Interactive flow behaviour and heat transfer enhancement in a microchannel with cross flow synthetic jet

This paper examines the effectiveness in combining a pulsating fluid jet for thermal enhancement in microchannel heat sinks. The proposed arrangement utilises an oscillating diaphragm to induce a high-frequency periodic fluid jet with zero net mass output at the jet orifice hence, termed "synthetic jet". The pulsed jet interacts with the fluid flow through microchannel passages altering their flow characteristics. The present study develops a 2-dimensional finite volume numerical simulation based on unsteady Reynolds-averaged Navier-Stokes equations for examining the microchannel-synthetic jet flow interaction. For a range of parametric conditions, the behaviour of this periodic flow with its special features is identified and the associated convective heat transfer rates are predicted. The results indicate that the pulsating jet leads to outstanding thermal performance in microchannel flow increasing its heat dissipation rate by about 4.3 times compared to a microchannel without jet interaction within the tested parametric range. The degree of thermal enhancement is seen to grow continuously to reach a steady value in the absence of fluid compressibility. The proposed strategy has an intrinsic ability for outstanding thermal characteristics without causing pressure drop increases in microchannel fluid passages, which is identified as a unique feature of the technique.The study also examines and presents the effects of fluid compressibility on the heat removal capacity of this arrangement. The technique is envisaged to have application potential in miniature electronic devices where localised cooling is desired over a base heat dissipation load

Cognition in schizophrenia improves with treatment of severe obstructive sleep apnoea: a pilot study

Previous studies have shown that people with schizophrenia have high rates of Obstructive Sleep Apnoea (OSA). Despite this, intervention studies to treat OSA in this population have not been undertaken. The ASSET (Assessing Sleep in Schizophrenia and Evaluating Treatment) pilot study investigated Continuous Positive Airway Pressure (CPAP) treatment of severe OSA in participants recruited from a clozapine clinic in Adelaide. Participants with severe untreated OSA (Apnoea-Hypopnoea Index (AHI) > 30), were provided with CPAP treatment, and assessed at baseline and six months across the following domains: physical health, quality of sleep, sleepiness, cognition, psychiatric symptoms and CPAP adherence. Six of the eight ASSET participants with severe OSA accepted CPAP. At baseline, half of the cohort had hypertension, all were obese with a mean BMI of 45, and they scored on average 1.47 standard deviations below the normal population in cognitive testing. The mean AHI was 76.8 and sleep architecture was markedly impaired with mean rapid eye movement (REM) sleep 4.1% and mean slow wave sleep (SWS) 4.8%. After six months of treatment there were improvements in cognition (BACS Z score improved by an average of 0.59) and weight loss (mean weight loss 7.3 ± 9 kg). Half of the participants no longer had hypertension and sleep architecture improved with mean REM sleep 31.4% of the night and mean SWS 24% of the night. Our data suggests CPAP may offer novel benefits to address cognitive impairment and sleep disturbance in people with schizophrenia.Hannah Myles, Nicholas Myles, Ching Li Chai Coetzer, Robert Adams, Madhu Chandratilleke, Dennis Liu, Jeremy Mercer, Andrew Vakulin, Andrew Vincent, Gary Wittert, Cherrie Galletl

Dem investigation of horizontal high shear mixer flow behaviour and implications for scale-up

In high shear granulation, various dimensionless or dimensioned parameter groups such as constant Froude number, tip speed, relative swept volume and specific energy input are commonly used as scale-up criteria, in order to maintain the powder bed internal flow or stress field across scales. One major challenge is obtaining the internal flow and stress field through experimentation given the lack of precise measurement techniques. Hence, this work employs DEM (discrete element method) simulations to study the internal flow patterns and behaviour of different scale batch, horizontal high shear mixers. The simulations provide a deeper understanding of the interaction of scale, impeller speed and fill level on the flow field, and show that the particle velocity is correlated with the relative swept volume in these mixers. It shows that the relative particle velocity is correlated, independent of scale, to the relative swept volume per rotation and highlights its values as a parameter for understanding and comparing mixer behaviour. The work also demonstrates the importance of the particle size chosen for the simulation as well as the tool-wall gap in the mixer, and highlights its importance as we interpret DEM results

A Synthetic Jet Heat Sink with Cross-flow for Electronic Cooling

This paper presents an investigation on the operational characteristics and thermal effectiveness of a pulsed (or synthetic) jet mechanism that periodically cools at a heated surface while acting in cross-flow fluid stream. The study uses a test rig having a variable-frequency pulsed air jet impinging at a heated surface that emulates an electronic device to be cooled. The cooling characteristics of the jet are observed over a wide parametric range. The results show that the pulsed jet mechanism delivers outstanding cooling performance that is primarily dependent on the jet-impinging distance and operating frequency. Without cross flow, the pulsed jet provides about 11 K temperature reduction and 7 times more heat removal rate compared to natural convection at the heated surface. The jet impingement height indicates a strong dependency with an optimum on the heat removal rate. With cross-flow fluid stream, the pulsed jet cooling is enhanced. This combined fluid action achieves about 13 K temperature drop and delivers 2.2 times more cooling compare to pulsed jet operating alone. The pulsed jet operation is numerically simulated to understand the associated flow characteristics leading to thermal enhancement. It is recognised that the pulsed jet arrangement has the unique surface cooling ability without additional fluid circuits, making it particularly desirable for high-capacity electronic cooling applications

LIFE CYCLE SAVINGS OF AN INDUSTRIAL SOLAR HOT WATER HEATER.

Solar Engineering2896-901SOLE

Economic evaluation of a solar water heating system

Energy Conversion and Management272197-204ECMA

Economic evaluation of a solar water heating system

This paper describes different methods of analysis of a solar water heating system to determine its economic viability. The solar fraction, required for this analysis, has been calculated with a stimulation program using hourly meteorological data of Singapore. A measured load profile, representing the average condition, was used for this program. The economic variables have been selected from the trends shown in previous years. When different economic optimization criteria were applied to the CIAS solar system, it was seen that both the life cycle saving and the annualized life cycle cost lead to the prediction of the same optimum collector area of 1200 m 2. The payback period and the internal rate of return analyses also predicted the same optimum collector area of 1000 m 2, which is smaller than that predicted by the method of life cycle costing. For the economic variables used in this analysis, the minimum payback period is about 14 years

Obstructive sleep apnea and schizophrenia: a systematic review to inform clinical practice

Abstract not availableHannah Myles, Nicholas Myles, Nick A. Antic, Robert Adams, Madhu Chandratilleke, Dennis Liua, Jeremy Mercer, Andrew Vakulind, Andrew Vincent, Gary Wittert, Cherrie Galletl