Water Mass Flow Research Articles

Multi-objective optimization and off-design evaluation of organic rankine cycle (ORC) for low-grade waste heat recovery

Organic Rankine Cycle (ORC) is a technically feasible way for low temperature waste heat recovery. Multi-objective optimization of the ORC using R245fa is conducted considering both thermodynamic performance and economic factors simultaneously, by means of Non-dominated sorting genetic algorithm-Ⅱ. The optimum operating parameters were achieved by sorting the Pareto-optimal solutions using the technique for order preference by similarity to ideal situation. A comprehensive analysis on the off-design performance of the optimized ORC system is examined. Rls is defined as the ratio of latent heat to sensible heat of the input heat to investigate the relation between the distribution of the input heat and the system performance. The effects of hot water temperature and mass flow rate, cooling water temperature and mass flow rate, superheated degree, subcooling degree and working pump rotational speed, on thermal efficiency, exergy efficiency, net power output, investment cost per unit power and Rls were investigated. The fitted correlations between Rls and the system performance indexes were derived. The novelties of the present paper are the multi-objective optimization for the further off-design behavior analysis and the quantitative relation investigation between Rls and system performance indexes. It is indicated that the direction of system optimization is to reduce Rls.

Experimental evaluation of two consecutive air-gap membrane distillation modules with heat recovery

Abstract Two rectangular modules with a total interior membrane surface area of 13.53 m2 were consecutively combined to evaluate the use of heat recovery in an air-gap membrane distillation (AGMD) system. Several operating inlet parameters including feed water temperature, mass water flow rate and salinity were investigated. The experimental results revealed that the performance of the system was improved by virtue of efficient heat recovery resulting from combining two AGMD membrane modules in series. Under optimal inlet operating parameters of cooling water temperature of 20 °C, salinity of 0.05% and flow rate of 3 l/min, the system productivity (Pp) increased up to 192.9%, 179.3%, 176.5% and 179.2%, and the thermal efficiency (ηth) by 261.5%, 232.6%, 239.4% and 227.3% at feed water temperatures of 45 °C, 55 °C, 65 °C and 75 °C, respectively. Concurrently, the specific waste heat input (Ew.h.i) decreased by 6.7%, 4.7%, 5.6% and 2.7% due to the efficient heat recovery. The results confirmed that heat recovery is an important factor affecting the AGMD system that could be improved by designing one of the two AGMD modules with polytetrafluoroethylene (PTFE) hollow fibers with a flow length shorter than the other one having a salt rejection rate of 99%.

A new method for evaluating nominal operating cell temperature (NOCT) of unglazed photovoltaic thermal module

Photovoltaic thermal (PVT) modules convert solar energy into electricity and heat. Unlike that of normal photovoltaic modules, the nominal operating cell temperature (NOCT) of PVT modules, which is used to evaluate the temperature and electrical power output, is unknown because it depends on the mass flow rate and inlet temperature of the working fluid in the module. In this paper, a new method for calculating the NOCT of PVT modules with water as the working fluid is presented. Four unglazed identical PVT modules in series were tested outdoors with various mass flow rates. The tests, which were similar to solar collector tests, were conducted from 8:30 to 16:30 on clear-sky days in Chiang Mai, Thailand, and the water inlet temperature of the first PVT module of the system was varied from 27 to 60 °C. The correlation between the NOCT of the unglazed PVT module, based on (Tfi−Ta)∕IT, and the water mass flow rate, ṁ, was determined. The calculated PVT module temperature determined with the new NOCT method agrees well with the experimental data, and 96% of the calculated results deviate only by up to ±10% from the experimental data.

Investigation of the effects of base fluid type of the nanofluid on heat pipe performance

Most recently, an ascending tendency in nanoparticles containing working fluid utilization has been observed in such thermal systems as double pipe heat exchangers and thermosiphons in so far as its advantages upon the performance of such systems. In order to investigate how the type of the base fluid affects the nanofluid’s properties used for thermal applications, an experimental test rig was setup and two different nanofluid each of which involves different base fluid, but same nanoparticles and surface active agent were tested. During the nanofluid preparation process, bauxite nanoparticles as nanoparticle material and sodium dodecyl benzene sulfonate as surface active agents were used in volume fractions of 2% and 0.5%, respectively. As the base fluid type, ethylene glycol and deionized water were utilized. The tests were conducted under diverse working conditions and vacuum pressure. Distribution of temperature ahead the heat pipe wall, efficiency and heat pipe’s thermal resistance was experimentally investigated. It was observed from the experiments that each nanofluid improved the heat pipe performance significantly; however, deionized water/bauxite nanofluid gave the best results in terms of heat pipe’s thermal performance. For each nanofluid, the maximum increment in efficiency was observed under 200 W heating power and 10 g/s cooling water mass flow rate conditions, and improvement rates were 29.5% and 13.3% for ethylene glycol-based and deionized water-based nanofluids, respectively. At least 20% of decline in thermal resistance of the heat pipe was also recorded, when nanofluid was employed as working fluid.

Thermal design of cooler in the fuel handling pneumatic system of RDE

A small size reactor called Reaktor Daya Eksperimen (RDE) is being designed by BATAN. The nuclear reactor with the power of 10 MWt based on the High Temperature Gas-Cooled Reactor (HTGR) type. The helium gas with high temperature is used to remove the heat generated from the reactor core. Therefore, the helium gas as primary cooling system of reactor is high temperature. The typical of reactor cooling system is that the primary coolant system pressure should be lower than the secondary coolant pressure. In order to load a nuclear fuel pebble into the reactor core, a fuel handling system (FHS) is applied. In the FHS, a carrier gas of pneumatic system is important to blow the fuel pebbles. The objective of the research is to calculate the thermal design of cooler heat exchanger in which the high temperature of helium gas as carrier gas is reduced to be lower temperature. In this case, a cooler is used to cool the helium gas by coolant water. Based on the specification data requirement to calculate the thermal design of cooler, the ChemCAD.6.1.4 software was performed. A shell-tube type of heat exchanger has been determined to reduce the temperature of helium gas from 250°C to be less than 60°C at pressure of 30 bars. The water as a coolant is passed into the shell-side at temperature of 28°C. In the design calculation, it has carried out through a various consideration on aspects of safety as well as optimization. The result of thermal design are as follows: the heat exchanger of shell-tube type using fixed tube sheet with heat duty of 0.3122 MJ/s, the coolant water mass flow rate is 3.55 kg/s, surface area for heat transfer is 51.4471 m2 and Log Mean Temperature Difference (LMTD) is 81.53°C. Furthermore, the design result requirement of heat exchanger based on the specification, design tolerance and manufacture in appropriate with the TEMA standard of shell-tube type. The thermal design of cooler in the carrier gas of pneumatic system is expected to provide the design of FHS.

Sınırlı Deneysel Verilerle Yapay Sinir Ağı Kullanılarak Chevron Tipi Isı Değiştirici için Termal Modelleme ve Performans Analizi

The problem of heat exchange between two or more fluids at different temperatures is one of the most important and most common problems of engineering applications. In order to solve this problem efficiently, the transfer of energy between two liquids at different temperatures is carried out by heat exchangers. Heat exchangers increase the energy efficiency as they can transfer the energy contained in the system to another part of the process instead of just pumping and wasting. A plate heat exchanger, a variant of heat exchanger, use a series of thin plates to transfer heat between two liquids. Thermal modelling of the heat exchanger is important due to determination of the outlet temperature of fluids depending on the system parameters. In this paper, an artificial neural network (ANN) model is used to simulate the thermal performance of a chevron type plate heat exchanger using water as working fluid. The ANN algorithms have a widely usage in thermal analysis studies of heat exchangers such as modelling of heat exchangers, estimation of heat exchanger parameters, estimation of phase change characteristics in heat exchangers and control of heat exchangers. The outer temperatures of the water are estimated depending on the cold water mass flow rate, inlet hot water temperature and inlet cold water temperature by using limited experimental data. Then the experimental results and the estimated results are compared for testing the accuracy and reliability of the developed algorithm. The results show that the experimental and estimated results have a good agreement. The developed network structure estimates the outlet temperatures with 2.58 % and 1.80 % for hot and cold water, respectively. In addition, the predicted performance of the network developed by applying untested input parameters was examined. Estimation accuracy was compared with theoretically calculated output temperatures by thermal analysis using the same inputs. According to the obtained results, it is seen that the theoretical results and prediction results are compatible with each other in determining the output for new inputs and the reliability of the developed network is proved in different inputs according to this result. After that, experimentally not obtained variations of the heat transfer rate, overall heat transfer coefficient and energy efficiency are determined depending on the inlet temperatures and mass flow rate of cold water.

Performance Analysis of a Heat Pipe with Stainless Steel Wick

In this study, the influences of different parameters on performance of a heat pipe with stainless steel net as wick have been presented. Experiments have been carried out for an input power range from 80 W to 160 W, constant cooling water mass flow rate of 0.0515 liter/s, and constant temperature at the inlet to condenser of 11°C. The temperatures were recorded at different power level by using a laser thermometer of the heater block, evaporator and condenser end at 50 second interval. Variation in the input power was done by varying the input voltage. It was done by a variack. Considering all criteria the copper is selected as the material of the container, water is selected as the working fluid of the heat pipe, stainless steel net is used as wick material. As copper/water heat pipes are able to tolerate storage temperatures between -65°C and 250°C, and can effectively operate between 10°C and 250°C. So a .9144 m copper tube is used to construct the heat pipe. Inside this tube stainless steel net is used as wick material to aid the flow of fluid. In the observation it is observed that the temperature of the evaporator end increases at a greater rate of the copper pipe than the heat pipe at different power level. It has been shown the variation of temperature of the heater block and the evaporator section at 80V, 100V, 120V, 140V, 160V respectively of the heat pipe and copper pipe.

Performance Analysis of Solar Desalination System for Improved Productivity by using Waste Heat of Household Chimney

This work deals with the analysis of the proposed innovative humidification-dehumidification (HD) desalination unit in which waste hot air of kitchen chimney has been used for heating brackish water. The proposed system is configured with solar air heater also, thus both heated air and heated water has been used to improve the water yield of desalination unit compared to conventional system. Mathematical modeling of propose unit based on energy balance of flat plate air heater, humidifier, dehumidifier and brackish water tank has been used to evaluate the effect of operating condition. Potable water yield found to increase (with highest productivity of 6.5 kg/day) when mass flow rate of process air increases from 0.6 kg/min to 3 kg/min. Strong dependency of water mass flow rate has also been found as productivity increases (with maximum value of 6.7 kg/day and 7.5 kg/day) by increasing the mass flow rate of brackish water in humidifier and cold water in dehumidifier respectively. The higher initial temperature of brackish water also found beneficial as it increases productivity. Finally, the thermal performance of desalination unit has been evaluated in terms of Gain in Output Ratio and comparison has been made with conventional system. The higher GOR of the proposed system ensures the better utilization of thermal energy in potable water production.

Experimental study of a novel solar multi-effect distillation unit using alternate storage tanks

Abstract In recent years, the use of solar energy has been growing exponentially and applied in a wider range of applications; one of the important applications for using solar energy is water desalination. The current work investigates the proof of concept experimental setup for a novel solar multi-effect distillation (MED) using alternate storage tanks. The experimental setup consists of a MED unit, two thermal storage tanks, and a solar collector. One storage tank is used as a charging tank while the other tank is used as a discharging tank. This unique dual-tank system stores the thermal energy to be used later in the MED unit, which improves the control of the water mass flow rate and water temperature throughout the MED process. The peak temperature achieved every day in the charging tank determines the MED production capacity. This system is designed for the tanks to alternate roles every 24 hours. The testing of this design was carried out during May 2019 in Saudi Arabia. The experimental results prove the novel concept design to work efficiently providing an average production rate of about 21 kg/day with total solar collector area of 2.7 m2 and average daily performance ratio of 2.5.

Parameter analysis and energy optimization of a four-bed, two-evaporator adsorption system

A four-bed two-evaporator adsorption chiller is a promising and environment-friendly technology that utilizes waste thermal/renewable energy to produce chilled water and high-grade potable water simultaneously. Unlike existing works that focus solely on improving chillers’ cooling performance under constant ambient conditions, this work develops optimal cycle time correlations, factoring varying external conditions, to maximize specific daily water production of a multi-bed adsorption chiller prototype. A poor selection of its operational parameters can negatively impact the chiller’s performance, particularly when the cooling and potable water demands vary. Accordingly, a dynamic-based model has been judiciously developed to study the operating characteristics of the chiller. Further, Monte Carlo simulations are employed to assess and rank the influencing strength of key operating parameters on the chiller’s performance. The parameter sensitivity on the chiller’s performance in terms of improving its cooling capacity, coefficient of performance, and specific daily water production are statistically analysed. Experiments have also been performed to validate the dynamic model. Comparisons showed good agreement between simulated specific daily water production results and experimental data with a maximum discrepancy of 4.1%. The developed correlation is able to estimate the chiller’s optimal cycle time with an R-square of 0.96. Key results revealed that the respective hot and cooling water mass flow rates entering the chiller are the most influencing parameters that quantify the chiller’s coefficient of performance. And chilled water mass flow rate and cycle time are critical parameters that impact the chiller’s cooling capacity, while the operational cycle time dictates its specific daily water production.

INVESTIGATION OF COUNTER-CURRENT FLOW LIMITATION FOR AIR-WATER IN A PWR HOT LEG EXPERIMENTAL LOOP FOR DIFFERENT GEOMETRY

Gas/liquid two-phase stratified flows in horizontal channels are frequently encountered in nuclear reactors, oil and gas pipelines, steam generators, refrigeration equipment, reflux condensers, packed columns, and heat pipes. The phenomenon known as countercurrent flow limitation, or flooding, is the limiting condition where the flow rates of neither the gas nor the liquid can be further increased without changing the flow pattern. This is the condition where the maximum air mass flow rate at which the down-flowing water mass flow rate is equal to the inlet water mass flow rate. This limiting condition, also known as onset of flooding, can occur in vertical or horizontal geometry. This work is a review of recent experimental investigations of countercurrent flow limitation (CCFL) for various hot-leg geometries of pressurized water reactors (PWRs). We compare results with those obtained from the Nuclear Technology Development Centre (CDTN) in 2005. Recent experimental results in the literature are in good agreement with the 2005 findings.

Prediction of outlet water temperature from cooling towers

This paper presents a very accurate method for water temperature prediction of outlet water from counter flow of cooling tower. This method was derived from the method of [hc A/Cpm] which is called NTU (Number of Transfer Units). The effect of the water and air mass flow rate, wet bulb temperature of the inlet air, outlet water temperature, tower range, and temperature approach have been studied. The results of comparison between the presented and the NTU methods show a very good match when the outlet water temperature is between 29 and 45°C and a difference reaches to 7.23% between 26 and 28°C. Another very good match has been noticed when the air mass flow rate is between 15.6 and 16.5 kg/s with difference reaches to 2.5 % when the air mass flow rate is between 10 and 15 kg/s. The last very good match has been noticed when the water mass flow rate is between 17.5 and 19 kg/s with the difference reaches to 1.2% when the water mass flow rate is (10 - 17 kg/s).

The non-glacial and non-cratonic origin of an early Archean felsic volcaniclastic unit, Barberton Greenstone Belt, South Africa

Recent studies have suggested that ~3.445 Ga felsic volcaniclastic rocks of member H6 of the Hooggeneoeg Formation in the Barberton Greenstone Belt, South Africa, show evidence for deposition above a major erosional unconformity under glacial to periglacial conditions and contain debris eroded from older, granitic continental crust. These conclusions represent fundamental re-interpretations of this sequence, its crustal setting, and processes of deposition. We here present evidence that these felsic strata represent terrestrial to shallow water mass flows deposits, storm-influenced shallow-marine units, and turbidity-current-like, storm-driven submarine flows, all of which lack any evidence of a glacial influence during sedimentation. They accumulated as part of a conformable stratigraphic sequence and show no evidence of mantling an erosional surface. The debris consists entirely of volcanic-derived materials. No clasts of plutonic rock are found in the conglomerates. Low-temperature diagenesis and potash metasomatism have altered primary volcanic feldspar in the volcaniclastic debris to tartan twinned microcline, previously thought to be characteristic of granitic plutonic rocks. This potassium feldspar is quite distinctive and unlike the microcline found in plutons surrounding the greenstone belt. This succession is part of a classic felsic volcaniclastic sequence deposited as an apron flanking a major felsic volcanic center.

Performance analysis of PV/T modules with and without glass cover and effect of mass flow rate on electricity and hot water generation

Two types of hybrid photovoltaic/thermal (PV/T) modules, with and without glass cover for generating hot water and electricity (combined heat and power, CHP) were tested to investigate power generation performance in terms of generated power (Pe) with module temperature (Tm) and solar radiation level (IT); and thermal performance in terms of thermal efficiency (ηm) with(Tfi−Ta)∕IT. A method for calculating the hot water temperature and the generated power was also developed and the results agreed well with the experimental data. With the model, the effect of water mass flow rate on the energy outputs was carried out by exergy analysis. It could be found that low second law efficiency was found with higher mass flow rate at low solar radiation level and high inlet water temperature.

Numerical analysis for enhancing transferred heat in porous counter flow heat exchanger

The numerical analysis is accomplished to simulate the heat transfer in double tube heat exchanger with and without porous media by utilizing ANSYS FLUENT 14.1. A geometry system is used to predict the heat transfers and pressure drop characteristics of the flow. Alumina (2.5mm diameter) as a porous media were added in to: inner tube (IP), outer tube (OP) and both tube of heat exchanger (IOP) were tested with the variation of hot and cold fluid inlet temperature, mass flow rate ratio (mr) to evaluate their influence on effectiveness of heat exchanger, Nusselt number, number of heat transfer unit. The evaluating has been performed in the steady-state. Water was used as a working fluid in a double tube heat exchanger. The study was conducted at the hot and cold water mass flow rates between ( 0.0166 - 0.0833kg / s), ( 0.05-0.116 kg/s) respectively. The inlet temperatures of cold and hot water were (20, 25 °C), (47, 55 °C) respectively. Noted from results that adding pad of porous increases effectiveness of the heat exchanger and the increasing rate of transferring heat as mass flow rate ratio increases and the highest value are obtained when alumina is in double pipe. Effectiveness decreases with increase in mass flow rate ratio but increases when using alumina as a porous media and the better value is obtained when alumina is in IOP, IP, OP and NP respectively. Effectiveness increased as the NTU increases.

Design and CFD Simulation of Solar Water Heater Used In Solar Assisted Biogas System

Difficulty in collecting conventional energy sources as well as their economic benefits including saving of time ,money, fertilizer of higher nutrient value, availability of waste easy and comfortable cooking, health benefits including the reduction diseases and environmental benefits such as saving of forest, clear surrounding were the main motivational factors for this research. However, climate temperatures in areas are too low to enable enough biogas production in small unheated digesters to meet the energy requirements of the institute, so the objectives of were to overcome the problem of energy by solar assisted with the hot water storage tank. In this research mathematical modeling of the solar water heater was designed and the analysis of heat transfer coefficient (losses) through the flat plate collector was done and the techniques that used to reduce these losses also mentioned. From the simulation results; the effect of mesh type on flat plate collector, temperature rise, and pressure drop were characterized including flow type in the laminar and turbulent using CFD approach. The FPC was needed for the preparation of the hot water for the heating of the waste food for the selected fixed dome digester with 2m2 was designed. The effect of water mass flow rate 0.01-0.05kg/s on flat plate collector, temperature rise, pressure drop, and velocity was characterized including the variation of flow types intensity using CFD approach. The optimal temperature to this process was 37 °C.The results obtained have been validated with analytical results.

The Effect of Inlet Water Mass Flow on a Double Glass Solar Still

This article describes a new method for increasing the inlet water temperature of an inclined solar still by utilizing double glass heat condensation by increasing the inlet water temperature, thereby enabling the productivity of an inclined solar still. In a conventional inclined solar still, heat condensation is the energy that is wasted into the environment. This research method uses a combination of simulation and experiments in the laboratory. The simulation was based on the energy balance of the main components of a developed and conventional inclined solar still. The authors found that the water inlet temperature on a developed inclined solar still was affected by the inlet water flow. Our method improves productivity compared to the conventional inclined solar still maximum of 35.2% on the mass flow of inlet water of 3 l/hr. The new method of evaluation was confirmed by simulation and experiments on the variation of inlet water mass flow of 1, 1.5, 2, 2.5, and 3 l/ hr. The current study provides new research results that improve the productivity of an inclined solar still that can be used for purifying water with ease and simplicity, especially when purifying water in remote areas.

Experimental study on effect of system pressure on two-phase flow pressure drop at sub-atmospheric conditions

The objective of the present work is to study two phase flow pressure drop in a helically coiled once through steam generator under sub-atmospheric conditions. Literature survey on two-phase flow pressure drop in a helical coil reveals that most of the research articles correspond to studies under high pressure and only few data are available for sub-atmospheric pressure conditions. In this study, an experimental investigation is carried out for a helically coiled tube of tube diameter 9.5 mm, coil diameter 282.7 mm and tube length 5330 mm. System is operated at sub-atmospheric pressure of 150 mbar and atmospheric pressure, respectively. Water and/or steam mass flow rate through the steam generator are taken at 36 kg/h, 54 kg/h and 72 kg/h. A 50 kW capacity DC power supply is used to supply required heat for steam generation. Experiment is carried out for power input ranging from 10 kW to 30 kW. The steam quality at helical coil exit is kept near to 0.5 and hence the power input is decided by amount of heat required to convert liquid water at inlet temperature to saturated vapour-liquid mixture with vapour quality of 0.5. The liquid to steam density ratio ranges from 7500 to 16000. In this study it is observed that the pressure drop at sub-atmospheric pressure is high as compared to atmospheric pressure.

Portable System for Sampling Liquid Atmospheric Precipitation

The paper considers the possibility of determining the permanent and random sources of pollution of the environment by the level of pollution of liquid atmospheric precipitation. The problems of liquid atmospheric precipitation testing and monitoring of pollution concentration during precipitation are outlined. The expediency of developing of a portable system that allows collecting samples of liquid atmospheric precipitation in autonomous modes at different time intervals and periods of rainfall, regardless of the place of its installation, is substantiated. The design features of the electric and mechanical parts of the device, as well as the algorithm of their work, are described. The results of modeling and checking of the working capacity of the portable device, which determine the total mass flow of water, are described.

PROCESS TOMOGRAPHY FOR MODEL FREE ADAPTIVE CONTROL (MFAC) VIA FLOW REGIME IDENTIFICATION IN MULTIPHASE FLOWS

Multiphase flows are frequently found with oil/gas/water/sand in the oil & gas industries, in processes handling dry particulates such as fluidized bed and particulate flow and slurries and sedimentation, to quote a few industrial applications. All these processes have different flow regimes with characteristic distribution of the different materials in the flow. With increasing sensor data from processes and associated possibilities for data fusion, process tomography offers non-intrusive real time sensing methods for identifying these flow regimes, which in certain cases can lead to hazards to personnel and plants in the process industries. In this paper, two scenarios of control using process tomography are presented from the oil and gas industries and powder technology. Twin plane Electrical Capacitance Tomography (ECT) with a plethora of other sensors for measuring pressure, flow rate in two phase flow involving water and air is one application. The other is particulate flow in a fluidized bed. In the case of water and air, ECT was used in a multiphase flow loop with different combinations of air and water mass flow rates enabling the generation of different flow regimes. In the case of particulate flow, different scenarios of flow conditions were generated using particulates and observing the flow regimes based on the distribution and flow rate of the particulates. For the identification of flow regimes, capacitance values from the 12-electrode ECT module at a rate of 100 frames in 200ms, were logged in for data analytics. In the final stages of using the processed data, in the case of two-phase flow 5 outputs consisting of the identified flow regimes, viz. plug, slug, annular, stratified and wavy flows were used as inputs for control and decision making. Similarly, in particulate flow ECT data were used to estimate the air velocity for fluidization as well as in identifying slug and plug flow, which are valuable to the process engineer in determining the range of air velocities for safe operation of the system used for particulate transport, often involving fluidization bed and pipelines. Tomography is used to discern features and tomometry is used in implementing the algorithms.