MODELING AND OPTIMIZATION  OF HEAT TRANSFER IN CRYOGENIC GASIFIERS:  CASE OF AN SGU-7KM-U GASIFICATION UNIT

This paper presents experimental data on oxygen gasification as performed on an SGU-7KM-U unit; data is used to find a differential parametric model of heat transfer in closed-loop gasification units. Reference experi-ments helped find the external parameters such as the heater power, the heat capacity of the evaporator, and the pumping rate. The internal parameters of the model, i.e., the numerical multipliers for coefficients of heat transfer in oxygen, coolant, and the environment, were identified by the passive strategy method. The paper further presents newly developed methods for optimizing the gasifier performance to reach the required range of output temperatures in steady-state and non-steady-state operation. The methods were tested on an SGU-7KM-U gasification unit.

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Set-Point Generation Using Kernel-Based Methods for Closed-Loop Combustion Control of a CIDI Engine

ASME 2009 Dynamic Systems and Control Conference, Volume 1 ◽

10.1115/dscc2009-2697 ◽

2009 ◽

Cited By ~ 2

Author(s):

Rajaram Maringanti ◽

Shawn Midlam-Mohler ◽

Ming Fang ◽

Fabio Chiara ◽

Marcello Canova

Keyword(s):

Steady State ◽

Degrees Of Freedom ◽

Closed Loop ◽

Exhaust Gas ◽

Loop Control ◽

Set Point ◽

Steady State Operation ◽

Engine Combustion ◽

Feedback Control Systems ◽

Homogenous Charge Compression Ignition

Closed-loop control of diesel combustion is of great interest for improving conventional Diesel engine combustion as well as facilitating new combustion modes such as Homogenous Charge Compression Ignition and other low NOx regimes. Most generalized feedback control systems that can be applied to this problem require a reference or set-point which the control attempts to achieve. Diesel engines are well known for having many degrees of freedom which poses a problem in generating valid set-points for all possible conditions encountered in practice. This problem is compounded by the fact that these set-points are usually determined in steady state operation further limiting the space where set-points can be defined. Kernel-based methods are applied to this problem as a method of generating valid setpoints when operating in regions outside of the space where set-points are defined. This is most useful during transient conditions where conditions such as exhaust gas recycle level, manifold air flow, and fuel mass are far from the steady state values.

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Steady State Parametric Modeling of Non-Conventional Loop Heat Pipes

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-63991 ◽

2013 ◽

Cited By ~ 1

Author(s):

Karthik S. Remella ◽

Frank M. Gerner ◽

Ahmed Shuja

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Steady State ◽

Transfer Coefficient ◽

Thermal Energy ◽

Heat Pipes ◽

Parametric Model ◽

Parametric Modeling ◽

Working Fluid ◽

Loop Heat Pipes

Loop Heat Pipes (LHPs) are used in many thermal management applications, especially for micro-electronics cooling, because of their ability to passively transport thermal energy from a source to a sink. This paper describes the development of a parametric model for a non-conventional LHP operating in steady state, employed to cool Light Emitting Diodes (LEDs). This device is comprised of a flat evaporator, and a finned circular loop wherein condensation and sub-cooling of the working fluid takes place. Unlike a conventional LHP, this device has no compensation chamber. In the mesh screen of the evaporator, the vapor flow entrains liquid and hence the quality of the two-phase mixture leaving the evaporator (xevap) is less than unity (unlike in a conventional LHP where saturated vapor leaves the evaporator). Since this lower quality (approximately 0.2) results in a smaller ratio of latent energy to sensible energy being removed by the condenser and sub-cooler respectively; the ratio of the length of the sub-cooler to condenser length is significantly larger. This results in more stable and controlled operation of the device. Mathematical models of the evaporator, the condenser and the sub-cooler sections are developed, and two closure conditions are employed in this model. For consistency and accuracy, some parameters in the model, such as the natural convection heat transfer coefficient (h o) and a few thermal resistances in the evaporator, are estimated empirically from test data on the device. The empirically obtained value of the heat transfer coefficient is in very good agreement with correlations from the literature. The parametric model accurately predicts the LED board temperature and other temperatures for a specific amount of thermal energy dissipated by the LEDs.

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Enhanced Heat Transfer Structure Design for Ion Dump of EAST-NBI System Based on Hypervapotron

Volume 2: Plant Systems, Structures, Components and Materials ◽

10.1115/icone25-67921 ◽

2017 ◽

Author(s):

Ling Tao ◽

Chundong Hu ◽

Yuanlai Xie

Keyword(s):

Heat Transfer ◽

Steady State ◽

Energy Deposition ◽

High Energy ◽

Operating Conditions ◽

Quasi Steady State ◽

Enhanced Heat Transfer ◽

Steady State Operation ◽

The Future ◽

Transfer Structure

Ion dump is an important functional component of the Neutral Beam Injection (NBI) system of Experimental Advanced Superconducting Tokamak (EAST) for absorbing un-neutralized particles deflected by deflection magnets during neutralization, and by means of the corresponding measurement and analyzing method on it, the total energy deposition value and instantaneous energy deposition distribution of the deflected ion beam can be obtained. According to the operation mechanism of the NBI system, ion dump is directly subjected to high-energy particle bombardment for long time, the corresponding heat-loaded on its plates is high, so the temperature rise control is demanding. In order to realize the running power of 2–4MW and running pulse length of more than 100s or even 1000s in the future NBI system, the structure of the ion dump must be designed in accordance with the quasi-steady state operation requirements to provide the guarantee for the steady state operation of EAST system. The Hypervapotron structure based on the subcooled boiling principle is used as an alternative structure to enhance the heat transfer of this high-heat-flux component. According to the operating requirements, space requirements, measurement requirements and beam power distribution characteristics, the engineering design and implementation of ion dump based on the enhanced heat transfer structure is realized for the future long pulse quasi-steady NBI system. The computational results of the heat-fluid-solid coupling simulation based on the two-phase heat transfer are also confirmed the feasibility of the proposed ion dump structure under quasi-steady-state operating conditions. This study is of great significance to explore the optimal heat transfer structure for quasi-steady ion dump to realize the high current, quasi-steady state and high power operation of EAST-NBI system.

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Jet Impingement Heat Transfer Visualization Using a Steady State Liquid Crystal Method

Journal of Heat Transfer ◽

10.1115/1.2221301 ◽

2006 ◽

Vol 128 (8) ◽

pp. 738-738 ◽

Cited By ~ 8

Author(s):

Eric Esposito ◽

Srinath V. Ekkad

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Liquid Crystal ◽

Steady State ◽

Calibration Curve ◽

Jet Impingement ◽

Test Plate ◽

Experimental Procedure ◽

Heater Power ◽

Impingement Heat Transfer

Experimental Procedure: •Blower is set appropriately for required jet Reynolds number •Heater is turned on and allowed to reach steady state •A picture is taken of the liquid crystal coated test plate and heater amperage and voltage measured •Heater power is incrementally increased and additional pictures taken to capture temperature and heater flux data at every point in the array •Pictures are converted to Hue and liquid crystal calibration curve used to determine temperature at corresponding point

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Modeling of Loop Heat Pipe Thermal Performance

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ◽

10.37934/arfmts.81.1.4172 ◽

2021 ◽

Vol 81 (1) ◽

pp. 41-72

Author(s):

Inès Gabsi ◽

Samah Maalej ◽

Mohamed Chaker Zaghdoudi

Keyword(s):

Heat Transfer ◽

Steady State ◽

Heat Pipe ◽

Loop Heat Pipe ◽

Conductive Heat ◽

Steady State Operation ◽

Evaporation Heat ◽

Compensation Chamber ◽

Heat Loads ◽

Good Agreement

The present work deals with the heat transfer performance of a copper-water loop heat pipe (LHP) with a flat oval evaporator in steady-state operation. Modeling the heat transfer in the evaporator was particularly studied, and the evaporation heat transfer coefficient was determined from a dimensionless correlation developed based on experimental data from the literature. The model was based on steady-state energy balance equations for each LHP component. The model results were compared to the experimental ones for various heat loads, cooling temperatures, and elevations, and a good agreement was obtained. Finally, a parametric study was conducted to show the effects of different key parameters, such as the axial conductive heat leaks between the evaporator and the compensation chamber cases, the capillary structure porosity and material, and the groove dimensions.

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THEORETICAL MODELING OF A TWO-PHASED THERMOSYPHON ASSUMING THE LIQUID RESERVATORY

Revista de Engenharia Térmica ◽

10.5380/reterm.v6i1.61820 ◽

2007 ◽

Vol 6 (1) ◽

pp. 74

Author(s):

M. A. Zanardi ◽

N. G. C. Leite

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Steady State ◽

Energy Conservation ◽

Theoretical Modeling ◽

General View ◽

Two Phase ◽

Conservation Equations ◽

Stable Level ◽

Steady State Operation

A theoretical modeling using the mass, momentum and energy conservation equations, about the intrinsic phenomena in the working of a cylindrical geometry two-phase thermosyphon operating on vertical was performed. The conservation equations were solved in steady-state operation for all the phases of the thermosyphon. Then model also assumed the presence of a liquid reservatory whose valves of the coefficient of heat transfer that determine the operation of functioning in the reservatory, were obtained from the correlation published in literature. The set of conservation equations was solved by using the method of finite volumes. The results achieved were checked with experimental data from literature and also from specific experiments performed in laboratory. In a general view, the theoric results matched reasonably well with those ones from the experiments, and the observed deviation were assumed by a inadequate prevision of the reservatory model used, besides keeping a stable level of the reservatory of liquid.

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Autoregressive modeling of cycle-to-cycle correlations in homogeneous charge compression ignition combustion

International Journal of Engine Research ◽

10.1177/1468087417731043 ◽

2017 ◽

Vol 19 (7) ◽

pp. 790-802 ◽

Cited By ~ 9

Author(s):

Jakob Andert ◽

Maximilian Wick ◽

Bastian Lehrheuer ◽

Christian Sohn ◽

Thivaharan Albin ◽

...

Keyword(s):

Steady State ◽

Real Time ◽

Autoregressive Model ◽

Closed Loop ◽

Homogeneous Charge Compression Ignition ◽

Compression Ignition ◽

Model Based Control ◽

Model Based ◽

Auto Ignition ◽

Steady State Operation

Homogeneous charge compression ignition or gasoline controlled auto-ignition combustion is characterized by a strong coupling of consecutive cycles, which is caused by residuals from the predecessor cycle. Closed-loop combustion control is considered a promising technology to actively stabilize the process. Model-based control algorithms require precise prediction models that are calculated in real time. In this article, a new approach for the transient measurement of the auto-ignition process and the data-driven modeling of combustion phasing and load is presented. Gasoline controlled auto-ignition combustion is modeled as an autoregressive process to represent the cycle-to-cycle coupling effects. The process order was estimated by partial autocorrelation analysis of steady-state operation measurements. No significant correlations are found for lags that are greater than one. This observation is consistent with the assumption that cycle coupling is mainly caused by the amount of exhaust gas that is directly transferred to the consecutive combustion. Because steady-state operation results in a hard coupling of actuation and feedback variables, only minor variations of the test data can be achieved. The steady-state tests delivered insufficient data for the generalized modeling of the transient autoregressive effects. A new transient testing and measurement approach is required, which maximizes the variation of the predecessor cycle’s characteristics. Dynamic measurements were performed with the individual actuation of the injection strategy for each combustion cycle. A polynomial model is proposed to predict the combustion phasing and load. The regression analysis shows no overfitting for higher polynomial orders; nevertheless, a first-order polynomial was selected because of the good extrapolation capabilities of extreme outliers. The prediction algorithm was implemented in MATLAB/Simulink and transferred to a real-time-capable engine control unit. The verification of the approach was performed by test bench measurements in dynamic operation. The combustion phasing was precisely predicted using the autoregressive model. The combustion phasing prediction error could be reduced by 53% in comparison to a state-of-the-art mean value-based prediction. This work provides the basis for the development of a closed-loop autoregressive model-based control for gasoline controlled auto-ignition combustion.

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