David M. Calamas

Performance Analysis of Biologically Inspired Honeycomb Structured Heat Exchanger

The process of heat exchange between two fluids that are at different temperatures and separated by a solid wall occurs in many engineering applications. The device used to implement this exchange is termed a heat exchanger (HE), and specific applications may be found in space heating and air-conditioning, power generation, waste heat recovery, and chemical processing. Increasing heat transfer coefficient and making heat exchanger compact for various applications like in spacecraft, underwater vehicle, unmanned Ariel vehicle is one of the main challenges. Biologically-inspired design (or BID) has become an important and increasingly wide-spread movement in design for environmentally-conscious sustainable development. By definition, BID is based on cross-domain analogies; further, biologically-inspired approaches to design have a certain degree of openness to innovation. Compact heat exchanger can reduce the space and weight of any locomotives and spacecraft. Structural elements inspired from nature possess compactness and stability. Honeycomb structure allows minimize the spacing between cells which makes it possible to use thinnest possible metal boundary wall between two fluids. A rectangle structure can also do the same thing but it has less surface area, which will essentially decrease the volume of heat exchanger. Honeycomb structure provides high surface area to volume ratio which can be utilized to increase heat transfer coefficient of a heat exchanger and thus make compact system.In this computational study, bio-inspired simple honeycomb structured and spiral finned honeycomb structured counter flow heat exchanger has been three dimensionally simulated using finite element methods in commercial software COMSOL. This work is used to reduce the weight of heat exchangers in steam reforming reactors. There is a good correlation when the fluid temperature is the same in all cells. There is also a good temperature gradient in the fluid owing to laminar flow. 3D modeling showed that a careful representation of the inlet is needed for realistic results. A tube-shell heat exchanger is also simulated using FEA in COMSOL. Spiral finned heat exchanger provides additional surface area in cost of pressure drop. The performance characteristics of honeycomb heat exchanger showed an increase in heat transfer rate with least vortex formation.Copyright

Electrospinning of Cisplatin-Loaded Cellulose Nanofibers for Cancer Drug Delivery

Cellulosic nanofibers have been electrospun with an antitumor agent Cisplatin. Cellulose acetate (CA) and Cisplatin were co-electrospun using a coaxial electrospinning system. For the outer sheath, a solution of 7.5wt% CA in Acetone and DMAc (2:1) was used. The inner core consisted of Cisplatin dissolved in DMF at a concentration of 5mg/ml. Drug-loaded nanofibers from Cellulose pulp (2wt%) dissolved in NMMO. H2O were also produced. The solutions were electrospun in a high voltage electric field of 25–30 kV. Characterization of neat and drug-loaded nanofibers was performed using Scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). The characterization studies have shown the formation of nanofibers having both sporadic beads with internal agglomeration and conjugation of Cisplatin on the nanofiber surfaces.Copyright

Performance of Thermally Radiating Fractal Extended Surfaces of Varying Cross-Section

The thermal performance of fractal fins with varying cross-sectional profiles thermally radiating to free space was computationally examined. The Sierpinski carpet fractal pattern was used to increase the surface area and decrease the system mass of extended surfaces used in waste heat rejection systems. Fin effectiveness per unit was used to quantify the thermal performance of the Sierpinski carpet extended surfaces of varying cross-sectional profile. The use of non-uniform cross-sectional profiles was found to increase the effectiveness per unit mass of Sierpinski carpet extended surfaces thermally radiating to free space. At higher order fractal iterations the use of non-uniform cross-sectional profiles also resulted in an increase in fin efficiency. The utilization of the Sierpinski carpet fractal pattern in combination with a non-uniform cross-sectional profile results in a significant increase in fin effectiveness per unit mass when compared with traditionally employed longitudinal fins of rectangular profile.