3,640 research outputs found
A project and competition to design and build a simple heat exchanger
To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production
Selection of teachers in Cambridge
Thesis (Ed.M.)--Boston University, 1938. This item was digitized by the Internet Archive
A comparison of pilot-scale supersonic direct steam injection to conventional steam infusion and tubular heating systems for the heat treatment of protein-enriched skim milk-based beverages
peer-reviewedDirect supersonic steam injection, direct steam infusion, and indirect tubular heating were each applied to protein-enriched skim milk-based beverages with 4, 6 and 8% (w/w) total protein, and the effect of final heat temperature on the physical properties of these beverages was investigated. Supersonic steam injection resulted in significantly lower levels of denaturation of β-lactoglobulin (34.5%), compared to both infusion (76.3%) and tubular (97.1%) heating technologies. Viscosity, particle size and accelerated physical stability of formulations did not differ significantly between the heating technologies, while noticeable colour differences due to heat treatment (mainly attributed to increasing b* value) were observed, particularly for tubular heating. Overall, the extent of protein denaturation in high-protein dairy products was significantly influenced by the particular heating technology applied. The application of supersonic steam injection technology, with rapid heating and high shear characteristics, may enable differenciated product characteristics for ready-to-drink ambient-delivery high-protein dairy beverages.
Industrial relevance:
The design and application of novel direct supersonic steam injection technology was comprehensively studied and found to provide significant benefits over direct steam infusion and indirect tubular heating technologies for skim milk-based protein beverages. This type of injection heating system resulted in heat-treated formulations with lower levels of denatured whey proteins, compared to tubular and infusion heating, offering an alternative opportunity to the industry in terms of producing shelf-stable dairy protein beverages
Characterizing the Youngest Herschel-detected Protostars I. Envelope Structure Revealed by CARMA Dust Continuum Observations
We present CARMA 2.9 mm dust continuum emission observations of a sample of
14 Herschel-detected Class 0 protostars in the Orion A and B molecular clouds,
drawn from the PACS Bright Red Sources (PBRS) sample (Stutz et al.). These
objects are characterized by very red 24 \micron\ to 70 \micron\ colors and
prominent submillimeter emission, suggesting that they are very young Class 0
protostars embedded in dense envelopes. We detect all of the PBRS in 2.9 mm
continuum emission and emission from 4 protostars and 1 starless core in the
fields toward the PBRS; we also report 1 new PBRS source. The ratio of 2.9 mm
luminosity to bolometric luminosity is higher by a factor of 5 on
average, compared to other well-studied protostars in the Perseus and Ophiuchus
clouds. The 2.9 mm visibility amplitudes for 6 of the 14 PBRS are very flat as
a function of uv-distance, with more than 50\% of the source emission arising
from radii 1500 AU. These flat visibility amplitudes are most consistent
with spherically symmetric envelope density profiles with
~~R. Alternatively, there could be a massive unresolved
structure like a disk or a high-density inner envelope departing from a smooth
power-law. The large amount of mass on scales 1500 AU (implying high
average central densities) leads us to suggest that that the PBRS with flat
visibility amplitude profiles are the youngest PBRS and may be undergoing a
brief phase of high mass infall/accretion and are possibly among the youngest
Class 0 protostars. The PBRS with more rapidly declining visibility amplitudes
still have large envelope masses, but could be slightly more evolved.Comment: Accepted to ApJ, 40 pages, 9 Figures, 4 Table
Protostellar accretion traced with chemistry. High resolution C18O and continuum observations towards deeply embedded protostars in Perseus
Context: Understanding how accretion proceeds is a key question of star
formation, with important implications for both the physical and chemical
evolution of young stellar objects. In particular, very little is known about
the accretion variability in the earliest stages of star formation.
Aims: To characterise protostellar accretion histories towards individual
sources by utilising sublimation and freeze-out chemistry of CO.
Methods: A sample of 24 embedded protostars are observed with the
Submillimeter Array (SMA) in context of the large program "Mass Assembly of
Stellar Systems and their Evolution with the SMA" (MASSES). The size of the
CO emitting region, where CO has sublimated into the gas-phase, is
measured towards each source and compared to the expected size of the region
given the current luminosity. The SMA observations also include 1.3 mm
continuum data, which are used to investigate whether a link can be established
between accretion bursts and massive circumstellar disks.
Results: Depending on the adopted sublimation temperature of the CO ice,
between 20% and 50% of the sources in the sample show extended CO
emission indicating that the gas was warm enough in the past that CO sublimated
and is currently in the process of refreezing; something which we attribute to
a recent accretion burst. Given the fraction of sources with extended CO
emission, we estimate an average interval between bursts of 20000-50000 yr,
which is consistent with previous estimates. No clear link can be established
between the presence of circumstellar disks and accretion bursts, however the
three closest known binaries in the sample (projected separations <20 AU) all
show evidence of a past accretion burst, indicating that close binary
interactions may also play a role in inducing accretion variability.Comment: Accepted for publication in A&A, 21 pages, 13 figure
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