 Mechanical Engineering  Research Publications
Mechanical Engineering  Research Publications
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ItemAn ice thermal storage computer modelCHAICHANA, C ; CHARTERS, WWS ; AYE, L (Elsevier, 20011201)In hot humid countries such as Thailand, air conditioning plant is installed in most commercial and industrial buildings. A conventional air conditioning system, which is normally operated when cooling is required, is the most favored option. Ice thermal storage on a large scale, used to provide a cool reservoir for use in peak periods, is however an attractive financial option for large buildings to supply coolness. There are two means of operating ice thermal storage systems, namely full storage and partial storage. In this paper, a computer model has been developed in order to compare energy use in conventional air cooling systems and ice thermal storage systems. Under Thailand electricity tariff rates, the results from the simulations show that the full ice thermal storage can save up to 55% of the electricity cost required for cooling per month when compared with the conventional system. It is also found that using full storage option can reduce the total energy consumption by 5% for the selected building.

ItemBenefits of cool thermal storage in ThailandCHAICHANA, C ; CHARTERS, W ; AYE, L (RERIC, 20010601)The use of thermal storage on a large to provide a cool reservoir for use in peak periods is an attractive financial option for large hotels, hospitals or office blocks. This enables the refrigeration plant to operate more effectively and to be completely or partially shut down during peak periods when the demand can be met in full or in part from the cool store. In this paper an overview is given of the power generation capacity and costing structure in Thailand and a typical load profile is presented to illustrate the advantages to be gained by shifting plant operation to offpeak periods. Specific load calculations have been utilized to demonstrate the cost savings possible by incorporation of such a cool thermal storage system into a traditional refrigeration and air conditioning plant for a major hotel complex.

ItemElectrical and engine driven heat pumps for effective utilisation of renewable energy resourcesAye, L ; Charters, WWS (PERGAMONELSEVIER SCIENCE LTD, 20030701)

ItemEffects of changing aspect ratio through a wind tunnel contractionCallan, J. ; Marusic, I. (American Institute of Aeronautics & Astronautics, 2001)No abstract.

ItemA wallwake model for the turbulence structure of boundary layers. Part 2. Further experimental supportMarusic, I. ; Perry, A. E. (Cambridge University Press, 1995)In Part 1 an extension of the attached eddy hypothesis was developed and applied to equilibrium pressure gradient turbulent boundary layers. In this paper the formulation is applied to data measured by the authors from nonequilibrium layers and agreement with the extended theory is encouraging. Also power spectra of the Reynolds stresses as developed from the extended theory compare favourably with experiment. The experimental data include a check of coneangle effects by using a flying hot wire.

ItemA wallwake model for the turbulence structure of boundary layers. Part 1. Extension of the attached eddy hypothesisPerry, A. E. ; Marusic, I. (Cambridge University Press, 1995)The attached eddy hypothesis developed for zero pressure gradient boundary layers and for pipe flow is extended here to boundary layers with arbitary streamwise pressure gradients, both favourable and adverse. It is found that in order to obtain the correct quantitative results for all components of the Reynolds stresses, two basiv types of eddy structure geometries are required. The first type, called typeA, is interpreted to give a 'wall structure' and the second, referred to as typeB, gives a 'wake structure'. This is an analogy with the conventional mean velocity formulation of Coles where the velocity is decomposed into a law of the wall and a law of the wake.If the above mean velocity formulation is accepted, then in principle, once the eddy geometries are fixed for the two eddy types, all Reynolds stresses and associated spectra contributed from the attached eddies can be computed without any further empirical constants. This is done by using the momentum equation and certain convolution integrals developed here based on the attached eddy hypothesis. The theory is developed using data from equilibrium and quasiequilibrium flows. In Part 2 the authors' nonequilibrium data are used.

ItemWall turbulence closure based on classical similarity laws and the attached eddy hypothesisPerry, A. E. ; Marusic, I. ; Li, J. D. ( 1994)A new look at the closure problem of turbulent boundary layers is taken here using recently derived analytical expressions for the shear stress distributions. These expressions are based on logarithmic law of the wall and law of the wake formulation of Coles [J. Fluid Mech. 1, 191 (1956)] with the mean continuity and the mean momentum differential and integral equations. The concept of equilibrium layers of Clauser [Adv. Mech. 4, 1 (1956)] is extended and using similar ideas as Rotta [Prog. Aeronaut. Sci. 2, 1(1962)] for selfsimilarity, a closure scheme is proposed for layers developing in arbitrary pressure gradients for the case where the streamwise derivative of the Coles wake factor is not too large. For a given flow case, this Coles wake condition can be tested with internal consistency checks. The mathematical framework is most suitable for incorporating Townsend’s attached eddy hypothesis as recently developed by Perry, Li, and Marusic [Phils. Trans. R. Soc. London. Ser. A 336, 67 (1991)] for closure. This gives an opportunity to incorporate coherent structure concepts into closure schemes. Possible ways of handling the difficult case where the streamwise derivative of the Coles wake factor is significant are discussed.

ItemOn the streamwise evolution of turbulent boundary layers in arbitrary pressure gradientsPerry, A. E. ; Marusic, I. ; Jones, M. B. (Cambridge University Press, 2002)A new approach to the classic closure problem for turbulent boundary layers is presented. This involves, first, using the wellknown meanflow scaling laws such asthe log law of the wall and the law of the wake of Coles (1956) together with the mean continuity and the mean momentum differential and integral equations. The important parameters governing the flow in the general nonequilibrium case are identified and are used for establishing a framework for closure. Initially closure is achieved here empirically and the potential for achieving closure in the future using the wallwake attached eddy model of Perry & Marusic (1995) is outlined. Comparisons are made with experiments covering adversepressuregradient flows in relaxing and developing states and flows approaching equilibrium sink flow. Mean velocity profiles, total shear stress and Reynolds stress profiles can be computed for different streamwise stations, given an initial upstream mean velocity profile and the streamwise variation of freestream velocity. The attached eddy model of Perry & Marusic (1995) can then be utilized, with some refinement, to compute the remaining unknown quantities such as Reynolds normal stresses and associated spectra and crosspower spectra in the fully turbulent part of the flow.

ItemTowards a closure scheme for turbulent boundary layers using the attached eddy hypothesisPerry, A. E. ; Li, J. D. ; Marusic, I. (Royal Society Publishing, 1991)In this paper, an attempt is made to formulate a closure hypothesis for adverse pressure gradient turbulent layers using the attached eddy hypothesis of Townsend and Perry & Chong, which was developed originally for zero pressure gradient layers and parallel duct flows.To the authors’ knowledge, this work represents one of the few attempts to use coherent structure ideas in the formulation of a closure scheme. At present this closure scheme is primitive and many of the assumptions are of an arbituary nature but the analysis at least points out where the difficulties are and which areas need more work.

ItemSimilarity law for the streamwise turbulence intensity in zeropressuregradient turbulent boundary layersMarusic, I. ; Uddin, A. K. M. ; Perry, A. E. ( 1997)A similarity relationship is proposed to describe the streamwise broadbandturbulence intensity in a zeropressuregradient boundary layer. The formulation is applicable to the entire region of the flow beyond the viscous buffer zone and is based on the attached eddy hypothesis, the Reynoldsnumbersimilarity hypothesis and the assumed existence of Kolmogorov eddies with a universal inertial subrange. Experimental data of the authors and those from various published works covering a large Reynolds number range are investigated in light of this formulation.