Fundamentals of heat transfer

Following over 170+ pages and additional appendixes are formed based on content of Course: Fundamentals of Heat Transfer. Mainly this summarizes relevant parts on Book of Fundamentals of Heat and Mass Transfer (Incropera), but also other references introducing the same concepts are included. Student’s point of view has been consideredwith following highlights: (1) Relevant topics are presented in a nutshell to provide fast digestion of principles of heat transfer. (2) Appendixes include terminology dictionary. (3) Totally 22 illustrating examples are connecting theory to practical applications and quantifying heat transfer to understandable forms as: temperatures, heat transfer rates, heat fluxes, resistances and etc. (4) Most important Learning outcomes are presented for each topic separately. The Book, Fundamentals of Heat and Mass Transfer (Incropera), is certainly recommended for those going beyond basic knowledge of heat transfer. Lecture Notes consists of four primary content-wise objectives: (1) Give understanding to physical mechanisms of heat transfer, (2)Present basic concepts and terminology relevant for conduction, convection and radiation (3) Introduce thermal performance analysis methods for steady state and transient conduction systems. (4) Provide fast-to-digest phenomenological understanding required for basic design of thermal models

Design of an amplifier and an instrumentation setup for a harsh environment heat flux measurement application – case axial flux electric machine

Measurement is a tool for researching. Therefore, it is important that the measuring process is carried out correctly, without distorting the signal or the measured event. Researches of thermoelectric phenomena have been focused more on transverse thermoelectric phenomena during recent decades. Transverse Seebeck effect enables to produce thinner and faster heat flux sensor than before. Studies about transverse Seebeck effect have so far focused on materials, so in this Master’s Thesis instrumentation of transverse Seebeck effect based heat flux sensor is studied, This Master’s Thesis examines an equivalent circuit of transverse Seebeck effect heat flux sensors, their connectivity to electronics and choosing and design a right type amplifier. The research is carried out with a case study which is Gradient Heat Flux Sensors and an electrical motor. In this work, a general equivalent circuit was presented for the transverse Seebeck effect-based heat flux sensor. An amplifier was designed for the sensor of the case study, and the solution was produced for the measurement of the local heat flux of the electric motor to improve the electromagnetic compatibility.

Development and evaluation of a loop-mediated isothermal amplification (LAMP) assay for rapid detection of Actinobacillus pleuropneumoniae based the dsbE-like gene

This paper reports on the development and validation of a loop-mediated isothermal amplification assay (LAMP) for the rapid and specific detection of Actinobacillus pleuropneumoniae (A. pleuropneumoniae). A set of six primers were designed derived from the dsbE-like gene of A.pleuropneumoniae and validate the assay using 9 A. pleuropneumoniae reference/field strains, 132 clinical isolates and 9 other pathogens. The results indicated that positive reactions were confirmed for all A. pleuropneumoniae strains and specimens by LAMP at 63ºC for 60 min and no cross-reactivity were observed from other non-A.pleuropneumoniae including Haemophilus parasuis, Escherichia coli, Pasteurella multocida, Bordetella bronchiseptica, Streptococcus suis, Salmonella enterica, Staphylococcus, porcine reproductive and respiratory syndrome virus (PRRSV), and Pseudorabies virus. The detection limit of the conventional PCR was 10² CFU per PCR test tube, while that of the LAMP was 5 copies per tube. Therefore, the sensitivity of LAMP was higher than that of PCR. Moreover, the LAMP assay provided a rapid yet simple test of A. pleuropneumoniae suitable for laboratory diagnosis and pen-side detection due to ease of operation and the requirement of only a regular water bath or heat block for the reaction.

The effects of welding heat input on the usability of high strength steels in welded structures

High strength steel (HSS) has been in use in workshops since the 1980s. At that time, the significance of the term HSS differed from the modern conception as the maximum yield strength of HSSs has increased nearly every year. There are three different ways to make HSS. The first and oldest method is QT (quenched and tempered) followed by the TMCP (thermomechanical controlled process) and DQ (direct quenching) methods. This thesis consists of two parts, the first of which part introduces the research topic and discusses welded HSS structures by characterizing the most important variables. In the second part of the thesis, the usability of welded HSS structures is examined through a set of laboratory tests. The results of this study explain the differences in the usability of the welded HSSs made by the three different methods. The results additionally indicate that usage of different HSSs in the welded structures presumes that manufacturers know what kind of HSS they are welding. As manufacturers use greater strength HSSs in welded structures, the demands for welding rise as well. Therefore, during the manufacturing process, factors such as heat input, cooling time, weld quality, and more must be under careful observation.

Heat transfer inside internal combustion engine: modelling and comparison with experimental data

The paper is devoted to study specific aspects of heat transfer in the combustion chamber of compression ignited reciprocating internal combustion engines and possibility to directly measure the heat flux by means of Gradient Heat Flux Sensors (GHFS). A one – dimensional single zone model proposed by Kyung Tae Yun et al. and implemented with the aid of Matlab, was used to obtain approximate picture of heat flux behavior in the combustion chamber with relation to the crank angle. The model’s numerical output was compared to the experimental results. The experiment was accomplished by A. Mityakov at four stroke diesel engine Indenor XL4D. Local heat fluxes on the surface of cylinder head were measured with fast – response, high – sensitive GHFS. The comparison of numerical data with experimental results has revealed a small deviation in obtained heat flux values throughout the cycle and different behavior of heat flux curve after Top Dead Center.

Heat flux measurement inside internal combustion engine with gradient heat flux sensor.

This master’s thesis is devoted to study different heat flux measurement techniques such as differential temperature sensors, semi-infinite surface temperature methods, calorimetric sensors and gradient heat flux sensors. The possibility to use Gradient Heat Flux Sensors (GHFS) to measure heat flux in the combustion chamber of compression ignited reciprocating internal combustion engines was considered in more detail. A. Mityakov conducted an experiment, where Gradient Heat Flux Sensor was placed in four stroke diesel engine Indenor XL4D to measure heat flux in the combustion chamber. The results which were obtained from the experiment were compared with model’s numerical output. This model (a one – dimensional single zone model) was implemented with help of MathCAD and the result of this implementation is graph of heat flux in combustion chamber in relation to the crank angle. The values of heat flux throughout the cycle obtained with aid of heat flux sensor and theoretically were sufficiently similar, but not identical. Such deviation is rather common for this type of experiment.

Enteral fluid therapy through nasogastric tube in rumen cannulated goats

This paper reports the effects of fluid therapy in goats through nasogastric route with an electrolyte solution composed by concentrations of sodium, potassium and chloride similar to goat plasma (140mmol/L of Na+, 4.5mmol/L of K+, 110mmol/L of Cl-). Four Alpine Chamoisee goats, two of them with evident leakage of the rumen cannulas, were used in a crossover experimental design of two periods and two groups. In one group the two goats were submitted to a treatment protocol to induce dehydration before the fluid therapy, whereas the other group was not. Fluid therapy consisted supplying 10mL/kg/h of the electrolyte solution during 8 hours. No signs of discomfort or stress were observed. The dehydration model employed caused a mild dehydration indicated by decrease in feces humidity, body weight and abdominal circumference, and increase in plasma total solids concentration. During fluid therapy globular volume and plasma total solids decreased, whereas % body weight and abdominal circumference increased. No signs of hyperhydration were observed and serum electrolytes (Na+, Cl-, K+) presented no significant alterations in both groups. Fluid therapy proposed in this study was efficient to treat dehydration, even for rumen cannulated animals with evident leakage, and can be administrated safely with no electrolyte imbalance.

Thermalhydraulic behavior of electrically heated rod during a critical heat flux transient

In nuclear reactors, the occurrence of critical heat flux leads to fuel rod overheating with clad fusion and radioactive products leakage. To predict the effects of such phenomenon, experiments are performed using electrically heated rods to simulate operational and accidental conditions of nuclear fuel rods. In the present work, it is performed a theoretical analysis of the drying and rewetting front propagation during a critical heat flux experiment, starting with the application of an electrical power step from steady state condition. After the occurrence of critical heat flux, the drying front propagation is predicted. After a few seconds, a power cut is considered and the rewetting front behavior is analytically observed. Studies performed with various values of coolant mass flow rate show that this variable has more influence on the drying front velocity than on the rewetting one.

Inverse convection problem of simultaneous estimation of two boundary heat fluxes in parallel plate channels

This paper deals with the use of the conjugate gradient method of function estimation for the simultaneous identification of two unknown boundary heat fluxes in parallel plate channels. The fluid flow is assumed to be laminar and hydrodynamically developed. Temperature measurements taken inside the channel are used in the inverse analysis. The accuracy of the present solution approach is examined by using simulated measurements containing random errors, for strict cases involving functional forms with discontinuities and sharp-corners for the unknown functions. Three different types of inverse problems are addressed in the paper, involving the estimation of: (i) Spatially dependent heat fluxes; (ii) Time-dependent heat fluxes; and (iii) Time and spatially dependent heat fluxes.

Heat Source Estimation with the Conjugate Gradient Method in Inverse Linear Diffusive Problems

In this work, we present the solution of a class of linear inverse heat conduction problems for the estimation of unknown heat source terms, with no prior information of the functional forms of timewise and spatial dependence of the source strength, using the conjugate gradient method with an adjoint problem. After describing the mathematical formulation of a general direct problem and the procedure for the solution of the inverse problem, we show applications to three transient heat transfer problems: a one-dimensional cylindrical problem; a two-dimensional cylindrical problem; and a one-dimensional problem with two plates.

Simulation of Steady-State Nonlinear Heat Transfer Problems Through the Minimization of Quadratic Functionals

In this work it is presented a systematic procedure for constructing the solution of a large class of nonlinear conduction heat transfer problems through the minimization of quadratic functionals like the ones usually employed for linear descriptions. The proposed procedure gives rise to an efficient and easy way for carrying out numerical simulations of nonlinear heat transfer problems by means of finite elements. To illustrate the procedure a particular problem is simulated by means of a finite element approximation.

Effects of condensation in microchannels with a porous boundary: analytical investigation on heat transfer and meniscus shape

In two-phase miniature and microchannel flows, the meniscus shape must be considered due to effects that are affected by condensation and/or evaporation and coupled with the transport phenomena in the thin film on the microchannel wall, when capillary forces drive the working fluid. This investigation presents an analytical model for microchannel condensers with a porous boundary, where capillary forces pump the fluid. Methanol was selected as the working fluid. Very low liquid Reynolds numbers were obtained (Re~6), but very high Nusselt numbers (Nu~150) could be found due to the channel size (1.5 mm) and the presence of the porous boundary. The meniscus calculation provided consistent results for the vapor interface temperature and pressure, as well as the meniscus curvature. The obtained results show that microchannel condensers with a porous boundary can be used for heat dissipation with reduced heat transfer area and very high heat dissipation capabilities.

Modeling of fireside deposit formation in two industrial furnaces

Fireside deposits can be found in many types of utility and industrial furnaces. The deposits in furnaces are problematic because they can reduce heat transfer, block gas paths and cause corrosion. To tackle these problems, it is vital to estimate the influence of deposits on heat transfer, to minimize deposit formation and to optimize deposit removal. It is beneficial to have a good understanding of the mechanisms of fireside deposit formation. Numerical modeling is a powerful tool for investigating the heat transfer in furnaces, and it can provide valuable information for understanding the mechanisms of deposit formation. In addition, a sub-model of deposit formation is generally an essential part of a comprehensive furnace model. This work investigates two specific processes of fireside deposit formation in two industrial furnaces. The first process is the slagging wall found in furnaces with molten deposits running on the wall. A slagging wall model is developed to take into account the two-layer structure of the deposits. With the slagging wall model, the thickness and the surface temperature of the molten deposit layer can be calculated. The slagging wall model is used to predict the surface temperature and the heat transfer to a specific section of a super-heater tube panel with the boundary condition obtained from a Kraft recovery furnace model. The slagging wall model is also incorporated into the computational fluid dynamics (CFD)-based Kraft recovery furnace model and applied on the lower furnace walls. The implementation of the slagging wall model includes a grid simplification scheme. The wall surface temperature calculated with the slagging wall model is used as the heat transfer boundary condition. Simulation of a Kraft recovery furnace is performed, and it is compared with two other cases and measurements. In the two other cases, a uniform wall surface temperature and a wall surface temperature calculated with a char bed burning model are used as the heat transfer boundary conditions. In this particular furnace, the wall surface temperatures from the three cases are similar and are in the correct range of the measurements. Nevertheless, the wall surface temperature profiles with the slagging wall model and the char bed burning model are different because the deposits are represented differently in the two models. In addition, the slagging wall model is proven to be computationally efficient. The second process is deposit formation due to thermophoresis of fine particles to the heat transfer surface. This process is considered in the simulation of a heat recovery boiler of the flash smelting process. In order to determine if the small dust particles stay on the wall, a criterion based on the analysis of forces acting on the particle is applied. Time-dependent simulation of deposit formation in the heat recovery boiler is carried out and the influence of deposits on heat transfer is investigated. The locations prone to deposit formation are also identified in the heat recovery boiler. Modeling of the two processes in the two industrial furnaces enhances the overall understanding of the processes. The sub-models developed in this work can be applied in other similar deposit formation processes with carefully-defined boundary conditions.