Increase In Outlet Temperature Research Articles

Numerical investigation in an indirect concentrated solar thermal dryer incorporated with discrete mirrors

The objective of this study is to promote the production for small scale drying industries by reducing the drying time of agricultural products. Discrete mirrors are arranged in a parabolic fashion and used as reflectors to concentrate the incoming solar radiation. The available solar flux is doubled by using this discrete arrangement of mirrors. Optical simulations are performed using Monte Carlo Ray tracing algorithm and various effects were studied to select the best arrangement of mirrors. The concentrated type dryer has been numerically simulated and no-load testing is performed using ANSYS Fluent. Simulation is carried out for various inlet velocities from 0.1 to 1 m s−1. The concentrated setup operates between 0.4 and 1 m s−1 of velocity to obtain temperature in the range of 40–70 °C. The maximum and minimum increase in outlet temperature is 23.52% and 2.87%, and the Nusselt number enhancement is 18.94% and 4.15%, respectively.

Thermal performance evaluation of the parabolic trough solar collector using nanofluids: A case study in the desert of Algeria

The use of Parabolic Trough Solar Collector (PTSC) is currently the best option for widespread application in industries operating at temperatures from 60 to 400 °C. Numerous studies have been conducted to enhance the thermal performance of the PTSC using synthetic oils as heat transfer fluids. In this study, the thermal performance of parabolic collectors was enhanced using Metallic Oxide Nanofluids (CuO, SiO2, Al2O3, TiO2) based on Therminol VP-1™ at 4 % volumetric concentration as heat-transmitting fluids. A thermal model was developed and validated through experimental and theoretical study, while the results showed good compatibility in the outlet temperature with an error rate of 0.184 % for experimental and 0.29 % for theoretical studies. Moreover, various theoretical models of the thermal properties of nanofluids were analyzed to determine the model that matches and simulates this study. The findings indicated that nanofluids enhanced the thermal efficiency of the PTSC system compared to pure Therminol VP-1™. Specifically, CuO/Therminol VP-1™ demonstrated the most significant improvement, increasing thermal efficiency by 1.03 %. Furthermore, the results also showed that the addition of CuO, TiO2, Al2O3, and SiO2 nanoparticles led to an increase in outlet temperature by 9.57 %, 6.04 %, 5.21 %, and 3.08 %, respectively.

Optimization research on energy consumption and carbon emissions in hydrogen-blended natural gas pipeline networks considering compressor performance - A case study of the west-east gas pipeline (line 1)

The blending of hydrogen into natural gas can utilize existing natural gas pipeline infrastructure to achieve long-distance, large-scale, and cost-effective hydrogen transportation. However, the introduction of hydrogen poses a series of new technical and safety challenges to the operation of natural gas pipelines. Addressing these issues, this paper focuses on minimizing compressor station energy consumption and carbon emissions as objective functions, conducting a comprehensive analysis of station operation modes. Incorporating the characteristics of the model, the soft frost search strategy, the hard frost penetration mechanism, and the positive greedy selection mechanism are introduced to propose the IRIME algorithm. Comparisons are made with well-performing optimization algorithms using classical test functions to evaluate algorithm performance. To further validate the algorithm's accuracy, the West-East Gas Pipeline (Line 1) is considered, comparing the convergence speed and precision of the IRIME algorithm, leading to its selection for solving the model. Furthermore, consider analyzing the impact of different hydrogen blending ratios on the performance curves and operating points of compressors. Results indicate that compared to conditions without hydrogen blending, the compressor outlet temperature and pressure drop increase for hydrogen blending ratios of 5%, 10%, 15%, and 20%; as the hydrogen blending ratio increases, the efficiency of fuel-driven compressors, efficiency of electrically driven compressors, and average efficiency of compressor units decrease; with an increase in hydrogen blending ratio, carbon emissions from fuel-driven compressors and electric-driven compressors both decrease. In conclusion, with an increasing hydrogen blending ratio, total energy consumption increases by 3.14%, 5.69%, 8.68%, and 10.90%, while total carbon emissions decrease by 2.99%, 5.36%, 8.32%, and 10.68%. These findings provide valuable insights for operational guidance in the field.

Numerical study of combustion flow field characteristics of industrial gas turbine under different fuel blending conditions

Numerous studies have shown that the mixture of fuel and oxidant significantly influences the flow characteristics and pollutant emissions within the combustion flow field. This study investigates the effects of various methane fuel blending ratios (0.19–0.41) on combustion flow, emission characteristics, performance parameters, and field synergies through numerical simulation. Combustion simulation employs the SST k-ω and flame-generated manifold models. The findings indicate that as the fuel blending ratio increases from 0.19 to 0.41, the temperature at the front end of the cyclone gradually rises, resulting in an average outlet temperature increase of 165 K. The outlet temperature uniformity index (γT) shows minimal variation, while the Pattern Factor (PF) and NO emissions at the outlet gradually increase. Additionally, the fuel blending ratio (α) exhibit a limited impact on CO emissions at the outlet. When α ≥ 0.39, the peak temperature is located in the cyclonic region, resulting in an extremely heterogeneous outlet temperature distribution. Under various operational conditions, NO is primarily concentrated in the high-temperature region near the wall, and the pollutant emission merit function (fe) gradually increase with α. The optimum field synergy and overall performance for the low-resistance heat transfer are attained at α = 0.37. Significant velocity shocks are observed in the near-wall regions on both sides of the combustion chamber, when α ≥ 0.35, based on DMD analysis. To achieve low NO emission, uniform outlet temperature, and ensure safe, long-term operation of the gas turbine, the fuel blending ratio of 0.3 to 0.35 is advised.

Numerical simulation on converting abandoned wells into double-well open-loop geothermal system

Converting abandoned oil wells into geothermal systems holds immense potential and has garnered international attention. However, research on converting abandoned oil wells into Open-Loop Geothermal Systems (OLGS) remains insufficient and requires further exploration. To address this gap, this study utilizes COMSOL software employing the Finite Element Method (FEM) to establish a numerical model of a double-well OLGS with 3D multi-physics field coupling, investigating geothermal extraction through numerical simulation. The findings indicate that in double-well OLGS, utilizing high flow rates in the early production stage and lower flow rates in the later stages enhances system thermal power. Additionally, employing lower inlet temperatures in the early production stage and higher inlet temperatures in the later stages favors geothermal extraction. Higher geothermal gradients and larger well spacings further benefit geothermal extraction. Increasing the length of the production well's insulating layer in the early production stage helps minimize heat loss. The outlet temperature exhibits high sensitivity to flow rate and geothermal gradient throughout the production phase, while sensitivity shifts towards inlet temperature and well spacing in the later stages. In the five-spot OLGS, outlet temperature and thermal power increase with a reduction in the number of production wells; moreover, assuming identical outlet temperatures (100 ℃) after 50 years of production, the thermal power of the five-spot OLGS exceeds that of the double-well OLGS by an average of 20937.88 kW per year.

Design consideration of a filled layer U-pipe evacuated tubular solar collector with flat diffuse reflector: energy and exergy analysis

A lack of research about critical design factors, notably the center-to-center tube spacing-to-tube diameter ratio (C/D) and the relationship between length and diameter, is conspicuously evident in the context of U-pipe evacuated tubular solar collectors (ETSCs) employing the filled-layer approach. Furthermore, using a U-pipe configuration in ETSCs coupled with a flat diffuse reflector (FDR) remains conspicuously absent from the scientific literature as a potential enhancement strategy. This study evaluates the influence of collector tube length, diameter and the C/D on output parameters, including T out , η En and η Ex . The findings reveal that while η En experiences a decrease with increasing C/D, the η Ex does not reach its minimum value when C/D was three due to the corresponding increase in outlet temperature. Furthermore, introducing the FDR into the filled U-pipe evacuated tubular solar collector enhances daily η En and η Ex by 12.91% and 0.65%, respectively. Moreover, a suggestion of the length and diameters of a filled type boosted with FDR is L = 2000 mm for Dg/Dp = 47/37 mm and L = 1800 mm when Dg/Dp = 58/47 mm, which has the maximum η Ex per day of 2.87% and 1.87%, respectively. However, if the objective is to maximise η En per day, lengths of L = 1450 mm for Dg/Dp = 47/37 mm or L = 1200 mm for Dg/Dp = 58/47 mm would be preferable. Abbreviations: ESC: evacuated solar collector; ETC: evacuated tubular collector; DUFET: filled-type evacuated tube with double U-tubes; ETSC: evacuated tubular solar collector; FDR: flat diffuse reflector; C/D: center-to-center tube spacing to the collector's tube diameter (cover tube); Dg/Dp : diameter of cover tube and diameter of absorber tube

Energy, exergy, economic, and environmental analysis of a high-temperature heat pump steam system

Industrial steam is widely recognized as a valuable form of heat currency, possessing considerable social and economic significance. As the industry shifts to low carbon emissions, there is an urgent need to reduce CO2 emissions from industrial steam generation. The analysis of a high-temperature heat pump steam system (HTHPSS), which recovers industrial waste heat to produce high-temperature steam at 170 °C, includes evaluations of its energy, exergy, economic, and environmental (4E) to determine whether it can replace a coal-fired boiler. The economic analysis considered the recovery value of waste heat and the effect of CO2 trading prices. Optimization calculations were performed to investigate changes in the waste heat temperature and condenser outlet temperature. The study also offers recommendations for operational conditions and optimization strategies for the HTHPSS. The results indicate a positive correlation between the system coefficient of performance (COP) and the waste heat utilization rate with waste heat temperature and condenser outlet temperature. The maximum COP value is 2.73. The total exergy efficiency initially increases and then decreases as waste heat temperature increases. It also decreases as the condenser outlet temperature increases, reaching a peak value of 43.26 %. The waste heat temperature needs to be at least 59 °C to generate a net profit, with a corresponding payback period (PBP) of 4.40 years. The minimum PBP is 0.03 years, independent of waste heat temperature. The annual emission reduction increases as waste heat temperature increases and decreases as condenser outlet temperature increases. These results indicate that a HTHPSS could replace a coal-fired boiler and offer guidance for design optimization.

Thermodynamic Analysis of Comprehensive Performance of Carbon Dioxide(R744) and Its Mixture With Ethane(R170) Used in Refrigeration and Heating System at Low Evaporation Temperature

Abstract In this paper, the system performance of R744 and R744/R170 mixed refrigerants used in a single-stage compression transcritical cycle at low evaporation temperature was studied by simulation method, and the effect of evaporation temperature, outlet temperature of gas cooler, R170 ratio on coefficient of performance (COP), discharge temperature, optimal pressure, and compression ratio were analyzed. The results show that Popt increases and decreases with the increase of outlet temperature and evaporation temperature of gas cooler and increases first and then decreases with the increase of R170 proportion. In the heating system, the maximum and minimum Popt of R744/R170 (25/75) were 1.35 MPa, 3.6 MPa, and 2.6 MPa and 1.23 MPa, 2.93 MPa, and 1.87 MPa lower than that of R170 (0%, 22.4%, and 50%); compared to pure R744, the system pressure of the mixed R744/R170 is lower. The COPe and COPh increase with the increase of evaporation temperature and decrease with the increase of outlet temperature of the gas cooler. With the increase of R170 proportion, they first decrease and then increase; the maximum COPe and COPh of R744 were 22.4%, 29.6%, and 21.2% and 10.3%, 13.8%, and 10.8% higher than those of R170 at 22.4%, 50% and 75%, respectively.

Energy Modeling of an Aquaculture Raceway

Abstract Large seasonal temperature variations in aquaculture source water leave aquaculture ponds and raceways susceptible to temperature variations leading to nonoptimal growing conditions. Such conditions may slow down the growth rate and make aquatic species vulnerable to disease and potential death, leading to economic setback for aquaculture farmers. Therefore, it is advantageous to predict the temperature of aquaculture raceways under the influence of seasonal variations and study the parameters that contribute to these variations. This allows one to develop strategies and processes to better regulate the raceway temperature to maximize its productivity. A numerical energy model was developed to simulate the temperature of water inside an aquaculture raceway, and a parametric study was conducted to investigate the influence of various key parameters on the raceway temperature. It was found that surface area and flowrate have a large effect on the raceway temperature, while depth of raceway had little effect. The largest surface area tested produced outlet temperatures and heat transfer values that were 6.2% and 76% higher, respectively, than the smallest surface area tested. Decreasing flowrate from the reference value of 43 L/s to 1 L/s resulted in an 83% increase in average outlet temperature. It was also observed that the variations in the ambient air temperature alone have negligible effect on the raceway temperature. The model was further implemented to simulate the temperature of raceways located at different geographical locations.

Experimental Study on the Cleaning Performance of Hot Air Flow Cleaning Device

When processing wet rice, the efficiency of the combine harvester diminishes due to the heightened surface water content of the paddy. To address this, a hot air flow cleaning apparatus was engineered, and the effects of its operational parameters on cleaning performance were investigated. Outlet temperature, fan speed, louver sieve temperature, louver sieve inclination, and eccentric wheel speed were selected as experimental factors, and a single-factor test was carried out, with cleaning loss rate and impurity rate as test indexes. The results of the single-factor test show that louver sieve inclination and eccentric wheel speed had no obvious influence on the cleaning loss rate or impurity rate. The cleaning loss rate decreased with the increase in outlet temperature and louver sieve temperature but increased with the increase in fan speed. The cleaning impurity rate increased with the increase in outlet temperature and louver sieve temperature but decreased with the increase in fan speed. Based on the results of the single-factor test, a central composite rotatable test was adopted to attain the optimal operation parameters of the hot air flow cleaning equipment. Parameters like outlet temperature, fan speed, and louver sieve temperature were established as test factors, with the loss and impurity rates chosen as the evaluation metrics. Optimization using response surface methodology yielded the following parameters: an outlet temperature of 40.7 °C, a fan speed of 1300 rpm, and a louver sieve temperature of 50 °C. Under these conditions, the loss rate was observed to be 0.75% and the impurity rate stood at 1.75%. These findings can guide the design of cleaning mechanisms and the determination of operational parameters.

A numerical simulation and analysis of the discharge characteristics and heat transfer performance during the ice-storage system

During the ice melting process of the external ice-melting ice storage system, there is uneven ice melting in the different height of the ice layer, which directly affects cold discharge characteristics. Reasonable water flowrate of the distributor can improve cold discharge characteristics. A 3D dynamic mesh model was built using the computational fluid dynamics (CFD) method, phase change interface movement with time was tracked. And the ice-water heat transfer characteristics at different heights were analyzed and the influence of water distributor's flowrate ice-water mixture heat transfer performance and cold discharge characteristics during ice-melting process were also explored. The results showed that the ice layer above 30 mm height, The Nusselt number of water space averagely increased 23.8 % when the height had 5 mm increment. When the water flowrate increased by 0.01 g/s, the average Nusselt number of the water space increased by 6.7 % and the water outlet temperature increased by 12 % on average. Though the increasing of water flowrate can improve the convective heat transfer between ice and water, it also resulted in the standard temperature deviation and water outlet temperature increase. Under the premise of satisfying the cooling load, the water flowrate of the distributor should not be excessive.

Performance investigation of an all glass evacuated tube solar collector with an innovative heat exchanger design using TiO2-H2O nanofluids- an experimental study

ABSTRACT The objective of the current study is to experimentally analyze the thermal performance of an all-glass evacuated tube solar collector (ETSC) with an innovative heat exchanger design by employing TiO2-H2O nanofluid as a heat transmission fluid. Different higher volume concentration (v/c) of TiO2 nanoparticles, i.e. 0.83%, 0.9%, and 0.94% are examined to explore the impact of the nanofluids on the ETSC performance in comparison with only water based ETSC. An outdoor experimental investigation has been carried out using nanofluid at 0.6, 0.7 and 0.8 l/min volumetric rates of flow and its impact using serpentine copper tube coil having uniform pitch distance of 14.3 cm with aluminum fins attached on both side of coil having diameter 12 mm and thickness 1 mm, respectively. The study indicates that thermal performance of ETSC increases with the rise in volumetric flow rate with higher v/c of nanoparticles. For this condition, the temperature rise of water using nanofluid is higher than simple water-based ETSC system, recording an increase in outlet temperature by 4.21%. The maximum thermal efficiency obtained is 52.33% at 0.9% v/c and 0.8 l/min. A comparative assessment between the obtained results and some of the published results reveals that by using serpentine copper coil attached with aluminum fins, with higher concentrations of TiO2 nanoparticles and maintaining higher volumetric flow rate, thermal efficiency of ETSC can be much improved.

Numerical investigation of heat transfer and fluid flow characteristics of ternary nanofluids through convergent and divergent channels.

The characteristics of nanomaterials have garnered significant attention in recent research on natural and forced convection. This study focuses on the forced convection characteristics of ternary nanofluids within convergent and divergent channels. The ternary nanofluid comprises titanium oxide (TiO2), zinc oxide (ZnO), and silver suspended in water, which serves as the base fluid. Using COMSOL Multiphysics 6.0, a reliable software for finite element analysis, numerical simulations were conducted for steady and incompressible two-dimensional flow. Reynolds numbers varying from 100 to 800 were employed to investigate forced convection. Additionally, we explored aspect ratios (channel height divided by the height of the convergent or divergent section) of -0.4, -0.2, 0, 0.2, and 0.4. Our findings revealed that only at aspect ratio a = 0.4 did the average outlet temperature increase as the Reynolds number rose, while other aspect ratios exhibited decreasing average temperatures with declining Reynolds numbers. Moreover, as the Reynolds number increased from 100 to 800 and the total volume fraction of the ternary nanofluids ranged from 0.003 to 0.15, there was a significant 100% enhancement in the average Nusselt number. For clarity, this article briefly presents essential information, such as the study's numerical nature, fluid properties (constant-property fluid), and the methodology (COMSOL Multiphysics 6.0, finite element analysis). Key conclusions are highlighted to enable readers to grasp the main outcomes at a glance. These details are also adequately covered in the manuscript to facilitate a comprehensive understanding of the research. The utilization of this emerging phenomenon holds immense potential in various applications, ranging from the development of highly efficient heat exchangers to the optimization of thermal energy systems. This phenomenon can be harnessed in scenarios in which effective cost management in thermal production is a critical consideration.

Contribution of the Provençal Well for the Improvement of the Thermal Comfort in the Building in Turbulent Regime

In the current energy context, geothermal systems are highly developed in the building field. Among these interesting systems on the energy plan, one finds in particular the earth-to-air heat exchanger commonly called ‘Canadian or Provençal well’. It consists of tubes buried in which the ambient air is pushed in order to be refreshed in contact with the ground whose temperature is quasi-constant throughout the year. In this work, a study of the performance of an earth-to-air heat exchanger was undertaken by means of numerical modeling of heat exchange by forced convection in a buried tube. The transfer equations in the tube are discretized using the finite volume method in turbulent regime and solved using the Thomas algorithm. For the determination of the ground temperature, the model of the semi-infinite mass subjected to a periodic excitation was adopted. The soil temperature was used as a boundary condition for the buried tube.
 The results show that the interest of the earth-to-air heat exchanger is major, since it improves throughout the year, the thermal conditions sought. It intervenes in an effective way on the damping of the thermal amplitudes in the building. The variation of the diameter and the length of earth-to-air heat exchanger does not influence notably the distribution of the streamlines and isotherms but affect significantly the values of stream function and temperature inside de tube of the earth-to-air heat exchanger. When diameter of the pipe increases, the outlet temperature increases. The increase of the length of the earth-to-air heat exchanger leads to the isotherms increase as a result of the intensification of heat exchange between the walls and the convective jet. The temperature in the air outlet compartment is lower as the length of the earth-to-air exchanger increases.

Performance improvement methods for quartz tube solid particle fluidized bed solar receiver

The conditions to improve performance of quartz tube silicon carbide (SiC) solid particle fluidized bed solar receiver was investigated with computational fluid dynamics (CFD) simulations. The difficulty of experimenting all possible operating conditions was overcome by preparing CFD base input with appropriate models and parameters. The amount of SiC in the bed, the size of particles, and the air inlet velocity were considered as variables. After model verification, in order to evaluate the effect of particle addition, bed without solid particles were simulated first. Outlet temperature of single-phase receiver was calculated as 421 K. Outlet temperatures of 913 K, 895 K, and 881 K were obtained for 400 μm diameter particles in 0.3 m bed height for air inlet velocities of 0.25, 0.3, and 0.35 m/s. Air outlet temperature decreases as air inlet velocity increases. On the other hand, too much reduction at inlet velocity retards the system performance since it affects fluidization. For 400 μm particle diameter and bed height of 0.2 m, outlet temperatures of 994 K, 974 K, and 955 K were found for the same air inlet velocities above. As bed height decreases, air outlet temperature increases. For particle diameters of 300 and 500 μm for bed height of 0.3 m, outlet temperatures of 980 K and 878 K were calculated for appropriate minimum fluidization velocities. Outlet temperature increased with decreasing particle size.

Long-term operation of tunnel-lining ground heat exchangers in tropical zones: Energy, environmental, and economic performance evaluation

The application of traditional borehole ground heat exchangers (GHEs) is extremely limited in tropical zones because of the performance degradation induced by thermal imbalances over the years. Unlike traditional borehole GHEs, tunnel-lining GHEs have absorber pipes between the primary and secondary linings, allowing tunnel ventilation to aid in ground temperature recovery during off periods. To date, the application potential of tunnel-lining GHEs in tropical zones has rarely been reported. In this study, a coupled heat transfer model for heat pumps and tunnel-lining GHEs was built to investigate the effects of tunnel ventilation on thermal imbalance and analyze the feasibility of tunnel-lining GHEs in tropical zones under different thermal conductivities of the surrounding rocks, annual average temperatures, and wind velocities. The results showed that tunnel-lining GHEs effectively reduce the influence of thermal imbalance. The maximum outlet temperature increase for absorber pipes induced by thermal imbalance was 0.54 °C for ten years under building cooling, implying that no obvious annual performance degradation of tunnel-lining GHEs occurs in the tropics of China. However, not all tropical zones of China are suitable for tunnel-lining GHEs because of their excessively high outlet temperatures ranging from 31.2 °C to 41.4 °C. Hence, parametric design charts were proposed to determine the outlet temperature for a preliminary evaluation of feasibility. Finally, parametric design charts were employed in an actual tunnel-lining GHEs project in a tropical zone. Energy, environmental, and economic performance were analyzed for this project. The electricity usage and CO2 emission of tunnel-lining GHEs decreased by 24.6% compared to the cooling towers, and the payback period was 5.9 years.

Performance enhancement of concentrated photovoltaic systems CPVS using a nanofluid optical filter

The exploitation of solar energy using hybrid photovoltaic/thermal (PVT) system can represent a viable choice for the rising energy demand. Due to the wide range of PVT applications, many designs have been developed to improve the solar system global performance by cooling PV cells. The proposed system offers a practical heat gain in addition to the electrical efficiency enhancement. The integration of optical water filters (OWF) in photovoltaic systems could be an advantageous solution for their performance improvement. In this work, three different optical water filter models are evaluated using Cinematic fluid dynamics CFD modeling and their effect on the global system operating is discussed. Three shapes of OWF models are considered. Model (I) is an OWF under the PV cell. Model II is an OWF which passes over and under PV cells with separated inputs. Model III consists of a double pass mode OWF. Results showed that the maximum photovoltaic efficiency is corresponding to model (III) and reaches 12.08% at 14 h. The paper highlighted the different impacts associated with different OWF models. The results showed a significant increase in water outlet temperature. Consequently, an enhancement of the PVT system thermal efficiency is achieved. Finally, various water-based nanofluid (Al 2 O 3 , Cu, Ag, Au) optical filters are elucidated. The optimal photovoltaic performance is obtained by the water-Au nanofluid which allowed an electrical efficiency varying between 2% and 10%. Nanofluid filters have thus been shown to improve the performance of the CPVS concentrated photovoltaic system, not only because of the thermodynamic properties but also as a spectrally separated cooling system.

Thermo-hydraulic characteristics of mixed convection of transition flow in a conduit at different tilts

In this study, numerical investigation was carried out on combined free and forced convection for transition flow of water in a conduit that has a mechanical component, which is a three-sided-polygon-perforations-tranverse-axes tape, inserted in its interior. The purpose of the investigation is to find out the thermo-hydraulic characteristics of mixed convection of transition flow in the tube, and compare them with those of forced convection. Fluent software was used to perform the numerical investigation for the transition flow at Reynolds number (Re) in the range 2,150≤Re≤3,700 for the tube bent at sundry tilts (λ) in the range〖 15〗^o≤λ≤〖 90〗^o. The results indicated that the inside temperature and surface temperature of the tube whose fluid flow is forced convection are lower than the case of the tube whose fluid flow is mixed convection, and that the temperatures (tube’s inside temperature, dimensionless outlet temperature, and surface temperature) increase as the tube tilt increases. Not only that, as the tube tilt increases, the dimensionless outlet temperature increases, but the outlet velocity decreases. The Nusselt number in the tube whose fluid flow is forced convection is lower than the case of mixed convection. For the tube with flow tilts of 15^o,30^o,〖 60〗^o, and 90^o, the Nusselt number are 4.01 to 6.10%, 4.60 to 7.41%, 5.32 to 8.71%, and 6.31 to 10.12%, respectively, greater than the case of the tube whose fluid flow is forced convection, for the Reynolds number considered. The validation of the numerical work with an experimental work confirms the correctness of the numerical work.

Identifying of Unsteady Performance of Oil to Water Heat Exchanger Integrated with Process

There are many approaches by which the heat exchanger can be modeled depending on how much information is available to start with. Grey-box model represents one of these approaches which is considered in the present study to modeling the unsteady operation heat exchanger. The available measurements of an unidentified heat exchanger integrated with a process involving oil circulation were statistically analyzed to extract the information that could aid in its identification. The proposed heat exchanger system included a hot oil stream coming from the thermal unit process and cooled by a cold-water circuit. The objective of this study is to develop a grey box model for the unspecified heat exchanger with a suitable nonlinear state-space structure and solved numerically using MATLAB-19 software and engineering equation solver (EES). Suitable parameters included oil and water inventories, heat addition, and conductance divisor factor are chosen to fully identify the heat exchanger from measured temperatures and flow rates. The parameters used to identify the oil process included the oil mass inventory within the process and the quantity of heat added. While for the heat exchanger; oil, water, and solid thermal masses were determined along with a conductance divisor to close its model. The results revealed that, comparing the model output with the measured data was satisfactory. The effect of 10% increment in the oil process heat as external excitation on a heat exchanger can only be controlled by water and oil flow rates and any fluctuation in inlet water temperature is insignificant and considered as a noise disturbance. An increment of 19% in the oil flowrate with unchanged water flowrate resulted in an increase in oil outlet temperature by about 4%. applying a noise of about ±10% on inlet water temperature to the system resulted in insignificant effects on the oil temperatures, and therefore it could be considered as uniform temperature. An effective control system to manage the heat exchanger and therefore the process can be designed according to the predictions of changing the water and oil flow rate responses.

Analysis of flow & heat transfer enhancement of turmeric cooking steam generator

In this study, the performance of an existing mobile boiling turmeric cooking steam generator is investigated. The CFD analysis results are validated with the field data (experiment results) and found to be in good agreement with the field data. The overall efficiency of the existing mobile boiling turmeric cooking steam generator is observed to be around 10% with measurement parameter. To enhance the rate of heat transfer, one of the passive techniques has been introduced into the existing mobile boiling turmeric cooking steam generator and its CFD analysis is presented. The flow divider type turbulator passive technique of heat transfer with a p/d ratio of 0.54 is used. The CFD results with use of flow divider type turbulator showed that the temperature of steam at the outlet as compared to the existing steam generator has been increased from 95 to 101°C. Novelty impact statement The conventional turmeric cooking plain tube steam generator was numerically simulated with the flow divider type turbulator passive heat augmentation technique. This modification outperformed over plain tube steam generator in terms of performance, and turbulence kinetic energy. The turbulence kinetic energy has been increased from 0.0031 to 0.014 J/kg. When compared to a plain tube steam generator, the flow divider type turbulator steam generator showed an increase in steam outlet temperature by 6.31%.