Mechanical & Manufacturing EngMechanical & Manufacturing Enghttp://hdl.handle.net/2262/792015-01-28T06:34:51Z2015-01-28T06:34:51ZFeasibility Study and Cost-Benefit Analysis of Tidal Energy: A Case Study for IrelandPERSOONS, TIMhttp://hdl.handle.net/2262/728872015-01-06T03:04:16Z2012-01-01T00:00:00ZFeasibility Study and Cost-Benefit Analysis of Tidal Energy: A Case Study for Ireland
PERSOONS, TIM
Ireland set out to produce 33% of its electricity
demand from renewable sources by 2020 and
reduce emissions to the level of 1990 in accordance
with
the
Kyoto agreement. These targets require
investments in a diverse range of power sources.
This paper investigates if Tidal Stream Generators
(TSG
)
can become an economically viable system.
Initially a levelised cost was established for tidal and
other energies at a baseline year of 2010. Due to t
he
early stage of development of tidal energy, it is
difficult to accurately predict its future capital
investment and operational cost. For this reason
future costs were estimated for all energy forms and
a present worth was established. From this a
level
ised cost over the project lifetime was
calculated
. At this point it was found that Tidal
Energy was a competitive form of energy. The
feasibility of tidal energy was assessed using both
constant and varying Renewable Feed In Tariffs
(REFIT). Using 2010 v
alues a profit of €1.671Billion
could be achieved with a maximum investment of
€135million. However if REFIT changed to
32€/MWh after the contractual 15 years, a profit of
around €200million can be achieved with a
maximum investment of around €213million.
2012-01-01T00:00:00ZGeneral Reduced-Order Model to Design and Operate Synthetic Jet ActuatorsPERSOONS, TIMhttp://hdl.handle.net/2262/728862015-01-06T03:04:07Z2012-01-01T00:00:00ZGeneral Reduced-Order Model to Design and Operate Synthetic Jet Actuators
PERSOONS, TIM
Synthetic jets are used in various applicat
ions from flow contro
l to thermal management
of electronics. Controlling the jet operating
point using a simple voltage to velocity
calibration becomes unreliable in case of ext
ernal pressure field disturbances or varying
actuator characteristics. This paper pres
ents a general lumped parameter model for a
synthetic jet actuator with electromagnetic
or piezoelectric driver. The fluidic model
accurately predicts the synthetic jet operati
ng point (i.e. Reynolds number and stroke
length) based on the measured cavity pre
ssure. The model requires only two empirical
coefficients characterizing
nozzle fluid damping and inertia
. These can be obtained via
calibration or estimated from pressure loss co
rrelations and the governing acoustic radiation
impedance. The model has been validated
experimentally for a ci
rcular and rectangular
orifice. The effect of nozzle damping on
the nonlinear system response is discussed.
Analytical expressions are given for the two resonance frequencies characterizing the system
response, as a function of the diaphragm a
nd Helmholtz resonance frequencies. The optimal
design of an impinging synthe
tic jet actuator is discusse
d in terms of the thermal and
acoustic efficiency. Guidelines for selectin
g the optimum combination of diaphragm and
Helmholtz resonance frequency are presente
d and compared to previous studies.
PUBLISHED
2012-01-01T00:00:00ZExperimental Validation of a Computational Fluid Dynamics Methodology for Transitional Flow Heat Transfer Characteristics of a Steady Impinging JetPERSOONS, TIMMURRAY, DARINA BRIDGEThttp://hdl.handle.net/2262/728852015-01-06T03:03:52Z2014-01-01T00:00:00ZExperimental Validation of a Computational Fluid Dynamics Methodology for Transitional Flow Heat Transfer Characteristics of a Steady Impinging Jet
PERSOONS, TIM; MURRAY, DARINA BRIDGET
This paper presents a computational fluid dynamics (CFD) methodology to accurately predict the heat transfer characteristics of an unconfined steady impinging air jet in the transitional flow regime, impinging on a planar constant-temperature surface. The CFD methodology is validated using detailed experimental measurements of the local surface heat transfer coefficient. The numerical model employs a transitional turbulence model which captures the laminar–turbulent transition in the wall jet which precisely predicts the intensity and extent of the secondary peak in the radial Nusselt number distribution. The paper proposes a computationally low-cost turbulence model which yields the most accurate results for a wide range of operating and geometrical conditions. A detailed analysis of the effect of mesh grid size and properties, inflow conditions, turbulence model, and turbulent Prandtl number Prt is presented. The numerical uncertainty is quantified by the grid convergence index (GCI) method. In the range of Reynolds number 6000 ≤ Re ≤ 14,000 and nozzle-to-surface distance 1 ≤ H/D ≤ 6, the model is in excellent agreement with the experimental data. For the case of H/D = 1 and Re = 14,000, the maximum deviations are 5%, 3%, and 2% in terms of local, area-averaged and stagnation point Nusselt numbers, respectively. Experimental and numerical correlations are presented for the stagnation point Nusselt number.
PUBLISHED
2014-01-01T00:00:00ZFlow regime characterisation of an impinging axisymmetric synthetic jetPERSOONS, TIMMURRAY, DARINA BRIDGEThttp://hdl.handle.net/2262/728842015-01-06T03:03:40Z2013-01-01T00:00:00ZFlow regime characterisation of an impinging axisymmetric synthetic jet
PERSOONS, TIM; MURRAY, DARINA BRIDGET
Impinging synthetic jets have excellent potential for energy-efficient local cooling in confined geometries. For a given geometry, synthetic jet flows are mainly characterised by the Reynolds number and the ratio of stroke length to a geometric length scale. The flow field of an impinging synthetic jet and the corresponding surface heat transfer distribution are strongly dependent on the dimensionless stroke length, yet few studies have investigated the flow field dependence for a wide range of stroke lengths. Therefore, the aim of this paper is to identify the various flow regimes as a function of stroke length. The experimental approach combines high speed particle image velocimetry and single point hot wire anemometry, and investigates an axisymmetric synthetic air jet impinging onto a smooth planar surface for a wide range of stroke length (3 < L0/D < 32) and nozzle-to-surface spacing (2 < H/D < 16). Since the Reynolds number effect is better understood, most of the presented results are for a single Reynolds number (Re = 1500). Four free synthetic jet flow morphology regimes are identified based on threshold values for the stroke length L0/D, which are in good agreement with previously published findings for an impulsively started jet flow. Furthermore, four impinging synthetic jet flow regimes are identified based on threshold values for the ratio of normalised stroke length to nozzle-to-surface spacing (L0 − 2D)/H, which are in good agreement with previously published thresholds for stagnation point heat transfer regimes.
PUBLISHED
2013-01-01T00:00:00Z