Numerical and Analytical Modeling of Solar for Chimney Combined Ventilation and Power in Buildings

Analytical and numerical studies were carried out to investigate the performance of the combined solar chimney for power generating system and ventilation based on a developed mathematical model. Numerical solution of the problem was based on the continuity, momentum and energy equations for turbulent, steady-flow using k-ε model and the finite volume method using ANSYS Fluent CFD package. The analysis domain was a 2-D room of 4 x 4 m2 with solar chimney of various dimension attached. The results obtained revealed that Chimney Height (CH), Collector Width (CW), Solar Heat Flux (SHF) and ambient wind speed were found to be the most important factors in the design of the SC. Results showed that the room mass flow rate increased from 1 kg/s with no wind effect to about 30 kg/s with induced wind of 1 m/s. The mass flow rate increased from about 6 to 9 kg/s at CH of 5 and 8 m respectively for no wind condition and SHF of 400 W/m2. Power outputs were obtained for the average velocity of the chimney, collector area and chimney height. It was observed from results obtained from both the numerical and analytical analysis that power outputs of the power generating systems increases with increase in heat energy in the collector space area which is a function of the global solar radiation intensity, the collector area, and the chimney height. The power outputs results showed that with SHF of 400 W/m2 for CH of 5 and 9 m were 33 and 85 W/m2 respectively. The respective power output for SHF of 200 and 1,000 W/m2 were 25 and 47 W/m2. Furthermore, the optimum values of CH, CW and SHF were 5 m, 1 m and 417 W/m2 respectively under no wind condition with room temperature of 300 K and chimney velocity 0.12 m/s. It was also observed that with the increase in the mass flow rate in the chimney, the ventilation requirements were adequately met

ANALYSES OF THE MOTION OF A PIPE CONVEYING A FLUID WITH AN INVISCID FLOW

The transverse motion of a fluid-conveying pipe with an inviscid flow was considered in this work. A comprehensive governing differential equation for the transverse vibration of a fluid-conveying pipe system was derived according to the principles of conservation of mass and momentum of fluid in a pipe. The derived equation was then analyzed and solved for an inviscid flow using the integral Fourier-Laplace Transformations. Effect of some flow parameters like mass ratios, damping coefficient and velocity of flow were investigated. Results revealed that the first natural frequency increased with increase in mass ratio for low velocities and reverse was the case for relatively high velocities. First natural frequency also increased with damping coefficients. Similar profiles can be observed about the second natural frequency. The response increased with increase in velocity. The study concluded that damping coefficient and mass ratio played significant roles in the motion of a fluid-conveying pipe with an inviscid flow

Numerical simulation of microchannel double-pipe heat exchanger with ribs

This study numerically investigates a double pipe heat exchanger with triangle and rectangle rib. The simulation is performed using ANSYS package, considering turbulent flow and k-e turbulence model. The working fluid is water in both tube and annulus and the flow arrangement is counter flow. The results show that, the heat transfer of triangle rib and rectangle rib are higher than that of normal DPHE and as the Reynolds number is increasing heat transfer, coefficient of heat transfers and Nusselt number are also increasing. Triangle rib has thermal performance factor of 0.9786 at Re of 40000 and rectangle rib has 1.0290 at Re of 30000. Furthermore, total heat transfer of DPHE with triangle rib is 33% better than normal DPHE at Re of 40000 and that of rectangle rib is 45%better at Re of 40000

A GIS – based method for assessment and mapping of noise pollution in Ota metropolis, Nigeria

A detailed method used for assessing and mapping noise pollution levels in Ota metropolis, Nigeria using ArcGIS 10.5 Software is presented in this paper. Noise readings were measured at a time interval of 30 min for each site considered using a precision grade soundlevel meter. The noise map developed was based on the computed values of average equivalent noise (LAeq) for the selected locations. Results of this study show that the A weighted sound level (LAeq), the background noise level (L10) and the peak noise level (L90) vary with location and period of the day due to traffic characteristics especially traffic volume, vehicle horns, vehicle mounted speakers, and unmuffled vehicles at road Junctions, major roads, motor parks and commercial centres. Based on the U.S. Department of Housing and Urban Development (HUD) recommendations and standards, only one (1) out of the 41 locations considered is under normally acceptable situation, while 12 locations are under normally unacceptable and the noise levels of the rest locations are clearly unacceptable. Results of this study are useful as reference and guideline for future planning and regulations on noise limit to be implemented for urban areas like Ota Metropolis

Inventory of Greenhouse Gases Emissions from Gasoline and Diesel Consumption in Nigeria

Emissions from fossil fuel combustion are of global concern due to their negative effects on public health and environment. This paper is an inventory of the greenhouse gases (GHGs) released into the environment through consumption of fuels (gasoline and diesel) in Nigeria from 1980 to 2014. The fuel consumption data for the period in view were sourced from bulletins released by Nigeria National Petroleum Corporation, (NNPC) and were utilized for GHGs estimation based on default emission factors (69300 kg/TJ (CO2; gasoline), 74100 kg/TJ (CO2; diesel), 18 kg/TJ (CH4; gasoline), 3.85 kg/TJ (CH4; diesel), 1.9 kg/TJ (N2O; gasoline) and 2.25 kg/TJ (N2O; diesel). In addition, the uncertainty and sensitivity analyses associated with the inventory were carried out. Total amount of GHGs emitted into the environment for the period under consideration was 7.30 x 108 tCO2 e (5.20 x 108 tCO2 e and 2.10 x 108 tCO2 e of gasoline and diesel, respectively). It is worth noting that gasoline consumption accounted for 71.23% of the total amount of GHGs with CO2 making up 98.72 % (CH4 = 1.39 % and N2O = 0.61 %) of the emissions. For this study, uncertainty of estimate was between -80.93 % and 78.36 % while volume of diesel is more sensitive than the volume of gasoline of the input parameters. National policy and enforcement on low or neutral emission fuels utilization are amongst the recommended actions toward reducing GHG emissions in the country

Inventory of Greenhouse Gases Emissions from Gasoline and Diesel Consumption in Nigeria

Emissions from fossil fuel combustion are of global concern due to their negative effects on public health and environment. This paper is an inventory of the greenhouse gases (GHGs) released into the environment through consumption of fuels (gasoline and diesel) in Nigeria from 1980 to 2014. The fuel consumption data for the period in view were sourced from bulletins released by Nigeria National Petroleum Corporation, (NNPC) and were utilized for GHGs estimation based on default emission factors (69300 kg/TJ (CO2; gasoline), 74100 kg/TJ (CO2; diesel), 18 kg/TJ (CH4; gasoline), 3.85 kg/TJ (CH4; diesel), 1.9 kg/TJ (N2O; gasoline) and 2.25 kg/TJ (N2O; diesel). In addition, the uncertainty and sensitivity analyses associated with the inventory were carried out. Total amount of GHGs emitted into the environment for the period under consideration was 7.30 x 108 tCO2 e (5.20 x 108 tCO2 e and 2.10 x 108 tCO2 e of gasoline and diesel, respectively). It is worth noting that gasoline consumption accounted for 71.23% of the total amount of GHGs with CO2 making up 98.72 % (CH4 = 1.39 % and N2O = 0.61 %) of the emissions. For this study, uncertainty of estimate was between -80.93 % and 78.36 % while volume of diesel is more sensitive than the volume of gasoline of the input parameters. National policy and enforcement on low or neutral emission fuels utilization are amongst the recommended actions toward reducing GHG emissions in the country

COMPARATIVE ENGINEERING ECONOMIC ANALYSIS OF A VARIABLE REFRIGERANT FLOW AND MINI-SPLIT AIR CONDITIONING SYSTEM DESIGN

The design and comparative engineering economic analysis of two Air-conditioning (AC) systems, mini-split and variable refrigerant flow (VRF), for the new Engineering Complex Building, at the College of Engineering and Environmental Studies, Ibogun Campus of Olabisi Onabanjo University, under the same indoor and outdoor conditions for a one-year period was carried out using Carrier Hourly Analysis (CHA) program software for determining cooling load estimation, and the Net Present Worth Approach for calculating the economic analysis of both systems’ design. The cooling load estimation was done using the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) transfer function method rooted within the Carrier software. The total cooling load for the building was found to be 239,243 W. Equipment used in analysis was selected from the Toshiba selection catalogues (Mini Split system), while that for the VRF system was selected using Toshiba simulation software. The annual energy cost analysis of both systems revealed that the VRF system require more energy to run annually than the mini split system. However, the analysis was carried out without considering the part load potential energy savings of the VRF system. Results further indicated from the net present worth analysis carried out, the mini split system, in terms of Net Present Value of both systems, is more favoured. On the bases of the Engineering Economic Analysis carried out on the two systems, the overall Net Present Value for the VRF system was about N78 million, while that of the mini-split system was about N47 million. These results show that the VRF system had a higher cost implication than the mini-split system. Therefore, in terms of cost, the mini-split system was found to be a more viable option being an older and more established technology to the VRF system. In terms of design, the mini-split system, with equal number of indoor and outdoor units, is generally a system with more component units than the VRF system, with less outdoor units to indoor units, was expected to be more complicated and complex in design. However, control and operation flexibilities favour the mini-split system to the VRF system