The research work in this dissertation focuses on turbulent air jet heat transfer for commercial cooking applications. As a part of this study, convective heat transfer coefficient and its interdependency with various key parameters is analyzed for single nozzle turbulent jet impingement. Air is used as the working fluid impinging on the flat surface. A thorough investigation of velocity and temperature distributions is performed by varying nozzle velocity and height over diameter ratio (H/D). Nusselt number and Turbulent Energy are presented for the impingement surface. It was found that for H/D ratios ranging between 6 and 8, nozzle velocities over 20 m/s provide a large percentage increase in heat transfer. Single nozzle jet impingement is followed by study of turbulent multi-jet impingement. Along with parameters mentioned above, spacing over diameter ratio (S/D) is varied. Convective heat transfer coefficient, average impingement surface temperature and heat transfer rate are calculated over the impingement surface. It was found that higher S/D ratios result in higher local heat transfer coefficient values near stagnation point. However, increased spacing between the neighboring jets results in reduced coverage of the impingement surface lowering the average heat transfer. Lower H/D ratios result in higher heat transfer coefficient peaks. The peaks for all three nozzles are more uniform for H/D ratios between 6 and 8. For a fixed nozzle velocity, heat transfer coefficient values are directly proportional to nozzle diameter. For a fixed H/D and S/D ratio, heat transfer rate and average impingement surface temperature increases as the nozzle velocity increases until it reaches a limiting value. Further increase in nozzle velocity causes drop in heat transfer rate due to ingress of large amounts of cold ambient air in the control volume. The final part of this dissertation focuses on case study of conveyor oven. Lessons learned from analysis of single and multi-jet impingement are implemented in the case study. A systematic approach is used to arrive to an optimal configuration of the oven. As compared to starting configuration, for optimized configuration the improvement in average heat transfer coefficient was 22.7%, improvement in average surface heat flux was 24.7% and improvement in leakage air mass flow rate was 59.1%.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Fabrice Veron, College of Marine and Earth Studies. Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Mechanical and Aerospace Engineering." Includes bibliographical references (p. 111-115).

A theoretical model was developed to predict the air distribution pattern and thus to design perforated ventilation ducts equipped with a fan. The analysis of the air distribution pattern of such systems requires accurate measurement procedures. Several experimental methods were tested and compared. Accordingly, the piezometric flush taps and thermo-anemometer were selected to measure respectively the duct air pressure and the outlet air flow. / Based on the equations of energy and momentum conservation, a model was formulated to predict the air flow performance of perforated ventilation ducts and to evaluate the outlet discharge angle and the duct regain coefficients without evaluating frictional losses. The basic assumptions of the model were validated by experimentally proving the equivalence of the friction losses expressed in the 2 cited equations. When compared to experimental results measured from four wooden perforated ventilation ducts with aperture ratios of 0.5, 1.0, 1.5, and 2.0, the model predicted the outlet air flow along the full length of perforated duct operated under turbulent flow conditions with a maximum error of 9%. The regain coefficient and the energy correction factor were equal to one, and the value of the discharge coefficient remained constant at 0.65, along the full length of the perforated duct. The outlet air jet discharge angle varied along the entire duct length, and was not influenced by friction losses for turbulent flow. / Assuming a common effective outlet area, the model was extended to match the performance of the fan and the perforated duct and to determine their balance operating point.

Discharge coefficients are an important parameter in the prediction of the air displacement performance of ventilation outlets and in the design of ventilation ducts. / Discharge coefficients of a wooden ventilation duct 8.54 metres in length and of a constant 0.17 m$ sp2$ cross sectional area were measured. Four different outlet shapes and 3 aperture ratios of each shape were tested. A split plot experimental design was used to evaluate the effect of outlet shape, outlet size, and distance from the fan on discharge coefficient. The relationship between duct performance characteristics and discharge coefficient was examined. A mathematical equation to predict the discharge coefficient was developed and tested. / Discharge coefficient values measured ranged from 0.19 to 1.25 depending on the aperture ratio and distance from the fan. Outlet shape had no significant effect. The apparent effects of aperture ratio and size are due to the effects of head ratio. The equation predicting the discharge coefficient had a maximum error of 5 percent for the aperture ratios of 0.5 and 1.0, and 15 percent at an aperture ratio of 1.5.

No description available.

Thesis (Ph. D.)--University of Adelaide, Dept. of Applied Mathematics, 1986. / Includes bibliographical references (leaves 95-97).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Jeter, Sheldon; Committee Member: Ghiaasiaan, S. Mostafa; Committee Member: Joshi, Yogendra.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.120-127).