Additional Heat Source Research Articles

Dissipative heat for the Casson fluid flow past an expanding cylindrical surface

AbstractA non‐Newtonian model is developed by considering the flow of non‐Newtonian Casson fluid past an expanding cylinder embedded in a porous medium. The novelty arises because of the conjunction of dissipative heat, and the additional heat source that enriches the heat transport phenomenon significantly. The application of the study is vital due to the flow of blood through the artery, a physiological study. Therefore, the study of Casson fluid plays an important role. The nonlinear partial differential equations that appeared in the formulation are now renovated to the coupled nonlinear ordinary differential equations. However, a numerical technique associated with shooting‐based followed by Runge–Kutta fourth‐order is employed for the solution of these transformed equations. The uniqueness of diverse pertinent parameters on the flow phenomena is scrutinized through graphs and numerically simulated results presented in tables. The important observations are as follows; the magnetic parameter and permeability augment the shear rate coefficients, whereas the Casson parameter rendered the opposite impact. Furthermore, the non‐Newtonian Casson parameter retards the fluid temperature, and the curvature parameter significantly enhances it.

Thermo-elastostatic analyzes of new dampers made of polymer springs with negative thermal expansion

The article presents original results of research of the dampers with passive and semi-active damping using polymer springs (also artificial muscles or nylon springs) with negative thermal expansion. Passive damping can be ensured by the strong damping effects of polymer springs. Semi-active damping can be provided by heating the springs from an additional heat source. According to design such dampers, mathematical models for analytical elastostatic and thermoelastostatic analyzes of dampers for selected load cases are processed in the paper. The permissible values of mechanical and thermal load of the dampers are determined. The obtained results are verified by numerical analysis using the finite element method. The elastostatics of the passive damper and its damping functionality have been verified on a real model of the damper. The compiled mathematical models can be used in the design of polymer dampers as well as in their automatic control. Designed and analysed dampers can be used in smaller mobile or stationary systems such as scooters, small car kits and the like. The elastodynamic functionality of the dampers with passive and semiactive damping will be presented and discussed in our further paper.

Using Heat Flow Density Values Obtained in the Gulf of Cadiz and Gorringe Bank, Atlantic Ocean

The geothermal heat flow measured at the surface of the Earth is originated by different heat sources located at different depths of the planet. The main sources of heat flow in the crust are associated with radioactive decay of Uranium, Thorium and Potassium, in rocks. In some regions, additional heat sources must be considered such as exothermic chemical reactions. The value of the heat flow coming from deep regions, designated by “heat from the mantle”, must be obtained using indirect methods. In this work, the geoid height was used as indicator of alterations “in heat from the mantle” values, considering that the density decrease in regions with geoid height increase is related to high temperature values in the upper part of the mantle. The region on study is located in the Atlantic Ocean, SW of Cape St. Vincent and Cadiz Gulf. Temperature-depth values were obtained in twelve points of the region considering heat flow by conduction in the vertical direction, using published heat flow and thermal conductivity data. Layered models were made using data obtained in published seismic profiles. Moho depth values were used as lower boundary of the crust and mantle heat flow variations were made according geoid height increases. Ocean depth values between 2.5 and 4.3 km were used. A value of 5°C was used for temperature at the upper boundary (ocean bottom) of the models. Temperature calculus stops when a value of 1350 °C was attained. Lithosphere thickness is obtained considering this temperature value as temperature at the bottom of the lithosphere. Heat flow density values from 36 to 65.8 mW m−2 were used in the work with “heat from the mantle” values from 33 to 35 mw m−2. Curie Point Temperature (600°C) depths from 33 to 36 km were obtained. Lithosphere thickness values about 97 km were obtained in all the models.

Performance of a shallow solar pond coupled with a heat pump cycle for thermal energy in net zero-energy buildings

Refrigerant evaporation, in heat pumping systems, is a particularly complex process. Since the evaporator is subjected to environmental conditions, several factors weigh in on overall system performance, mainly, the additional energy input from the surroundings. This renders the evaporation process especially susceptible to gaps and fluctuations of said energy availability, particularly in solar-assisted setups. Despite the, comparatively, high heat flux associated to this source, these occurrences make them suitable mostly for low-to-medium thermal requirements, especially in regions with more extreme climates. The present work introduces a novel evaporator design, based on solar ponds. The proposed evaporation device incorporates a short-term, passive, thermal storage solution to compensate for gaps in energy availability. A mathematical-thermal model is developed and a performance assessment is conducted based on real seasonal atmospheric and operation conditions. For this study R134a, R152a, R1234yf and R1234ze(E) were used as working fluids. The proposed heat pump configuration is evaluated for hot water production at 55 °C, indoor air heating at 18–22 °C and a combined simultaneous scheme. The results show that this configuration performs well under moderate climate conditions. For hot water production during spring, highest outlet temperature of 68.54 °C for the R1234yf working fluid, were reached and maintained after the first 13 h. Internal thermal capacitor reached an average temperature of 61.88 °C for R1234yf. During winter, these temperatures decrease almost by a third, with 40.6 °C for R1234yf working fluid. However, daily average outlet temperature of 64.8°Care reached within the first 15 h of operation. Despite a lower thermal storage, with average capacitor, the system yielded consistent average outlet temperature of 20.7 °C. For a simultaneous operation scheme, desired outlet water temperature, is reached within the first 16 h of operation, whilst the indoor air temperature reaches comfort levels within the first 12 h. Despite employing part of the energy absorbed to maintain a stable comfort condition within the dwelling, instead of compensating the heat loss of the hot water tank, both goals are achieved. The inclusion of an inner thermal capacitor that collects and stores energy at a much higher rate provides the refrigerant with an additional heat source. This results in a more effective overall energy absorption of the evaporator, which exceeds the rate at which heat is dissipated from the tank/dwelling to the environment. This heat loss buffer lessens, considerably, the thermal demand during periods with lower energy availability, resulting in achievable outlet conditions.

An investigation of libration heating and the thermal state of Enceladus's ice shell

Tidal dissipation is thought to be responsible for the observed high heat loss on Enceladus. Forced librations can enhance tidal dissipation in the ice shell, but how such librations affect the thermal state of Enceladus has not been investigated. Here we investigate the heating effect of forced librations using the model of Van Hoolst et al., 2013, which includes the elasticity of the ice shell. We find that libration heating in the ice shell is insufficient to match the inferred conductive heat loss of Enceladus. This suggests that either Enceladus is not in a thermal steady state, or additional heating mechanisms beneath the ice shell are contributing the bulk of the power. In the presence of such an additional heat source, Enceladus resides in a stable thermal equilibrium, resisting small perturbations to the shell thickness. Our results do not support the occurrence of a runaway melting process proposed by Luan and Goldreich (2017). In our study, the strong dependence of conductive loss on shell thickness stabilizes the thermal state of Enceladus's ice shell. Our study implies that thermal runaway (if it occurred) or episodic heating on Enceladus is unlikely to originate from librations of the ice shell.

Автоматизация проектирования трехфазного двухскоростного асинхронного двигателя

The subject of research is double-speed asynchronous motors of the type produced by SPA ELSIB PJSC with two independent windings in the stator designed to drive the main circulating pumps of nuclear power plants as well as similar mechanisms in other sectors of the national economy. The article deals with specific issues of the full cycle of calculating the considered electric ma-chine. We propose a method of research on mutual influence of stator windings when the motor works based on the fundamental positions of the theory of electrical machines using numerical modeling. Also, a method of choosing an air cooler to be used in thermal calculation taking into account the features of the machine type under investigation is proposed. The research purpose is to optimize the full cycle of calculating a new motor of this type under development. This is due to the occurrence of additional heating in one stator winding due to the operation of the other, which increases labor costs caused by the need to take into account an additional heat source during thermal calculation. In addi-tion, the existing empirical dependencies do not fully reflect the entire physical picture of the ongoing processes. The originality of the research lies in the fact that based on the known provisions the algo-rithm for calculating the applied air cooler has been modified due to automation, which contributes to correct protection against thermal overheating effects. It is shown that by numerical modeling it is possible to minimize labor costs for determining the parameters taken into account in the subsequent thermal calculation that arise as a result of the mutual influence of the selected machine type stator windings. The research results are tried out in SPA ELSIB PJSC manufacture and presented by the motor specific example.

Feasibility Analysis of Utilization of Shallow Geothermal Energy through LNG Tank Pile Foundation

Liquefied Natural Gas (LNG) needs an additional heat source to meet its heat demand in the process of gasification. Based on the background of using shallow geothermal energy, the feasibility of using LNG tank piles as heat exchangers for LNG gasification was studied. A two-dimensional finite element heat transfer model of energy piles was established, and the heat transfer capacity and long-term stability of different buried pipe options were analyzed. The results show that the LNG tank energy piles can meet part of the heat demand for LNG gasification to a certain extent.

Effect of external heat source on temperature and moisture variation for composting of food waste

This paper investigates the outcome of having an external heat source on temperature and moisture variations in the food waste composting process. Food waste accumulation is a growing concern in many countries. Converting food waste into usable compost is a more desirable tactic than dumping to crowded landfill sites. Closed composting was applied in this work, which relies on a controlled but uninterrupted airflow during the organic material degradation process. However, undesirable odour released at low aeration rate due to low temperature and high moisture content found in the compost. Finding the ideal aeration rate with the least possible loss of moisture is needed, which was discussed in this paper. The vegetable-fruit waste used in the experiment was given an aeration rate of 0.3 L/min at a moisture setting of 60% and 70%. For 15 mins/day, the forced aeration was carried out at 3-day intervals. Results showed that 0.3 L/min with 60% and 70% moisture content attained best temperature peaks of 32.4°C and 31.6°C, respectively at day 13 for 28 days composting. A strong odour continued to exist with the compost and was mitigated by using an external additional heat source (light bulb). The light bulb also helped to provide a higher temperature for the compost of 41.5°C by day 1 for 10 days composting.

Lower crustal resistivity signature of an orogenic gold system

Orogenic gold deposits provide a significant source of the world’s gold and form along faults over a wide range of crustal depths spanning sub-greenschist to granulite grade faces, but the source depths of the gold remains poorly understood. In this paper we compiled thirty years of long-period magnetotelluric (MT) and geomagnetic depth sounding (GDS) data across western Victoria and south-eastern South Australia that have sensitivity to the electrical resistivity of the crust and mantle, which in turn depend on past thermal and fluid processes. This region contains one of the world’s foremost and largest Phanerozoic (440 Ma) orogenic gold provinces that has produced 2% of historic worldwide gold production. Three-dimensional inversion of the long-period MT and GDS data shows a remarkable correlation between orogenic gold deposits with > 1 t production and a < 20 Ω m low-resistivity region at crustal depths > 20 km. This low-resistivity region is consistent with seismically-imaged tectonically thickened marine sediments in the Lachlan Orogen that contain organic carbon (C), sulphides such as pyrite (FeS2) and colloidal gold (Au). Additional heat sources at 440 Ma due to slab break-off after subduction have been suggested to rapidly increase the temperature of the marine sediments at mid to lower crustal depth, releasing HS− ligands for Au, and CO2. We argue that the low electrical resistivity signature of the lower crust we see today is from a combination of flake graphite produced in situ from the amphibolite grade metamorphism of organic-carbon in the marine sediments, and precipitated graphite through retrograde hydration reactions of CO2 released during the rapid heating of the sediments. Thus, these geophysical data image a fossil source and pathway zone for one of the world’s richest orogenic gold provinces.

Experimental study on the backdraft phenomenon of solid fuel.

In this study, a series of small-scale experiments were conducted to investigate the backdraft phenomenon in a compartment (1.1 × 0.4 × 0.75 m) with woodblocks as fuel. This research focused on the effects of compartment window woodblock areas on backdraft time, with a video recording of the experimental phenomena. Thermocouples and a gas analyzer were used to measure the temperature and the concentration of gas components in the compartment, respectively. There was no additional heat source or ignition source pre-set in the compartment at the beginning of the experiments; the experimental processes only depended on the heat released from the burning or smoldering of woodblocks. When compartment ventilation improved, smoldering of woodblocks became intense, and backdraft occurred. The results show that backdraft time is shorten with increases of compartment window and woodblock areas, and opening the upper window of a compartment could avoid the backdraft phenomenon. The results help to understand the backdraft phenomenon of solid fuel and, more importantly, could help firefighters adopt reasonable fire-fighting strategies for restraining backdraft occurrence.

Mechanism clarification of mitigating welding induced buckling by transient thermal tensioning based on inherent strain theory

Welding induced buckling in thin plate structures significantly affects productivity and fabrication cost due to post-weld correction works. Transient thermal tensioning (TTT) as an in-process treatment was employed for mitigating welding induced buckling, and its mechanism was clarified by inherent strain theory. Butt welding experiment with 304 L stainless steel was conducted. A finite element (FE) model was established to examine thermal-mechanical response during the entire welding process. Computed results were validated by the measured out-of-plane welding distortion, which was obtained using a three-dimensional optical scanning system. Then, two additional heat sources on both sides of the welding line were applied to achieve TTT treatment with the established numerical model. Moreover, the influence of heating location on mitigating welding induced buckling was discussed. The results show that the maximum deflections along and perpendicular to welding direction were reduced by 82.6% and 74.7%, respectively. The heating location has a decisive influence on the mitigation of welding induced buckling, which should be kept away from the welding line with appropriate distance. The thermal stretching from additional heat sources enhances the self-constraint of the base material on the welding region during the cooling process, resulting in more tensile plastic strain generated to reduce welding inherent strain and tendon force.

On the merit of hot ion mode for tearing mode stabilization

The stabilization of tearing modes with rf driven current benefits from the cooperative feedback loop between rf power deposition and electron temperature within the island. This effect, termed rf current condensation, can greatly enhance and localize current driven within magnetic islands. It has previously been shown that the condensation effect opens the possibility of passive stabilization with broad rf profiles, as would be typical of LHCD for steady state operation. Here we show that this self-healing effect can be dramatically amplified by operation in a hot ion mode, due to the additional electron heat source provided by the hotter ions.

Modular Approach for Modelling Warming up Process in Water Installations with Flow-Regulating Elements

The paper presents a new method for modelling the warming up process of a water system with elements regulating the flow in a stochastic manner. The paper presents the basic equations describing the work of typical elements which the water installation is composed of. In the proposed method, a new computational algorithm was used in the form of an iterative procedure enabling the use of boundary conditions that can be stochastically modified during the warming-up process. A typical situation, when such a modification is processed, is the regulation of the medium flow through two-way or three-way valves or applying additional heat source. Moreover, the presented method does not require the transformation of the differential equations, describing the operation of individual elements, into a linear form, which significantly facilitates analytical work and makes it more flexible. The example of analysis of the operation of water installation used for controlling temperature of the process gases in a chemical installation shows the functionality and flexibility of the method. The adopted calculation schematics enable changing the direction of the heat flow while the heat exchanger is in operation. Additionally, the sequence of calculation processed in modules describing operation of installation elements is elective (there is no situation that output parameters from one element are used as input parameters for other element in the same calculation step).

Improvements of Micro-CHP SOFC System Operation by Efficient Dynamic Simulation Methods

Solid Oxide Fuel Cell (SOFC) technology is of high interest for stationary decentralized generation of electricity and heat in combined heat and power systems (CHP) for the residential sector. Application scenarios for SOFC systems in an electricity-regulated mode play an important role, especially in places where an electrical grid connection is not available or rather unstable. The advantages of SOFC systems are the high fuel flexibility and the high efficiencies also under partial load operation compared to other decentralized power generation technologies. Due to the long, energy-consuming system heat-up and the limited partial load capability, SOFC systems do not reach the performance of conventional power generation technologies. Furthermore, stack thermal cycling is associated with power degradation and should be minimized. In this paper, the improvement of these drawbacks are investigated for hotbox-based SOFC systems in the 1 kWel-class for residential applications. Since experimental investigations of the high-temperature systems are limited, modeling tools are established, enabling the visualization of internal system characteristics and providing the opportunity to simulate system operation in critical regions. To achieve this, a methodology for dynamic SOFC system modeling in a process engineering manner is developed based on the modeling language Modelica. A suitable approach is particularly important for modeling and simulation of the strong thermal interaction between the hot system components within the hotbox. The parametrized and validated models are used for the investigation of different dynamic effects, such as the system heat-up and the operation in low partial load points. A second reduced thermal system model aims for annual simulations of the SOFC system together with a battery to investigate the number of thermal cycles and the advantage of a hot standby operation. As a result, it is found that an adequate control of the power input at the start-up device and the cathode air flow has a high improvement potential to increase the stack heating rate and accelerate the heat-up in an energy-saving way. The hotbox-internal thermal management is identified as a crucial issue to reach low partial load points. To avoid the risk of stack cooling, lower heat losses and/or additional heat sources are of importance. Furthermore, the robustness of the tail gas oxidizer is found to be crucial for a higher load flexibility during partial load and the end of life stack operation. The annual simulation results indicate that operating the battery hybrid system with a hot standby mode requires much lower battery capacity for a high grid independence and a complete avoidance of system shutdown and associated power degradation.

Experimental Investigation of Solar Absorption Refrigeration System.(Dept.M)

In this paper, an investigation of aqua-ammonia solar absorption refrigeration system for domestic use is presented. The refrigeration system investigated here is a conventional aqua-ammonia absorption refrigeration system powered by solar heater. The solar heater used is a stationary, hyperbolic sprial solar concentrator equipped with a glass tube for convection loss suppression. A generator temperature as high as 140°C is reached. The lowest temperature reached in evaporator is 2°C, with an additional external heating Source. The various parameters affected the cycle performance and cooling ratio, such as, the generator temperature, evaporator temperature, collector performance and condenser temperature are presented. For fixed initial conditions, higher generator temperature and lower condenser temperature increases the coefficient of performance and improves the operation of the system.

Recent Advances in the Prediction of Weld Residual Stress and Distortion - Part 2

Weld residual stress can contribute to the reduction of structure lifetime and accelerate the formation of fatigue cracks, brittle fractures, or stress corrosion cracking. Distortion can have a significant impact on the dimensional ac-curacy of assembly, structure strength, and fabrication cost. In the past two decades, there have been many significant and exciting developments in the prediction and mitigation of weld residual stress and distortion. This paper reviews the recent advances in mitigation techniques that have been applied in the structure design, manufacturing, and postweld stages. The techniques used in the structure design stage include selecting the type of weld joint and weld groove, using balanced welding, determining appropriate plate thickness and stiffener spacing, and considering distortion compensation. Mitigation techniques used in the manufacturing stage include welding sequence optimization, reducing welding heating input, selecting low-transformation-temperature filler metals, prebending, precambering, constraints, trailing and stationary cooling, in-processing rolling, transient thermal tensioning, and additional heat sources. Postweld mitigation techniques include postweld heating and mechanical treatment. Finally, the remaining challenges and new development needs were discussed to guide future development in the field of mitigating weld residual stress and distortion.

Development of thermo-electrical model of photovoltaic panel under hot-spot conditions with experimental validation

This work was focused on development of thermo-electrical numerical model for circumstance of free-standing photovoltaic (PV) panel exposed to hot-spot effect. The model was developed for partial hot-spot situation and for serial cell connection. The developed 3D model uses a novel approach via two-way coupling of thermal and electrical models. The model was experimentally validated for geographical location of Mediterranean climate, using the readings from temperature sensors, as well as thermal imaging data. The comparison of results between measured and simulated values were shown to be well matched, with deviation not more than 1.5 °C. The model could be useful for optimization of the bypass diodes and better understanding of hot-spot coupled with other thermal effects. Also, the model can be used for examinations in the case of building integrated photovoltaics (BIPV), since hot-spot effects could be utilized as additional heat sources that could be properly managed. The effect of temperature non-uniformity could be also examined with herein proposed modelling approach and which is beneficial in the case of cooled PV panels.

The Anatomy of an Unusual Edge-on Protoplanetary Disk. II. Gas Temperature and a Warm Outer Region

Abstract We present high-resolution 12CO and 13CO 2–1 ALMA observations, as well as optical and near-infrared spectroscopy, of the highly inclined protoplanetary disk around SSTC2D J163131.2–242627. The spectral type we derive for the source is consistent with a 1.2 M ⊙ star inferred from the ALMA observations. Despite its massive circumstellar disk, we find little to no evidence for ongoing accretion on the star. The CO maps reveal a disk that is unusually compact along the vertical direction, consistent with its appearance in scattered light images. The gas disk extends about twice as far away as both the submillimeter continuum and the optical scattered light. CO is detected from two surface layers separated by a midplane region in which CO emission is suppressed, as expected from freeze-out in the cold midplane. We apply a modified version of the tomographically reconstructed distribution method presented by Dutrey et al. to derive the temperature structure of the disk. We find a temperature in the CO-emitting layers and the midplane of ∼33 K and ∼20 K at R &lt; 200 au, respectively. Outside of R &gt; 200 au, the disk’s midplane temperature increases to ∼30 K, with a nearly vertically isothermal profile. The transition in CO temperature coincides with a dramatic reduction in the submicron and submillimeter emission from the disk. We interpret this as interstellar UV radiation providing an additional source of heating to the outer part of the disk.

Plasma-Assisted Hybrid Dissimilar Friction Stir Welding for Joining of DH36 Steel and AISI 1008 Steel: Thermal Modelling and Experimental Analysis

Dissimilar materials joining by hybrid FSW involve preheating the harder material ahead of the FSW tool, which reduces the vertical force and improves the weld quality by enhancing the material flow. In this work, both experimental and numerical analyses were conducted for the friction stir welding (FSW) and plasma-assisted friction stir welding (PAFSW) of dissimilar steels such as DH36 shipbuilding steel and AISI 1008 steel. The comparative study was performed on the thermal history, vertical force, mechanical and microstructural characterizations under different welding conditions. The 3D transient thermal phenomenological models were established using Abaqus/CAE 2017 finite element (FE) software package. The moving heat source models for FSW and PAFSW were successfully established, which were embedded in a Fortran code and fed to Abaqus/CAE through DFLUX subroutine. The additional heat source, i.e. plasma arc heat source, was modelled using the Gaussian distribution of heat flux. The stir zone isotherms of the developed numerical models and the transient thermal profiles in the FSW and PAFSW were matched fairly well with experimental results. For the reliable comparative study, the consequence of FSW parameters (i.e. traverse speed and rotational speed) and preheating parameters (i.e. plasma offset and preheating current) on thermal history was investigated. It was observed that the assistance of the plasma preheating ahead of FSW tool was significantly reduced the grain size and vertical force. In contrast, the hardness and the impact toughness values were increased compared to that of FSW.

Thermo-economic analysis of the pumped thermal energy storage with thermal integration in different application scenarios

Pumped thermal energy storage (PTES) refers to a promising electricity storage technology that converts electricity into heat using the heat pump for cheaper storage, and then converts it back into electricity through a heat engine. The integration of an additional low-grade heat source can increase the coefficient of performance (COP) of the heat pump and thus significantly improve the storage efficiency. To evaluate the economic impact of different heat sources including waste heat, solar, or district heating network, this paper constructs the thermodynamic and economic model of thermally integrated PTES (TI-PTES), evaluates the round-trip efficiency and storage cost in five typical scenarios, and explores the effects of key system parameters (storage temperature, temperature difference, component efficiency) and heat source conditions (flow rate, temperature). Results indicate that the storage efficiency competes with the storage cost and capacity for a fixed heat source condition. As the power-to-power efficiency increases from 50% to 120%, the cost could increase by 47%, while the storage capacity could decrease from 1544 kW to 163 kW with a heat source flow rate of 50 kg·s−1. Detailed parameter analysis indicates that a higher heat source flow rate/temperature leads to higher component efficiency. A smaller pinch point temperature difference results in higher efficiency or lower costs. In particular, the energy storage cost is more sensitive to the turbine's efficiency than that of compressor, so it is necessary to prioritize improving the turbine. In terms of typical heat source scenarios, TI-PTES is more suitable to couple with waste heat rather than district heating network or solar thermal scenarios, resulting in a minimum Levelized cost of storage (LCOS) of 0.23 $·kWh−1.