Types Of Heat Sources Research Articles

Economic analysis and optimization of combined solar district heating technologies and systems

To find an optimal economic solution for solar district heating (SDH) in China, an evaluation model based on the levelized cost of heat (LCoH) is developed. A Python program is developed to calculate the LCoH of SDH systems using the quasi-dynamic test method. Based on these calculations, the trend of LCoH with solar collector area under different heating load intensities, heating terminal units, heated areas and land rents is discussed. The optimal solar collector area and the solar fraction are determined for combinations of solar thermal with four types of auxiliary heat sources, including air source heat pumps, ground source heat pumps, gas boilers and gas boilers with seasonal heat storage. The calculations show an economic optimal solar fraction of 11%–33% for a SDH system with heat pumps. High dependency of LCoH on network temperature is found for a SDH system with gas boilers. Seasonal heat storage minimizes LCoH of a SDH system with gas boilers at 100% solar fraction. The findings can be used as a reference for local authorities, consultants and engineers in the early energy planning to determine the optimal proportion of solar energy in a district heating system with the lowest operating cost.

PSII-11 Comparison of multiple heat sources in the farrowing house: Effect on production and energy efficiency

Abstract Pre-weaning mortality, currently 20% in the United States, continues to rise and has been estimated to cost $400 to $600 million annually. Creep heat accounts for 36% (125 watt heat lamps) of the estimated 685,000 kWh electrical subtotal used in a 3000 sow farm. The objective of this study was to determine the effect of heat source type on production and electrical usage in the farrowing house at the Iowa State University Allen E. Christian Swine Teaching Farm. Seven multiparous crossbred sows housed in farrowing stalls were randomly assigned to a heat source treatment; Baby Pig Heat Mat – Single 48 (Kane Manufacturing, Pleasant Hill, IA; MAT n = 4) or Hog Slat® Poly Heat Lamp Fixture (Hogslat, Newton Grove, NC; LAMP n = 3). LAMP was controlled via a thermostat and varied by height and MAT was controlled via Thermostat Programmable 1 Zone (Kane Manufacturing, Pleasant Hill, IA). Both heat sources were set at 32.2⁰C and this was confirmed using an infrared temperature gun. Kill-A-Watt EZ Meter P4460 were connected to the individual heat source for group lactation duration to measure kilowatt hours (kWh) and were read twice weekly. Piglets were weighed on D1 (farrowing = D0) and at weaning. Production data including pre-weaning mortality and piglet weight at weaning were analyzed using a mixed model with parity, room and covariate of litter birth weight being fixed effects and sow being random. There was no difference in production values, pre-weaning mortality (P > 0.63,MAT=11.11%, LAMP = 11.76%) and piglet weaning weight (P > 0.13, MAT = 5.30 ± 0.18 kg, LAMP = 5.99 ± 0.21 kg), due to heat source type. The MAT (LS Mean 11.59 ± 1.31 kWh) used 4.2 times less electricity than LAMP (LS Mean 57.30 ± 1.56 kWh) (P < 0.05). In conclusion, with no difference in production values heat mats controlled with a programmable thermostat can decrease the high energy needs in the farrowing house.

Numerical study on the effects of blood perfusion and body metabolism on the temperature profile of human forearm in hyperthermia conditions.

The development of mathematical models for describing the thermal behavior of living tissues under normal or hyperthermia conditions is of increasing importance. In this research, a 3D forearm model based on anthropometric measurement of 25 samples in Tehran, Iran was developed. The tissue temperature distribution is obtained via the Finite Volume Method (FVM) by considering the appropriate boundary conditions, blood perfusion, body metabolism, and the application of hyperthermia conditions on the tissue. The Pennes Bioheat Transfer Equation (PBHTE) is considered in this regard. Also, various thermophysical properties are assumed for the model in order to clarify the effects of such parameters on the tissue temperature distribution. The results of this study indicate that it is possible to provide the desired conditions for many therapeutic processes by controlling the parameters such as blood perfusion, body metabolism and the type of external heat source applied on the tissue. Generally, by decreasing the body metabolism, increasing the blood perfusion rate in tissue and applying a fluctuating heat flux, instead of uniform heat flux on the surface of the forearm skin, it is possible to provide the hyperthermia conditions without causing damages such as burn injuries to the other parts of the tissue. By using the results of this study, the appropriate conditions of hyperthermia can be obtained.

Selection and Evaluation of Dry and Isentropic Organic Working Fluids Used in Organic Rankine Cycle Based on the Turning Point on Their Saturated Vapor Curves

The organic Rankine cycle (ORC) is a popular technique used in the utilization of low-grade thermal energy. Among wet, dry, and isentropic organic working fluids, the latter two types are more appropriate for ORC systems. In this paper, the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram. On this basis, the model of near-critical region triangle was established. Using this model, the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated. The performance includes the relation between turning point temperature and cycle thermal efficiency, the relation between near-critical region triangle area and cycle thermal efficiency, the relation between near-critical region triangle area and exergy at turning point temperature, the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve. Moreover, working fluid selection was also conducted in terms of heat source type. It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source. Considering it will be phased out in near future, then cis-butene, butane, trans-butene, and isobutene are worth studying as its successor. Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.

Thermal and structural modelling of arc welding processes: A literature review

This paper presents a state-of-the-art critical review of the thermal and structural modelling of the arc welding process. During the welding process, high temperature in the welding zone leads to generation of unwanted residual stresses and results in weld distortion. Measurement of the temperature distribution was a key issue and challenge in the past decade. Thermomechanical analysis is among the best-known techniques to simulate and investigate the temperature distribution, welding distortion and residual stresses in the weld zone. The main emphasis of this review is the thermal and structural modelling of welding processes and the measurement of welding residual stresses using different techniques. The study also provides information about the various types of heat sources and models used to predict the weld bead characteristics and thermomechanical analysis for different welding processes such as tungsten inert gas welding, metal inert gas welding and shielded metal arc welding.

Identifying heat source intensity in treatment of cancerous tumor using therapy based on local hyperthermia - The Trefftz method approachs.

The presented study considers the equation of hyperbolic conduction of heat with perfusion in order to identify such intensity of spatial heat source that will lead to hyperthermia of a cancerous tumor placed in healthy tissue. The tumor is assumed to be in the form of a sphere with a small radius. In order that the determined intensity of the heat source does not damage healthy tissue, different temperature distributions as a function of time are anticipated at the tumor's border. The mathematical tools used are based on the Trefftz method. The results are presented in the form of numbers and graphs illustrating the intensity of the identified heat source and matching the obtained temperature distributions in the tumor to the predicted ones.

Modelling framework for integration of large-scale heat pumps in district heating using low-temperature heat sources

The paper presents a modelling framework that may be used to plan the integration of large-scale HPs in district heating (DH) areas. By use of the methodology both optimal HP capacities to be installed and optimal choice of heat source to be used during the year are identified by minimizing total cost of ownership including investment and operational costs. The modelling framework uses mixed-integer linear programming and hourly calculations over one year. Seasonal variations of the heat source temperatures, capacity limitations and HP coefficient of performance as well as technical constraints were taken into account. The DH network of Tallinn, Estonia, was used as a case study. Six different heat source types were identified for 13 potential locations of large-scale HPs. The results showed that the integration of large-scale HPs in the DH network of Tallinn is economically feasible. It was found that 122 MW HP capacity could be installed without compromising the operation of sustainable base load units. The heat sources needed for obtaining this solution were sewage water, river water, ambient air, seawater and groundwater. It was further shown that the Lorenz efficiency depends on the variations of heat source temperatures.

A Study on the Thermal Effect by Multi Heat Sources and Machining Characteristics of Laser and Induction Assisted Milling.

Thermally assisted machining (TAM) is an effective method for difficult-to-cut materials, and works by locally preheating the workpiece using various heat sources, such as laser, induction, and plasma. Recently, many researchers have studied TAM because of its low manufacturing costs, high productivity, and quality of materials. Laser assisted machining (LAM) has been studied by many researchers, but studies on TAM using induction or plasma heat sources, which are much cheaper than lasers, have been carried out by only a few researchers. Lasers have an excellent preheating effect, but are expensive, and the temperature of the heated workpiece drops quickly. Here, multi heat sources were used to solve the shortage in supplied heat source with a single heat source. Induction was applied as an additional heat source. The purpose of this study is to analyze the thermal effect and temperature distribution of single heat source and multi heat sources, and compare the machining characteristics according to heat source types. In order to analyze the preheating effect according to the feed rate of the heat sources, a temperature measurement experiment using thermocouples was carried out, and the efficiency of the thermal effect using multi heat sources was verified. In addition, the effectiveness of the thermal analysis results was verified by comparison with the measured temperature distribution. The machining characteristics of Inconel 718 and Ti-6Al-4V with laser, induction, and laser-induction assisted milling (LIAMill) were analyzed, by cutting force and surface roughness.

Coupled consolidation and heat flow analysis of layered soils surrounding cylindrical heat sources using a precise integration technique

SummaryThe engineering applications of energy piles, geological radioactive waste disposals, and mining wells of geothermal and petroleum are usually associated with strong coupled behaviour of consolidation and heat flow. This paper aims to present an efficient precise integration technique (PIT) for the analysis of such behaviour within layered saturated soils surrounding cylindrical heat sources (ie, with a cross section as a point, ring, or disc). Each soil layer, together with its embedded part of heat source, is divided into 2N layer elements with equal thickness. Then any pair of adjacent two layer elements are merged into a heat source on the interface. With the aid of Taylor series expansion and recurrence formula for adjacent layer elements combination, such problems can be solved by means of an improved PIT. Typical examples are performed to examine the effects of heat source type and soils layered properties on the coupled consolidation and heat flow responses. The elevation of the clay surface increases with time because of thermal expansion and reaches a peak value before showing a tendency of getting stabilised because of the dissipation of pore pressure becoming dominant. Such a peak cannot be achieved in sand case because of no accumulation of pore pressure. The influencing area of the heat source was found to be limited to near the source. These quantitative results serve as good verification of the presented technique, which proves to be remarkably efficient and several orders more accurate than traditional numerical techniques in that it ideally reaches the accuracy limit of the hardware of the computers used.

Grinding temperature field prediction by meshless finite block method with double infinite element

Simulation is an important method to investigate grinding temperature and prevent unwanted heat damages of workpiece by excessive grinding heat. Most previous numerical studies on grinding process analysis were based on finite element method, however, meshing is an arduous task especially for a complex geometry, and the convergence of finite element method has been proved to be bad in some cases. To address this, more numerical algorithms with higher adaptiveness and lower cost have been proposed such as meshless formulation. Meshless finite block method with double infinite element is a numerical method developed from meshless method. This method has higher accuracy and convergence. The grinding model is closer to the real fact. The mapping technique is used to transform a block of quadratic type from Cartesian coordinate (x, y) to normalized coordinate (ξ, η) with three or five seeds for double or single infinite element. The Lagrange series approximation is applied to construct differential matrices in normalized domain with nodes following Chebyshev's roots. The static and transient heat transfer processes were simulated by meshless finite block method with double infinite element, and a better convergence was demonstrated by comparison with the finite element method (ABAQUS). This study has also proved that the convergence depended on the workpiece feed velocity for both the present method and the finite element method. In addition, six different types of heat source were applied on simulating the grinding temperature field of titanium alloy TC4 and compared with experimental results, which shows that simulated result with triangular distribution heat source showed a good agreement with that of experiments.

Analysis of Annual Energy Use Intensities (EUIs) by End-Use in Apartment Units According to Stratification Variables (2017 – 2018)

To achieve the goal of reducing greenhouses gases, many countries have recognized the importance of energy conservation in the building sector, and such countries are considerably strengthening their building energy conservation policies by reinforcing design standards, encouraging remodeling, and requiring zero-energy construction. In order to effectively strengthen these policies, it is necessary to provide information concerning energy consumption in the building sector to ensure the technical and economic feasibility of policies in the marketplace, and to allow building users and policy makers to easily access and understand energy consumption characteristics. It is important to provide information that allows people to effectively understand the state of energy consumption by end-use (space heating, space cooling, domestic hot water, etc.) as part of the creation of a concrete plan for energy reduction that incorporates various service systems and is familiar to people. This is because providing such information plays an important role in establishing concrete policies and encouraging voluntary energy performance improvements by building occupants. South Korea operates the Korea Energy Statistics Information System (KESIS) and the information provided by this type of information system consists mainly of energy consumption by energy source (electricity, gas, etc.), and such systems remain inadequate for providing effective information on energy consumption and energy use intensity (EUI) by end-use (space heating, space cooling, domestic hot water, etc.) as part of the creation of a concrete plan for energy conservation. In order to accurately provide energy consumption information by end-use rather than limit the information to mainly consumption corresponding to energy sources, in this study, measurement systems were installed in 2014 ~ 2016 based on the overall sampling designs of previous studies for apartment units, classifications, measurement and data gathering methods for energy consumption by end-use. The annual statistical values for EUI by end-use were collected from the measurement data for 71 sample apartment units from May 2017 to April 2018. This data was calculated and analyzed using stratification variable levels for completion year, supplied area, and the heat source type.

Design of Heat Pump System in Air Heat Source Type

Design of Heat Pump System in Air Heat Source Type

Numerical Prediction of Penetration Shape in Metal Active Gas Welded Joints of Steel Plates

It is important to predict the penetration shape of welded joints because the penetration shape strongly affects the strength of joints. As one of the methods for simulating gas metal arc welding (GMAW) process, a three-dimensional, non-stationary thermal model has been developed. By using a finite differential model based on the heat flow equation and taking account of the balance of gravity, surface tension and arc pressure, both molten pool and the penetration shape are successively demonstrated. Although the finger type penetration which is generally observed in metal insert gas (MIG) welding of aluminum alloy can reproduced by developing an additional line heat source, the finger type penetration obtained in metal active gas (MAG) welding of the steel plates cannot be predicted. In this research, a new point heat source was developed instead of the line type heat source and the applicability of this new model was examined. From the serial computations for the penetration shape of bead-on welding, the dominant parameters in the new model which are thermal efficiency, ratio of heat source and radius of arc pressure were determined. Then, by using these values obtained, the penetration shapes of lap and fillet joints of steel plates can be successively reproduced, where the influence of arc radius change on the ratio of heat source was taken into account.

Energy Analysis of the S-CO2 Brayton Cycle with Improved Heat Regeneration

Supercritical carbon dioxide (S-CO2) Brayton cycles (BC) are promising alternatives for power generation. Many variants of S-CO2 BC have already been studied to make this technology economically more viable and efficient. In comparison to other BC and Rankine cycles, S-CO2 BC is less complex and more compact, which may reduce the overall plant size, maintenance, and the cost of operation and installation. In this paper, we consider one of the configurations of S-CO2 BC called the recompression Brayton cycle with partial cooling (RBC-PC) to which some modifications are suggested with an aim to improve the overall cycle’s thermal efficiency. The type of heat source is not considered in this study; thus, any heat source may be considered that is capable of supplying temperature to the S-CO2 in the range from 500 °C to 850 °C, like solar heaters, or nuclear and gas turbine waste heat. The commercial software Aspen HYSYS V9 (Aspen Technology, Inc., Bedford, MA, USA) is used for simulations. RBC-PC serves as a base cycle in this study; thus, the simulation results for RBC-PC are compared with the already published data in the literature. Energy analysis is done for both layouts and an efficiency comparison is made for a range of turbine operating temperatures (from 500 °C to 850 °C). The heat exchanger effectiveness and its influence on both layouts are also discussed.

Transient response in a thermoelastic half-space solid due to a laser pulse under three theories with memory-dependent derivative

Enlightened by the Caputo fractional derivative, the present study deals with a novel mathematical model of generalized thermoelasticity to investigate the transient phenomena due to the influence of a non-Gaussian pulsed laser type heat source in a stress free isothermal half-space in the context of Lord–Shulman (LS), dual-phase lag (DPL), and three-phase lag (TPL) theories of thermoelasticity simultaneously. The memory-dependent derivative is defined in an integral form of a common derivative on a slipping interval by incorporating the memory-dependent heat transfer. Employing Laplace transform as a tool, the problem has been transformed to the space-domain, and it is then solved analytically. To get back all the thermophysical quantities as a function of real time, we use two Laplace inversion formulas, viz. Fourier series expansion technique (Honig in J Comput Appl Math10(1):113–132, 1984) and Zakian method (Electron Lett 6(21):677–679, 1970). According to the graphical representations corresponding to the numerical results, a comparison among LS, DPL, and TPL model has been studied in the presence and absence of a memory effect simultaneously. Moreover, the effects of a laser pulse have been studied in all the thermophysical quantities for different kernels (randomly chosen) and different delay times. Then, the results are depicted graphically. Finally, a comparison of results, deriving from the two numerical inversion formulas, has been made.

Thermo-mechanical performance of layered transversely isotropic media around a cylindrical/tubular heat source

We develop a new numerical model based on a precise integration method to investigate the coupled thermo-mechanical performance of layered transversely isotropic media around a cylindrical/tubular heat source. To obtain the relational matrices of the extended precise integration method, we first convert the governing equations of the problem into ordinary differential matrix equations through the Laplace–Hankel transform. Then, the cylindrical heat source is divided into a series of plane heat sources, and the plane temperature load term is added to the state vector between layer elements. By combining the layer elements, we build a layered transversely isotropic numerical model containing a cylindrical heat source in the transformed domain. Finally, we solve the model in the transformed domain and obtain the solution of the problem in the real domain through the Laplace–Hankel transform inversion. The accuracy of this method is verified by comparing the solutions with the results of the analytical method and the finite element method. Then, we study the influence of the anisotropy of thermal parameters, the embedded depth, the length/radius ratio, the type of heat source and the stratification of the medium on the thermo-mechanical coupled performance.

Investigations on the Characteristics of Thermally Sprayed NiCrBSi Coatings Fused by Flame and Inductive Processing

Ni-based materials are some of the most used hardfacing alloys to improve wear and corrosion resistance for parts functioning under severe conditions. For the current study, a NiCrBSi self-fluxing alloy powder with particle size in range of 45-106 μm was employed as feedstock material and deposited onto a steel substrate material using the oxyacetylene thermal spraying process. The as-sprayed components have been subsequently subjected to thermal post-processing in order to increase the adhesion to the substrate and to reduce the inherent porosity of the coatings. Consequently, two types of heating sources were chosen. One of them was the neutral oxyacetylene flame and the second one was based on high frequency currents. The aim of this work was to study the influence of the heat source type of the post treatment on the final characteristics of the coatings. Evaluation of the morphology and microstructure of the developed coatings was performed after the remelting process by means of scanning electron microscopy. Hardness tests were carried out in cross-section complying with the ASTM E384 standard. In both cases, after fusing, the microstructure was refined, with a drastic decrease in porosity. Evaluation of the hardness distribution along the coating cross-section revealed similar values of microhardness.

Optimizing the insulation thickness of walls and roofs of existing buildings based on primary energy consumption, global cost and pollutant emissions

An optimization model used to determine the optimum insulation thickness (OIT) of walls and roofs of existing buildings was established. Primary energy saving ratio (PESR), global cost saving ratio (GCSR) and pollutant emission reduction ratio (PERR) were used as evaluation criteria. Least square method was used to fit the polynomials which indicated the relationship between annual air-conditioning demand and insulation thickness. An existing building was used as the basis of the case study. The average relative error on annual heating and cooling demand was 0.23% and 0.035%, respectively, which indicated the accuracy of both fitting polynomials. Four types of heat and cold sources were considered to be used for the case building, respectively. Sensitivity analysis was carried out to investigate the impact of economic and energy factors on the optimization results. Results showed that the OIT of walls and roofs could be obtained by using the optimization model. The OIT of walls and roofs, building performance indicators and overall evaluation criterion during building envelope retrofit depended on the weight coefficients of evaluation criteria and types of heat and cold sources. The impact of sensitivity factors on the optimization results for the four types of heat and cold sources were different.

Efficient 3D-TLM Modeling and Simulation for the Thermal Management of Microwave AlGaN/GaN HEMT Used in High Power Amplifiers SSPA

A three-dimensional thermal simulation investigation for the thermal management of GaN-on-SiC monolithic microwave integrated circuits (MMICs) of consisting multi-fingers (HEMTs) is presented. The purpose of this work is to demonstrate the utility and efficiency of the three-dimensional Transmission Line Matrix method (3D-TLM) in a thermal analysis of high power AlGaN/GaN heterostructures single gate and multi-fingers HEMT SSPA (solid state power amplifiers). The self-heating effects induce thermal cross-talk between individual fingers in multi-finger AlGaN/GaN that affect device performance and reliability. Gate-finger temperature differences only arise after a transient state, due to the beginning of thermal crosstalk which is attributed to the finite rate of heat diffusion between gate fingers. The TLM method accounts for the real geometrical structure and the non-linear thermal conductivities of GaN and SiC in order to improve the realistic calculations accuracy heat dissipation and thermal behavior of the device. In addition, two types of heat sources located on the top of GaN layer are considered in thermal simulations: Nano-scale hotspot as a pulsed wave heat source under gate and micro-scale hotspot as a continuous wave heat source, between gate and drain. Heat diffusion however, occurs not only between individual gate fingers (inter-finger) in a multi-finger HEMT, but also within each gate finger (intra-finger). To compare results, a Micro-Raman Spectroscopy experience is conducted to obtain a detailed and accurate temperature distribution. Good agreement between the microscopic spectral measurement and TLM simulation results is observed by accepting an error less than 2.2% relative to a maximum temperature. Results show that the 3D-TLM method is suitable for understanding heat management in particular for microwave devices AlGaN/GaN HEMTs SSPA amplifier. TLM method helps to select and locates the expected hot spots and to highlight the need of thermal study pre-design in order to minimize the system-level thermal dissipation and lead therefore to higher reliability.

A computational algorithm and the method of determining the temperature field along the length of the rod of variable cross section

Abstract Bearing elements of a number of strategic equipment are limited length rods with a variable cross-section. Most of them are exposed to certain types of heat sources. To ensure reliable operation of these equipment it is necessary to know the temperature field along the length of the rod with a variable cross section. This paper proposes a computational algorithm and method to determine the temperature field along the length of the rod with limited length and variable cross-section. They are based on fundamental laws of energy conservation. Also obtained is an approximate analytical solution of the problem.