PhD, University of Cincinnati, 2011, Engineering and Applied Science: Mechanical Engineering

Compact heat exchangers are employed in many different applications because of their high surface area density. Plate-fin heat exchangers in particular are well suited for gas-to-gas and air-to-air recuperators and heat recovery units, among many other applications. In this thesis, constant property, fully or periodically developed laminar flows of air (Pr = 0.72) inside a variety of different inter-fin channels of plate-fin heat exchangers are studied computationally, with the goal of achieving better understanding of plate-fin heat exchangers and providing new designs with superior performance to the existing ones. Majority of plate-fin channels have rectangular, trapezoidal or triangular cross-sectional shapes. Their convective behavior for air flows is investigated and solutions and polynomial equations to predict the Nusselt number are provided. Besides the limiting cases of a perfectly conducting and insulated fin, the actual conduction in the fin is also considered by applying a conjugate conduction-convection boundary condition at the fin surface between partition plates. For the latter, new sets of solutions and charts to determine the heat transfer coefficient based on the fin materials, channel aspect ratio, and fin density are presented. Furthermore, while large fin density increases the heat transfer surface area, the convection coefficient can be increased by geometrical modification of the fins. To this end, two different novel plate-fin configurations are proposed and their convective behavior investigated in this thesis. These include (1) slotted plate-fins with trapezoidal converging-diverging corrugations, and (2) offset-strip fins with in-phase sinusoidal corrugations. The enhanced heat transfer performance of the plate-fin compact core with perforated fin-walls of symmetric, trapezoidally profiled, converging-diverging corrugations is modeled computationally. Air flow rates in the range 10=Re=1000 are considered in a two dimensional duct geome (open full item for complete abstract)

Committee: Milind Jog PhD (Committee Chair); Raj Manglik PhD (Committee Chair); Shaaban Abdallah PhD (Committee Member); Manish Kumar PhD (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2004, Engineering : Mechanical Engineering

Substantial thermal performance improvement in ice-on-tube TES (thermal energy storage) systems is possible by making use of porous copper mesh as a HCED (Heat Conducting Enhancement Device). HCEDs are inexpensive heat transfer augmentation devices that will result in faster rate of ice growth and larger final steady state ice build volume by reducing the controlling thermal conduction resistance of the ice layer. This will improve the competitiveness of external ice-on-tube systems as compared to other TES systems such as dynamic ice harvesters and static internal melt systems. In this study the degree of ice growth enhancement is predicted theoretically, by performing simplified calculations, and is then validated in the laboratory through carefully controlled experiments. This study shows ice volume increase between 50-90% is possible.

Committee: Dr. Michael Kazmierczak (Advisor) Subjects: Engineering, Mechanical