Somchart Chantasiriwan

• Doctor of Philosophy
• Professor (Full) at Thammasat University

For a biomass power plant, which uses a biomass fuel having a high moisture content, flue gas drying is an effective method of increasing the overall power plant efficiency. However, this method requires flue gas that has a high temperature. Most biomass power plants, however, are designed so that flue gas temperature is already reduced to a low va...

There is an enormous amount of water vapor in ambient air that can be converted into liquid water by several methods. A method that is capable of producing a large amount of water is a vapor compression system. However, this method requires significant power input, which may cause the cost of producing water to be prohibitive. In this paper, it is...

Fuels used in biomass power plants usually have high moisture contents. Two methods of fuel drying that have been proposed are steam drying and flue gas drying. Steam drying requires extracted steam as its energy source, whereas flue gas drying requires flue gas leaving the boiler as its energy source. Previous works have mostly been concerned with...

Conventionally, the thermal design a biomass power plant is aimed at maximizing the energy efficiency by using extracted steam to increase feed water temperature in feed water heaters and installing heating surface areas of heat exchangers in boiler to recover flue gas energy. The temperature of flue gas at the boiler outlet must not be so low that...

Net power plant efficiency is the ratio of exportable electrical power output to the product of fuel consumption rate and fuel heating value. Conventionally, power plants are designed to attain the maximum net power plant efficiency by using regenerative feed water heating, in which extracted steam from steam turbine is used to increase feed water...

The conventional design of thermal power plant uses regenerative feed water heating to increase the overall power plant efficiency. This method is limited by the number of feed water heaters and the amount of extracted steam supplied to each feed water heater. It is proposed in this paper that the improvement of the conventional design is possible...

Conventionally, regenerative feed water heating is used to increase the net efficiency of a thermal power plant. In this method, extracted steam from the steam turbine is used to increase feed water temperature before feed water is sent to the boiler. Increasing the number of feed water heaters or the mass flow rates of extracted steam causes the n...

Solar feed water heating using parabolic trough collectors may be integrated into an existing power plant to reduce the amount of extracted steam and increase power output. Two systems are possible. The first system requires a heat transfer fluid with a high boiling point and an oil-water heat exchanger in addition to parabolic trough collectors. T...

Parabolic trough collectors may be used to increase the temperature of a heat transfer fluid flowing inside absorber tubes. A method of solar-aided power generation in thermal power plants is using heat transfer from the high-temperature heat transfer fluid for feed water heating. In doing so, less steam is extracted from steam turbine, and power o...

Five configurations of regenerative Rankine cycle with two feed water heaters are compared in this paper. One configuration has two open feed water heaters (OFWH). The other four configurations have an open feed water heater placed before or after a closed feed water heater, which may be either closed feed water heater with drain pumped forward (FF...

Heat recovery devices that may be installed in biomass boiler are economizer, air heater, and flue gas dryer. Economizer increases feed water temperature, air heater increases air temperature before combustion, and flue gas dryer decreases fuel moisture content. Each of them can equally increase boiler efficiency. Since all of them require heat tra...

Utility boilers are used in thermal power plants. If exhaust flue gas temperature of a boiler is sufficiently high, heat recovery devices may be installed to increase the boiler efficiency. Previous investigations have focused on increasing boiler efficiency by using heat transfer from flue gas to remove moisture from fuel in flue gas dryer. Anothe...

Industrial processes require thermal energy in form of saturated steam. Cogeneration system in a process industry uses an industrial boiler to produce superheated steam, which is subsequently expanded in a condensing-extraction steam turbine. The extracted steam is sent to the process, and the remaining steam is condensed in a condenser. Since the...

The efficiency of bagasse boiler increases as the final flue gas temperature decreases. High-temperature flue gas temperature may be used to reduce the moisture content of bagasse in a flue gas dryer. Alternatively, increasing surface areas of economizer and air heater can also decrease flue gas temperature. In this paper, an investigation is made...

The evaporation process, boiler, and turbine are the main components of the cogeneration system of the sugar factory. In the conventional process, the evaporator requires extracted steam from the turbine, and bled vapor from the evaporator is supplied to the juice heater and the pan stage. The evaporation process may be modified by using extracted...

The cogeneration system of a sugar factory consists of boiler, steam turbine, and sugar juice evaporation process. The multiple-effect evaporator used for the conventional sugar juice evaporation process is the forward-feed multiple-effect evaporator, in which steam and sugar juice flow in the same direction. The main objective of this paper is to...

Superheated steam drying has previously been shown to improve the performance of the cogeneration system in sugar factory because it can reduce bagasse moisture content, which increases the efficiency of the steam generation unit, and recover water that would be lost with flue gases. The performance of this system depends on the degree of superheat...

Biomass boiler uses thermal energy from the combustion of biomass fuel and air to produce superheated steam from feed water. Biomass fuel usually has a high moisture content, which leads to low boiler efficiency. The boiler efficiency can be increased by using heat recovery devices to decrease the temperature of flue gas before it is exhausted from...

Industrial boiler consists of a furnace and a set of heat exchangers, which are evaporator, superheater, boiler bank, economizer, and air heater. Combustion of fuel in the furnace produces thermal energy that is used to evaporate feed water and increase steam temperature in the superheater. Hot flue gas from the furnace also contributes to increasi...

The conversion of diluted sugar juice into raw sugar and molasses requires thermal energy for evaporating the water content in sugar juice. The supply of thermal energy is saturated steam at around 200 kPa. The efficiency of energy use by the process is determined from the amount of saturated steam to process a given amount of sugar juice. It depen...

Main components of a bagasse boiler are furnace, evaporator, superheater, boiler bank, economizer, and air heater. Combustion of fuel and air in the furnace produces thermal energy that is used to evaporate feed water in the evaporator. Hot flue gases from the furnace also contribute to increasing steam temperature in the superheater. Hot flue gase...

The cogeneration system in sugar factory uses bagasse with high moisture content as the fuel for the boiler, which results in low boiler efficiency. The system also produces superheated steam, which is extracted from the turbine, and mixed with cooling water to produce saturated steam required by the evaporation system. The potential use superheate...

In the sugar juice evaporation process, the temperature of incoming juice is raised to the boiling point, and the water content of the juice is reduced by evaporation. The main process outputs are raw sugar and molasses. Heat transfer coefficients are important parameters in the simulation of this process. Due to scaling, the values of heat transfe...

The cogeneration system in sugar factories consists of four main processes: juice extraction, evaporation, steam generation, and turbogenerator. The juice extraction process converts sugar cane into sugar juice and moist bagasse. Water content of the juice is removed in the evaporation process, and moist bagasse is used as fuel in the steam generat...

The evaporation process in raw sugar manufacturing consists of juice heater, multiple-effect evaporator, and crystallizer. Two performance parameters of the evaporation process are the rate of processed sugar juice and the steam economy, defined as the ratio between water content of sugar juice entering the process to the amount of steam required t...

The sugar juice evaporation process consists of juice heater, evaporator, and crystallizer. The juice heater increases the temperature of diluted sugar juice from the ambient temperature to the boiling point. The evaporator removes most water content of diluted sugar juice. The crystallizer removes the remaining water content, yielding raw sugar as...

A multiple-effect evaporator is used to evaporate water from sugar juice in a series of pressure vessels. Steam is used for evaporation in the first vessel, and vapor from all vessels except the last one is used for evaporation in subsequent vessels. In order for evaporator surfaces to be used efficiently, juice entering the evaporator should be at...

The evaporation process in raw sugar manufacturing turns diluted juice into granulated sugar. It consists of three main components: juice heater, multiple-effect evaporator, and crystallizer. Previous studies are concerned mostly with multiple-effect evaporator with the assumption that sugar juice entering the evaporator is at the saturation temper...

The cogeneration system in sugar factories consists of four main components: the juice extraction unit, the evaporation unit, the steam generation unit, and the turbo-generator. The juice extraction unit converts sugar cane into extracted juice, which is sent to the evaporation unit, and bagasse, which is sent to the steam generation unit. Combusti...

Quadruple-effect evaporator is used to increase the concentration of sugar juice in a series of four pressure vessels. Vapor bled from the first three vessels is used to increase the juice temperature in juice heater to the saturation temperature at the inlet of the evaporator. This paper presents the model of heating and evaporation of sugar juice...

Multiple-effect evaporator is used to increase the concentration of a solution in a series of pressure vessels. If the total surface area of the evaporator is fixed, the performance of the evaporator is affected by the distribution of surface area among vessels. Previous studies have been concerned with optimization of surface area distribution wit...

The multiple-effect evaporator is commonly used in the sugar industry. The final effect of the evaporator operates under a vacuum, which is created by the mixing of cooling water and vapor in a condenser. The complete analysis of the multiple-effect evaporator must take into account the interaction between the evaporator and the condenser. To date,...

Subjected to fixed total heat transfer surface area, the distribution of surface in multiple-effect evaporator affects the performance of the evaporator. Previous studies have been concerned with optimization of surface distribution with the assumption that no fouling occurs. The present study considers a more realistic case when the last-effect ve...

Variable-speed control of centrifugal pumps is gaining popularity because the affinity laws promise that substantial energy saving is to be expected. Estimation of energy saving using the affinity laws, however, will be erroneous if there is static head in the pump system. This paper presents a method for investigating the performance of a centrifu...

Compound imbibition is a well-known imbibition scheme widely used in sugar mills. In this scheme, the mixture of fibre and juice retained by the screen or cush cush is returned to either the first mill or the second mill. A model has been developed to simulate the operation of sugar mills that use compound imbibition. In addition to mass balances o...

For an oversized pump operating at a reduced load, variable-speed control is a good energy-conserving method. It is popular among pump users to estimate energy saving by using the affinity laws, which imply that power input varies with the cube of flow rate. However, this estimation is erroneous if the pump must deliver the fluid against not only f...

The problem of seepage flow through a dam is free boundary problem that is more conveniently solved by a meshless method than a mesh-based method such as finite element method (FEM) and finite difference method (FDM). This paper presents method of fundamental solutions, which is one kind of meshless methods, to solve a dam problem using the fundame...

Modal analysis of free vibration of liquid in a rigid container having arbitrary shape requires a numerical method. The method of fundamental solutions has an advantage over the finite element method and the boundary element method in that it does not require either volume mesh generation or surface mesh generation. This paper presents the formulat...

In this paper, free surface problems of Stefan-type for the parabolic heat equation are investigated using the method of fundamental solutions. The additional measurement necessary to determine the free surface could be a boundary temperature, a heat flux or an energy measurement. Both one- and two-phase flows are investigated. Numerical results ar...

Behaviors of the global and local collocation methods that use multiquadrics as basis functions in solving problems having continuous boundary conditions are well known. In this paper, harmonic and biharmonic problems having discontinuous boundary conditions are solved by these methods. Solutions to two test problems are investigated. The first tes...

Conventional approaches for solving the Navier–Stokes equations of incompressible fluid dynamics are the primitive-variable approach and the vorticity–velocity approach. In this paper, an alternative approach is presented. In this approach, pressure and one of the velocity components are eliminated from the governing equations. The result is one hi...

The multiquadric collocation method is a meshless method that uses multiquadrics as its basis function. Problems of nonlinear time-dependent heat conduction in materials having temperature-dependent thermal properties are solved by using this method and the Kirchhoff transformation. Variable transformation is simplified by assuming that thermal pro...

The multiquadric collocation method is the collocation method based on radial basis function known as multiquadrics. It has been successfully used to solve several linear and nonlinear problems. Although fluid flow problems are among problems previously solved by this method, there is still an outstanding issue regarding the influence of the free p...

A time-dependent heat conduction problem can be solved by the method of fundamental solutions using the fundamental solution to the modified Helmholtz equation or the fundamental solution to the heat equation. This paper presents solutions using both formulations in terms of initial and boundary conditions. Such formulations enable calculation of e...

Collocation methods based on radial basis functions can be used to provide accurate solutions to deterministic problems. For stochastic problems, accurate solutions may not be desirable if they are too sensitive to random inputs. In this paper, four methods are used to solve stochastic Poisson problems by expressing solutions in terms of source ter...

Error and variance of the solution to the heat conduction problem having stochastic initial and boundary conditions are determined by a formulation based on a meshless method known as the multiquadric collocation method. This formulation expresses the solution in terms of initial and boundary conditions. Inspection of solutions to two test problems...

The stationary three-dimensional Navier-Stokes equations consisting of four equations and four unknowns have been solved by conventional methods using the primitive-variable approach. By getting rid of pressure and one of the velocity components, the Navier-Stokes equations can be reduced to two higher-order partial differential equations with the...

The applicability of Born’s criterion for the assessment of structural stability of perfect crystals under mechanical loading is examined for the case of face-centered-cubic (fcc) crystals subjected to uniaxial [111] loading. The analysis is based on the results of lattice-statics calculations and isostress molecular-dynamics simulations of the mec...

Problems described by deterministic partial differential equations with random Dirichlet boundary conditions are considered. Formulation of the solution to such a problem by the global collocation method using multiquadrics is presented. The quality of the solution to a stochastic problem depends on both its expected value and its variance. It is p...

Two methods for solving the Poisson problem on an automatically generated Cartesian grid are proposed. The first method is a combination of the finite-element method and the boundary-element method. The second method is a combination of the finite-difference method and the method of fundamental solutions. Both methods split the problem into an inho...

Four methods that solve the Poisson, Helmholtz, and diffusion–convection problems on Cartesian grid by collocation with radial basis functions are presented. Each problem is split into a problem with an inhomogeneous equation and homogeneous boundary conditions, and a problem with a homogeneous equation and inhomogeneous boundary conditions. The fo...

Multidimensional diffusion problems can be solved by a local collocation method using radial basis functions. This method is computationally efficient because it is meshless and yields a sparse system of algebraic equations. Three types of radial basis functions—the generalized multiquadric function, the Gaussian function, and the generalized thin-...

An algorithm is proposed for solving the inverse problem of determining thermal conductivity, which is assumed to be a polynomial function of temperature. The problem model can be either two-dimensional or axisymmetric. Necessary input data for the algorithm are total heat inputs and temperature measurements, but not heat input distribution. An axi...

The unknown time-dependent boundary heat flux of a multidimensional body is determined from temperature measurements inside the body or on its boundary. The sequential function specification method with the assumption that future-boundary heat flux varies linearly with time is used to solve the inverse problem. The method of discretization used by...

An experimental setup for the inverse determination of steady-state heat transfer coefficient in a two-dimensional system is proposed. This setup requires temperatures mmeasurements at accessible and non-intrusive locations, but does not require heat flux measurement. The mathematical model of the system is solved numerically by using the boundary...

The time-dependent Biot number in a one-dimensional linear heat conduction problem is obtained from the solutions of the inverse heat conduction problems of determining boundary heat flux and boundary temperature. The sequential function specification method with the linear basis function and the assumption of linearly varying future boundary heat...

Three algorithms for implementing the sequential function specification method of estimating boundary heat flux in the inverse heat conduction problem are compared. They differ from one another in the type of piecewise function used to describe the heat flux and the assumed variation of heat flux over future time. The results of the comparison show...

An embeded-atom method (EAM) formulation that can reproduce identically the empirically determined second-order and third-order elastic moduli is employed in constructing the EAM models of 12 cubic metals (Ag, Al, Au, Cu, Fe, K, Li, Mo, Na, Nb, Ni, and Rb). The models yield phase stabilities, pressure-volume curves, and phonon-frequency spectra tha...

The theoretical mechanical response of 12 cubic metals (Al, Cu, Mo, Na, Li, K, Rb, Nb, Fe, Ni, Au, and Ag) to unconstrained uniaxial loadings, coaxial with each of the three principal symmetry directions, is analyzed, at finite strain, in the framework of the embedded-atom method model calculations. The models have been formulated to reproduce, ide...

The random-walk solution for linear, time-dependent, multidimensional, nonhomogeneous heat conduction problems is presented in a general form, which is expressed in terms of transition probabilities. The boundary conditions considered include the Dirichlet, the Neumann, and the mixed boundary conditions. The random-walk method is shown to be an eff...

The higher-order elasticity of cubic metals in the framework of the embedded-atom method (EAM) is investigated. Proper groupings of the second- and third-order elastic moduli are shown to yield expressions that depend solely on either the electron density function or the pair potential and which therefore facilitate the construction of EAM models....