Development, modelling and evaluation of a (laminar) entrained flow reactor for the determination of the pyrolysis kinetics of polymers.

Laminar Entrained Flow Reactors were examined to determine whether this type of reactor can be used to measure the kinetic parameters of the pyrolysis reaction of polymers. In case the EFR was operated in the turbulent regime or the diameter of the reactor was to small, sticking of polymer to the reactor wall, became a major problem. In the laminar flow regime this problem did not occur and this operation regime was determined as a function of the Reynolds number. Due to the necessity of operation in the laminar regime significant temperature and velocity gradients exist in the EFR. To correct for these gradients a model was developedincorporating the Navier - Stokes equations to describe the gas phase velocity and temperature distributions and a single particle model to describe the conversion of the individual particles. While correction of the experimental data for the axial gradients proved to be possible, it was not possible to correct this data for radial gradients in the reactor due to the uncertainty in the radial position of the particle. Experiments were performed and corrected for the aforementioned gradients to obtain the first order kinetic parameters for the pyrolysis of LDPE. However, these parameters are inaccurate and therefore a LEFR is preferably not to be used to determine kinetics of particles, if operation of the EFR in the laminar regime is necessary (sticking particles). If possible (non-sticking particles) the EFR should be operated in the turbulent regime. Finally our pyrolysis experiments of LDPE showed that intermediate wax - like products are produced during the pyrolysis reaction, which are pyrolysed further in the gas phase

Study of Multilouvered Heat Exchangers at Low Reynolds numbers

Air Conditioning and Refrigeration Project 13

Numerical and experimental analysis of a thin liquid film on a rotating disk related to development of a spacecraft absorption cooling system

The numerical and experimental analysis of a thin liquid film on a rotating and a stationary disk related to the development of an absorber unit for a high capacity spacecraft absorption cooling system, is described. The creation of artificial gravity by the use of a centrifugal field was focused upon in this report. Areas covered include: (1) One-dimensional computation of thin liquid film flows; (2) Experimental measurement of film height and visualization of flow; (3) Two-dimensional computation of the free surface flow of a thin liquid film using a pressure optimization method; (4) Computation of heat transfer in two-dimensional thin film flow; (5) Development of a new computational methodology for the free surface flows using a permeable wall; (6) Analysis of fluid flow and heat transfer in a thin film in the presence and absence of gravity; and (7) Comparison of theoretical prediction and experimental data. The basic phenomena related to fluid flow and heat transfer on rotating systems reported here can also be applied to other areas of space systems

Stonehenge remodelled

We are pleased to present the latest account of the sequence of burial and construction at the site of Stonehenge, deduced by its most recent excavators and anchored in time by the application of Bayesian radiocarbon modelling. Five prehistoric stages are proposed, of varied duration, and related by our authors to neighbouring monuments in the Stonehenge environs. While it may never be possible to produce a definitive chronology for this most complex of monuments, the comprehensive and integrated achievement owed to these researchers has brought us much closer to that goal. It is from this firm platform that Stonehenge can begin its new era of communication with the public at large

Internal pressure measurements in microchannels of different shapes

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.This paper presents the experimental results of determining friction factors for two microchannels with circular cross-sections: rectilinear and curvilinear. The inner diameter of the channels is 68.9 and 70.3 μm. The Reynolds numbers ranged from 320 to 3215. Pressure measurements are carried out simultaneously in 16 locations along the straight microchannel and in 12 locations for the curved microchannel. The friction factor for the straight microchannel is in good agreement with the theoretical value for the round smooth tubes. For the curved microchannel, the friction factor value of the curved section is less than the reference value for smoothly curved tubes. The Reynolds number for the laminar-turbulent transition in a straight microchannel is 2300–2600. In the curved microchannel the transition is not observed. The length of the developing region was identified, and the inlet minor loss coefficient is calculated.This work was supported by the Siberian Branch of the Russian Academy of Sciences (integration project of SB RAS no. 110)

Laboratory performances of the solar multichannel resonant scattering spectrometer prototype of the GOLF-New Generation instrument

This article quickly summarizes the performances and results of the GOLF/SoHO resonant spectrometer, thus justifying to go a step further. We then recall the characteristics of the multichannel resonant GOLF-NG spectrometer and present the first successful performances of the laboratory tests on the prototype and also the limitations of this first technological instrument. Scientific questions and an observation strategy are discussed.Comment: 8 pages, 8 figures, published in Astronomical Note

Developing and evaluating a hybrid wind instrument

A hybrid wind instrument generates self-sustained sounds via a real-time interaction between a computed excitation model (such as the physical model of human lips interacting with a mouthpiece) and a real acoustic resonator. Attempts to produce a hybrid instrument have so far fallen short, in terms of both the accuracy and the variation in the sound produced. The principal reason for the failings of previous hybrid instruments is the actuator which, controlled by the excitation model, introduces a fluctuating component into the air flow injected into the resonator. In the present paper, the possibility of using a loudspeaker to supply the calculated excitation signal is evaluated. A theoretical study has facilitated the modeling of the loudspeaker-resonator system and the design of a feedback and feedforward filter to successfully compensate for the presence of the loudspeaker. The resulting self-sustained sounds are evaluated by a mapping of their sound descriptors to the input parameters of the physical model of the embouchure, both for sustained and attack sounds. Results are compared with simulations. The largely coherent functioning confirms the usefulness of the device in both musical and research contexts

Modelling and simulation techniques for forced convection heat transfer in heat sinks with rectangular fins

The official published version of this article can be found at the link below.This paper provides a comprehensive description of the thermal conditions within a heat sink with rectangular fins under conditions of cooling by laminar forced convection. The analysis, in which increasing complexity is progressively introduced, uses both classical heat transfer theory and a computational approach to model the increase in air temperature through the channels formed by adjacent fins and the results agree well with published experimental data. The calculations show how key heat transfer parameters vary with axial distance, in particular the rapid changes in heat transfer coefficient and fin efficiency near the leading edges of the cooling fins. Despite these rapid changes and the somewhat ill-defined flow conditions which would exist in practice at the entry to the heat sink, the results clearly show that, compared with the most complex case of a full numerical simulation, accurate predictions of heat sink performance are attainable using analytical methods which incorporate average values of heat transfer coefficient and fin efficiency. The mathematical modelling and solution techniques for each method are described in detail.This work was part of a project funded by Solas Technology Limited, Ireland