Heat Source Sink Research Articles

Micro-scale heat and electricity generation by a hybrid solar collector-chimney, thermoelectric, and wind turbine

In the present study, a hybrid system that is fueled with solar energy is proposed. The system includes a solar air collector, solar chimney, thermoelectric generators, and Savonius wind turbine. The absorber plate and the passing air in the duct of the collector act as the heat source and heat sink of the thermoelectric generators respectively. As the air receives heat, it becomes less dense and goes up in the chimney due to buoyancy and the chimney effect. The chimney provides the required air velocity for the wind turbine. In addition, the hot air can be used for other purposes later, such as heating, or drying processes. The results reveal that the efficiency of solar air collector, thermoelectric generator efficiency, and power coefficient of Savonius wind turbine in a certain hour are 61%, 4.54%, and 19.56%, respectively. The average velocity of outlet air from the chimney is 2.32 m/s which can produce 2.17 W by the wind turbine. Additionally, the economic analysis demonstrated that net present value, and payback are approximately 19,707 $ and 1.34 years. Finally, the environmental analysis showed that this system has the potential to reduce emitted carbon dioxide by 5111 kg/year.

Performance of binary zeotropic mixtures in organic Rankine cycles (ORCs)

Compared to pure fluids, zeotropic mixtures have the potential to lower the irreversibilities in low temperature Rankine cycles by better temperature profile matching of the working fluid with the heat source/sink. However, having a gliding temperature does not guarantee performance boost over pure fluids, as many factors influence the exergy efficiency of the cycle. In this study, 25 pure fluids and 104 binary mixtures of natural working fluids are analyzed in subcritical ORCs with heat source temperature range of 125–300 ℃ and different condensing conditions and the results are investigated within two frameworks: (1) comparing the mixtures to their pure constituents, (2) comparing the mixtures to the best performing pure fluid. In one behavior type, the performance of the mixture falls between the performance of its pure constituents for all evaporator pressure range, and the mixture provides no benefit. However, some mixtures could provide performance boost in a specific evaporator range. Therefore, the maximum allowable evaporator pressure plays an important role in the performance comparison of zeotropic mixtures to their pure constituents. Mixtures which outperform their pure constituents in the first perspective, are further analyzed in the second perspective. Finally, a screening method is presented to map the binary mixtures with performance boost compared to their pure constituents and high absolute exergy efficiency. This method is based on the key thermophysical properties of the fluids including critical temperature and normal boiling point, as well as working conditions such as heat source and heat sink temperature and PPTD in the evaporator and the condenser.

Aiding (opponent) flow of hybrid copper–aluminum oxide nanofluid towards an exponentially extending (lessening) sheet with thermal radiation and heat source (sink) impact

This project considers a hybrid nanofluid flow of heat transmission towards an extending (lessening) surface with the effects of thermal radiation and non-uniform heat source/sink. The mixture nanofluid involves copper (Cu) and alumina (Al2O3) nano-molecules which are diluted into H2O to form Cu–Al2O3/H2O hybrid nanofluid. The governing partial differential equations derived from Navier-Stokes equations are converted into nonlinear ordinary differential equations via similarity transformations. The model of nonlinear coupled equations is then resolved numerically by applying the boundary-value problem solver (bvp4c) using MATLAB package. The numerical computations have been performed for different amounts of potential factors like nano-molecules size Al2O3(φ1) and Cu (φ2), Prandtl number (Pr⁡), radiative parameter (R), velocity ratio parameter ε, and assisting/opposing parameter (λ) on the fluid flow. The effect of the parameters on speed and energy outlines, drag force coefficient, and local Nusselt number at the wall of the nanofluid flowing and heat transmission features are presented graphically and evaluated. Radiation and heat generation parameters have a significant effect on flow profiles and their physical properties. We also observe that the heat boundary-layer thickener boosts with rising amounts of R and heat raises with big amounts of the heat source (sink). Cu–Al2O3/water has a higher heat transmission rate in comparison with Cu-water water nanofluid and water (base fluid). Comparison between the earlier available works and the current computational consequence for the restrictive status is in an adequate covenant.

Effect of heat source supplies on system behaviors of ORCs with different capacities: An experimental comparison between the 3 kW and 10 kW unit

Organic Rankine cycle (ORC) is one of promising technologies for reducing energy consumption and carbon emission. In this work, the experiments of ORC systems with rated power capacities of 3 kW and 10 kW under the heat source of 150 °C were conducted, respectively. According to the theoretic analysis and experiment measurements, the ORC system performs differently with various heat sources. The heat source and heat sink primarily affect the pump and expander behaviors and then contribute to the overall performance. For the heat sources with the temperature of 81.5 °C–118.3 °C and 68.6 °C–123.5 °C, the overall system efficiencies of the 3 kW ORC and 10 kW ORC vary within the ranges of 2.67%–3.91% and 0.61%–4.59%, respectively. The optimal efficiencies of the systems are 3.91% and 4.59%, and the best outputs are 2.1 kW and 6.3 kW, with the corresponding supplied thermal power of 42 kW and 113 kW, respectively. The results indicate that, considering the similar structure and the same environmental conditions, the larger system has better performance when the heating supply is sufficient, and the coordination between system capacity, heat source, and heat sink is highlighted. The findings provide theoretical and experimental guidelines for the capacity arrangement of the ORC industrial design.

Fracture mechanism and temperature/size-dependent thermal conductivity in gallium selenide monolayer

Gallium selenide monolayer (GSM) was recently proposed as a potential two-dimension material in electronic, spintronic, and optoelectronic applications. This work investigates the anisotropic mechanical properties and thermal conductivity of the GSM structure using molecular dynamics (MD) and non-equilibrium MD (NEMD) simulations, which are the key for designing nanodevices. First, we evaluate the GSM atomistic deformation mechanisms and mechanical properties influenced by tensile strain rate and temperature under uniaxial and biaxial tension. Second, impacts on thermal conductivity are investigated concerning modifications of temperature, model length and temperature differences between the heat source and heat sink. The results show that GSM exhibits excellent mechanical properties with sustaining a uniaxial tensile strain of 38.84% and 27.35% in the zigzag (Zz) and armchair (Ac) direction according to that is 31.47% for both directions of biaxial (Bi) tension at a temperature of 1 K. We found that the GSM has a weak-anisotropy in mechanical property with the Youngs modulus is around 66.77 GPa and 67.56 GPa under uniaxial tension in the Zz and Ac directions. Likewise, it reaches 80.52 in both Zz and Ac directions with biaxial tension. Besides, the temperature strongly impacts both mechanical properties and thermal conductivity of GSM, which have a steady reduction as raising the temperature. However, these parameters have a reasonably weak dependence on the tensile strain rate, except for the highest applied strain rate of 5 × 109 s−1with the highest YM of 62.77, 64.41, and 80.00 GPa for the Zz, Ac, and biaxial tension. We have obtained that effective thermal conductivity k gets the lowest value of 26.90 W/m.K and 35.37 W/m.K for Zz and Ac direction of a GSM size of (20 × 15) nm. These values are determined at an infinite length of approximately 62.50 W/m.K and 54.05 W/m.K in the two directions. Although thermal conductivities have minor fluctuations when changing temperature differences, the investigated results are correct, notwithstanding any temperature difference values between the two thermal baths.

Analysis of the thermodynamic performance of transcritical CO2 power cycle configurations for low grade waste heat recovery

Organic Rankine cycles employing carbon dioxide (CO2) for waste heat recovery became popular in the last years thanks to its excellent heat transfer characteristics and small environmental footprint. Low-grade waste heat (<240 °C) represents the major portion of excess heat globally, but it is hard to recover due to the small temperature gap of heat source and heat sink leading to a poor efficiency of the Rankine cycle. Therefore, numerous modifications of the power cycle layout were proposed by academia and industry — reheated expansion, recuperation and intercooled compression among them. This work compares ten cycle architectures for a defined waste heat source (60–100 °C) and heat sink (20 °C). Firstly, CO2 cycle architectures from literature are examined with its original operational parameters. Secondly, the predefined low-grade heat source is implemented into the cycle. The cycles are assessed regarding efficiency, mass flow and pressure. Results show that for source temperatures higher than 80 °C, recuperation and reheated expansion enhance the cycle performance whereas intercooled compression negatively affects the efficiency. The conventional configuration operated most efficiently for temperatures until 80 °C. A road map of thermodynamic efficiencies of CO2 cycle architectures for low-grade waste heat recovery up to 100 °C is delivered.

Multi-criteria evaluation, and dynamic modeling of combining thermal photovoltaic and thermoelectric generators to extend electricity generation at night

Thermoelectric-generator is combined with thermal-photovoltaic in two proposed cycles. The first cycle is an once-through water flow from the collector to the storage tank, and the second one with circulating water from the storage tank to the collector. The thermoelectric-generator extends electricity generation using the stored hot water in the storage tank during the night and also can reduce the size of battery bank and solar panels in off-grid systems. Both cycles are modeled and the thermal-photovoltaic, and thermoelectric-generator models are validated, and good agreement is achieved. The heat source and heat sink fins are designed in details. The thermoelectric-generator efficiency is low due to low temperature of hot water. According to the results, the first cycle is more efficient from the energy, exergy, environmentally, and economic point of views. In addition, both cycles have positive net present value (NPV) for interest rates of less than 10% but the first cycle is more safe for investment because its NPV will be zero at interest rate of 15%. The sensitivity analysis showed that the economics of the cycles is more sensitive to the interest rate. In addition, the first cycle with a photovoltaic thermal (PVT) area of 1.623 m2 reduces carbon dioxide generation of about 365.1 kg per year.

Shear thinning and shear thickening aspects in magnetized 3D cross-nanofluid flow with activation energy and motile microorganisms

Bioconvection has recently become a point of contention in several biotechnological fields that rely on fluids and their physical properties. Bioconvection tends to happen when mixed nanofluids are subjected to elevated and mass transmission. I'm fascinated by the widespread use of bioconvective nanofluids in the construction of microbial fuel cells, microbial oil extraction mechanisms, processing plants, and other applications. Current research looks at the heat and mass transport properties of cross-nanofluid. Effects of stratification for double diffusion are also considered. Variable thickness sheets are increasingly being used in civil engineering, mechanical, aeronautical, and maritime processes and constructions. Flow and heat transfer across stretching surfaces is used in many technical processes, including polymer extrusion, plastic film stretching, food, and paper processing, fiberglass manufacturing, wire drawing, and continuous casting. Primary goal of the ongoing research is to learn about the properties of activation energy, nonlinear thermal radiation, heat sink source, and motile microorganisms of three-dimensional cross nanofluid flow. The bvp4c structure is used to numerically encode the boundary value problem in the MATLAB mathematical code. To retrieve numerical and graphical reports on velocity, thermal, and energy profiles versus the values of the most important physical parameters, graphs and tables were used.

Uncertainty and Sensitivity Analysis of a Dry Cask for Spent Nuclear Fuel

Nuclear safety relies to a good extent on thoroughly validated codes. However, code predictions are affected by uncertainties that need to be quantified for a more accurate evaluation of safety margins. In this regard, the present paper proposes a preliminary uncertainty and sensitivity analysis of the thermal behavior of a concrete-based dry cask for spent nuclear fuel storage, employing the MELCOR code and a series of MATLAB scripts. As thermal behavior is of utmost importance for the fulfillment of United States Nuclear Regulatory Commission (USNRC) safety requirements, the Peak Cladding Temperature (PCT) has been addressed as the key Figure of Merit (FOM). Variables related to the main heat transfer mechanisms have been selected as input parameters for the uncertainty quantification, whereas heat source and heat sink, namely decay power and external air temperature, have been dealt with in a separate sensitivity analysis. The results show that the selected parameters have a weak influence on the PCT, whereas it is strongly related to the decay power and external air temperature values. In any case, PCT stays below the regulatory threshold even under the considered off-normal conditions.

Improvement of Heat Transfer Properties through TiO2 Nanosphere Monolayer Embedded Polymers as Thermal Interface Materials

A thermal interface material (TIM) is a substance that reduces the thermal resistance between a heat source and heat sink, which facilitates heat conduction towards the outside. In this study, a TiO2 nanosphere (NS)-filler based TIM was fabricated via facile processes such as spin-coating and icing methods. Thermal conductivity of the fabricated TiO2 NS-based TIM was enhanced by increasing the loading contents of the TiO2 NS-filler and successfully cooling down the GPU chipset temperature from 62 °C to 50 °C. Moreover, the TIM with the TiO2 NS-monolayer additionally lowered the GPU temperature by 1–7 °C. The COMSOL simulation results show that the TiO2 NS-monolayer, which was in contact with the heat source, boosts the heat transfer characteristics from the heat source toward the inside of the TIM. The suggested metal oxide monolayer-based TIM is an effective structure that reduces the temperature of the device without an additional filler loading, and it is expected to have a wide range of applications for the thermal management of advanced devices.

Dynamics of a two-layer flow with an interfacial heat source/sink: viscosity stratification

The temporal stability of a two-layer plane Couette flow with an interfacial heat source/sink is studied, in the presence of a viscosity stratification, predicting unstable streamwise and spanwise perturbations. Based on the wavenumber at onset, the perturbations are further classified as long-wave and finite-wave, where the long-wave mode is investigated using asymptotic and numerical analyses. The finite-wave instability is expected to be relevant for highly viscous fluids. Generally, a heat source (sink) at the interface is found to have a stabilising (destabilising) effect on the flow. However, if the rate of heat release exceeds a certain threshold, a new instability emerges, referred to here as an ‘explosive’ instability, characterised by an unbounded growth rate of the perturbations. The interaction between the viscosity stratification, thermocapillarity and inertia leads to the emergence of another new mode of streamwise instability, termed the ‘interaction’ instability. The spanwise perturbations possess higher growth rates than the streamwise perturbations for the heat sink along the interface when inertia has a stabilising influence, and vice versa. The heat sink leads to the emergence of thermocapillary instability by generating a negative temperature gradient across the fluids. In contrast, a heat source increases the temperature of the interface, resulting in a positive temperature gradient across the fluids, leading to the suppression of the instabilities by the thermocapillary effect. If the heat source provides energy at a faster rate than the energy lost due to Marangoni convection and heat diffusion, then it leads to an accumulation of energy, which presumably leads to the explosive instability.

Heat and mass transfer analysis of natural convection in a liquid desiccant closed-loop system: The effect of heat source and heat sink temperature

Considering the importance of providing healthy and suitable indoor air condition efficiently, liquid desiccant air condition systems are the focus of study in recent years. The concept of natural convection heat and mass transfer loop is introduced. The system is a closed-loop consisting of two three-fluid hollow fiber membrane heat and mass transfer exchangers played as absorber and regenerator. The system was run under standard conditions with an inlet air flow rate of 6 m3/h. The sensitivity analysis was made to reveal the effect of heat source and heat sink temperature on the system performance. The heat sink and heat source temperature lie between 15–25 °C and 50–70 °C respectively and the outlet air temperature and humidity ratio, moisture removal rate, cooling capacity and coefficient of performance are the evaluating indexes. The results show that despite the convectional desiccant loops the high solution flow rate is not desirable and instead the concentration gradient in the loop is the most important factor. For each heat source temperature, there is an interval of heat sink temperature for which the solution flow rate is the maximum and the concentration gradient is the minimum. Under operating conditions of the present study, the maximum obtained COP is 0.71 which is for temperature pair of (55 °C, 20 °C).

Inclined magnetic dipole and nanoscale energy exchange with infinite shear rate viscosity of 3D radiative cross nanofluid

AbstractWorking nanoliquids are used in bionomical concerns and to enhance the energy in the refrigeration system. The unique thermophysical characteristics of nanoliquids made nanoscience interesting and beneficial for fields of engineering, medical, and industry with real applications, like, food science, employing nanoparticles to deliver drugs, food microbiology, detection of foodborne pathogens, detection of foodborne pathogens, electronic device cooling, controlling fusion, magnetic cell separation, cancer therapeutics, nanocryosurgery, and so forth. The aim of this study is to deliver a broad analysis on nanoscale energy exchange and inclined magnetic dipole impact with the mathematical model of cross nanofluid. Scrutiny of movement of fluid is made by placing the magnetic dipole and buoyancy force. Transport of energy is investigated by thermal radiation, nonuniform heat sink–source while checking of mass transfer facts of activation energy and the chemical process is taken into consideration. Moreover, the nanostructured concepts of thermophoresis and Brownian movement along with zero‐mass flux constraint are also utilized for the comprehensiveness of this study. Mathematical relations of cross nanofluid are processed with similarity transformation, shooting methodology, and bvp4c Matlab procedure is rehearsed to get the numerical results of this attempt.

Hydrodynamic and heat transfer analysis of dissimilar shaped nanoparticles-based hybrid nanofluids in a rotating frame with convective boundary condition

Solar thermal systems have low efficiency due to the working fluid's weak thermophysical characteristics. Thermo-physical characteristics of base fluid depend on particle concentration, diameter, and shapes. To assess a nanofluid's thermal performance in a solar collector, it is important to first understand the thermophysical changes that occur when nanoparticles are introduced to the base fluid. The aim of this study is, therefore, to analyze the hydrodynamic and heat characteristics of two different water-based hybrid nanofluids (used as a solar energy absorber) with varied particle shapes in a porous medium. As the heat transfer surface is exposed to the surrounding environment, the convective boundary condition is employed. Additionally, the flow of nanoliquid between two plates (in parallel) is observed influenced by velocity slip, non-uniform heat source-sink, linear thermal radiation. To make two targeted hybrid nanofluids, graphene is added as a cylindrical particle to water to make a nanofluid, and then silver is added as a platelet particle to the graphene/water nanofluid. For the second hybrid nanofluid, CuO spherical shape particles are introduced to the graphene/water nanofluid. The entropy of the system is also assessed. The Tiwari-Das nanofluid model is used. The translated mathematical formulations are then solved numerically. The physical and graphical behavior of significant parameters is studied.

Experimental study on power generation plant of a 1 kW small‐scale Organic Rankine Cycle system using R290

AbstractThis work presents an experimental investigation of a small‐scale cryogenic Organic Rankine Cycle (ORC) power generation plant for cold energy utilization using scroll expander and R290. The fresh water and liquid nitrogen were used as heat source and heat sink, respectively. Furthermore, expander gross output power and isentropic efficiency, system thermal efficiency, and cold energy utilization efficiency were calculated as a principle to evaluate the overall system performance. The experimental results demonstrate that increasing pressure drop and heat source temperature will benefit the system performance in some extent, and the pressure drop exhibits a relative sensitivity to heat source temperature about the system performance. Moreover, the expander gross output power will get the peak value while the heat source and heat sink in the best matching. When the mass flow rate of liquid nitrogen at 120 kg/h, optimum pressure drop is 1.02 Mpa, and the corresponding expander gross output power, thermal efficiency, and cold energy utilization efficiency were 638.2W, 0.0586, and 0.0976, respectively. The optimum heat source temperature is 50℃ under liquid nitrogen mass flow rate of 120 kg/h, and the corresponding expander gross output power, thermal efficiency, and cold energy utilization efficiency were 674.2 W, 0.0594, and 0.099, respectively.

The effects of water-CuO nanofluid flow on heat transfer inside a heated 2D channel

The velocity distribution and heat transfer improvement in a two-dimensional channel filled with a water-CuO nanofluid is numerically studied. The nanofluid flow is assumed laminar and one-phase with Newtonian behaviour. Pure water is considered as the base fluid, and water-CuO nanofluid with four different volume fractions of CuO nanoparticles are examined. A constant heat source–sink is considered to cover the entire length of the bottom wall of the channel while the upper wall is assumed thermally insulated. The control volume technique is used to discretize the governing differential equations, and the SIMPLE algorithm is used to solve the velocity-pressure coupling. A CFD simulation is applied on nanofluid flow utilizing ANSYS FLUENT to solve the governing equations of the flow. The effects of nanoparticle volume fraction on the heat transfer, velocity profile, wall shear stress, skin friction coefficient, and Nusselt number along the channel have also been examined. The results confirm that the volume fraction of nanoparticles plays an important role in heat transfer enhancement and hydrodynamic behaviour of flow. The results are presented in figures and tables.

Dynamics of ternary-hybrid nanofluid subject to magnetic flux density and heat source or sink on a convectively heated surface

The size and intensity of the system of delocalized electrons are reflected in the form of the induced magnetic field. Even though this also affects nearby molecules, nothing is known on the significance of stagnant water conveying silver Ag, aluminum oxide Al2O3, and aluminum Al nanoparticles of different shapes on a horizontal surface experiencing convectively heating as applicable in the industry. Relevant similarity transformations were adopted to non-dimenzionalized the governing equations and solved numerically using the 3-stage Lobatto IIIa integration formula for a finite difference (MATLAB package bvp4c). Based on the analysis of the new results, it is worth concluding that either in the case of heat source or heat sink, an increment in the convective heating of the wall is a factor capable to boost the temperature distribution. Increasing effects of an inclined magnetic field are capable to cause the distance between the turning points of shear stress and that of the gradient of magnetic flux density to be located at the middle of the domain.

Thermal Analysis of 3D Electromagnetic Radiative Nanofluid Flow with Suction/Blowing: Darcy-Forchheimer Scheme.

This paper discusses the Darcy–Forchheimer three dimensional (3D) flow of a permeable nanofluid through a convectively heated porous extending surface under the influences of the magnetic field and nonlinear radiation. The higher-order chemical reactions with activation energy and heat source (sink) impacts are considered. We integrate the nanofluid model by using Brownian diffusion and thermophoresis. To convert PDEs (partial differential equations) into non-linear ODEs (ordinary differential equations), an effective, self-similar transformation is used. With the fourth–fifth order Runge–Kutta–Fehlberg (RKF45) approach using the shooting technique, the consequent differential system set is numerically solved. The influence of dimensionless parameters on velocity, temperature, and nanoparticle volume fraction profiles is revealed via graphs. Results of nanofluid flow and heat as well as the convective heat transport coefficient, drag force coefficient, and Nusselt and Sherwood numbers under the impact of the studied parameters are discussed and presented through graphs and tables. Numerical simulations show that the increment in activation energy and the order of the chemical reaction boosts the concentration, and the reverse happens with thermal radiation. Applications of such attractive nanofluids include plastic and rubber sheet production, oil production, metalworking processes such as hot rolling, water in reservoirs, melt spinning as a metal forming technique, elastic polymer substances, heat exchangers, emollient production, paints, catalytic reactors, and glass fiber production.

Inclined magnetized and energy transportation aspect of infinite shear rate viscosity model of Carreau nanofluid with multiple features over wedge geometry

AbstractHeat transference in fluid mechanism has a deep influence in real‐life applications like hot‐mix paving, recovery of energy, concrete heating, heat spacing, refineries, distillation, autoclaves, reactors, air conditioning, and so forth. In this attempt, findings related to energy exchange with features of infinite shear rate viscosity model of Carreau nanofluid by placing inclined magnetic dipole over the wedge are made. The main role in the transportation of heat is exercised by incorporating facts of radiation, nonuniform heat sink source, Brownian motion, thermophoresis, and chemical reaction. The mathematical system of the infinite shear rate viscosity model of Carreau nanofluid gives a system of partial differential equations and furthermore, these are moved into ordinary differential equations. A numerical procedure is applied via shooting/bvp4c to obtain numerical results. Inclined magnetic dipole gives a lower velocity of Carreau nanofluid. Due to the relaxation time factor velocity of Carreau fluid gets down. A* causes to generate the heat internally, so due to this, temperature increases rapidly. The increasing rate of temperature is found very high for the growing Hartmann number. The rate of mass transport becomes low for gradual increment in the parameter of thermophoresis, wedge angle, and Prandtl. Inclined magnetic dipole gives a lower velocity of Carreau nanofluid. Due to the relaxation time factor, the velocity of the Carreau fluid goes down. The absence and presence of magnetic numbers have no influence on velocity, temperature, and concentration files for Le, Rd, θf, γ, We, β, Pr, Nb, Nt, A.

Analysis of Newtonian heating and higher-order chemical reaction on a Maxwell nanofluid in a rotating frame with gyrotactic microorganisms and variable heat source/sink

The goal of this study is to investigate the rotating Maxwell nanoliquid flow incorporating gyrotactic microbes with Newtonian heating and irregular heat source sink. The motion of the flow is induced due to linearly unidirectional elongated surface. The uniqueness of the flow is enhanced by the inclusion of additional phenomenon of higher order chemical reaction incorporated with Darcy Forchheimer flow, Fourier and Fick law. Numerical solution of the formulated problem is developed via bvp4c function in MATLAB. The influence of the embroiled parameters on the flow distribution is demonstrated through various graphs and tables. It is noticed that fluid velocity declines on incrementing the rotation parameter. An upsurge in thermal field is portrayed on augmenting the Newtonian heating. Comparative analysis of the results of the proposed model with previous published research is included which confirms the validity of the current model.