Water Volume Flow Research Articles

Система автоматичного регулювання співвідношення тверде/рідке в млинах з циркулюючим навантаженням

The operation of a ball mill operating in a closed loop with a spiral classifier depends on the vacuum of the pulp in it, which is characterized by a solid / liquid ratio. Supply to the entrance of the ball mill at the same time ore and sand classifier, as well as changes in the circulating load in a wide range greatly complicate the definition of this technological parameter. This situation has led to the fact that the solid / liquid ratio in mills operating in such conditions can not be automatically adjusted, in turn, the deviation of the pulp vacuum from the required value leads to significant losses. The study of the ball mill as a controlled object on the pulp vacuum channel made it possible to describe it using the mathematical expression given in the article. The solution of this expression makes it possible to characterize the change in the mass of the material in the mill over time, provided that a stepwise action is introduced at the entrance - the volume flow of water or ore. A constant value of the mass of material in the mill will clearly characterize the corresponding solid/liquid ratio. It has been found that it is important to study the filtering capabilities of the control object, as control actions on water and disturbing actions on ore can significantly change the vacuum of the pulp in some areas of the mill. The filtering capabilities of the mill can be investigated by its amplitude frequency characteristics, which showed that at low circular frequencies the amplitude frequency characteristics depend on the mode of operation of the mill - the magnitude of the circulating load and the cost of the source ore. Using computer technology, spatial diagrams of the relative oscillations of the mass of material in the mill from the amplitude and frequency of influences at its entrance through the ore and water. In the course of theoretical research it was determined that the only approach to ensure the required accuracy of determining the solid / liquid ratio in these conditions is to filter the signals before applying to the input of the identification unit of the ratio. Thus, the system of automatic control of the solid/liquid ratio at the entrance to the mill is implemented on microprocessor means. Its operation on the laboratory test bench made on the microcontroller showed high accuracy of stabilization of technological parameter, reliability in various conditions of change of characteristics of input signals.

EXPERIMENTAL STUDY OF HEAT EXCHANGE FROM A STEAM-GAS MIXTURE DURING HEAT TRANSFER THROUGH A RIBBED SURFACE

This article deals with the problem of heat energy transfer from a steam-gas mixture with a constant temperature of 220 °C. An experimental study of the transfer of heat energy from a steam-gas mixture by a recuperative heat exchanger with a ribbed surface at the industrial enterprise “PULP Invest”, located at the production site of the industrial park Technopolis “Khimgrad” in Kazan, is presented. The design of a heat exchanger with a ribbed surface is described. The finned surface of the recuperative heat exchanger allowed intensifying the transfer of heat flow, due to the appearance of turbulent vortices of the vapor-gas medium when it moves between the transversely arranged fins. For a heated heat carrier, water was used, which in the future is planned to be used for technological and economic needs. This paper presents the experimental method and measuring instruments. During the experiments, the initial temperature of the cold coolant (water) varied from 28.8 to 31.9 °C. The series of experiments included 7 experiments with a different volume flow of water from 60 to 120 liters/hour. The initial volume flow rate was 60 l/h, the flow rate change step was 10 l/h. The results of the studies showed that the time of the output of the studied parameters: temperature head, heat flow and heat transfer coefficient to the stationary mode was 265 s. When entering the stationary mode with a volume flow rate of cold coolant in the range from 60 to 120 l/h, the temperature head varied from 32.2 to 63 °C, the heat flow varied from 4.1 to 4.5 kW, the heat transfer coefficient varied in the range of 24.4-27.9 W/(m2 · K). The obtained results allowed establishing that the heat transfer coefficient is inversely proportional to the thermal resistance of the vapor-gas phase.

ОЦЕНКА МАССОПЕРЕНОСА ГЛАВНЫХ ИОНОВ, ЖЕЛЕЗА И МЕТАНА ПРИ РАЗГРУЗКЕ ПОДЗЕМНЫХ ВОД ЧЕТВЕРТИЧНОГО ВОДОНОСНОГО КОМПЛЕКСА В АЗОВСКОЕ МОРЕ

The specificity of the chemical composition of underground waters of the Quaternary aquifer complex of the Azov sea catchment basin, which dominates the flow volume, is considered. Using deterministic models, the volumes of runoff of the main ions, common iron, and methane are calculated. The predominant ones are sulphate, chloride-sulphate or sulphate-chloride, less often bicarbonate and chloride waters, usually of a sodium or calcium cationic composition. The average annual volume of underground water flow in the Quaternary complex is about 0.024 km3/year (66,300 m3/day). The average annual value of underground ion runoff is ~387,000 t/year, with 47.2% of this value being accounted for by sulfate ions. The average annual underground runoff of total iron and methane is ~0.968 t/year and ~0.037 t/year, respectively. The dominant contribution (over 98%) to the volume of underground runoff of the main ions, common iron and methane is made by their runoff from the Northern sections of the sea catchment basin, which is mainly due to the distribution of the module of underground water flow.

Standoff Distance in Ultrasonic Pulsating Water Jet.

The water hammer effect is the basis of technologies which is artificially responsible for the decay of continuous jets. A recently developed technique enhances the pressure fluctuations using an acoustic chamber, leading to enhanced erosion effects for various water volume flow rates. The optimum standoff distance for an ultrasonic enhanced water jet is not appropriately estimated using an inclined trajectory. The objective of this study is to comprehend the true nature of the interaction of the standoff distance following the stair trajectory and traverse speed of the nozzle on the erosion depth. Additionally, it also critically compares the new method (staircase trajectory) that obeys the variation in frequency of the impingements for defined volume flow rates with the inclined trajectory. In this study, at constant pressure (p = 70 MPa), the role of impingement distribution with the variation of traverse speed (v = 5–35 mm/s) along the centerline of the footprint was investigated. The maximum erosion depth corresponding to each traverse speed is observed at approximately same standoff distance (65 ± 5 mm) and decreases with the increment in traverse speed (h = 1042 and 47 µm at v = 5 and 35 mm/s, respectively). The results are attributed to the variation in the number of impingements per unit length. The surface and morphology analysis of the cross-section using SEM manifested the presence of erosion characteristics (micro-cracks, cavities, voids, and upheaved surface). By varying the water cluster, different impingement densities can be achieved that are suitable for technological operations such as surface peening, material disintegration, or surface roughening.

Assessing the capabilities of the Surface Water and Ocean Topography (SWOT) mission for large lake water surface elevation monitoring under different wind conditions

Abstract. Lakes are important sources of freshwater and provide essential ecosystem services. Monitoring their spatial and temporal variability, and their functions, is an important task within the development of sustainable water management strategies. The Surface Water and Ocean Topography (SWOT) mission will provide continuous information on the dynamics of continental (rivers, lakes, wetlands and reservoirs) and ocean water bodies. This work aims to contribute to the international effort evaluating the SWOT satellite (2022 launch) performance for water balance assessment over large lakes (e.g., >100 km2). For this purpose, a hydrodynamic model was set up over Mamawi Lake, Canada, and different wind scenarios on lake hydrodynamics were simulated. The derived water surface elevations (WSEs) were compared to synthetic elevations produced by the Jet Propulsion Laboratory (JPL) SWOT high resolution (SWOT-HR) simulator. Moreover, water storages and net flows were retrieved from different possible SWOT orbital configurations and synthetic gauge measurements. In general, a good agreement was found between the WSE simulated from the model and those mimicked by the SWOT-HR simulator. Depending on the wind scenario, errors ranged between approximately −2 and 5 cm for mean error and from 30 to 70 cm root mean square error. Low spatial coverage of the lake was found to generate important biases in the retrievals of water volume or net flow between two satellite passes in the presence of local heterogeneities in WSE. However, the precision of retrievals was found to increase as spatial coverage increases, becoming more reliable than the retrievals from three synthetic gauges when spatial coverage approaches 100 %, demonstrating the capabilities of the future SWOT mission in monitoring dynamic WSE for large lakes across Canada.

A Miniature Intermittent-Flow Respirometry System with a 3D-Printed, Palm-Sized Zebrafish Treadmill for Measuring Rest and Activity Metabolic Rates

Zebrafish are a preferred vertebrate model for evaluating metabolism during development, and for toxicity studies. However, commercially available intermittent-flow respirometry systems (IFRS) do not provide a suitable zebrafish-scaled swimming tunnel with a low water volume and proper flow velocities. We developed a miniature IFRS (mIFRS) with a 3D-printed, palm-sized zebrafish treadmill for measuring the swimming ability and metabolic rate of a single one- or three-month-old zebrafish with and without toxicity treatment. The 3D-printed zebrafish treadmill consists of discrete components assembled together which enables the provision of a temporary closed circulating water flow. The results showed that three-month-old zebrafish of normal physiological status had higher energetic efficiency and could swim at a higher critical swimming speed (Ucrit) of 16.79 cm/s with a lower cost of transport (COTopt) of 0.11 μmol g−1m−1. However, for a single three-month-old zebrafish treated with an antibacterial agent, Ucrit decreased to 45% of normal zebrafish and the COTopt increased to 0.24 μmol g−1m−1, due to the impairment of mitochondria. Our mIFRS provides a low-cost, portable, and readily adaptable tool for studying the swimming performance and energetic metabolism of zebrafish.

Time assessment of tectonic and climatic forcing on the formation of Khari bedrock gorge, Kachchh, western India: A mathematical approach

Formation of large-scale deformations in the upper part of the crust during Quaternary resulted in the opening of cracks on the rising/bulging landscape of the E-W trending Kachchh basin. The present study pertains to the development of a deep Khari bedrock gorge (an open crack) in the mainland region of Central Kachchh, western India. The length of the crack, the narrow bedrock gorge is 220 m and the maximum depth is 27.3 m. The estimated results show the maximum dip dimension 49.9 m and a minimum 3.1 m. The study shows that there is a regular and direct connection between the size (length) of crack openings and the rate of displacement. However, the controlling dimension of displacement and widening of the fracture depends on volumetric fluid flow, overpressure of fluid, the ratio of length-displacement/width, and an elastic limit of sandstone, the host rock. The controlling dimension of a crack is geometrically denoted by the strike and dip of a fracture. The volume of water flow, the volumetric rate on the horizontal bedrock surface, and the subsequent crack opening is directed by the fracture aperture. The opening of a crack within the contact of two surfaces may have a variable aperture corresponding to the rate of volumetric fluid flow over the crack. The statistical parameter shows that the Young's modulus of sandstone is 6 MPa and the Poisson's ratio is 0.2 and the Tensile strength 14 MPa of the fault zone. Our estimates show that the initial opening displacement of Khari gorge is ~0.6–0.8 mm with an initial volumetric rate of fluid is 22 Qc indicates enhanced discharge. Further, it is noticed that the fluid passing through the crack caused its widening by 0.2 mm with a gradual decrease of volumetric fluid rate 3Qc through the cracks during the decline condition of fluid discharge. The empirical relation of fracture direction with time factor suggests that the initial stage of gorge formation took place around 125 ka (Late Pleistocene) ago during the effective climatic condition and continuous modification for shaping the gorge took place until around 8 ka (Holocene). After that, the modification through climate is completely ceased.

Fabrication of magnetic water system for drip irrigation by using solar energy

In present investigation solar power-driven irrigation system for magnetic water was established experimentally via the improvement of greater efficiency, economic solar Photovoltaic (PV) cell panels. This system reduced the using the oil fuel for power-driven irrigation systems and reduction in greenhouse gasses. The work was established in outdoor for 7 days and seven different water volume flow rates namely 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2 Litter per minute (L/min).experiment tests on a half hourly foundation, from 8:00am to 16:00pm, with gage pressure, water flow rate, moisture, solar intensity, temperature, current, voltage measurements throughout each experiment. The results shown that directly influence of solar intensity on energy construction, also it is shown inversely proportional relationship between water flow rate and salinity of water. This system can pump and desalinate water from sewage or groundwater into the ground.

C INVESTIGATION OF HEAT TRANSFER COEFFICIENT AUGMENTATION IN DIVERGENT RECTANGULAR DUCT FOR TWO PHASES FLOW (AIR-WATER)

In this project, the flow distribution for air and water, and the enhancement of the heattransfer coefficient are experimentally studied. Experimental studies have been performed totest the influence of discharge, pitch, the height of ribs at a constant heat flux on thetemperature and pressure distributions. Along the channel of the test and the heat transfercoefficient, the water volume flow rate was about (5-12 L/min), the air volume flow rate wasabout (5.83-16.66 L/min), and heat were (80, 100,120, watt). An experimental rig wasconstructed within the test whole system. On the other hands, the channel has a divergentsection with an angle =15o with vertical axis. The study included changing in the ribs heightby using three values (12, 15, 18 mm) and changing the ribs pitch into three values (5, 8, 10mm).The results indicated an increasing in the local heat transfer coefficient as a result ofincreasing the discharge. While there was an inverse influence for the temperature distributionalong the test channel which drops when the discharge rise. The results also confirm that theincreasing in the pitch distance leads to reduce the heat transfer coefficient. Increasing theribs height increases the coefficient of heat transfer. However, the experiment heat transfercoefficient improves about (15.6 %) when the water volume flow rate increased from (5 to 12L/min), and about (18.7%) when the air volume flow rate increased from (5.83 to 16.66L/min). The best heat transfer coefficient was about (35.6 %) which can be achieved whenthe pitch decreased from (10 to 5mm). The increasing of the height from (12 to 18) mmimproves the heat transfer coefficient about (11.2 %). The best rib dimension was 18 mmheight, and 5 mm pitch, which give a maximum heat transfer coefficient (1212.02 W/m2. oC).

The Predictive Model of Surface Texture Generated by Abrasive Water Jet for Austenitic Steels

Austenitic stainless steel belongs to the best oxidation-resistant alloys, which must function effectively and reliably when used in a corrosion environment. Their attractive combination of properties ensures their stable position in the steel industry. They belong to a group of difficult-to-cut materials, and the abrasive water jet cutting technology is often used for their processing. Samples made of stainless steel AISI 304 has been used as the experimental material. Data generated during experiments were used to study the effects of AWJ process parameters (high-pressure water volume flow rate, the diameter of the abrasive nozzle, the distance of the nozzle from the material surface, cutting head feed rate, abrasive mass flow, and material thickness) on surface roughness. Based on the analysis and interpretation of all data, a prediction model was created. The main goal of the long-term research was to create the simplest and most usable prediction model for the group of austenitic steels, based on the evaluation of the practical results obtained in the company Watting Ltd. (Budovateľská 3598/38, Prešov, Slovakia) during 20 years of operation and cooperation with customers from industrial practice. Based on specific customer requirements from practice, the publication also contains specific recommendations for practice and a proposal for the classification of the predicted cut quality.

Experimental and Numerical Analysis for Earth-Fill Dam Seepage

Earth-fill dams are the most common types of dam and the most economical choice. However, they are more vulnerable to internal erosion and piping due to seepage problems that are the main causes of dam failure. In this study, the seepage through earth-fill dams was investigated using physical, mathematical, and numerical models. Results from the three methods revealed that both mathematical calculations using L. Casagrande solutions and the SEEP/W numerical model have a plotted seepage line compatible with the observed seepage line in the physical model. However, when the seepage flow intersected the downstream slope and when piping took place, the use of SEEP/W to calculate the flow rate became useless as it was unable to calculate the volume of water flow in pipes. This was revealed by the big difference in results between physical and numerical models in the first physical model, while the results were compatible in the second physical model when the seepage line stayed within the body of the dam and low compacted soil was adopted. Seepage analysis for seven different configurations of an earth-fill dam was conducted using the SEEP/W model at normal and maximum water levels to find the most appropriate configuration among them. The seven dam configurations consisted of four homogenous dams and three zoned dams. Seepage analysis revealed that if sufficient quantity of silty sand soil is available around the proposed dam location, a homogenous earth-fill dam with a medium drain length of 0.5 m thickness is the best design configuration. Otherwise, a zoned earth-fill dam with a central core and 1:0.5 Horizontal to Vertical ratio (H:V) is preferred.

On the influence of the anodic porous transport layer on PEM electrolysis performance at high current densities

In this study, the influence of the anodic porous transport layer (PTL) on the performance of a proton exchange membrane (PEM) electrolysis laboratory test cell was investigated up to a current density of 5 A*cm−2. Operation parameters such as water volume flow rate (0.2–0.8 l*min−1), temperature (40–80 °C) and pressure (1–30 barg) have been varied to study their influence on the polarisation curve. Special attention has been paid to the appearance of mass transport losses (MTL) and their dependency on the operation parameters. Two stack designs that are commercially in use - one with and one without flow channels underneath the PTL - were tested and evaluated. Fundamental differences in performance have been observed between the two cell designs. Operation parameters only show impact on performance for the configuration without flow channels. Here, MTL were observed in several cases already for current densities around and above 1.0 A*cm−2. An increase in pressure, temperature or water flow rate reduces MTL for these configurations.

Experimental Study of Heat Transfer Enhancement in Double-Pipe Heat Exchanger Integrated with Metal Foam Fins

The influence of adding fins of copper foam on the characteristics of heat transfer in a double-pipe heat exchanger is investigated experimentally. The test rig consists of two concentric pipes (copper and Perspex) to form the required double-pipe heat exchanger. The metal foam fins of 40 PPI are made from copper and set at 30° angle with the tube entrance and are distributed in sections inside the annular gap around the inner copper tube to guide the fluid flow and to disturb its structure inside the annular gap. The Reynolds number range for air is from 616 to 2343, with a constant water volume flow rate (2 lpm) in these experiments. The inlet water temperature is controlled at three values (80 °C, 85 °C, and 90 °C). Both parallel and counterflows are examined in this study. The comparison is made between the two cases of with and without insertion of copper foam fins and between parallel and counterflow mode. Results show that the average heat transfer coefficient and the average Nusselt number are increased as the Reynolds number increased, and their largest values are obtained in case of copper foam fins insertion and for counterflow mode. The important finding is no significant pressure drop is found with the enhancement of heat transfer throughout the annular gap of heat exchanger. Results also showed that the effectiveness values are doubled in case of insertion of the copper foam fins. The counterflow pattern is the most efficient flow pattern than the parallel flow.

Some Approaches to the Assessment of the Ecological State of Different-Type Reservoirs Based on the Relationship among their Main Hydrochemical Parameters

An attempt has been made to assess the status and trends of ecosystems of differenttype reservoirs in Europe and Asia (the Saratov and Volgograd ones, closing the Volga cascade, and the Iriklinsky one, which is the largest on the Ural river) on the basis of the relationship of basic hydrochemical parameters. The ecological status of water bodies was considered from the position of the stability of their ecosystems, which was evaluated using some statistical approaches based on the data of long-term monitoring. The proportion of variability of the main components, the index of plasticity (reliability) corresponding to the average module of the correlation coefficients of hydrochemical parameters were calculated. The desirability function method for qualitative assessment of aquatic ecosystems, characterized by a large number of hydrochemical parameters, was applied. This method allowed minimizing a large amount of information and overcoming the dimension problem. The results of the application of the calculated statistical indices allow us to consider the volume of water flow and summer water temperature as the main factors affecting the content of basic hydrochemical ingredients in the Volgograd and Iriklin reservoirs. The hydrochemical regime of the Saratov reservoir, due to its high flow rate, is determined mainly by the waters coming from the Kuibyshev storage reservoir, and therefore such dependencies were not established. During the study period, the entropy index in the Volga reservoirs fluctuated at the same level, but significantly increased in the Iriklinsky one. The highest values of plasticity are characteristic for the Iriklinsky reservoir, which has the greatest spatial and seasonal heterogeneity of its aquatic environment. During the study period, there have been trends of increasing plasticity in the Saratov reservoir and decreasing in the Iriklinsky one. A decrease in the desirability function indicates some destabilization of their ecosystems.

Design and analysis of double-pipe heat exchanger with new arrangements of corrugated tubes using honeycomb arrangements

Double-pipe heat exchangers are utilized as a part of mechanical procedure to recuperate heat between two process liquids. The main objective of this project to augment the heat transfer in a counter flow double-pipe heat exchanger filled with inner tube of honeycomb arrangements. To increase the efficiency of double-pipe heat exchanger is made up of concave and convex corrugated type of outer and inner tubes. Hot water (inner tube) and cold water (outer tube) inlet temperatures were maintained at 40°C and 8°C, respectively. Investigation were performed for inward tube (high temperature water) and external tube (cool water) volume flow rate was kept at 15 L per minute and 20 L per minute. Different parameters such as overall heat transfer coefficient, Nusselt number, pressure drop, friction factor, convective heat transfer coefficient, and effectiveness were obtained and compared for new arrangements of corrugated tubes filled with and without honeycomb arrangements. The analysis was carried out for porosity range is 0.8 and pore density (greater than 9 parts per litre) to ensure high effectiveness. Maximum effectiveness was obtained for heat exchanger made of concave corrugated outer tube and convex corrugated inner tube with honeycomb structure. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/TSCI200331157E">10.2298/TSCI200331157E</a><u></b></font>

Evaluation of thermal performance for natural and forced draft wet cooling tower

This paper presents an experimental and numerical investigation of the thermal performance of natural draft wet cooling tower (NDWCT). The experimental investigation is carried out under natural draft condition and forced draft condition created by an axial fan. The operational parameters considered in this study are the thickness of the fill (10 and 20 cm), inlet water temperature (40, 45, and 50 °C) and inlet water volume flow rate (5.68, 7.75, and 9.46 L/min). The experimental results showed that the thermal performance is improved when the fans are used with the NDWCT. The temperature difference between inlet and outlet and effectiveness increase by 35% and 37.2%, respectively at fill thickness of 20 cm and water volume flow rate of 11.35 L/min. The temperature distribution of the air and the relative humidity were numerically simulated for both cases of natural and forced draft by employing the commercial CFD software ANSYS Fluent 15. The experimental and numerical results were validated with results from a previous work and showed a good agreement. The experimental results showed that the effectiveness increase by 22% and 30% for NDWCT and FDWCT respectively when in case of fill thickness 20 cm.

Research on film condensation heat transfer at the inside of spiral coil tube

In this paper, especially considering the influence of viscous force, gravity and centrifugal force on condensation heat transfer, a theoretical model of laminar flow for film condensation heat transfer of pure steam in the spiral coil tube was presented. The solution method of film thickness and heat transfer coefficient was analyzed theoretically, the condensation heat transfer coefficient in the spiral coil tube under different steam volume flow rates was obtained. In order to verify the correctness of the new correlation, the experimental platform of film condensation heat transfer was designed and built up. Heat transfer measurements were performed for the saturated steam volume flow rate from 2.7 to 5.2 m3/min, and for the cooling water volume flow rate from 1.5 to 7.0 m3/h, and cooling tube wall temperature is 20 °C. The experimental results were compared with the calculation results of the well-known Kang's correlation and the new correlation. The relative error of results between the new correlation and the experiment is within 15%, which verifies the accuracy of the new correlation proposed in this paper. And the new correlation can be used to calculate the heat transfer coefficient of film condensation in the spiral coil tube. In addition, the experimental results show that the condensation heat transfer coefficient increase with the increasement of steam volume flow rate.

Simulation and experiment on direct contact membrane distillation regenerator in the liquid dehumidification air-conditioning system

Liquid dehumidification air-conditioning (LDAC) systems are a promising dehumidification technology that reduce energy consumption. However, in hot and humid climates, liquid regeneration deteriorates the performance of regenerators and limits their applications. Therefore, developing methods to ensure regeneration performance in harsh climates as well as to reduce the droplet splatter is a challenging task that must be undertaken to advance the technology and make it viable. In this study, a novel regeneration method using the direct contact membrane distillation (DCMD) regenerator was applied to the LDAC system. The mathematical model of the DCMD solution regeneration process was developed and verified through PTFE hollow fiber membrane liquid regeneration experiments. The impacts of membrane length, temperature, concentration, and solution volume flow on the temperature and concentration of the resultant solution at the outlet, regeneration capacity mass transfer coefficient, membrane water flux, and heat flow were analyzed. The results indicate that the concentration of the solution at the outlet linearly increases from 34.9% to 35.9% when the solution is heated from 40 to 85 °C. However, when the temperature of the solution is less than 45 °C, the solution concentration at the outlet is lower than that at the inlet, which indicates that the regeneration capacity is negative. Thus, the solution temperature at the DCMD regenerator inlet should be maintained at >65 °C to provide a higher and stable regeneration efficiency. Finally, it was established that a flow rate that is either extremely high or low would impair the DCMD regeneration, whilst a volume flow of 1800 ml min−1 is still most appropriate for the regenerator to regenerate high-concentration solutions. Research on the cold side indicates that when the temperature of the water does not exceed 30 °C, the regenerator still has the ability to regenerate, and increasing the volume flow of water can enhance the regeneration effect.

Experimental study on the flow and heat transfer characteristics of nanofluids in double-tube heat exchangers based on thermal efficiency assessment

Thermal performance and pressure drop of TiO2-H2O nanofluids in double-tube heat exchangers are investigated. The influence of the thermal fluid (water) volume flow rates (qv = 1–5 L/min), nanoparticle mass frictions (ω = 0.0%, 0.1%, 0.3% and 0.5%), nanofluids locations (shell-side and tube-side), Reynolds numbers of nanofluids (Re = 3000–12000), and the structures of inner tubes (smooth tube and corrugated tube) is analyzed. Results indicate that nanofluids (ω = 0.1%, 0.3% and 0.5%) can improve the heat transfer rate by 10.8%, 13.4% and 14.8% at best compared with deionized water respectively, and the number of transfer units (NTU) and effectiveness are all improved. The pressure drop can be increased by 51.9% (tube-side) and 40.7% (shell-side) at best under the condition of using both nanofluids and corrugated inner tube. When the nanofluids flow in the shell-side of the corrugated double-tube heat exchanger, the comprehensive performance of nanofluids-side is better than that of the smooth double-tube heat exchanger.

Thermal Performance of Plastic Receiver in Solar Collector

A plastic tubes used as absorber of active flat plate solar collector (FPSC) for heating water were studied numerically and experimentally. The set-up is located in Babylon (republic of Iraq) 43.80 East longitude and 32.30 North latitude with titled of 450 toward the south direction. The study involved three dimensions mathematical model for flat coil plastic absorber which solved by FLUENT-ANSYS-R.18 program. Experiments were conducted at outdoor conditions for clear days on January and February 2018 with various water volume flow rates namely (500, 750, 1000, 1250, and 1500 Liter per hour LPH) on each month for Reynolds number range of (1 x 104 to 5 x 104) through the receiver. The experimental results showed improvement in absorber input - output temperature difference, collector efficiency, and water storage temperature; the maximum input - output temperature difference is 3.1 °C, the maximum collector efficiency is 79%, and the maximum water storage temperature is 67 °C. The comparison validates a good agreement between the numerical and experimental results at variable operation conditions with maximum deviation of 4.2%. Also the experimental results were compared with previous study for similar condition and gave a good improvement.&#x0D;