Th.H. Van Der Meer

University of Twente | UT · Department of Thermal Engineering

Magnetic refrigeration (MR) is a cutting-edge technology that promises high energy efficiency and eco-friendliness, making it an exciting alternative to traditional refrigeration systems. However, the main challenge to its widespread adoption is cost competitiveness. In this context, the use of liquid metals as heat transfer liquids in the MR has b...

A numerical study is performed to examine the influence of a non-uniform magnetic field on the thermo-hydraulic behaviour of a ferrofluid. The analysis is done in the context of a differentially heated semi-circular annulus where a magnetic dipole with its distinct location and dipole strength is used to obtain different configurations. The field v...

Ferrofluids have always been the centre of interest for a broad range of applications where the flow manipulation is achieved using different types of magnetic fields. In the present work, a Finite Volume Method based numerical study is performed to investigate the ferrofluid behaviour in the laminar flow regime using the complete set of Ferrohydro...

A system consisting of magneto-caloric fluid, which releases (absorbs) heat in the presence (absence) of a magnetic field, is used to achieve refrigeration. Gadolinium is used as a magneto-caloric material. The influence of using water and galinstan as heat transfer liquid, on the refrigerator performance is numerically analysed by varying the mass...

A numerical study is performed to investigate the effect of a non - uniform magnetic field from a current carrying wire on the ferrofluid flow. The analysis is carried out for a semi circular annulus with three different locations of wire relative to it, by solving coupled set of flow field equations, energy equations and the Maxwell’s magnetostati...

A thermoacoustic model is used to efficiently implement a bidirectional impulse turbine into a thermoacoustic refrigerator. Experiments are done for several gas types and mean pressures to identify its influence on the turbine efficiency. A scaling is investigated in an attempt to provide a unique function of the turbine efficiency for all operatin...

The present work is an effort to find a feasible design proposal which can ensure the continuous flow and self-sustained heat transfer within a circular annulus, solely because of magnetic forces. The objective is to study the change in flow characteristics because of magnetocaloric response of the nanoparticles used. In the present work, Mean Fiel...

The design of a bidirectional impulse turbine to convert thermoacoustic power into electricity is experimentally optimized. The turbine efficiency is measured for rotors with and without a shroud ring and for a varying tip clearance. Furthermore, the axial spacing between the guide vanes and rotor is varied with respect to the displacement amplitud...

A bidirectional impulse turbine to convert thermoacoustic power into electricity is investigated. Experimental measurements are done with a loudspeaker for varying acoustic conditions and turbine loads. The results are used to characterize the turbine performance and compare it to steady flow turbomachinery and turbines in oscillating water columns...

Thermoacoustic engines convert heat energy into high amplitude acoustic waves and subsequently into electric power. This article provides a review of the four main methods to convert the (thermo)acoustic power into electricity. First, loudspeakers and linear alternators are discussed in a section on electromagnetic devices. This is followed by sect...

In the past 25 years high temperature air combustion (HiTAC) technology has been proved and utilized in industry as a promising way to increase thermal efficiency, create a relatively uniform temperature distribution, and reduce emissions of harmful pollutants such as NOX and CO. However, due to the complexity of fuel-oil combustion, to date HiTAC...

Bioenergy is the most widely used type of renewable energy. A drawback of crops applied for bioenergy is that they compete with food and use the same natural resources like water. From a natural resources perspective, it would be more efficient to apply the large potential of available crop residues. In this paper, we calculate the water footprint...

The effect of flow separation and turbulence on the performance of a jet pump in oscillatory flows is investigated. A jet pump is a static device whose shape induces asymmetric hydrodynamic end effects when placed in an oscillatory flow. This will result in a time-averaged pressure drop which can be used to suppress acoustic streaming in closed-loo...

The major hurdle for commercialization of room temperature magnetic refrigeration is the inadequate power density of a device due to the low operating frequency. Limitation in the heat transfer rate imposed by solid-fluid convection is the primary cause. Applying Peltier Thermal Diodes in combination with microchannel heat exchangers has been inves...

Unsteady direct numerical simulations of the flow around a circular cylinder have been performed at Re = 2000. Both two-dimensional and three-dimensional simulations were validated with laminar cold flow simulations and experiments. Heat transfer simulations were carried out and the time-averaged local Nusselt number at the cylinder surface was obt...

In this work, heat transfer surface modification is made by layers of carbon nanofiber (CNF) on a 50 μm nickel wire using Thermal chemical vapor deposition process (TCVD). Three different CNF layer morphologies are made, at 500 °C, 600 °C and 700 °C, to investigate the influence of morphology on heat transfer performance characteristics. Experiment...

An experimental heat transfer investigation was carried out to examine the influence of carbon nanotubes (CNTs) layer deposits on the convective heat transfer performance inside rectangular microchannels. Successful synthesis of vertically aligned CNTs was achieved using a catalytic vapor deposition (CVD) process on a silicon sample substrate. By v...

The design of compact thermoacoustic devices requires compact jet pump geometries, which can be realized by employing jet pumps with multiple orifices. The oscillatory flow through the orifice(s) of a jet pump generates asymmetric hydrodynamic end effects, which result in a time-averaged pressure drop that can counteract Gedeon streaming in traveli...

A variety of fractal grids is used to investigate how fractal-grid-generated turbulence affects the turbulent flame speed for premixed flames. The grids are placed inside a rectangular duct and a V-shaped flame is stabilized downstream of the duct, using a metal wire. This flame is characterized using OH-LIF. The turbulent flow is characterized by...

Fractal-grid-generated turbulence is a successful technique to significantly increase the reaction rate in the center of a low-swirl flame. Previous results (Verbeek et al. Combust. Flame 162(1), 129–143, 2015) are promising, but the experiments are only performed using natural gas at a single equivalence ratio and flow rate. In industry, the need...

The effect of surface roughness on heat transfer and fluid flow phenomena within a microchannel has been investigated by using the lattice Boltzmann method. The surface roughness has been generated by using Gaussian function. Gaussian function is an efficient and convenient method to create surface roughness. Influence of the roughness cut-off freq...

A computational fluid dynamics model is used to predict the oscillatory flow through tapered cylindrical tube sections (jet pumps). The asymmetric shape of jet pumps results in a time-averaged pressure drop that can be used to suppress Gedeon streaming in closed-loop thermoacoustic devices. However, previous work has shown that flow separation in t...

An experimental approach has been used to investigate the influence of a thin layer of carbon nanotubes (CNTs) on the convective heat transfer performance under impinging flow conditions. A successful synthesis of CNT layers was achieved using a thermal catalytic vapor deposition process (TCVD) on silicon sample substrates. Three different structur...

The oscillatory flow through tapered cylindrical tube sections (jet pumps) is characterized by a numerical parameter study. The shape of a jet pump results in asymmetric hydrodynamic end effects which cause a time-averaged pressure drop to occur under oscillatory flow conditions. Hence, jet pumps are used as streaming suppressors in closed-loop the...

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nanostructures was achieved using catalytic chemical vapor deposition process on a 50 μm nicke...

A methanol spray flame in a combustion chamber of the NIST was simulated using an Eulerian-Lagrangian RANS model. Experimental data and previous numerical investigations by other researchers on this flame were analysed to develop methods for more comprehensive model validation. The inlet boundary conditions of the spray were generated using semi-em...

In thermoacoustic devises, the thermoacoustic effect occurs in the regenerator placed between two heat exchangers. The entrance effects of such heat exchanger are investigated with two computational fluid dynamics (CFD) test cases. The first CFD test case models an ideal heat exchanger adjacent to an open space. The influence of heat conduction on...

A two-dimensional computational fluid dynamics model is used to predict the oscillatory flow through a tapered cylindrical tube section (jet pump) placed in a larger outer tube. Due to the shape of the jet pump, there will exist an asymmetry in the hydrodynamic end effects which will cause a time-averaged pressure drop to occur that can be used to...

The use of fractal grids in a low-swirl burner can significantly increase the turbulent combustion rate, realizing a higher power density in these flames. The standard turbulence generating blocking grid has been replaced by one consisting of a pattern of cruciform structures of different sizes, forming a multi-scale grid derived by truncating an u...

A two-dimensional CFD model for predicting the oscillating flow through a jet pump is developed. Various taper angles are investigated and total minor loss coefficients are derived. A good correspondence is achieved with experimental results from the literature. However, at higher taper angles a dramatic decay in the jet pump pressure drop is obser...

In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic chemical vapor deposition process (CCVD) on a 50...

A compact active grid is developed with which a pipe flow can be stirred in order to enhance the turbulence. The active grid is composed of a stationary and a rotating disk with characteristic hole patterns. This active grid is placed inside the pipe, allowing flow to pass through it. With only one moving part, the design is much less complicated t...

The flameless combustion is a promising approach to increase the combustion efficiency and decrease the pollutant emission. In contrast with the wide range of investigations of its gaseous counterpart, the flameless combustion of liquid fuel is still in its infant stage. Numerical simulation provides an efficient way for the understanding of the fl...

In this study, several conditions in a 9 MW heavy fuel-oil boiler were numerically studied in order to get a better understanding of the application of HiTAC in such a boiler. Simulations were done with an Euler-Lagrange approach. The Eddy Dissipation model was used for combustion. Simulation results showed that by recycling various ratios of flue...

Thermoacoustic functions are important parameters of one-dimensional codes used for the design of thermoacoustic engines. The thermal and viscous thermoacoustic functions allow the inclusion of three dimensional effects in one-dimensional codes. These functions are especially important in the regenerator of a thermoacoustic engine, where the thermo...

Rayleigh streaming is a time-averaged flow that can exist in the thermal buffer tubes of thermoacoustic prime movers and refrigerators and is driven by the viscous stresses close to the solid boundaries. This mean flow leads to mean convective heat transport, which can have large impact on the performance of thermoacoustic devices. Rayleigh streami...

Rayleigh streaming is a time-averaged flow that can exist in the thermal buffer tubes of thermoacoustic prime movers and refrigerators and is driven by the viscous stresses close to the solid boundaries. This mean flow leads to mean convective heat transport, which can have large impact on the performance of thermoacoustic devices. Rayleigh streami...

Thermoacoustic functions are important parameters of one-dimensional codes used for the design of thermoacoustic engines. The thermal and viscous thermoacoustic functions allow the inclusion of three dimensional effects in one-dimensional codes. These functions are especially important in the regenerator of a thermoacoustic engine, where the thermo...

Numerical simulations of flow and heat transfer have been performed for flow over a plate surface covered with carbon nano fibers (CNFs). The CNFs influence on fluid flow and heat transfer has been investigated. Firstly, a stochastic model for CNFs deposition has been explained. Secondly, the lattice Boltzmann model for simulating fluid flow and he...

A concentric gas-to-gas heat exchanger is designed for application as a recuperator in the domestic boiler industry. The recuperator recovers heat from the exhaust gases of a combustion process to preheat the ingoing gaseous fuel mixture resulting in increased fuel efficiency. This applied study shows the use of computational fluid dynamics simulat...

The lattice Boltzmann model is proposed for numerical modeling of energy transport in side nano-fluids. Firstly, the lattice Boltzmann model is briefly in-troduced. Secondly, a lattice Boltzmann model for simulating nano-fluids is described. Finally, results from calculations for the effective thermal conductiv- ity of nano-fluids are presented and...

In this work, heat transfer surface modification and heat transfer measurement technique is developed. Heat transfer investigation was aimed to study the effect of carbon nano fibers (extremely high thermal conductive material) on the enhancement level in heat transfer. Synthesis of these carbon nano structures is achieved using thermal catalytic c...

Carbon nanofibers (CNF), with fishbone and parallel wall structures, were grown by catalytic chemical vapor deposition on the surface of carbon foam and stainless steel foam, in order to improve their heat exchange performance. Enhancement in heat transfer efficiency between 30% and 75% was achieved with CNF-modified stainless steel foam as measure...

Agriculture is by far the largest water user. This chapter reviews studies on the water footprints (WFs) of bioenergy (in the form of bioethanol, biodiesel, and heat and electricity produced from biomass) and compares their results with the WFs of fossil energy and other types of renewables (wind power, solar thermal energy, and hydropower). WFs fo...

Is it possible to optimize the turbulent combustion of a low swirl burner by using resonance in turbulence? To that end an active grid is constructed that consists of two perforated disks of which one is rotating, creating a system of pulsating jets, which in the end can be used as a central blocking grid of a low swirl burner. The turbulence origi...

The concept of using rapid adiabatic compression-expansion for doing chemical reactions promises to be an energy efficient alternative to conventional chemical reactors. In this article, the production of synthesis gas by steam methane reforming using the rapid adiabatic compression-expansion principle is investigated. This was done experimentally...

A concentric gas-to-gas heat exchanger is designed for application as a recuperator in the domestic boiler industry. The recuperator recovers heat from the exhaust gases of a combustion process to preheat the ingoing gaseous fuel mixture resulting in increased fuel efficiency. This applied study shows the use of computational fluid dynamics (CFD) s...

Is it possible to optimize the turbulent combustion of a low swirl burner by using resonance in turbulence? To answer that question an active grid with periodically opening and closing holes is constructed and placed upstream of a low swirl burner geometry. The presence of this grid introduces large scale turbulent fluctuations to the flow with fre...

The modeling and simulation of the turbulent spray combustion is necessary for a better understanding of the characteristics of the turbulent spray combustion in detail. However, many complex processes are involved and strongly coupled which makes the validation of the simulation essential. Light oils are often used in the experiment for the valida...

Is it possible to optimize the turbulent combustion of a low swirl burner by using resonance in turbulence? To answer that question an active grid with periodically opening and closing holes is constructed and placed upstream of a burner geometry. The presence of this grid introduces large scale turbulent fluctuations to the flow with frequencies r...

In this study, the methanol spray flame in a chamber of the NIST was modelled, and the results were compared and validated by the experimental data. Features of this flame, including the boundary conditions of the inlet air and the spray, were analyzed according to the experiment for the numerical study. The standard k-$epsilon$ model with the enha...

The Pulsed Compression Reactor (PCR) promises to be a compact, economical and energy efficient alternative to conventional chemical reactors. In this article, the production of synthesis gas using the Pulsed Compression Reactor is investigated. This is done experimentally as well as with simulations. The experiments are done by means of a single sh...

The pulsed compression reactor promises to be a compact, economical and energy efficient alternative to conventional chemical reactors. While its design and operation is similar to that of a free piston internal combustion engine, it does not benefit from any controllability through the load. Experimental data and simulation results are presented i...

The newly invented pulsed compression reactor functions similarly to an internal combustion (IC) engine, but unlike the IC, it does not suffer the IC's limitations. While peak temperatures are in the order of 1500–5000K, and peak pressures in the order of 100–2000bar, the average temperature and pressure of the reaction zones are much lower. The pi...

The trend towards substitution of conventional transport fuels by biofuels requires additional water. The EU aims In the last two centuries, fossil fuels have been our major source of energy. However, issues concerning energy security and the quality of the environment have given an impulse to the development of alternative, renewable fuels. Partic...

The Pulsed Compression Reactor promises to be a compact, economical and energy efficient alternative to conventional chemical reactors. In this article, the production of synthesis gas using the Pulsed Compression Reactor is investigated. This is done experimentally as well as with simulations. The experiments are done by means of a single shot rea...

Heat transfer enhancement of carbon-nano fibers (CNF's) attached on a wall surface within a micro-channel is investigated in this paper using a three-dimensional numerical method. Carbon-nanofibers, also known as graphite nanofibers, can be grown by catalytic decomposition of certain hydrocarbon at a metal surface such as iron, cobalt, nickel and s...

In response to our article on the blue and green water footprint (WF) of bioenergy (1), others propose to multiply each blue WF component by a water-stress index and neglect green WFs, because impacts would be nil (2). They propose to redefine the WF from a volumetric measure to an index resulting from multiplying volumes by impact factors. Framing...

In response to our article on the water footprint (WF) of bioenergy (1), Maes et al. (2) argue that we overestimated the WF of jatropha oil, used data from a limited number of plantations, and made methodological errors. We did use little data, because hardly any data on jatropha production are available. Although we took data from various plantati...

The water footprint (WF) of a product refers to freshwater consumed during production (1). We calculated bioenergy WFs assuming crop water requirements are met (2); Jongschaap et al. (3) correctly point out that this is not always true, giving an example for jatropha grown under poor, rain-fed conditions in South Africa.

A photovoltaic-thermal panel or PVT panel simultaneously generates heat and electricity. This paper reports about the design of a new PVT panel by paying specific attention to user requirements, costs, manufacturing, building integration and installation. The panel's technical aspects and energy performance where also optimized. The result is a plu...

All energy scenarios show a shift toward an increased percentage of renewable energy sources, including biomass. This study gives an overview of water footprints (WFs) of bioenergy from 12 crops that currently contribute the most to global agricultural production: barley, cassava, maize, potato, rapeseed, rice, rye, sorghum, soybean, sugar beet, su...

The ultra rich combustion (partial oxidation) of natural gas to hydrogen and carbon monoxide is theoretically and experimentally investigated. The effect of the process parameters equivalence ratio, residence time, pressure, and composition of the oxidizer is explored. Computations are performed with the use of the chemical kinetics simulation pack...

This paper assesses the water footprint (WF) of different primary energy carriers derived from biomass expressed as the amount of water consumed to produce a unit of energy (m3/GJ). The paper observes large differences among the WFs for specific types of primary bio-energy carriers. The WF depends on crop type, agricultural production system and cl...

Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change from an attached swirling flame (unidirectional or...

Freshwater is essential for life on earth, not only for basic human needs such as food, fibre and drinking water, but also for a healthy environment. In the near future, important challenges are to meet basic needs and to ensure that the extraction of water does not affect freshwater ecosystems. At present, humanity already uses 26 percent of the t...

Steady state and transient heat transfer is a very important aspect of any combustion process. To properly simulate gas to wall heat transfer in a turbulent flow, an accurate prediction of the flow and the thermal boundary layer is required. A typical gas turbine combustion chamber flow presents similarities with the academic backward facing step c...

The life time of a typical gas turbine is mostly limited by thermal and mechanical loads occurring on the turbine blades and in the combustion chamber liner. During the lean combustion, the flame with its enormous thermal power amplifies acoustic pressure changes inside the combustion chamber. The flame is an acoustic source and produces the sound...

The stability of thermo-acoustic pressure oscillations in a lean premixed methane-fired generic gas turbine combustor is investigated. A key element in predicting the acoustically unstable operating conditions of the combustor is the flame transfer function. This function represents the dynamic relationship between a fluctuation in the combustor in...

A new synthesis gas production process based on partial oxidation (POX) of natural gas is investigated. Synthesis gas and mechanical power are generated in a plant that integrates a POX reactor, a synthesis gas turbine and an air separation unit. The synthesis gas is expanded in the turbine which runs the air separation unit. By means of an exergy...

The application of partial oxidation in a gas turbine (PO-GT) in the production of synthesis gas for methanol production is explored. In PO-GT, methane is compressed, preheated, partial oxidized and expanded. For the methanol synthesis a 12% gain in thermal efficiency has been calculated for the PO-GT process, while the product cost decrease with 7...

The thermo-acoustic behaviour of non-premixed turbulent syngas flames is investigated by means of transient RaNS Computational Fluid Dynamics simulations. Three cases with two different fuel compositions are considered. Both fuels are combusted in a turbulent non-premixed swirl stabilised mode, and are mixtures of hydrogen, carbon monoxide and nitr...

Syngas is a fuel, obtained from gasification of coal or other heavy hydrocarbons. It is used to fire gas turbines. Syngas consists of hydrogen (H2), carbon monoxide (CO) and some inert components like nitrogen (N2) or water vapour (H2O). Sometimes methane (CH4) is present. It has shown in practice that syngas fired gas turbines can suffer from ther...

The thermo-acoustic behaviour of non-premixed turbulent syngas flames is investigated. For that purpose the flame transfer functions of two syngas fuel compositions are calculated with transient RaNS. Both compositions contain hydrogen (H2), carbon monoxide (CO) and nitrogen (N2). One of them, also contains methane (CH4). Syngas is combusted in a n...

The minimum gas speed for a heat exchanger (HE) at which particulate fouling is avoided is investigated. Fouling experiments have been done with particles of different sizes and different materials running under different gas speeds. It is found that the smallest particles in the flow deposit first on the tubes of the HE at areas of minimum flow ve...

In the field of heat transfer and fluid flow, the application of numerical simulations using commercial CFD (Computational Fluid Dynamics) software for development of combustion equipment has become widespread with the improvement of power and the fall in price of computers. However, there are few reports concerning the examination of CFD performan...

Combustion of liquid fuel under gas turbine conditions is investigated with a focus on the chemistry in turbulent flames. A route is presented to model turbulent premixed, prevapourized n-heptane combustion. On basis of laminar flame simulations, a CSP reduced mechanism is created. This reduced mechanism is projected on a set of reaction progress v...

We investigated flame structure and stability characteristics of swirling flames in a natural-gas-fired experimental burner in which the swirl is generated by the rotating outer pipe of the annular air passage. Stability characteristics, defined in terms of gas flow rate and pipe rotation speed, show a hysteresis area in which two regimes are possi...

Laser-Doppler measurements of mean velocity components and Reynolds stresses are reported in the near-field of a stable swirling flame of a newly designed natural-gas-fired experimental burner. The swirling motion is generated by the rotating outer pipe of the annular air passage, thus providing well defined inflow conditions which can be easily re...

In this paper the acoustic stability of a premixed turbulent natural gas flame confined in a combustor is investigated. Specifically when the flame is operated in a lean premixed mode, the thermoacoustic system is known to exhibit instabilities. These arise from a feedback mechanism between the oscillatory flow and heat release rate perturbations i...

The two dimensional Navier Stokes equations have been solved for a falling film flow, i.e. a laminar flow running down a vertical wall driven by gravity. The aim of this research is to describe the onset of natural waves by using full simulation of the Navier-Stokes equations. In order to find the natural wave the flow velocity at the the inlet bou...

We report a series of Raman-Rayleigh-LIF measurements in two turbulent natural-gas jet diffusion flames produced by the Delft piloted jet diffusion flame burner. The main objective of the Raman-Rayleigh-LIF measurements was to obtain detailed information on the major species concentrations in the flames. The measurements provide simultaneous data o...

The two dimensional Navier Stokes equations have been solved for a falling film flow, i.e. a laminar flow running down a vertical wall driven by gravity. The aim of this research is to describe the onset of natural waves by using full simulation of the Navier-Stokes equations. In order to find the natural wave the flow velocity at the the inlet bou...

Laser Doppler Anemometry (LDA) and Planar Laser-Induced Fluorescence (PLIF) measurements have been performed in a turbulent nonpremixed jet flame. One of the features of this configuration is a central co-axial fuel jet surrounded by a turbulent annular air flow. The whole is placed within a low-speed coflowing air stream. This three-flow system wi...

 This paper presents the experimental investigation of the application of an image restoration technique aimed at improving the accuracy of infrared surface temperature measurements of cubes placed in a vertical channel flow. These cubes, used to determine distributions of the local heat transfer coefficient, show large spatial temperature gradient...