Heat transfer coefficients from spheres were measured in a naturally turbulent, outdoor environment and compared to measurements made in wind tunnels at various turbulent intensities. The experiments were performed using spheres of three different diameters placed at different heights relative to the ground surface. The time-average values of Nusselt number and Reynolds number were obtained over 5-min time periods. Over the Reynolds number range 2000–35,000, the value of the Nusselt number obtained outdoors was up to 2.2 times the values determined in low turbulent intensity wind tunnels. The data, averaged for each sphere at each height, showed an average enhancement of the Nusselt number that decreased with height from 1.8 to 1.1. The heat transfer enhancement was found to be essentially independent of Reynolds number and correlated with the ratio of height above the surface to the sphere diameter. Standard micrometeorological theory was used to estimate the turbulence intensity as a function of height above the ground. The enhancement in heat transfer was found to be mainly correlated with turbulence intensity. The results for all but the lowest placed spheres are in substantial agreement with results using artificially induced turbulence.

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In the Mechanical and Industrial Engineering department at Northeastern University, Capstone Design is a two semester course offered in one of two sequences. In one sequence, the two semesters follow each other directly, with students taking the first semester in late summer, followed immediately by the second semester in the Fall. In the other sequence, the students take the first semester in early summer, and then spend 6 months on coop before returning in the Spring to complete the second semester of Capstone. Although these two sequences were developed simply to accommodate student schedules, this fact provides an opportunity to determine whether the lag between semesters hinders, aids, or has no effect on whether students generate quality designs and use good project management techniques. Students who take the consecutive sequence have the advantage of working continually on their design problem for 2 terms, allowing them to keep momentum going. However, it is possible that the students who interrupt their sequence with coop are able to use that time to continue independent learning, even if they are not actively working on the problem. Both cohorts spend the same total amount of time on coop. However, the group with the interrupted sequence can apply the valuable skills in project management and other real-world work skills that they learn in Capstone I to their coop, reinforcing their skills in a timely manner. This could provide the groups in the interrupted sequence with an organizational advantage upon their return. The purpose of this study is to determine whether there is a distinct difference between the two cohorts in the quality of the final projects produced.. Several measures of project quality will be used to study the two groups. Final course grades for each group will be an initial indicator of any distinction. Another measure is whether or not the groups have reached the prototyping stage at a point two weeks from the end of the course. This can be determined from the executive summaries the groups submit at that point. The number of patent disclosures and provisional patents awarded per term will indicate both the quality of the project and the performance of the groups, as groups that file patents typically are further along in their project. Finally, the two cohorts will be compared based on feedback from the alumni jury members who judge the final projects. Results indicate that the nonconsecutive groups have slightly better grades, more projects which reach the prototyping stage 2 weeks prior to the end of term, and more projects rated successful by the alumni jury. Patent applications did not prove to be conclusively indicative of any difference between cohorts.

A computational analysis of the reacting flow field, species diffusion and heat transfer processes with thermal boundary layer effects in a microchannel reactor with a coflow configuration was performed. Two parallel adjacent streams of aqueous reactants flow along a wide, shallow, enclosed channel in contact with a substrate, which is affixed to a temperature controlled plate. The Fluent computational fluid dynamics package solved the Navier–Stokes, mass transport and energy equations. The energy model, including the enthalpy of reaction as a nonuniform heat source, was validated by calculating the energy balance at several control volumes in the microchannel. Analysis reveals that the temperature is nearly uniform across the channel thickness, in the direction normal to the substrate surface; hence, measurements made by sensors at or near the surface are representative of the average temperature. Additionally, modeling the channel with a glass substrate and a silicone cover shows that heat transfer is predominantly due to the glass substrate. Finally, using the numerical results, we suggest that a microcalorimeter could be based on this configuration, and that temperature sensors such as optical nanohole array sensors could have sufficient spatial resolution to determine enthalpy of reaction.

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