WSEAS Transactions on Heat and Mass Transfer
Print ISSN: 1790-5044
E-ISSN: 2224-3461
Volume 11, 2016
Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of WSEAS Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.
Volume 11, 2016
Title of the Paper: Water Storage Parameters of Plaster with Inner Hydrophobic Additive
Authors: Radka Pernicova, Milena Pavlikova
Abstract: In this paper water storage parameters of hydrophobic plasters are determined. This article is focus on hygric properties of lime-metakaolin plaster connected with hydrophobicity. Most physic-chemical deterioration of building materials related to the penetration of moisture into building structure. Therefore, the aim of the testing was in description of influence of inner hydrophobic additive, which was applied to the interior structure of the element. Higher resistance of penetration water into materials show samples with hydrophobic additive. Water storage parameters are slightly better for plaster without hydrophobsation. However from the quantitative point of view the difference was not so important. Measurement involves not only properties of hydrophobic plaster, but comparative measurements with pure lime-metakaolin plaster were done as well.
Keywords: Plaster, hydrophobic additive, hydric properties, storage, transport
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #15, pp. 128-131
Title of the Paper: Modeling and Simulation of Heat Transfer in Conduction-Convection Systems
Authors: Luis Antonio Beltrán Prieto, Juan Carlos Beltrán Prieto, Zuzana Komínková Oplatková
Abstract: The use of cooling systems in electronics is an important part of their design to provide a correct functioning of the device and improve its lifespan by controlling the temperature and avoiding overheating that could be of risk and cause any damage. One alternative to reduce the temperature is to use heat sinks that distribute the heat along their length by conduction and convection. The mathematical model of this process is important for design purposes as it can give information of the temperature distribution along the rod and the chip surface. Additionally, the use of dynamic models helps to know the influence of several parameters that affect the transfer of heat in the device, for example in the case of having specific dimensions of the rod. The present research contributes to explain the mathematical model of cooling fins in transistors. Equations for the temperature distribution along the length of the rod and the chip surface were obtained and used for simulation purposes. Accordingly, the evaluation of the ratio between the real heat transfer rate from the fin and he ideal heat transfer rate was performed.
Keywords: conduction, convection, cooling fins, heat transfer
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #14, pp. 121-127
Title of the Paper: Determination of Soil Parameters Under Gravitation and Centrifugal Forces in 3D Infiltration
Authors: Jozef Kacur, Patrik Mihala, Michal Toth
Abstract: A novel set-up for the study of unsaturated flow characteristics in porous media is examined. In this set-up, a sample of cylindrical shape is submerged in water chamber and the water infiltrates into it. The top of the cylinder is isolated and from its bottom water flows out to the collection chamber. Both chambers except of the sample bottom (resp. its part) are mutually isolated. Determination of soil parameters (in fundamental flow characteristics) requires non-invasive measuremets of global characteristics as amount of infiltrated and outflow water in some time moments (see the figure 1 below). When using centrifuge the measurement data could be extended also by measurements of centrifugal force. A precise and efficient numerical method is developed for solution of mathematical model based on Richard’s strongly nonlinear and degenerate equation expressed in terms of van Genuchten/Mualem experimental model describing effective saturation and hydraulic permeability versus pressure. The previously used 1D models (tube shape samples) experience serious issues with the effects of fingering, where due to the small inhomogenities preferable streams in the tube can emerge. Moreover, the isolation of sample mantle is technically difficult, especially in centrifugation mode. On the other hand the numerical realization is much more difficult as in 1D mathematical model. The numerical experiments support our method requiring only simple non-invasive measurements.
Keywords: water transport, unsaturated porous media, soil parameters, scaling of mathematical model, gravitation and centrifugal forces
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #13, pp. 115-120
Title of the Paper: Heat Energy Transfers Inside the Double Circular Flow Heating System
Authors: Drago Franciskovic
Abstract: The paper discusses the transfer of heat energy within the system containing double heating. Presented is an original mathematical model that describes the considered transfer of heat energy. The paper describes mathematical functions applicable for the model. Defined are typical scenarios that may arise within the system and given are conditions of their occurrence. Presented is a problem of measurement of heat energy using available calorimeters and proposed a solution for its elimination.
Keywords: mathematical model, transfer of heat energy, regulation, heating system, calorimeter, fluid flow, heat transfer rate
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #12, pp. 107-114
Title of the Paper: Properties of the Heat Energy Allocation Models in Systems with Partial Distribution of Heat Allocators
Authors: Aleksandar Hatzivelkos
Abstract: Systems with partial distribution of heat allocators present a problem in terms of energy allocation. Since heat allocators provide pure numerical, and not the consumed energy value, energy consumed in the apartments without heat allocators is unknown. Furthermore, energy loss within the building is also unknown. Therefore, models for heat energy allocation are used. With those models, based upon partial (numerical) consumption readings, allocation to all apartments is formed. This paper addresses the allocation methods used for allocation of the heat energy in systems with partial distribution of the heat allocators. Mathematical definition and analysis of three heat energy allocation methods is given. Two of them were officially legislated in Croatia, and in use since year 2008. Third one is proposed in works of Hatzivelkos. Properties of allocation methods are introduced: consistency, monotonicity and local consistency. While consistency, as a global property can be viewed as a necessary allocation property, special attention is given to later two properties, monotonicity and local consistency. Those properties describe allocation methods from the perspective of a consumer. Mathematical analysis of allocation methods behavior in worst case scenario is given, i.e. scenario that produces the greatest error for observed allocation model. Another high consumer visibility concept is analyzed: consumption reading point value. For a consumer, it is only natural to seek relation between consumption reading and energy allocation, which is described with concept of allocated energy value of consumption reading points. Criteria for consumption reading point value comparison is introduced and described by usage of simulations. Finally, notions of new areas of heat allocation model analysis are given.
Keywords: Heat energy allocation model, heat allocators, non-linear algorithms
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #11, pp. 87-106
Title of the Paper: Simulation and Calculation of Temperature Fields PIR Detector
Authors: Rudolf Drga, Dagmar Janacova, Hana Charvatova
Abstract: Work solves function of the PIR detector located in an environment where there are thermal sources with a surface temperature that is close to human body temperature. There simulating and calculating thermal behavior of the sensor in COMSOL Multiphysics and the Maple in environment with terms of different types of heating rooms in order to show that the detector can operate on as a passive type detector, but as an active type detector, where the heating works as a transmitter of heat radiation and own detector as its receiver. In this case, the detector is able to detect objects that are for the standard type masked or hidden.
Keywords: PIR detector, simulation, temperature fields, temperature radiation, heating sensor
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #10, pp. 79-86
Title of the Paper: Modeling a Direct Contact Heat Recovery Process from Molten Salt Droplets in Various Gases for Thermochemical Hydrogen Production
Authors: Samane Ghandehariun, Marc A. Rosen, Martin Agelin-Chaab
Abstract: The copper-chlorine cycle for hydrogen production is based on thermochemical water decomposition. Heat recovery within the cycle is necessary for high efficiency, and significant heat recovery can be achieved by cooling and solidifying the molten salt exiting the oxygen reactor step of the cycle. Heat can be recovered from the molten salt by breaking the molten stream into smaller dispersed droplets. A predictive model is developed here for direct contact heat recovery process from molten salt using various gases such as nitrogen, helium, argon and air. As CuCl may react with water vapor in the presence of oxygen, inert gases are considered as alternative coolants for the direct contact heat recovery process. It is observed that heat transfer is better for helium than the other gases considered.
Keywords: hydrogen, thermochemical water decomposition, direct contact heat transfer, molten salt
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #9, pp. 72-78
Title of the Paper: LQ Digital Control of Coupled Liquid Level Equal Atmospheric Tanks – Design and Simulation
Authors: Vladimír Bobál, Stanislav Talaš, Marek Kubalčík
Abstract: The flow coupled liquid level control systems are extensively used e. g. in chemical processes and refineries in the petrochemical industry. These processes are characterized by high-order dynamic behaviour or large time constants and time-delays. Time-delays (dead time) are mainly caused by the duration needed to transport mass, energy or information. In many cases time-delay is caused by the effect produced by the accumulation of a large number of low-order systems. One of the possibilities to control such processes is their approximation by lower-order model with time-delay. The contribution is focused on the design of the control of a set of equal liquid cylinder atmospheric tanks. The designed digital control algorithm is based on approximation of high-order process by a second-order model with time-delay. The controller algorithms use the digital modification of the linear quadratic (LQ) Smith predictor (SP). The LQ criterion was combined with pole assignment principle. These algorithms were successfully verified in simulated conditions in the MATLAB/SIMULINK programme environment.
Keywords: Set of atmospheric tanks, Flow liquid level control, Time-delay system, Smith predictor, LQ digital control
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #8, pp. 62-71
Title of the Paper: Heat Transfer by Forced Convection from a Vertical PCM Plate
Authors: Martin Kolacek, Stanislav Sehnalek
Abstract: The article describes the possibility to obtain stored energy from PCM materials by using forced convection. The PCMs are very popular in many different applications for temperature stabilization of the microclimate inside buildings. The acceleration of releasing the stored energy is important for discharging cycle, which is very difficult to achieve because of the supercooling effect. Forced convection was used as an option for speeding-up the energy release. It is important to know some of the simple relations in fluid dynamics and boundary layer analysis to understand the forced convection heat transfer. Thermal imager was used for visualization of stored energy release. The paper also focuses on boundary layer with forced convection and the flow visualization around the surface of the vertical plate. It is possible to use the stored energy within several cycles. This energy can be used in various ways, such as a device with intermittent heating and cooling equipment. The aim is to develop a device which can be used for cooling or maintaining steady thermal conditions.
Keywords: Phase change materials, heat transfer, forced convection, natural convection, thermal imager
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #7, pp. 56-61
Title of the Paper: The Simulation of the Water Temperature Rising Using ARIMA Models
Authors: Dana Halmova, Pavla Pekarova, Jan Pekar, Katarina Kucarova
Abstract: The methodological approach to measuring the water temperature was historically developing. The economic importance of knowledge on flowing water temperature and thus the responsibility of the observer for the proper and reliable measurements has been known for over a century. In Slovakia, the water temperature in streams is measured according to sectorial technical environmental standards (Measurement of water levels, water temperature and ice phenomena on the surface flows) of 2005. Water temperature plays a key role from environmental, biochemical as well as chemical point of view. Increase in water temperature, e.g. during extreme and long-lasting heat waves and drought, can cause undesirable chemical and biochemical reactions. In the study we have focused on water temperature simulation in twenty one streams in the Slovak part of the Morava River basin. The aim was to assess the impact of the expected air temperature increase to a temperature rise of water in the streams. While processing the data, we used the time series of the average daily water temperature in selected gauging stations in the Morava River basin and the average daily air temperature measured in Bratislava-airport, for the period 2006–2011. Scenarios of extreme monthly air temperatures at the Bratislava-airport were compiled based on statistical analysis of daily air temperatures during 1951–2011. Extreme water temperatures were simulated based on a scenario of air temperature using several ARIMA models (Autoregressive Integrated models of Moving Averages). Results of the simulations show, that for increasing the maximum air temperature by 1°C, the water temperature may be increased by 0.7–0.9°C, depending on the model used.
Keywords: ARIMA models, water temperature simulation, Water Framework Directive, climate change
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #6, pp. 46-55
Title of the Paper: MHD Nanofluid Flow Containing Gyrotactic Microorganisms
Authors: R.Kandasamy, Radiah Muhamad
Abstract: In this paper, we investigate the bioconvection induced by the magnetohydrodynamic flow of water based nanofluid containing nanoparticles and motile microorganisms over a vertical plate. Nanofluid bioconvection is generated by buoyancy forces on the interaction of motile microorganisms and nanoparticles. The microorganisms are imposed into the nanofluid to stabilize the nanoparticles to suspend due to a phenomenon called bioconvection. The bioconvection parameters tend to decelerate the concentration of motile microorganisms depend strongly upon the chemical reaction, magnetic, buoyancy, nanofluid and bioconvection parameters.
Keywords: Bioconvection, MHD boundary layer nanofluid flow, Gyrotactic microorganisms, Brownian motion, thermophoresis particle deposition, chemical reaction
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #5, pp. 30-45
Title of the Paper: Using on Results of External Heat Exchange Local Coefficients Study for Formation of Hydrodynamic Structure of Fluidized Bed Optimal for Burning Low Grades Solids Fuels
Authors: Rafail Isemin, Dmitry Klimov, Sergey Kuzmin, Aleksandr Mikhalev, Valentin Konyakhin, Oleg Milovanov, Natalia Muratova
Abstract: The type of air entry distribution is essential in the formation of hydrodynamic structures of fluidized bed. The present study is aimed to form a hydrodynamic structure of fluidized bed optimal for burning low-grade solids fuels. In order to determine the uniformity of the fluidized bed in the bed heat exchange rate between the bed and a heat exchange member immersed therein was measured. At a first approximation, heat exchange with the member immersed into the bed imitates heat exchange between the fluidized bed and a fuel particle. It is allowed to determine that an optimal hydrodynamic structure of the bed can be formed by using a lattice supplying the major portion of air near the furnace wall. The above conclusion was confirmed by experiments using a real furnace with a fluidized bed.
Keywords: Air distribution, anthracite culm, biomass, combustion, fluidized bed, heat transfer, straw pellets
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #4, pp. 21-29
Title of the Paper: Impact of Porous Structure of the AAC Material on Moisture Distribution throughout the Cross Section of the AAC Masonry Blocks
Authors: Sanita Rubene, Martins Vilnitis
Abstract: Autoclaved aerated concrete (AAC) is known to be a construction material with high heat insulation parameters. Therefore, it is widely used in construction where high heat insulation parameters of external delimiting constructions have to be met. However, there is a factor that has significant impact of the insulation properties of AAC. This factor is moisture content of the AAC material and its distribution throughout the cross section of the AAC masonry blocks. The moisture distribution and transfer processes depend on the pore distribution throughout the volume of the material and differ in different directions of the material volume. Therefore, the drying process of the AAC has to monitored in order to make sure that the material has reached air dry state and can reach its optimal heat insulation properties.
Keywords: moisture distribution, autoclaved aerated concrete, EIS measurements, non-destructive testing
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #3, pp. 13-20
Title of the Paper: Influence of Hydrophobic Additives on Protection Against Alkali Environment
Authors: Radka Pernicova
Abstract: Influence of hydrophobic additives on resistance to alkali environment is described in this paper. This article is focus on surface properties of vibropressed concrete connected with hydrophobicity. The aim of the testing was in description of influence of several types of hydrophobic additives, which were applied either to the interior structure or either as a coating on the surface of the element. In some cases, it was a combination of both. The article is about specific measurement of resistance against alkalis. Higher resistance to alkali and therefore better durability properties show samples with hydrophobic coating than with inner additives. All the samples with inner impregnation exceeded its permitted limits established for the alkali resistance multi-times. Measurement involves not only resistance to alkalis but also tests of frost resistance and water absorption depending on time.
Keywords: vibropressed concrete, hydrophobic additives, resistance to alkali, frost resistance
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #2, pp. 8-12
Title of the Paper: Investigation of Heat Transfer Decrement of Wall Structures Comparison of Measurements and Calculations
Authors: Akos Lakatos
Abstract: In these days, the examinations of the thermal behavior of different wall structures are so important from the point of view of reducing energy efficiency of Buildings. The mainly used thermal insulating materials are the plastic foams (expanded and extruded) and the mineral wool materials. Nowadays, the use of the ceramic based insulating paints is also spread over. Thermal parameters of buildings, such as thermal capacity, heat-loss coefficient, time constant, thermal delay, etc. are useful in the analysis of the dynamic thermal behaviour and the characterization of buildings. This paper presents measurement methods to reach the decrement factor of different building structures by using a heat flux meter and hot box method. Moreover, calculations for the investigation of the decrement factor of wall structures were also presented. Here has to be emphasized that this method can be useful as well for everyone who is about to describe and carry out thermal sizing of buildings. In this paper three types of building structures were measured. These measurements were accomplished through an inbuilt plaster/brick/plaster wall construction insulated internally with a ceramic material at the first time and externally with an Expanded Polystyrene later. The calculations were carried out on a concrete and brick based walls covered with different insulators.
Keywords: thermal decrement factor, building structures, thermal energy, brick wall, hukseflux apparatus, hot box
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 11, 2016, Art. #1, pp. 1-7
