Maximum Heat Input Research Articles

Experimental investigation of natural convection heat transfer coefficient for roughed inclined plate

Natural Convection is the process of heat transfer from one fluid to another with temperature difference without external agency and heat transfer from electronic circuits, refrigerators, heat exchangers, fuel elements in nuclear reactors, cooling towers and home ventilation etc. through naturally. In this research investigated heat transfer coefficient on plain, semi roughed and roughed plate. The parameters varied during the experimentation are heat input ranges from 30.6 to 174.75 Watts and the angle of inclination for plate from (0°, 15°,30°, 45°, 60°, 75°, and 90°). It has been observed that the heat transfer coefficient is enhanced up to 6.63% from plain to semi roughed, 3.87% from semi rough to rough and 10.75% from plain to rough plate at maximum heat input. The heat transfer enhancement has been investigated experimentally and experimental results have been validated with CFD simulation (Ansys software).

Fluid Choice Based on Thermal Model and Performance Testing for Direct Cooled Electric Drive

In this publication, the cooling fluid for direct oil-cooled electric traction drive is investigated. A dedicated thermal resistance model was developed in order to show the influence of the fluid properties on the continuous performance. For this purpose, the heat transfer parameters are adjusted in the simulation using an exponential approach in order to evaluate the cooling fluid. In a sensitivity study, density, heat capacity, thermal conductivity, and viscosity are investigated. Because viscosity, within the range investigated, shows the largest percentage deviation from the reference fluid, the greatest effect on performance can be seen here. In order to check the plausibility of the calculated results of the thermal simulation, two fluids were chosen for performance testing on a dedicated electro motor cooling (EMC) test. Beyond the investigation of heat transfer, aging of the defined fluid at maximum heat input over several hours is also evaluated. Only slight changes of the fluid properties are detected. This publication presents a thermal model for direct oil-cooled drive trains, which consider fluid properties. Furthermore, the model was tested for plausibility on real hardware.

Energy and exergy analyses of a new integrated thermochemical copper-chlorine cycle for hydrogen production

This paper presents a thermodynamic study on a newly built lab-scale thermochemical copper-chlorine (Cu-Cl) cycle installed at the Clean Energy Research Laboratory (CERL) at the Ontario Tech University. This study analyzes every component of the system through energy and exergy analysis by considering the heat inputs, outputs and exergy destruction within the various units of the Cu–Cl cycle. The system is modeled and simulated using the Aspen-plus software. The mass, energy and exergy balance equations for each system component are written for analysis and assessment purposes. Based on the analysis, the maximum heat input is required for the hydrolysis reactor while the HCl-condenser-1 is found to reject the maximum heat. The results suggest that the thermolysis reactor experienced the highest exergy destruction. The effect of the flow rates of certain species within the cycle on the performance of various system units, such as heat transfer rates and production flow rates are also investigated. The overall energy and exergy efficiencies of the system are evaluated to be 6.8% and 10.4%, respectively.

Experimental Analysis on Influencing Factors of NOx emission in Gas-Fired Heating and Hot Water Combi-Boilers

To study the influencing factors of NOx emission in gas-fired heating and hot water combi-boilers, a boiler with the maximum heat input of 26.0 kW was selected, and influencing factors including flue restrictor diameter, fan power, nozzle aperture, nozzle ejection distance and air relative humidity on NOx formation were determined. The NOx test rig has been built and the concentration of NOx at the rated heat input and the NOx weight value (NOx)pond with different heat input in the dry flue gas have been tested respectively according to the test methods in Chinese national standard GB 25034-2010. The results show that with the increase of the diameter of flue restrictor at exhaust outlet, the NOx concentration at the rated heat input and the NOx weight value (NOx)pond with different heat input in the dry flue gas decreased by 26.9% and 5.9%; with the increase of the diameter of flue restrictor at air intake inlet, the NOx and (NOx)pond decreased by 36.5% and 16.0%; with the increase of fan power, the NOx and (NOx)pond can be decreased by 48.4% and 16.1%; with the increase of ejection distance of nozzle, the NOx and (NOx)pond decreased by 7.7% and 6.8%; with the increase of aperture of nozzle, the NOx and (NOx)pond increased by 5.2% and 2.3%; with the increase of air relative humidity, the NOx decreased by 16.4% and the (NOx)pond basically remains unchanged. The analysis of the influence factors of NOx emission can be provided as reference for the optimization design of combi-boilers with low NOx emission.

An experimental and theoretical investigation of thermo-mechanical issues in friction surfacing of Al–Mg aluminum alloys: material flow and residual stress

Material flow and residual stress distribution during friction surfacing of aluminum alloy AA5083 on aluminum alloy AA5052 substrate have been evaluated employing a three-dimensional model and the finite element software, ABAQUS, as well as experimental investigation. Based on the results, the nature of residual stress in the coating was tensile while getting compressive by straying away from the boundary of the coating. An increment in heat input per unit length of coating has caused a decrease in the maximum tensile residual stress albeit increasing the extent of the region with tensile residual stress. On the advancing side, the velocity vector was larger than the retreating side due to the larger velocity difference between rotating rod and substrate. Moreover, the velocity difference between advancing and retreating sides was much lower in sample with minimum heat input compared to a sample with maximum heat input.

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively. Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input. The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

Augmented heat transfer by hybrid thermosyphon assisted thermal energy storage system for electronic cooling

Abstract Thermal management of electronic systems is investigated with a hybrid thermosyphon assisted thermal energy storage system. Various circulating coolants namely DI water, acetone, methanol and ethanol are used in this work. The heat input to the system varies between 50 and 90 W. Lauric acid is used as phase change material (PCM) and stored in an annular which helps to remove heat from the vapourized coolants. The molten PCM is then solidified by supplying cold water through a copper tube when the power is switched OFF. The influence of heat input on heat transfer performance such as percentage of heat removal, heat transfer coefficient (HTC) and thermal resistance of various circulating coolants is analysed. In addition, the temperature variation during the charging and discharging performance of PCM is studied by the effect of different coolants at a given heat flux. Results show that (i) the maximum percentage of heat removal and HTC of about 98.9% and 205.78 W/(m2.K) are obtained for acetone at 90 W due to low boiling point, low latent heat of vapourization (LHV), low viscosity and less effect on subcooling (ii) the low thermal resistance of acetone is 0.316 K/W owing to the high vapour flow rate at maximum heat input (iii) PCM attains steady state temperature at a faster rate and the maximum thermal power absorbed is about 6.18 W when the acetone is used as a circulating coolant at 90 W.

Investigations on effect of noncondensable gas in a loop heat pipe with flat evaporator on deprime

Noncondensable gas (NCG) in a loop heat pipe (LHP) results in degradation of its performance. In an LHP operating on the ground with low pressure working fluids, atmospheric air entering into it acts as NCG. The goal of this paper is to estimate the NCG mass in an LHP with flat evaporator with a low-pressure working fluid based on the pressure and liquid volume measurements inside the compensation chamber (CC) and study its effect on deprime (i.e., dry out or capillary limit). An LHP with flat evaporator was tested with acetone for various heat inputs till deprime for two sink temperature, namely, −20 °C and 0 °C, by allowing entry of atmospheric air into the LHP through an intentionally fixed defective gasket. The NCG mass is estimated at various heat inputs based on the CC pressure measured using an absolute pressure transducer and the CC liquid volume measured using a capacitance gauge. Comparison of the test results with the results of previous tests without the NCG shows that the NCG causes increased operating temperature and decreased heat transport. Analysis of the test results at the maximum heat input prior to deprime reveals that the capillary pressure developed in the pores of the wick in the LHP with the NCG is less than that without the NCG and the radius of evaporating meniscus in the pores of the wick with the NCG is more than that without the NCG.

Microstructural evolution and chemical corrosion of electron beam wire-feed additively manufactured AISI 304 stainless steel

Using an electron beam wire-feed additive manufacturing three sets of samples were obtained at different heat input levels. The samples contained different amounts of vermicular δ-ferrite that depended on the heat input value used. Chemical corrosion tests were carried out to find out that the corrosion resistance of a sample is determined by the δ-ferrite amount in it. High δ-ferrite content in the sample obtained at medium used heat input value caused enhanced corrosion in the Cr-depleted austenite grains. Otherwise, when using the maximum heat input the additively manufactured sample contained the minimum amount of δ-ferrite and demonstrated the highest corrosion resistance as well as formation of a cubic crystallographic texture. No such texture was found in samples grown at lower heat input values. In addition, no inter-granular corrosion induced open cracks have been observed on all samples after 90° angle flexural test.

Numerical Study on an Electrohydrodynamically Driven Axially Grooved Flat Miniature Heat Pipe

This study deals with the use of the electrohydrodynamic effects in flat miniature heat pipes (FMHP). A prototype is conceived and modeled. The equations of the model are developed on the basis of the mass, momentum, and energy balance equations as well as the Laplace–Young equation, which is modified in order to take into account the action of the electric field on the liquid–vapor interface. The electric field promotes the condensate flow back to the evaporator section. Hence, the capillary driving pressure, which is ensured by the capillary grooves, is diminished because the electrohydrodynamic pumping becomes responsible of the liquid flow from the condenser to the evaporator. The electric field decreases the liquid velocity and hardly affects the vapor velocity. Moreover, it increases the vapor pressure drop, and it decreases the liquid pressure drop. The effect of the fill charge on the capillary limit is particularly highlighted. For given groove dimensions, it is demonstrated that there exists an optimum fill charge that ensures a maximum capillary limit. The evolution of the flow parameters is given and discussed for different fill charges and maximum heat input powers.

Ultrasonic Assisted Thermal Direct Joining of Thermoplastic Composites and Aluminum for Multi Material Design

The trend towards multi material design is strongly driven by improved functionality and decreased total weight of hybrid parts. Conventional joining techniques for metals and polymers usually require a complex process and are thus time consuming and expensive. A novel technique addressing these shortcomings is ultrasonic assisted thermal direct joining of metals and thermoplastic polymers. The metallic joining partner is laser pre-treated to generate a specific surface topology. The subsequent joining process is a combination of thermal direct joining and ultrasonic joining. This hybrid joining process results in short cycle times, and the maximum heat input is localized to the joining area. The joint performance was measured by lap shear tests, resulting in strength values exceeding 18 MPa, while the duration of the joining process was about 1.5 seconds. The relevant joining parameters were identified and a process window was obtained. The results indicate that there may be an optimum energy range for successful joining. An appropriate energy map may allow a deeper understanding of the process and enables prediction of process windows for various material combinations.

Experimental Investigation of Gas Metal Arc Welding (GMAW) Process Using Developed Articulator

Gas Metal Arc Welding (GMAW) process is used in fabrication of structures and welding of pressure vessel components because of some advantages, such as higher weld metal deposition rate, requirement of lower welder skill, and good quality of weld in versatile positions. Further, GMAW process can be automated for achieving higher rate of production. In present work, GMAW process is automated using an articulator that can control welding speed. Experiments are carried out using welding process specification prepared as per ASME section-IX. Weld samples are manufactured using single “ V” butt weld joint design. Welding parameters, such as welding current, open circuit voltage and welding speed, are varied in the range of values as per ASME section-IX. Further, the test samples are subjected to physical and chemical testing for evaluating welding process capability. Desirable quality characteristics of weld are assessed based on the value of ultimate tensile strength, chemical composition and root penetration. An effective range of welding current, open circuit voltage and welding speed is identified for sound quality of weld with constraint over maximum heat input.

Microstructure evolution and metallurgical characteristic of bead-on-plate TIG welding of Ti-6Al-4V alloy

The bead geometry of autogenous bead-on-plate tungsten inert gas (TIG) welding performed on Ti-6Al-4 V alloy inside an argon inert box chamber was measured for different processing conditions. The microstructural evolution of the weldment was evaluated through optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) technique. The development of residual stress and the texture in the weldment were assessed through the XRD techniques. The full penetration melting for bead-on-plate welding was obtained for high current and low scan speed combination that induces maximum heat input within the experimental domain. Owing to intense heat of the TIG arc, a complex microstructural evolution occurred in the Ti-6Al-4 V alloy, which causes transformation of initial β phase to martensitic α’ phases. The transformation of initial α + β phase to martensitic α’ phase enhances the hardness value of the melt pool upto 365 HV0.2, and further at heat affected zone (upto 385 HV0.2) owing to grain refinement. The residual stress developed in the weld melt pool was recorded tensile type, and for increasing the welding current, due to the enhancement of induced heat, the residual stress increased from 140 to 200 MPa (for 80 A) to 240–270 MPa (for 100 A).

Experimental investigation of the thermoacoustic traveling-wave engine

Thermoacoustic engines are devices with external heat input, in which thermal energy is converted into energy of acoustic oscillations. Their main advantages include high energy conversion efficiency (up to 35%), minimal number of moving parts, high reliability, absence of contact seals and operation from a variety of heat sources (hydrocarbon fuels, thermal emissions, nuclear sources, solar radiation, etc.). The main goal of this work is to develop, manufacture and carry out the experimental investigations of the thermoacoustic traveling wave engine with a maximum heat input from the electric heating element up to 1000 W. The thermoacoustic engine includes an inertance tube, three heat exchangers, a regenerator, a thermal buffer tube and an acoustic resonator. Helium acts as the working fluid in the engine at an average pressure of 1.0 to 3.0 MPa. The frequency of acoustic oscillations on the steady-state operating mode of the engine is 96-98 Hz. The regenerator is made in the form of a package of metal screens and is the main element of the engine, in which thermoacoustic energy conversion is carried out. In experimental research the following tasks were solved: - determination of the optimal conditions for the excitation of acoustic oscillations in the internal contour of the thermoacoustic engine; - determination of the minimum onset temperature at which acoustic oscillation are excited; - determination of the dependences of the onset temperature, the frequency and the amplitude of acoustic oscillations from the input thermal power; - determination of the efficiency of the rmoacoustic energy conversion; In experimental studies, an optimal mean helium pressure is determined, which ensures the minimum heat exchanger temperature 436 К (163 C) required to start the engine. The maximum value of the acoustic power generated by the regenerator was 90 W. At the same time, the efficiency of conversion of thermal energy into acoustic energy reached 22.5% at a heat exchanger-heater temperature of 317 C. Also during the tests, it was possible to establish the dependences of the onset temperature, the frequency of acoustic oscillations and the amplitude of the acoustic pressure on the supplied thermal power. This type of engine described in this paper can be used in many practical applications.

Thermal performance of a novel helically coiled oscillating heat pipe (HCOHP) for isothermal adsorption. An experimental study

Helically Coiled Oscillating Heat Pipes (HCOHPs) have been designed and tested under laboratory conditions to investigate their potential to achieve isothermal adsorption when integrated with a cylindrical solid desiccant packed bed system. The HCOHPs fabricated out of copper, are essentially single turn closed loop oscillating heat pipes with their evaporator and condenser sections helically coiled. They were charged with ethanol, methanol and deionized water respectively at approximately 60% volume fill ratio and tested by slotting through their helically coiled evaporators an empty cylindrical copper vessel which allowed hot air to be blown through at various heat loads to ascertain their thermal performances.The results showed there were critical heat fluxes which varied with heat input amount at the evaporator, beyond which dry-out commenced and thermal resistance increased. These heat fluxes were ≤70W for the ethanol HCOHP and ≤105W for both the methanol and deionized water HCOHPs. Performance instabilities owing to liquid phase of the working fluid transitioning in the drying-out stage was observed for the methanol HCOHP beyond 234W. The variation of the effective thermal conductivities at the evaporators were found to influence the thermal contact resistance experienced at the contact interface of integration and the maximum heat input amount at the evaporators. Optimum performance between the HCOHPs was observed with the deionized water type. Overall, the HCOHPs were capable of managing relatively large amounts of heat input due to their helically coiled sections creating comparatively larger evaporator sections holding relatively more working fluid than the conventional serpentine single turn closed loop OHP system of the same volume and fill ratio. Investigations involving the visualization of the internal flow dynamics is recommended for future studies.

A modeling comparison between a two-stage and three-stage cascaded thermoelectric generator

In this work, a comparison between the performance of two- and three-stage cascaded thermoelectric generator (TEG) devices is analyzed based on a prescribed maximum hot side temperature of 973 K, an imposed maximum heat input of 505 W, and a fixed cold side temperature of 473 K. Half-Heusler is used as a thermoelectric (TE) material in the top higher temperature stage and skutterudite as a TE in the bottom lower temperature stage for the two-stage structure. Lead telluride is added in the middle stage to form the three-stage structure. Based on the prescribed constraints, the two-stage cascaded TEG is found to produce a power output of 42 W with an efficiency of 8.3%. The three-stage cascaded TEG produces a power output of 51 W with an efficiency of 10.2%. The three-stage cascaded TEG produces 21% more power than the two-stage does; however, if the system complexity, mechanical robustness, manufacturability, and/or cost of three-stage cascaded TEG outweigh the 21% percent power production increase, the two-stage TEG could be preferable.

Experimental evaluation of the heat output/input and coefficient of performance characteristics of a chemical heat pump in the heat upgrading cycle of CaCl2 hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat produced during the hydration of CaCl2. The reactor module employed was an aluminum plate-tube heat exchanger bearing corrugated fins, a porous Ni plate, and the CaCl2 sample in the form of a packed bed. The volumetric heat output and input characteristics of the reactor module were evaluated experimentally, the coefficient of performance (COP) was calculated for the heat upgrading cycle, and the hourly heat output for the system was determined. We found that the obtained waste heat could be upgraded from 100 to 155°C, and the maximum volumetric heat output and input obtained were 380 and −280kW·m−3, respectively. It was therefore apparent that a high performance reactor module could be obtained by reducing the heat and mass transfer resistances in the packed bed. In addition, using this reactor model, a coefficient of performance (COP) value of 0.48 was achieved for the heat upgrading cycle. Furthermore, upon switching the step time of the heat release and storage steps, an hourly heat output of 72kWh·m−3 was achieved with a reaction fraction of 0.8. Our results therefore demonstrate that the use of our CHP system for upgrading waste heat would be expected to improve the energy efficiencies of industrial processes.

The Optimization of Process Parameters and Microstructural Characterization of Fiber Laser Welded Dissimilar HSLA and MART Steel Joints

Nowadays, environmental impact, safety and fuel efficiency are fundamental issues for the automotive industry. These objectives are met by using a combination of different types of steels in the auto bodies. Therefore, it is important to have an understanding of how dissimilar materials behave when they are welded. This paper presents the process parameters’ optimization procedure of fiber laser welded dissimilar high strength low alloy (HSLA) and martensitic steel (MART) steel using a Taguchi approach. The influence of laser power, welding speed and focal position on the mechanical and microstructural properties of the joints was determined. The optimum parameters for the maximum tensile load-minimum heat input were predicted, and the individual significance of parameters on the response was evaluated by ANOVA results. The optimum levels of the process parameters were defined. Furthermore, microstructural examination and microhardness measurements of the selected welds were conducted. The samples of the dissimilar joints showed a remarkable microstructural change from nearly fully martensitic in the weld bead to the unchanged microstructure in the base metals. The heat affected zone (HAZ) region of joints was divided into five subzones. The fusion zone resulted in an important hardness increase, but the formation of a soft zone in the HAZ region.

커버 플레이트를 이용한 이종 3겹 저항 점 용접성 평가

Low carbon steel is usually used as the outer panel with low base metal resistance compared to the inner reinforced panel made with high strength steel, which makes it difficult to form a robust nugget. To overcome welding problems of a dissimilar three-sheet combination made of SGACEN, DP980 and CP1180, a cover plate was inserted between the upper electrode and SGACEN. The quality of the nugget was analyzed by comparing the welding signals and cross sectional images under maximum heat input both with and without the cover plate. To analyze the mechanical of weld properties, a hardness test analysis was conducted. To enhance the reliability of experimental results, temperature distributions were obtained using a simulation program. The method of inserting a cover plate led to a change in the heat input, which induced a larger nugget size between SGACEN and DP980.

Cold metal transfer welding of AA1050 aluminum thin sheets

This study was aimed to investigate the welding parameters on mechanical behavior of 2 mm thick AA1050 sheet materials joined by cold metal transfer (CMT) method. Macro structural examination showed that decreasing heat input decreased the pore size in the weld metal. Tensile test was applied and failure occurred in heat affected zone of aluminum sheet metal. Maximum tensile strength was found in the sample with minimum heat input. Heat affected zone was observed explicitly in the sample produced with the maximum heat input. Decreasing joint gap affected the bending strength positively. Bending strength was found superior with maximum bonding line length.