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Featured researches published by Sunita Kruger.


ASME 2013 International Mechanical Engineering Congress and Exposition | 2013

Numerical Assessment of the Aerodynamic Properties of a Solar Vehicle

Warrick D. Kin; Sunita Kruger; Nickey Janse van Rensburg; Leon Pretorius

Due to wide emphasis on climate change today, alternative fuel research is necessary. Consequently, the South African Solar Challenge has created a competitive platform for research into alternative energies, particularly solar. The University of Johannesburg (UJ) competed in the competition using their uniquely designed and built solar vehicle, Ilanga I. However, due to the constraints of the energy available, the aerodynamics of the vehicle has to be exceptionally good. Subsequently, a large proportion of the total power of the vehicle is used to overcome the aerodynamic resistance posed by the vehicle. Furthermore, much of the remaining power of the vehicle is used to overcome rolling resistance. Consequently, solar vehicles have to be as lightweight as possible in order to effectively reduce the rolling resistance. However, reducing weight of the vehicle results in the vehicle’s stability being greatly affected by side-wind effects. In order to improve on the vehicle, it is very important to test for and obtain its aerodynamic characteristics. This research article aims at obtaining the average drag coefficient felt during the majority of the race as well as the lift coefficients for side-wind cases, in order to investigate vehicle safety. Thus, through the use of Computational Fluid Dynamics (CFD), it was possible to obtain an assessment of the vehicle’s performance. Simulations were performed using the Reynold’s Averaged Navier Stokes (RANS) method with use of the k-ω SST turbulence model. This method of simulation showed reasonable predictions of the results as compared to literature.Copyright


Volume 2: Applied Fluid Mechanics; Electromechanical Systems and Mechatronics; Advanced Energy Systems; Thermal Engineering; Human Factors and Cognitive Engineering | 2012

Numerical Investigation of Natural Convection in a Mono-Span Greenhouse

Sunita Kruger; Leon Pretorius

In this paper, the use of computational fluid dynamics is evaluated as a design tool to investigate the indoor climate of a confined greenhouse. The finite volume method using polyhedral cells is used to solve the governing mass, momentum and energy equations. Natural convection in a cavity corresponding to a mono-span venlo-type greenhouse is numerically investigated using Computational Fluid Dynamics. The CFD model is designed so as to simulate the climate above a plant canopy in an actual multi-span greenhouse heated by solar radiation. The aim of this paper is to investigate the influence of various design parameters such as pitch angle and roof asymmetry and on the velocity and temperature patterns inside a confined single span greenhouse heated from below. In the study reported in this paper a two-dimensional CFD model was generated for the mono-span venlo-type greenhouse, and a mesh sensitivity analysis was conducted to determine the mesh independence of the solution. Similar two-dimensional flow patterns were observed in the obtained CFD results as the experimental results reported by Lamrani et al [2]. The CFD model was then modified and used to explore the effect of roof pitch angle and roof asymmetry at floor level on the development of the flow and temperature patterns inside the cavity for various Rayleigh numbers. Results are presented in the form of vector and contour plots. It was found that considerable temperature and velocity gradients were observed in the centre of the greenhouse for each case in the first 40mm above the ground, as well as in the last 24mm close to the roof. Results also indicated that the Rayleigh number did not have a significant impact on the flow and temperature patterns inside the greenhouse, although roof angle and asymmetry did. The current results demonstrate the importance of CFD as a design tool in the case of greenhouse design.Copyright


ASME 2010 International Mechanical Engineering Congress and Exposition | 2010

The Effect of Time-Varying Wind Direction on the Indoor Climate of a Naturally Ventilated Greenhouse

Sunita Kruger; Leon Pretorius

This paper presents a numerical investigation into the indoor climate of a four span naturally ventilated, four span greenhouse subject to a time-varying wind direction. The effect of transient wind conditions on the temperature and velocity distribution inside the greenhouse is numerically determined using Computational Fluid Dynamics (CFD). The research in this paper is an extension of work previously conducted on two-dimensional models of greenhouses. Current work concentrates on the three-dimensional effect of external winds. Results indicate that for a wind direction of 22.5 degrees, the microclimate at plant level varies throughout the length of the greenhouse. It was also found from transient simulations that even a slight change in wind direction have a pronounced effect on the indoor climate at plant level.Copyright


2010 14th International Heat Transfer Conference, Volume 8 | 2010

An Assessment of Different Boundary Conditions in a Naturally Ventilated Venlo-Type Greenhouse

Sunita Kruger; Leon Pretorius

This paper presents a parametric study of the indoor climate of a four span greenhouse subjected to natural ventilation. The effect of different heat fluxes through the greenhouse covering on the airflow patterns as well as temperature and velocity distributions were determined. Appropriate effective heat flux boundary conditions were introduced in the CFD model to investigate temperature and velocity distributions at plant level. Initially, three different simulations were done to represent zero wind speed conditions. Secondly, a velocity of 1m/s was specified at the domain inlet boundary. Results indicated that for all cases, the velocity distribution was heterogeneous and quite high for wind still days around midday. Temperature distributions were more homogeneous, decreased with the presence of a wind. Results indicated that a parametric value of 20% of the maximum daily solar radiation approximates previously simulated wall temperatures. It was also concluded that design changes such as additional openings including side and/or more roof ventilators be utilized to enhance ventilation on wind still days, as well as the warmer parts of the day.Copyright


ASME 2015 International Mechanical Engineering Congress and Exposition | 2015

The Effect of Raised Benches Containing Crops on the Indoor Environment in Greenhouses

Sunita Kruger; Leon Pretorius

The purpose of this paper is to investigate the influence of peninsular arranged perforated benches containing plants on the indoor environment of a naturally ventilated greenhouse. The results are compared to a greenhouse containing peninsular arranged solid benches with no plants. The investigation will be conducted numerically using three-dimensional Computational Fluid Dynamics (CFD) models. The overall temperature and velocity distribution were investigated at different sections of the greenhouse. The temperature and velocity distributions at plant level were of particular interest. Results indicated that the greenhouse containing the perforated benches were in general cooler, but also exhibited higher velocities throughout. The velocities observed were higher than those recommended by ASHRAE [1]. It was concluded that care should be taken when placing plants on the perforated benches especially in the regions adjacent to the walls, as this can lead to non-uniform crop production.Copyright


international conference on fuel cell science engineering and technology fuelcell collocated with asme international conference on energy sustainability | 2013

The Effect of Vertical and Horizontal Partitions on Natural Convection in a Heated Enclosure

Sunita Kruger; Leon Pretorius

In this paper, turbulent buoyancy induced convection in a partitioned square cavity with conducting baffles is numerically investigated to determine overall heat transfer performance. The finite volume method using polyhedral cells is used to solve the governing mass, momentum and energy equations and to predict the flow patterns and heat transfer in the cavity. The cavity consisted of two adiabatic vertical walls, an isothermal horizontal wall located at the bottom at Th and the top wall isothermal at Tc. The configuration was investigated for Ra = 9.1 × 107 to Ra = 1.9 × 109 (turbulent). The conducting baffles are assigned various values of effective thermal resistances, calculated using thermal conductivity. The effects of these conducting baffles and their effective thermal resistance are shown in terms of temperature and velocity contour plots and average Nusselt number. Results indicated that the presence of baffles influenced the heat transfer from the hot wall considerably, and it was concluded that a partitioned enclosure containing conducting partitions can be used to represent an enclosed greenhouse containing raised benches with single/multiple racks.Copyright


ASME 2013 International Mechanical Engineering Congress and Exposition | 2013

The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse

Sunita Kruger; Leon Pretorius

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably.Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.Copyright


Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis | 2017

Numerical and Experimental Aerodynamic Evaluation of a Solar Vehicle

J. P. de Kock; R.F. Laubscher; Sunita Kruger; N. Janse van Rensburg


ASME 2017 International Mechanical Engineering Congress and Exposition | 2017

Heat Transfer in Three-Dimensional Single-Span Greenhouses Containing a Roof Ventilator

Sunita Kruger; Leon Pretorius


Archive | 2015

The effect of geometrical electrical cable configurations on heat transfer in cable ducts

Sunita Kruger; Leon Pretorius

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J. P. de Kock

University of Johannesburg

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R.F. Laubscher

University of Johannesburg

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Warrick D. Kin

University of Johannesburg

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