under the ambit of the circular economy many nations are looking for, additional effort must be made to be sure of acquiring the most updated information and paving a sustainable path for managing MSW in such a frame. In this regard, we have undertaken a critical review of various technologies, with their updated progress, involved in the exploitation of MSW as a renewable resource, along with the critical advantages and limitations on energy and material cycling for sustainable MSW management. Incineration, the most widely used method, is nowadays difficult to further apply due to its dubious reputation and social opposition. Meanwhile, to address the organic fraction of MSW which currently is mostly unrecycled and causes disposal issues, the biological approach presents an attractive option. The new emphasis of bioeconomy leads us to understand how environmental biotechnologies should be better connected/integrated for more sustainable MSW management. This article is concluded with advances of future prospects, which can serve as a timely reminder to encourage competent authorities/researchers to work towards further improvement of the present MSW management system.

In this study, five models are considered for the use of biogas-based electricity and sewage sludge obtained from a municipal wastewater treatment plant for green hydrogen production. These models include alkaline, PEM, high temperature water electrolysis, alkaline hydrogen sulfide electrolysis and dark fermentation biohydrogen production processes. Energy and exergy analyses are performed on these models by applying thermodynamic procedures and the results are compared. The daily hydrogen production rates of the

The interactive influences of oscillation frequency and velocity amplitude ratio on onset of transition in pulsatile pipe flow are investigated experimentally in the ranges of time-averaged and oscillating Reynolds numbers of 1019±35≤ ta Re ≤4817±164 and 107±4≤ os Re ≤4261±145 with velocity amplitude ratio of 0.05±0.0017≤ 1 A ≤0.96±0.03 for 227 runs. Oscillation frequency is in the range of 0.1 Hz≤ f ≤14 Hz corresponding to Womersley number range of 2.72≤ ω ′ ≤32.21 covering quasi-steady, intermediate and beginning of inertia dominant regimes of pulsatile laminar flow. The onset of transition in laminar pulsatile pipe flow can be retarded up to crit ta, Re =4817 at ω ′ =3.85 in the covered experimental range. No more effect of 1 A on crit ta, Re is seen for ω ′ >8.61 although there is a considerable effect of 1 A on crit os, Re. The effect of ω ′ on crit ta, Re and crit os, Re is not observed for 1 A <0.30. The interactive influences of ω ′ and 1 A are also investigated on crit ta,

This paper presents a thermoeconomic analysis and assessment of a municipal solid waste power plant system in Gaziantep. The operation of an existing municipal solid waste power plant is described in detail and a thermoeconomical methodology based on exergoeconomic relations and specific exergy costing (SPECO) method is provided to allocate cost flows through subcomponents of the plant. SPECO method is based on a step by step procedure which begins from identification of energy and exergy values of all states defined in the present system through fuel (F) and product (P) approach and ends at the point of establishing related exergy based cost balance equations together with auxiliary equations. The actual exergy efficiency of the solid waste power plant is determined to be 47.84% which shows that 52.16% of the total exergy input to the plant is destroyed. The net electrical power output of the Gaziantep municipal solid waste power plant is 5.655 MW. The total cost rate of the power plant is evaluated as 18.44$/h as a result of thermoeconomic analyses.

This paper presents the energy and exergy analyses of some different organic fluids which can be used in an organic Rankine cycle adapted to a municipal solid waste power plant in the frame of energy recovery. The novelty of the study is to adapt a well-known organic Rankine cycle system theoretically to the existing municipal solid waste power plant where the exhaust gas with a temperature of almost 560 • C is sent to atmosphere causing both energy loss and air pollution, and also violating the related legislation. The efficient organic fluid that can be used in such a plant is estimated by means of the thermodynamic analyses. It is known that, in a typical municipal solid waste power plant, a considerable amount of energy is sent up from a plant chimney to the atmosphere. This waste energy can be utilized by using an adapted organic Rankine cycle system with a proper organic fluid. In this frame, some different organic fluids were examined and compared thermodynamically in this study. The optimal operation conditions of some organic fluids, R141b, isobutane, R245fa, n-pentane and n-hexane have been evaluated by means of ASPEN and EES software programs. The effects of the outlet temperature of heat source on the energetic and exergetic efficiencies and the net power output at a given pinch point temperature difference were investigated. It can be deduced from the analyses that n-hexane has the highest energetic and exergetic efficiencies at all outlet temperatures of the heat source such as 8.92% and 34.47% at 82.08 • C, respectively. It can also be stated that the maximum net power output is obtained by using the organic fluid n-hexane.

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