Amount Of Heat Flow Research Articles

ИССЛЕДОВАНИЕ ЭФФЕКТИВНОСТИ РАБОТЫ КОНФОРМНЫХ КАНАЛОВ ОХЛАЖДЕНИЯ КОМПОЗИТНЫХ ПРЕСС-ФОРМ

The article deals with the issue of evaluating the performance of a composite metal-metal-polymer mold. The use of a composite mold, including a forming plate consisting of a metal, and a metal polymer introduced with a low cooling efficiency of such a mold. For this reason, it is important to develop technological solutions that ensure the efficient operation of the cooling system. The article provides mathematical calculations of the required amount of heat flow when molding thermoplastics into a mold. Further, based on the calculated data, a study is made using finite elements of the thermal conductivity of the metal-polymer part. The design of the composite forming plate of the mold described in the article involves the manufacture of a cooling channel profile as close as possible to the forming part of the mold and located in the metal-polymer part. Based on the analysis of the temperature viscosity of the metal-polymer part of the mold, conclusions and recommendations are given for the design of a curved investment mold. It allows designers to calculate the optimal geometric parameters of the cooling system. The design and manufacture of conformal cooling stages in the metal-polymer part is likely to be preferable for cooling the forming part of the mold by bringing the cooling reversal surface closer to the surface of the forming mold, resulting in increased durability and productivity of the composite mold.

Disperse systems temperature field finding at reception of firm crystal-amorphous structures

The temperature field of firm crystal-amorphous structures receiption from liquid systems in the fluid bed is explored. The stable conducting terms of process are certain.
 Previous studies have shown that increasing the irrigation density increases the probability of formation of agglomerates, which causes a decrease in temperature; therefore, it is advisable to measure the temperature field in the environment of the dispersant and compare it with the values of temperatures at the characteristic point, according to which the regulation of the flow of liquid phase to the granulator is carried out.
 The objective of the experimental research was to determine the change of the temperature field in disperse systems in obtaining crystalline-amorphous solid structures in a fluidized-bed apparatus.
 In case of an increase in the amount of heat flow, an adequate increase in the flow of liquid phase occurs. This results in the local overturning of solid particles and, as a result, the formation of large aggregates and loss of quality of fluidization. To eliminate this disadvantage it is advisable to create conditions for uneven distribution of the coolant speed.
 In the downstream right and left fluxes, the coolant speed should not exceed the rate of gas filtration through the material. In the left upward flow, in which the direction of motion of the granular material is opposite to the direction of the vector of the linear velocity of the dispersed droplets of the liquid phase, it is expedient to increase the flow of the coolant in a direction that coincides with the downstream flow. To verify these provisions, it is expedient to conduct a study of the continuous process of formation of solid multilayer composites.

Thermal analysis of nanostructured alumina stabilized zirconia coating on exhaust manifold

ABSTRACTRapid rise in pollution has increased the number of automobiles usage worldwide. The exhaust manifold is an important part in the automobile since it acts as a passage for the transport of exhaust gases from the combustion chamber to the atmosphere. It is a sensitive component since it handles high-temperature exhaust gases. Continuous exposure of high-temperature exhaust gas may cause thermal stress which decreases the life of the exhaust manifold. Cast iron or steel is the most common material used for exhaust manifold. The present study deals with the improvement of material properties of exhaust manifold. In order to optimize the cast iron properties such as thermal conductivity and corrosion resistance, a zirconia-based nanocomposite coating such as alumina stabilized Zirconia (ASZ) can be coated on both sides of the exhaust manifold, instead of replacing the whole material. By coating nano structured ASZ, the amount of heat flow from exhaust gases to the exhaust manifold is decreased, thereby reducing the thermal fatigue. The method of coating can be achieved by radio frequency Magnetron sputtering technique. A steady-state thermal analysis is performed by simulation approach using ANSYS R17.2 to validate the output in the numerical approach. The results obtained shows that ASZ nanocomposite coating acts as an efficient thermal barrier coating for the exhaust manifold thus increasing its reliability.

THE EFFECT OF WHOLE BODY GAS CRYOTHERAPY ON THE HUMAN THERMAL STATE

The therapeutic effect of the whole body gas cryotherapy (WBGC) procedure is achieved when the average temperature of the human’s (patient’s) skin surface during the procedure is in a certain temperature range, and the rate of reduction of this temperature exceeds a certain threshold value. The paper presents the results of a theoretical analysis of the patient’s thermal state at the stage of the therapeutic effect of WBGC. The analysis was based on the results of the numerical simulation of temperature distribution in different parts of patients (mеn) of different body constitution (height, cm × mass, kg) 160 × 60, 175 × 75, 190 × 90. Particular attention was paid to the relationship between the amount of heat flow removed from the skin surface and the rate of cooling of the skin of a patient. The results of numerical modeling are presented graphically and are summarized as the ratio between the dimensionless average temperature of the skin at the treatment stage of the WBGC procedure and the time of the patient’s stay in the procedural chamber, referred to the time of the beginning of this stage. With regard to WBGC within the temperatures range of –160 to –110 °C the following regularities were found: 1) approximate constancy (descripancy less than 1 %) at the stage of therapeutic modality of the coefficient of heat transfer from the skin surface to the gas medium in the treatment chamber; 2) the exponential dependence of the value of cutaneous blood flow rate (blood perfusion) on the mean temperature of cooled cutaneous coverings; 3) linear dependence of the logarithm of the ratio of the rate of skin temperature reduction to the value of heat flux density removed by convection and radiation on the logarithm time.

Heat transfer in Oldroyd-B fluid flow due to an exponentially stretching wall utilizing Cattaneo–Christov heat flux model

Here we are concerned with the Oldroyd-B fluid flow resulting from the deformation of a non-isothermal flat surface with exponentially varying velocity. The objective is to resolve the heat transfer problem by assuming an exponentially varying wall temperature. A non-Fourier model is followed that enables one to investigate the features of thermal relaxation time phenomenon. Using local similarity method, the governing system is changed to a set of locally similar equations which have been tackled by optimal homotopy analysis method. The solution profiles are obtained and elucidated for broad parameter values. The direction and amount of heat flow are governed by a parameter measuring the exponential growth/decay rate of wall temperature with horizontal distance. An important implication of this research is that thermal field is substantially altered by thermal relaxation time. Also, the change in temperature profiles with variation in other parameters become prominent as thermal relaxation time enlarges. A comparative study of current computations with the existing literature appears convincing.

Efficiency of mixed-flow heat exchangers

It has been shown that studies are aimed at improving existing apparatuses and their elements in the agitating zone of liquids. A great deal of attention is devoted to investigating heat exchange upon stirring, the problem of the intensification of which has not been solved completely. For this reason, apparatuses with vertical heat-exchange units are considered to be promising. A model that allows for the assumption of the effect of the features of the design of agitator and heat-exchange units designed as vertical tubes on the heat-exchange efficiency in the stirring apparatus has been suggested. Results of experimental investigations of hydrodynamics and heat exchange in the apparatuses under study have been given and their high heat effectiveness has been demonstrated. The effectiveness of heat transfer has been compared in the blocks with parallel and series-connected tubes at identical flow rates of the heat carrier in the pipes of each block. No difference in the effectiveness of heat transfer is observed in the entire range of the rotation frequency of a stirrer. At higher water consumption, a block with parallel-connected pipes provides a higher amount of heat flow due to the larger driving force of heat transfer. Experimental data are generalized based on the theoretical dependence for calculating the coefficient of heat withdrawal from the agitated medium. The possibility of increasing coefficients of heat withdrawal from the agitated medium is only restricted by the supplied mechanical energy. An example of the calculation of apparatuses has been given.

The Mechanism of a Temperature Decrement of Porous Materials Immersed in a Fluidized Bed in Drying

The temperature decrement in the inner parts of porous materials immersed in a gas-solid fluidized bed was observed in drying. To clarify the mechanism of this phenomenon, a theoretical calculation includes heat and mass transfers in a porous material (sample) was performed, and the heat balance in the sample was estimated. The effects of temperature of drying gas and the thermal conductivity of the sample on the temperature decrement were also examined.In the case of fluidized bed drying, the amount of heat flow in a sample is very large at the earlier period of drying (surface evaporation period). After the sample surface dried, the amount of heat flow in the inner parts of the sample is governed by the thermal conductivity of the sample. During the period, the amount of heat consumption for evaporation increases and it becomes larger than that of heat conduction in the inner parts of the sample in drying. This inversion is the reason of the temperature decrement in the inner parts of the sample in fluidized bed drying. The decrement degree of temperature becomes larger as the temperature of drying gas increases. The temperature decrement occurs more easily as the thermal conductivity becomes lower.

Heat transfer over an exponentially stretching continuous surface with suction

Similary solutions of the laminar boundary layer equations describing heat and flow in a quiescent fluid driven by an exponentially stretching surface subject to suction are examined numerically. The direction and amount of heat flow were found to be dependent on the magnitude of γ (parameter of temperature) for the same Prandtl number. Nusselt number increases with increasing γ and the Prandtl number. The effect of decreasing suction parameter is found to be significant particularly for the Prandtl number.

Development of kA-class gas-cooled HTS current lead for superconducting fault current limiter

A current lead with kA capacity and small AC loss is being developed for use in superconducting current limiting devices cooled with liquid helium. A gas-cooled type current lead using Bi-based oxide superconducting bulk materials was examined to clarify the effects of the current lead geometry and the use of multiple current leads. This paper presents the results of experiments and numerical simulations based on the finite element method taking consideration of nonuniform transport current distribution among multiple current leads connected in parallel. The simulations are performed to investigate the relationship between the geometry of current leads and the amount of heat flow into a cryostat. In the simulations, the AC loss caused by both mutual and self-induced magnetic fields of multiple current leads is taken into account. The influence of AC loss, the joule heat generated by the contact resistance at joints of NbTi/CuNi multi-strand cables and the HTS bars, and the return passage for gas on the operating characteristics of the HTS current leads are evaluated.

形状記憶合金アクチュエータの動特性の改善

An actuator using shape memory alloy (SMA) has large power/weight ratio and is able to generate relatively large displacement. However there are only few examples of practical application in precision engineering because its dynamic characteristics are very poor. An SMA actuator deforms by being heated up and cooled down with deforming force. It is usually easy to heat up fast, but difficult to cool down quickly since the cooling time depends on the amount of heat flow from inside to outside of SMA. So dynamic response of the actuator mainly depends on the time to cool down. In order to improve the dynamic characteristics of the SMA actuator, the present paper proposes to put the actuator in water bath for cooling down actuator quickly. The effect of setting the SMA in water bath is experimentally examined. Responses of linear actuators of SMA wires set in air and/or water are compared with each other. For miniaturization, water jackets should be small. However if they are small, cooling ability becomes poor and temperature of water in the jacket rises up fast by repetitive drive. Therefore influences of size of the jackets, cycle time of repetitive drive and water temperature in the jacket are investigated.

Heat transfer characteristics of a continuous stretching surface

The similarity solutions for the governing ordinary differential equations of the boundary layer corresponding to a stretching surface have been reported. Power law velocity and temperature distribution were assumed for velocity exponent 3≥m≥−0.41176, −1.1≥m≥−3, and for temperature exponent 3≥n≥−3. Solutions have been found forn=0 and allm where heat transferred from the stretching surface to the ambient. The direction and amount of heat flow were found to be dependent on the magnitude ofn andm for the same Prandtl number. Nusselt number increases with increasingm andPr for uniform and variable surface temperature however, for uniform surface heat flux it decreases with increasingm for constantPr.

Application of Fully Integrated Quantitative Basin Analysis Model: Oseberg Area, Norwegian North Sea: ABSTRACT

A new deterministic dynamic basin model was developed to quantify basin evolution in terms of geologic, hydrodynamic, geothermal, and geochemical histories. Quantification of the processes occurring in sedimentary sequences was based on series of equations defining fluid flow, grain velocity, conductive and convective heat flow, maturation of organic matter, isomerization of steranes and hopanes, hydrocarbon generation, and potential migration directions. One-dimensional studies on 12 wells were used to optimize (1) the conceptual model in terms of tectonic history, basin formation, stratigraphy, lithology, paleoclimate, and paleodepositional environments and (2) the parameters of the equations used. Two-dimensional studies were undertaken on three seismic profiles from the region. The model results were checked against all the available data on geology, hydrodynamics, geothermics, seismics, and geochemistry. The modeling results showed that the crust was not thinned much, contrary to the amounts cited in literature. The maximum amount of heat flow was 1.20 heat-flow units (HFU) during Late Jurassic. The heat flow steadily decreased, reaching a value of 1.0 HFU at the beginning of the Cretaceous. A slight increase in heat flow during middle to late Eocene was computed. Petroleum generation started 66 Ma and continued at different rates until the present. Petroleum then migratedmore » eastward and southward into the Oseberg structures. The modeling results indicated two major petroleum types in the area. All the modeling results indicated two major petroleum types in the area. All the modeling results have been confirmed by geochemical data in terms of pyrolysis, biomarkers, and isotopes.« less

A few measurements on the heat conductivity of liquid helium II

The heat conductivity of liquid helium II in a capillary, length 35 cm, width 0.30 mm, was examined. It appears to depend on the amount of heat flow, the heat conductivity decreasing when the heat flow increases. As function of temperature it has a very pronounced maximum at 1.7—2.0°K. Heat conductivities of about 810 cal sec −1 cm −1 degr −1 , that is more than 800 times that of copper at room temperatures, were measured.