Dr Hobina Rajakaruna

Job: Principal Lecturer

Faculty: Technology

School/department: School of Engineering and Sustainable Development

Research group(s): Centre for Engineering Science and Advanced Systems (CESAS)

Address: De Montfort University, The Gateway, Leicester, LE1 9BH

T: +44 (0)116 207 8095

E: hobina@dmu.ac.uk

W: www.dmu.ac.uk

 

Personal profile

Dr Hobina Rajakaruna’s current research interests are mainly focused on solar crop dryer design and alternative energy sources.  Hobina is the Course Leader BSc Green Energy Technology programme and Engineering Year-0 Programme at De Montfort University. 

Research group affiliations

Centre for Engineering Science and Advanced Systems (CESAS)

Publications and outputs 

  • Mathematical modelling and validation of the drying process in a chimney-dependent solar crop dryer
    Mathematical modelling and validation of the drying process in a chimney-dependent solar crop dryer Afriyie, John Kwasi; Rajakaruna, Hobina; Nazha, Marouan A. A.; Forson, F. K. A simulation procedure describing the drying process within a Chimney-Dependent Solar Crop Dryer (CDSCD) has been developed. The simulation follows the authors’ experimental work on the effect of varying drying chamber roof inclination on the ventilation and drying processes, and their work on the development of simulation code to help optimise ventilation in such dryers. The current paper presents the modelling and subsequent validation of the drying process inside the dryer, to come out with a design tool for the CDSCD. The work considers the height of the crop shelf above the drying-chamber base, crop resistance to airflow and the shading on the drying-chamber base and their effects on the drying process. The under-load condition temperatures and velocities are predicted to within a relative difference of 1.5% and 10%, respectively of the observed values. Even though the heat inertia of the physical model causes deviation between the predicted drying path and the observed drying path, the two paths tend to converge at the end of each drying cycle, with a general prediction to within 10% relative difference of the observed crop moisture content. The validation results show that the simulation code can serve as an effective tool for comparing and refining the designs of the CDSCD for optimum drying performance
  • Simulation and optimisation of the ventilation in a chimney-dependent solar crop dryer.
    Simulation and optimisation of the ventilation in a chimney-dependent solar crop dryer. Afriyie, John Kwasi; Rajakaruna, Hobina; Nazha, Marouan A. A.; Forson, F. K.
  • Experimental investigations of a chimney-dependent solar crop dryer.
    Experimental investigations of a chimney-dependent solar crop dryer. Afriyie, John Kwasi; Nazha, Marouan A. A.; Rajakaruna, Hobina; Forson, F. K.
  • Modelling and experimental studies on a mixed-mode natural convection solar crop dryer.
    Modelling and experimental studies on a mixed-mode natural convection solar crop dryer. Forson, Francis Kofi; Nazha, Marouan A. A.; Rajakaruna, Hobina An output from collaboration with Kwame Nkrumah University in Ghana. The mathematical model developed at DMU was used to build a full-scale dryer in Ghana, which in turn helped to further validate the model. This research is relevant to developing countries where use of conventional energy in food drying is too expensive. The Ghanian government is sponsoring follow on research at DMU (Dr F. Forson, Dep. of Mech. Eng., Kwame Nkrumah University of Science and Technology, Kumasi, Ghana).
  • Experimental and simulation studies on a single pass, double duct solar air-heater.
    Experimental and simulation studies on a single pass, double duct solar air-heater. Forson, Francis Kofi; Nazha, Marouan A. A.; Rajakaruna, Hobina A mathematical model of a single pass, double duct solar air heater (SPDDSAH) is described. The model provides a design tool capable of predicting: incident solar radiation, heat transfer coefficients, mean air flow rates, mean air temperature and relative humidity at the exit. Results from the simulation are presented and compared with experimental ones obtained on a full scale air heater and a small scale laboratory one. Reasonable agreement between the predicted and measured values is demonstrated. Predicted results from a parametric study are also presented. It is shown that significant improvement in the SPDDSAH performance can be obtained with an appropriate choice of the collector parameters and the top to bottom channel depth ratio of the two ducts. The air mass flow rate is shown to be the dominant factor in determining the overall efficiency of the heater.
  • Prediction and measurement of soot particulate formation in a confined diesel fuel spray-flame at 2.1 MPa
    Prediction and measurement of soot particulate formation in a confined diesel fuel spray-flame at 2.1 MPa Crookes, R. J. (Roy J.); Sivalingam, G.; Nazha, Marouan A. A.; Rajakaruna, Hobina The output of collaborative work between researchers in two universities. The experimental work was carried out at Queen Mary University of London (QMUL) while the theoretical predictions were conducted at De Montfort University. This collaborative study resulted in improving knowledge regarding soot particles formation during liquid fuel combustion. The collaboration in this field is on-going through a parametric study aimed at identifying factors influencing soot formation and oxidation in spray combustion (Prof. R. J. Crookes QMUL, tel. 0207 8825270).
  • The use of emulsion, water induction and EGR for controlling diesel engine emissions.
    The use of emulsion, water induction and EGR for controlling diesel engine emissions. Nazha, Marouan A. A.; Rajakaruna, Hobina; Wagstaff, S. A. This paper was initially presented at an SAE Fuel & Lubricant Conference. It was selected for inclusion in the Transactions. SAE Transactions represent only the best papers from many thousands published during the year. The technique was applied to biodiesel resulting in a paper presented at the clean air conference, Portugal, July 07 and resulted in invitation to produce a follow on journal paper.

Click here to view a full listing of Hobina Rajakaruna's publications and outputs.

Key research outputs

Journal Papers:

Afriyie, J.K., Rajakaruna, H., Nazha, M.A.A. and Forson, F.K. (2013) Mathematical modelling and validation of the drying process in a chimney-dependent solar crop dryer. Energy Conversion and Management, 67, pp. 103-116

Afriyie, J.K., Rajakaruna, H., Nazha, M.A.A., Forson, F.K.  Simulation and optimisation of the ventilation in a chimney-dependent solar crop dryer, Solar Energy, Vol:85, Issue 7, July 2011, Pages 1560-1573 

J. K. Afriyie, M. A. A. Nazha, H. Rajakaruna and F. K. Forson, Experimental investigations of a chimney-dependent solar crop dryer, Renewable Energy, Vol:34  issues 1, ( January 2009) pages 217-222

Refereed Conference:

M. Goman, J. Dimitrov, M. Nazha and H. Rajakaruna “A Methodology for On-Line Enforced Learning”, Proceedings of IASK Teaching and Learning Conference, Aveiro, Portugal, May 2008

Research interests/expertise

Solar Crop Dryer Design

Alternative Energy and Fuels

Modelling of droplet evaporation and combustion processes

CFD modelling of two-phase reactive flows

Areas of teaching

ENGZ0002 Engineering Applications

ENGD1005 Mechanical Principles

ENGD3036 Thermal Plant and Sustainability

ENGD3000 Final Year Projects

Qualifications

BSc PhD

Honours and awards

Vice-chancellor’s Distinguished Teaching Award (2012)

De Montfort University Research informed teaching award (2007)

Vice-chancellor’s Distinguished Teaching Award (2005)

Key research outputs

 

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