Heat Transfer and Fluid Flow Characteristics Study for In-Line Tube Bank in Cross-Flow

This research investigates the heat transfer coefficient as a function of tube position and pressure drop, for in-line tube bank in cross-flow. Experimentation was essentially used to generate log-mean temperature curves and pressure heads upstream and down stream of the test section. The heat transfer and flow parameters such as Nusselt number, Reynolds number, and pressure drop across the bank were calculated. In addition, heat transfer correlations, Nusselt number (Nu) were obtained by power-law curve fitting for each position of the tube in the tube bank. FEMLAB 3.0 was use for numerical simulation and the results obtained compared favourably with that of the experimental results. Numerical results also reveal the important aspects of the local heat transfer and flow features within the tube bank. These characteristics include boundary layer developments between tubes, formation of vortices, local variations of the velocity and temperature distribution

Wind Energy Systems for Omu Aran, Kwara State, Nigeria

The quest for energy from renewable and sustainable sources has led to the investment on exploration and installations of wind energy systems to harness energy from wind for use by mankind. Various wind energy systems exist and they are quite expensive. Selections of appropriate systems for installation are dependent on the wind power available in a location. It is therefore important that proper wind assessment is done before investments on infrastructures for harnessing wind power are put in place. Wind data between 2014 and 2018 were obtained from the Landmark University Weather Station in Omu Aran and the pattern of wind speed distribution in the location over the years in focus were determined by the Weibull function. The power law was used to estimate the wind speeds at heights of 10 and 20 metres respectively. Recommendations on appropriate wind energy systems suitable for Omu Aran region were made based on the wind speed pattern

A COMPARATIVE STUDY OF FLOW AND HEAT TRANSFER CHARACTERISTICS OF STAGGERED AND IN-LINE CROSS-FLOW TUBE-TYPE HEAT EXCHANGERS, PART II: THE FINITE ELEMENT ANALYSIS

Numerical analysis of fluid flow and heat transfer were performed for cross-flow tube-type heat exchanger in staggered and in-line arrangement. The purpose of this project was to simulate the process of forced convection heat transfer of air over a heated cylindrical pure copper rod using finite element scheme and compared the results with experimentally obtained data. Also, the work was to compare the performance of both staggered and in-line tube bundle configurations. The cross-flow tube-type heat exchangers consist of 25 mm transverse pitch, 18.75 mm longitudinal pitch, 20 cylindrical rods of Ø12.5 mm in a 125 x 125 mm cross section. Finite element simulation was carried out by modeling the working sections of the cross flow heat exchangers. In this, Model geometry was created, meshed, calculated, and post-processed using FEMLAB 3.0 for ten different air inlet velocities corresponding to experimental data obtained. The simulation results revealed 29.77% and 25.31% deviation in Nusselt number from experimental results for staggered and in-line tube bank respectivel

Experimental Comparison of Staggered and In-line Tube-bank Thermal Performance.

Experimental investigation of fluid flow and heat transfer were performed for cross-flow tube-type heat exchanger in staggered and in-line arrangement. The purpose of this work was to determine the process of forced convection heat transfer of air over a heated cylindrical pure copper rod. Also, the work was to compare the performance of both staggered and in-line tube bundle configurations. Tube bank with staggered arrangement consisted of 25 mm transverse pitch, 18.75 mm longitudinal pitch, 20 cylindrical rods of diameter12.5 mm, in a 125 x 125 mm cross section. An in-line tube arrangement was constructed based on the staggered tube bank dimensions. During the test, the working sections were placed one after the other in a specially design testing rig air channel through which the fluid flowed normal to the tube. A complete set of test were taken with the heated element in each of the four banks of tube for ten different throttle openings in the range of 10 to 100%. The test results show that the heat transfer coefficient associated with the tube is a function of its position in the tube bank. Higher heat transfer coefficients were obtained in the subsequent tube bank downstream of the first row. However, the heat transfer coefficients stabilize, such that little change occurs for tube beyond the fourth row. The overall heat transfer coefficient for staggered tube arrangement was found to be 4.28% higher than of the in-line tube arrangement

Experimental and Numerical Investigations of Forced Convection in Tube-Type Heat Exchanger

Experimental and numerical studies of forced convectionheat transfer in tube-type heat exchanger consisting four columns of five cylindrical tubes arranged so that every second column is displaced (i.estaggered configuration) were carried out. Experiments were conductedtodeterminethe effects of flow pattern on heat transfer and pressure dropwithin the heat exchanger and the heat transfer dependence on position. In the analytical approach, the dimensionless representationsof the rates of forced convection (i.eNusselt number) and pressure loss(i.e drag coefficient) were obtained. The numerical simulation is carried out using FEMLAB 3.0 and the results compared favourably with the experimental. The flow visualization featuressuch as boundary layer developments between tubes, formation of vortices, local variations of the velocity and temperature distribution within the heat transfer device were revealed by numerical solution. The resultsshowed that the average Nusselt number increases with increasing Reynolds number and the heated element position in the bank. The drag coefficient decrease with increasing Reynolds numbers

A STUDY OF HEAT TRANSFER AND FLUID FLOW CHARACTERISTICS IN TUBE BANKS

Heat exchangers are devices in which heat is transferred from one fluid to another at different temperatures with wide applications in many field of engineering such as power generation, chemical processing, electronics cooling, automotive, refrigeration and air-conditioning. They are classified typically according to type operation, construction and flow arrangement into shell-and-tube, double-pipe, compact, cross-flow, etc. The heat transfer from bank of tubes depends on geometric arrangement, Reynolds number and the position of tube in the bank. However, the determination of the number of tube rows required to enhance heat transfer has been one of the major challenge in exchanger design. The aim of this study was to investigate the heat transfer and fluid flow characteristics associated with a staggered and in-line tube banks in cross-flow using experimental and numerical methods. The cross-flow heat exchanger (Plint & Partner, Ltd, Workingham, England) was used for the experimentation. During this process, a complete set of test were taken with the heated element in each of the four ranks of tube for ten different throttle openings in the range of 10-100% to determined the Nusselt number and pressure drop across the bank. Based on the experimental data, numerical simulation was carried out using FEMLAB 3.0. This was done by modeling the working sections of the cross-flow heat exchanger. Both the experimental and numerical results were compared. The experimental results show that the heat transfer coefficient in terms of Nusselt number associate with tube was determined by its position in the bank of tubes. The heat transfer coefficient for the tube in the first row was approximately equal to that of a single tube in cross-flow whereas larger heat transfer coefficients were associated with tubes of the inner rows. The tubes of the first row act as turbulence grid, which increases the heat transfer coefficient for tubes in the subsequent downstream ranks. However, the heat transfer conditions stabilize such that little change occurs in the convection coefficient for tube beyond the forth rank. The pressure drop across the bank of tubes was observed to increase with increasing Reynolds number. The numerical results reveal the important aspects of the local heat transfer and flow features of the tube banks. These include boundary layer developments between tubes, formation of vortices, local variations of the velocity and temperature within the banks. The boundary layers developments and vortices between tube surfaces were found to be dependent substantially on Reynolds number. The numerical heat transfer and pressure drop results deviated by approximately ± 30 % and ± 20 % respectively from experimental values in both tube banks. The present numerical investigations suggest a good estimate of the Nusselt number and pressure drop for the tube banks. The heat transfer rate of staggered array was moderately higher than those of the in-line array. The maximum enhancement relative to the in-line array was 20% for the staggered array. However, a comparison of the two arrays reveals marked differences in terms of the pressure drop. It was seen that the pressure drop of the staggered array was 35.2% higher than the in-line. It can be infer from this study that the maximum number of tube rows required to obtain high heat transfer may not be more than four or five. This will facilitate the design of a compact heat exchanger. Additional tube rows would result to infinitesimal increase in heat transfer, large and bulky exchanger and high cost of design. The pumping power which is a function of the pressure drop was dependent on the tube banks arrangement

Stand-alone wind energy systems for power generation in Nigeria

The realization of a stable and adequate electricity generation and supply has been a serious challenge in Nigeria, especially in the remote areas of the country. The interest of the government and private firms has been on the installation of power plant running on fossil fuel while neglecting the renewable energy resources the country is endowed with. To achieve adequate generation and supply of electricity to the populace in urban and remote areas, appropriate stand-alone wind energy systems are recommended for installation in wind sites, on buildings and communication masts based on the wind pattern of the various locations in the country. A brief review of the wind potentials of the various locations in the country is done. A review on the HAWT and the various configurations of the VAWT is done with emphasis on its merits and demerits and also a brief review on building-mounted wind power systems is done, with recommendations on appropriate wind energy systems for installation

Influence of Commercial Gasoline Samples on the Performance Characteristics of SI Engines

It has been observed though not documented that some gas filling stations in Nigeria adulterate their fuel before selling to customers. Numerous engine users had also complained of fuel obtained from some petrol filling stations burn faster than others. Engines used in automobile vehicles and power plants always developed one fault or the other leading to frequent visit to mechanics. In view of these preceding issues, experimental study was conducted to determine the influence of gasoline sold in Nigeria market on engine performance characteristics. Four samples of commercial gasoline were collected from different petrol stations within Omu-Aran metropolis, Kwara State, Nigeria and tested on a four stroke single cylinder spark ignition engine (P8161) automotive test bed at wide throttle opening. However, the octane rating of the selected fuel samples could not be ascertain because gasoline supplied at Nigeria petrol stations are no longer rated as it used to be as regular, premium and regular unleaded. The results of this investigation show that the performance parameters such as torque, brake power, brake mean effective pressure and thermal efficiency for each fuel sample increase with increase engine speed up to a maximum value and begin to decrease as engine speed increase due to frictional loss. Maximum brake power obtained with fuel sample A was 5.751 kW at 3083 rpm. For fuel sample B, the maximum brake power was 5.025kW at 2884 rpm, 5.269 kW at 2727 for fuel sample C and 5.019 kW at 2718 rpm for fuel sample D. From this test, brake maximum power and torque occur at the same engine speed for each sample of fuel sample studied. Also the maximum power obtained from fuel sample B and D were approximately the same at different engine speed. It may suffice to say that fuel sample B and D were likely supplied to the different petrol filling stations by the same source. The minimum amount of fuel consumed in order to attain maximum power was more with fuel sample D and B corresponding to 36.73 g/kW.hr and 36.63 g/kW.hr respectively. The minimum brake specific fuel consumption was lower for fuel sample A and C with value 32.21 g/kW.hr and 35.44 g/kW.hr respectively. Therefore, it is more economical and reliable to run spark ignition engines with fuel sample A and C. Analysis of fuel variability shows that the coefficient of variation in engine speed for fuel sample A, B, C and D were 32.6%, 34.2%, 33.1% and 35.2% respectively. In terms of brake power developed the coefficients of variation were 52.2%, 56%, 53.8% and 60.6% for fuels A, B, C and D respectively. The coefficient of variation in terms brake specific fuel consumption are 101.3%, 142.8%, 111.5% and 131.9% for fuel samples A, B, C and D respectively. It means that more of fuel B was consumed follow by fuel sample D during the combustions process compared to fuel samples A and C. For fuel sample B approximately 43% additional fuel is required to attain the maximum power and about 32% of fuel sample D. Approximately 12% additional of fuel sample C is required while only 2% of fuel sample A is needed. From the results fuel sample A is more reliable for achieving engine performance specifications follow by fuel sample C and B while fuel sample D is less reliable. One of the factors that may be responsible for the variation is fuel octane rating which is a measure of how smooth an engine runs or resistance to knocking. If this is true, engines running on fuel samples D and B are more prone to pre-ignition or engine knock than fuel sample A and C. It then means there is strong relationship between fuel samples and engine performance

Intertwined Helical Tube Insertion Impact on Thermal-Hydrodynamic Characteristics Associated with Internal Flows

Heat transfer improvement has attracted a great deal of interest owing to the concern for energy saving and high thermal system performance requirement. For example, heat exchangers that operate in parallel flow are limited in engineering applications because of their inability to recover much heat. Tube inserts such as wire coil and twisted tapes are used to enhance heat transfer. Unfortunately, the attendant increase in pressure drop associated with wire coil and twisted tube inserts has become an increasing concern in industries. Therefore, an experimental investigation was carried out to determine the effect of intertwined helical tube insert on convective heat transfer coefficient and pressure drop for concurrent and countercurrent flow in tube heat exchanger. Pressure drop associated with the use of the tube insert was 10% and 12% greater than that of using plain tube for concurrent and countercurrent flows respectively. Such low resulting pressure drop could be due to the tube insert pitch ratio and well ordered flow within the tube. Thermal improvement results were 3.2 and 3.8 for concurrent and countercurrent flows respectively. This implies that the use of intertwined helical tube insert justify the additional pumping power required. In addition, much energy was recovered in concurrent flow using helical tube inserts

An Inclusive Approach to Hands-on STEM Programs in Underserved Secondary Schools: An Epistemological STEAM Model

<p><strong>Abstract: </strong>Underserved schools globally do not usually have sufficient resources and requisite models to run inclusive and sustainable hands-on STEM programs. This often lead to exclusion of more students from opportunities in STEM, especially those with disabilities and learning difficulties. The marginalization of disadvantaged learners and exclusion of majority of students in resource-poor schools creates an internal STEM gap. Some schools having resources but lacking skilled instructors also face the same challenges. After more than a decade of casual observations, these problems have remained consistent, persistent and widespread; especially in developing countries. This mixed and longitudinal study therefore proposes an inclusive framework to address these inequities in STEM. Our model comprises seven components, after inductive analysis of empirical observations. A survey of 214 participants comprising 36 teachers and 178 students, who have participated in hands-on STEM programs was analyzed using simple statistical method to evaluate their perceptions on our hypothesized propositions. Our findings reveal that teachers' and students' responses validate our proposed framework; which informs the development of our Epistemological STEAM Model. This framework would serve as an effective guide for underserved secondary schools to implement sustainable hands-on programs with limited resources. It would also help policy makers enforce inclusion in the selection of students who participate annually in sponsored STEM programs and competitions; as well as drive optimal utilization of public STEM infrastructures.</p&gt