Heat Source Configuration Research Articles

The impact of suction/injection with radiation effect on natural convection flow over a vertical channel in the existence of point/line heat source configuration

The present study manifests the significance of a heat source concentrated at a point or along a line on the natural convection flow featuring suction/injection and radiation effect within a vertical channel. The consistent heat source is modeled with the Heaviside step function and converted to a point/line heat source. The governing equations modeling the flow are resolved by the Laplace transform technique. Shear stress, Nusselt coefficient, and mass flow rate, along with respective values, are examined through the analysis presented in tables whilst the physical components like suction/injection ( K ), Prandtl number (Pr), heat source (S), and radiation (N) are explored graphically on the velocity and the temperature field. Results illustrate that the temperature and the fluid velocity intensify with the escalation of point/heat source attributes. However, as the parameters Pr, K and N increase, the velocity distribution decelerates. In addition, the heat transfer rate gradually diminishes with an elevation in radiation, and reducing the line heat source to that of point heat source parameters corresponds to a decrease in the rate of heat transfer. Also, in the absence of radiation, the current finding aligns seamlessly with the established research in the literature.

Solar-assisted biogas system with air-source heat pump for the energy-saving of indoor heating in north China

Abstract To address the challenges associated with winter heating in high-latitude regions of China, solar-assisted biogas heating systems have emerged as the predominant focus of research due to their cost-effectiveness, accessibility, and environmentally friendly attributes. However, traditional solar-assisted biogas heating systems encounter issues of low efficiency and limited practicality resulting from unstable solar radiation and extreme ambient temperatures during the heating season. To improve the economy and stability of the system, this study proposed a novel operational control method for a small-scale energy station system in rural regions of North China, named Solar-Biomass-Air Source Heat Pump Hybrid Heating System (SBHP-HHS). The integration of solar energy, biogas energy, and air-source heat pump (ASHP) systems in this proposed work has shown to create effective complementarity and enhances the production efficiency of the existing system. Test and simulation studies have been carried out for this system. The layout of buildings and equipment within a university campus in Beijing is reconfigured and redesigned, incorporating an ASHP into the existing heat source configuration. To begin with, a mathematical model is established for the complementary heating system that incorporates solar energy, a biogas digester, and an ASHP. Subsequently, a dynamic simulation model is developed using the TRNSYS platform, and a corresponding operational control strategy for the multi-energy complementary heating system is proposed. Dynamic simulation and analysis of the newly implemented system are performed using the TRNSYS platform, focusing on energy flow and thermodynamic performance. Throughout the heating season, the solar-biogas integrated system achieves a remarkable assurance rate of up to 79%. Additionally, ASHP maintains a relatively high heating efficiency, coefficient of performance (COP) reaches 3.02. Finally, an economic evaluation of the multi-energy complementary system was conducted based on the annual cost method. This was compared with the clean approach of using only an ASHP unit. The results indicate that the SBHP-HHS is more economical when the anticipated useful life is 6 years or longer. The results indicate that the proposed can achieve significant energy-saving and carbon-reduction benefits in rural areas, catering to their heating needs.

INFLUENCE OF HYBRID NANOFLUIDS AND SOURCE CONFIGURATION ON NATURAL CONVECTION IN SQUARE CAVITY

A numerical investigation was conducted of steady laminar natural convection within a heated square enclosure filled with a mixture of water, carbon nanotubes (CNT), and aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) (hybrid CNT-Al<sub>2</sub>O<sub>3</sub>/water nanofluid). Various heat source configurations and different volume fractions for the hybrid nanofluids were examined. The obtained results were analyzed through numerical simulation using ANSYS Fluent software. Thermal and dynamic fields were acquired, along with the Nusselt number (Nu). The influence of parameters such as Rayleigh number (Ra), nanofluid type, and heat source configuration was taken into account. Correlations between the Nusselt number and the various control parameters of our configuration were also established. The acquired findings clearly indicate that the introduction of nanoparticles has notably amplified heat transfer within the cavity (φ = 0.09). Furthermore, the heat source configuration has proven to be a pivotal element that effectively expedites the heat transfer process. Additionally, a direct correlation is observed between the increase in average Nusselt number and the augmentation in volume fraction. Notably, the most favorable outcomes are derived from the implementation of the (CNT-Al<sub>2</sub>O<sub>3</sub>)/water hybrid nanofluid.

Insight into heat dissipation in fractured rock influenced by groundwater influx and heat source configurations using numerical analysis

The characterization and evaluation of heat dissipation effects in fractured rock is becoming a priority topic with respect to the potential application of low-temperature thermal remediation in these settings. A three-dimensional numerical model was utilized to investigate heat dissipation-related thermo-hydrological processes in an upper fractured rock layer and a lower impermeable bedrock layer. To identify the factors controlling spatial temperature variances in the fractured rock layer accounting for a scaled heat source and variable groundwater flow, global sensitivity analyses were conducted on the variables using three categories: heat source, groundwater flow, and rock properties. A discrete Latin-hypercube-one-at-a-time method was used to conduct the analyses. A heat dissipation coefficient was proposed to evaluate the correlation between heat dissipation effects and transmissivity based on a case study using the hydrogeological setting of a well-characterized Canadian field site. The results show a significance ranking of three sets of variables controlling heat dissipation processes in both the central and the bottom areas of the heating zone: specifically, heat source > groundwater > rock. The groundwater influx and heat conduction in the rock matrix are key factors determining heat dissipation at the upstream and bottom areas of the heating zone, respectively. The heat dissipation coefficient is closely associated with the transmissivity of the fractured rock in a monotonic relationship. A significant growth rate of the heat dissipation coefficient appears when the transmissivity is between 1 × 10−6 and 2 × 10−5m2/s. The results suggest that the low-temperature thermal remediation can be a promising technique to adapt the significant heat dissipation in highly weathered fractured rock.

Optimal configuration of discrete heat sources in a channel with sudden expansion and contraction by lattice Boltzmann method

Optimal configuration of discrete heat sources in a channel with sudden expansion and contraction by lattice Boltzmann method

Numerical Analysis of Heat Transfer Behaviours of Melting Process for Ice Thermal Storage Based on Various Heat Source Configurations

Ice thermal storage (ITS) performance for cooling systems is greatly influenced by the poor thermal conductivity of phase change material (PCM). The effect of natural convection on the melting process is significant for heat transfer enhancement. Thus, the melting performance of PCM in a shell-and-tube latent heat storage (STLHS) unit is numerically studied by considering natural convection in terms of various heat source positions and configurations, i.e., central position, eccentric position, and flat-tube type. Temperature distribution, melting time, and the overall heat transfer coefficient during the process are investigated. The results show that the circulation vortex formed by natural convection is a dominant factor that affects melting front evolution and the overall heat transfer coefficient. When input heat flux is relatively weak, PCM below the heat source is liquefied first. In contrast, PCM in the upper part melts earlier when the heat flux is excellent. The overall heat transfer coefficient decreases sharply with the increase in melting time in the early stage. Then, the heat transfer coefficient tends to be constant. PCM in an STLHS unit with a heat source in a lower position and a configuration of vertical flat-tube type has a desirable performance when compared with other cases, which could provide good support for ITS application.

A Semi‐Analytical Solution for Heat Transport in Rock With Parallel Fractures and a Heat Source in Both Fracture and Matrix

AbstractIn recent decades, numerous analytical solutions have been developed to quantify temperature perturbations in fractured rock having mobile and immobile fluid phases. The assumption of one‐dimensional heat conduction in the matrix, or neglecting heat dispersion and storage in fractures, however, are typical simplifications adopted to overcome the difficulties in mathematically representing the problem. In this study, we propose a two‐dimensional semi‐analytical solution framework based on Green's function approach for a flexible heat source definition, including source dimensions, energy delivery strength and duration, and the presence of a heat source in the matrix and/or fracture. The solution fully accounts for heat conduction, advection, dispersion, and transient heat exchange between the fracture fluid and rock matrix in a system of parallel fractures. The solution having a strip heat source extending from a fracture into the matrix indicates that one‐dimensional heat conduction in the matrix underestimates and overestimates temperature responses at early and later times, respectively. Additionally, the temperature peak arrival time is also substantially delayed by simplification. The fracture temperature grows slower near the heat source area as the fracture aperture increases. The fracture temperature growth is enhanced via the overlapped heating areas between the parallel fractures. The transient temperature analyses imply that the spatial temperature variation is strongly associated with heat delivery strength. The early time temperature variances are closely related to the heat source configurations, and the later time temperatures in the domain are mainly determined by the total energy being delivered into the domain.

Thermal analysis of composite beam structure based on a variable separation method for any volume heat source locations and temporal variations

This paper deals with an efficient method to compute thermal solutions with arbitrary heat source location and temporal variation for composite beams. For that, the associated Green’s function is first computed. It is approximated as a sum of products of five separated 1D functions (depending on spatial coordinates x and z, the time t and impulse heat source locations xs and zs). A dedicated iterative algorithm is proposed to control the computations of these five 1D functions. A regularized procedure has also to be carried out. Once the Green’s function is computed, the temperature field can be deduced easily by computing 1D integrals for any heat source configurations. This interesting feature could be used in an iterative process such as identification problems. The present approach is assessed with different composite beam configurations submitted to various heat sources. Reference solutions issued from a finite element software are provided for comparison purpose.

Performance of flat-plate, flexible polymeric pulsating heat pipes at different bending angles

The heat transfer performance of a flat-plate, flexible polypropylene pulsating heat pipe (PHP) is evaluated experimentally when the device is bent at different angles, and for different layouts of the evaporator and the condenser. Flexible pulsating heat pipes are a passive thermal management technology with important prospective applications in foldable portable electronics, deployable systems (such as cube satellites), soft robotics, and many others. While a number flexible PHPs have been developed in the recent past, to date, there is insufficient information about the influence of the bending angle (conformation) and of the reciprocal positions of the heat sink and source (configuration) on their thermal performance. Several polypropylene PHP prototypes (250 mm ×100 mm ×1.5 mm) with a channel width of 5 mm and different loop geometries were fabricated using selective transmission laser welding technology. Ethanol and FC-72 were used as heat transfer fluids at a filling ratio of 50%. The PHP performance was evaluated through the equivalent thermal resistance of the device, calculated from the surface temperatures of both the evaporator and the condenser during an ascending/descending stepped heat input ramp applied to the evaporator. The experimental results show that conformation arrangements have no significant effect on the thermal performance, however it may affect the PHP start-up.

Effects of heat source configuration on the welding process and joint formation in ultra-high power laser-MAG hybrid welding

Ultra-high power laser-MAG hybrid welding technology provides an effective method for joining thick plates with high-quality and efficiency. Heat source configuration of laser and arc was verified to play a vital role in conventional hybrid welding process. In this paper, ultra-high power laser-MAG hybrid welding was utilized to weld 20 mm thick Q235 steel for clarifying the effect of heat source configuration on welding process and joint formation. By high-speed photography, welding process was systematically recorded including hybrid plasma morphology, droplet orientation-transfer and molten pool flow. Subsequently, the joint formation was further analyzed via dynamic behaviors of liquid column and keyhole. Results exhibited that a stable arc characteristic and smooth molten pool flow was formed under HM (ultra-high power laser and MAG-leading) mode. Besides, the enlarged and stabilized keyhole would inhibit the height of liquid column and formation of spatters. Finally, a sound weld joint without “ant-colony-like defect” joint formation and 15.82 mm penetration was produced in HM mode. This work provides an effective method and reference for realizing thick plate single pass weldments in the practical industry.

Mathematical modelling and development of a computational algorithm for the study of thermo-stressed state of a heat-resistant alloy

The problem of increasing the thermal stability of structural elements made of heat-resistant metals and alloys operating in a complex force and thermal field is one of the key priorities of modern high technology research. The most important case is the study of the thermal stability of structural elements in real conditions of heat fluxes with varying intensity, with a complex configuration of heat-insulated local surfaces and internal point heat sources. Many basic load-bearing structural elements operating in a large thermal field (elements of gas turbine and jet engines, etc.), are made of heat-resistant alloys. The physical feature of such alloys is that the coefficient of thermal expansion and the modulus of elasticity of the material strictly depends on the temperature distribution field, that is, the coefficients are a function of temperature. The purpose of this study is to simulate a thermo-stressed state in rod elements of a structure based on the law of conservation of energy, in the presence of a heat flux applied on the lateral surface, which varies along the coordinate in a linear manner. To solve the outlined problem, a potential energy minimisation method is used in combination of a quadratic finite element with three nodes. As a result, from the condition of the minimum of the functional defining the potential energy, a resolving system of linear algebraic equations is obtained. All possible natural boundary conditions are taken into account. In this system, all integrals used are calculated analytically. Moreover, the law of conservation of energy is fulfilled for each of the equations of the resulting system. As a result, the values of displacement, deformation and stresses were calculated, as well as the values of elastic temperature and thermoelastic components of deformations and stresses for a specific example.

Optimization of the supercritical CO2 power conversion system based on the net efficiency under conditions of the pulse-operated fusion power reactor DEMO

Fusion power plants represent a new energy technology with specific features including multiple heat sources with different outlet temperature and power, fluctuating high self-consumption, and in the case of the demonstration fusion power plant, the pulse operation of the heat sources. The supercritical CO2 (S-CO2) Brayton cycle was applied and optimized under DEMO conditions with the nuclear net efficiency as the main optimization criterion. The optimization was performed for helium-cooled and water-cooled reactor blanket concepts, and for simple and recompression S-CO2 cycle layouts with four heat sources. The optimization process used a brute-force search problem-solving technique applied to multiparametric space. The model data was taken from the European model of the fusion power plant DEMO1 2019. When applying the simple S-CO2 cycle, the net efficiency of the model power plant with the helium-cooled and water-cooled blanket was found to be 19.5% and 12.3%, respectively, whereas when applying the recompression S-CO2 cycle, the net efficiency was found to be 16.4% and 8.1%, respectively. The simple S-CO2 cycle provided higher net efficiency for the model fusion power plants with the given configuration of multiple heat sources than the recompression S-CO2 cycle, and the model power plants using the helium-cooled blanket achieved higher net efficiency compared to the power plants using the water-cooled blanket despite significantly higher self-consumption. The application of the simple S-CO2 cycle allowed the model fusion power plant with the helium-cooled blanket to achieve the net efficiency higher than the reference net efficiency of 17.9% of the current DEMO model using the steam cycle. For the power plants with the water-cooled blankets, S-CO2 cycles were found to be less efficient than the steam cycles.

Natural convection and wall radiation in a cubical cavity with different discrete heat source configurations: Geometric parameters effect

The heat transfer by natural convection and wall radiation in filled air partially heated 3-D cavity is a problem related to different practical situations. In this study, the effects of several geometric parameters (form, orientation, size, position) of a discreet heat source on the flow structure and heat transfer characteristics are discussed for a wide range of the Rayleigh number 103≤Ra≤107 and the different wall-emissivities 0≤ε≤1. The heater is maintained at a high-temperature and positioned on a given vertical or horizontal passive wall of the enclosure. The right vertical surface of the cavity is completely isothermal at a fixed cold temperature. Flow and thermal fields were exhibited using of velocity vectors (or streamlines) and isotherms, respectively. The local and average Nusselt numbers were also presented. A numerical procedure based on both the finite volume and the discrete ordinate methods are used to solve the governing equations. It is found that the rate of heat transfer is not so sensitive to the form and the orientation of the discreet heat source. On the other hand, the position and the size of the heater are found to play a significant role in the global Nusselt number.

Wire based plasma arc and laser hybrid additive manufacture of Ti-6Al-4V

In this study, a novel wire based plasma transferred arc (PTA)-laser hybrid additive manufacture process was proposed for deposition of large-scale titanium parts with high deposition rate and near-net shape. The optimum processing conditions, including the heat source configuration, wire feeding position, and arc-to-laser separation distance, were investigated. The benefits of using the hybrid process over the single PTA and laser deposition processes on their own were studied. The results show that compared to the single PTA process, the hybrid process has extended energy distribution and melt pool size, giving more interaction time of the wire with the heat sources and therefore a higher deposition rate. Compared to the laser process, the hybrid process has a much higher wire melting efficiency and tolerance to wire positioning accuracy. Owing to more distributed energy across the two heat sources, the likelihood of keyhole formation in the hybrid process is lower than that in the single PTA process. The best configuration for the hybrid process is the PTA leading, combined with front feeding of the wire. In this configuration, the PTA is used to melt the feedstock and the laser is used to control the melt pool size, which allows independent control of deposition rate and bead shape. A set of multi-layer walls was built to demonstrate the feasibility of this process for the manufacture of engineering parts. The results show that the achieved flat beads are very desirable for low surface waviness and lead to near-net-shape deposition. The main limitation of the hybrid process is remelting into the underlying layer. To overcome this, a multi-energy source process with more evenly distributed energy has been proposed.

A Convolution Residual Network for Heating-Invariant Defect Segmentation in Composite Materials Inspected by Lock-in Thermography

This article proposes an automatic approach for segmenting inclusion defects in composite materials inspected by lock-in thermography (LT) in a heat source invariant way. In the proposed pipeline, temperature maps are preliminarily processed to enhance the contrast between sound and defective areas, reduce the acquisition noise, and mitigate the effect of nonuniform heat excitation. Then, the enhanced sequences are grouped in highly local sets, the input of a convolution residual neural network, which segments the defects focusing on the temporal evolution of the temperature. Experiments have been run on a dataset acquired from a CFRP specimen tested under five different heat source configurations. Here, a brief study of signal variations associated with the heat source configuration is presented. Then, an ablation study has been presented to compare different architectures of increasing complexity. The best results are achieved by using the proposed preliminary processing, the residual layers, and an input set of temperature signals of size $3 \times 3$ . This network can reach a global intersection over union (IOU) of 0.78, while defects are segmented with an IOU value of 0.58. In addition, the balanced segmentation accuracy of the test reaches 94.78%, with a maximum recall of the defective class of 91.41%. Further cross validation changing the source configurations of the training and test sets produces comparable results of IOU and balanced accuracy, which are on average equal to 0.71 and 84.02%, respectively. A final evaluation of the trained network is performed on a new dataset augmented through a vertical stretch. Results are still comparable with an average IOU and balanced accuracy of 0.74 and 87.15%, respectively. These results prove the capability of the method to segment inclusion defects of any shape without being affected by the configuration of the heating sources used in the LT inspections.

Methodological Approach to the Integrated Optimization of the Heat-Source Structure in the Problems of Developing Heat-Supply Systems

The question on the optimal development of the heat sources in the developing heat-supply systems (HSSs) is considered. The current state of research in the field in question is analyzed. It is noted that this issue has aroused increased interest in recent years. The description and mathematical formulation of the problem of optimizing the structure of the heat sources in the developing HSSs are provided. The best distribution of the load between the former is determined and the choice of the optimal parameters of the heat-supply networks under permissible technical, economic, and ecological restrictions is made. For the first time, the problem has been formulated and implemented using the method of directed search for possible variants of the heat source’s power and equipment content in a preplanned redundant heat-source configuration that was previously used to search for the best configuration of the heat-supply network. To devise redundant configurations and subsequently calculate them, methodological approaches oriented towards the construction of P-graphs and energy hubs that have been developed in recent years can be successfully applied. Every heat-source structure variant outlined within the framework of the redundant configuration competes with other variants not only in terms of the minimum costs but also in terms of the minimum impact on the environment. The proposed methodology was implemented in the form of a software package that enables the user to interactively communicate with the digital model of the system to obtain a solution for the development and reconstruction of the HSS under investigation. The practical application of the methodological and computational tools to solve the problem of the development of heat-supply systems is exemplified by the configuration of the heat-supply system of the settlement of Magistralnyi, Irkutsk region.

Comparative analysis of solar-air dual source heat pump system with different heat source configurations

The concept of solar-air dual source heat pump has been proposed to overcome the limitations of single source heat pump system. In this paper, a comparative investigation is presented among three types of solar-air dual source heat pump with different heat source configurations: solar-air series source heat pump (SA-SHP), solar-air parallel source heat pump (SA-PHP) and air-solar series source heat pump (AS-SHP). The impact of environmental parameters has been discussed, and the optimal working condition for each system has been identified. The results indicate that SA-SHP is suitable for working under the environment with low solar irradiation, AS-SHP shows the best performance under the condition with low ambient temperature and high solar irradiation, and SA-PHP can achieve the optimal state at high ambient temperature or high solar irradiation. The dynamic performance of SA-SHP, SA-PHP and AS-SHP in the daytime has been compared. The dynamic behavior of each system is significantly different. The COP of SA-PHP is the highest ranging from 4.50 to 4.58, followed by AS-SHP ranging from 4.39 to 4.50, and the COP of SA-SHP is the lowest ranging from 4.33 to 4.41. Moreover, the annual performance and economic feasibility for each system in different climatic regions are evaluated.

Experimental study on the effect of various heat source configurations on the thermal performance of an axial swallow-tailed micro-grooved heat pipe

An experimental testing station with the constant circular water-cooling system is assembled to study the heat transfer characteristics of an axial swallow-tailed micro-grooved heat pipe subjected to heating with discrete heat sources. Influence of different heat source arrangement under single and double heat source working condition on performance parameter of heat transfer are investigated. Experimental results indicated that the temperature of the existing heat source is apparently higher than the temperature of the non-existent heat source. The condensing section length affects the transient thermal response of heat pipe, and the steady wall temperature decreases with an increase in condensing section length. Different configurations of heat source will affect the maximum heat transfer capability of the heat pipe, and the maximum heat transfer capability is relevant to the distance between the heat source and heat sink. The smaller the distance between the heat source and the heat sink, the greater the maximum heat transfer capability of the heat pipe. If the heat pipe is not heated from the starting point, the heat pipe can enter a steady state when it reaches maximum heat transfer capability, but the temperature at the heat source is much higher than the normal working temperature. The temperature response in front of heat source is slower than that in other position when heat pipe is not heated from the initial end of evaporating section.

Natural convection in a cubical cavity with different heat source configurations

Numerical investigation of laminar unsteady natural convection in closed cubical cavity having local heat source of different geometric shapes has been performed. Particularly, five various shapes of heater have been analyzed, namely, one shape with a rectangular cross-section, three shapes with trapezoidal cross-sections and one shape with a triangular cross-section. The considered shapes illustrate a smooth transition from rectangular cross-section to triangular one through trapezoidal forms. The effects of Rayleigh number and these heater configurations on fluid flow and heat transfer have been studied. It has been found that trapezoidal shapes are more effective taking into account high heat removal rate from the heater.

Heat source effects on thermal comfort for active chilled beam systems

In this study, the effects of the configuration and strength of heat sources on thermal comfort are investigated in a mock-up room with an active chilled beam (ACB) system. Full-scale air temperature, speed, and humidity distributions are demonstrated. In addition, the uniformity of the distributions is evaluated. Several common thermal comfort indices, including the air diffusion performance index (ADPI), predicted mean vote (PMV), draft rate (DR), and vertical air temperature difference (VATD) are calculated and compared based on the experimental results. The results reveal that the heat sources increase the average air speed of the occupied zone. However, the air speed distribution is not significantly affected by the heat source configuration for a primary airflow rate of 32.2 L/s. In contrast, the heat source configuration has a notable impact on the temperature distribution. One humidity sensor is sufficient to measure the occupied zone humidity for ACB systems with no significant humidity source because the absolute humidity distributions are extremely uniform for all cases. The points outside the ADPI criteria (−1.7°C<Ted<+1.1°Candv<0.35m/s) are mostly because its air speed is greater than 0.35 m/s. PMV is reduced as the air speed increases. Thus, there is a higher risk of cold feeling at the ankel level where the air speed is relatively greater than other levels. The overall evaluation shows that symmetrical heat source placement results in better thermal comfort performance than asymmetrical heat sources.