Experimental Thermal Analysis Research Articles

Experimental thermal analysis of a novel prosthetic socket along with silicone and PCM liners

Prosthetic liners and sockets insulate a residual limb, causing excessive heat, sweating, skin irritation and maceration. Circulation of a fluid through the socket wall has been shown to have positive cooling effects on the internal surface of the socket, i.e. skin temperature. Moreover, Phase Change Materials (PCMs) have been recognized as a practical method for cooling garments. These materials, such as water or many synthesized polymers, have a high latent heat and their application within a prosthetic liner allows for absorbing heat from the limb for retaining a constant temperature. In this study, a novel prosthetic socket has been designed and prototyped to investigate the interactive effects of fluid circulation and PCM materials on thermal comfort of prosthetic sockets. The results indicate a statistically significant difference (p-value < 0.001) in the duration a PCM liner can retain the appropriate skin temperature, compared to regular silicone liners. Likewise, the presence of air circulation within the socket wall was shown to have statistically significant influences (p-value = 0.018) on providing the efficient cooling effects compared to regular sockets. Hence, incorporating circulation cooling mechanisms along with PCM liners as proposed in this study holds a promising solution to enhance the thermal comfort of prosthetic socket systems.

Experimental thermal analysis of a turbulent nano enriched water flow in a circular tube

In the present study the effect of adding MgO nanoparticles to the water on the turbulent flow thermal properties in a counter-flow heat exchanger is investigated experimentally. Experiments have been done in Reynolds number of 6,000 to 32,000 and nanoparticles volume fraction of 0.005 to 0.02. In this investigation convective heat transfer coefficient, pressure drop, friction factor and Nusselt number are measured and discussed. According to experimental data convective heat transfer coefficient, average Nusselt number, and pressure drop have direct mathematical relation with nanoparticles volume fraction and Reynolds number (with maximum enhancement of 31.96% in nanoparticles volume fraction of 2%). However, at certain nanoparticle volume fractions and Reynolds numbers, increasing nanoparticle volume fraction led to a reduction of the flow friction factor (1.63% when φ=0.5%). Also, irrespective of the nanoparticle volume fraction, increasing the Reynolds numbers caused decreases of the flow friction factor. Considering high cost of experimental studies as a problem, a new mathematical and statistical based correlation is presented to predict the Nusselt number with independent variables of φ, Pr and Re.

Thermo-dynamical modelisation of the degradation of a ball bearing in variables use conditions

Many sources of heat can emanate from the operation of a rotating machine, and one of which is the friction among the different parts of the ball bearings. Over time, these frictions may lead to a tearing of matter of the rings or on the rolling elements that cause some type of degradation by flaking. Flaking, in turn, produces a repetitive shock as a new source of thermal energy. This work proposes a physical model for the study of the thermal heating of a ball bearing during operation. The resolution of the energy balance is achieved by the Nodal method where both the heating due to friction and the heat induced by the passage of the balls on defect are taken into account. The proposed thermal model is validated through an experimental thermal analysis. The obtained results show that the temperature increases in the position of defect ball ring with increasing rotational speed. The same results are obtained for the influence of radial load.

Estimation of friction surface temperature of a dry clutch

This paper presents an approach to estimate the temperature on the friction surface of a dry clutch. The study comprises both experimental measurements and transient thermal numerical analysis of heavy duty truck clutches for the successive engagements on a slope road. Compared to previous mathematical models in the literature; pressure plate surface convection coefficient, energy dissipation, engagement duration and variation of the clutch housing air temperature were obtained on the basis of experimental data and have been applied as input in the 3D clutch transient thermal finite element analysis. Simulation results show that the design of clutch plate has a significant effect on the temperature rise at the friction surface.

Experimental thermal performance analysis of finned tube-phase change material based double pass solar air heater

The present experimental study is performed to investigate the thermal performances of double pass solar air heater comprising of phase change materials (PCM) contained in metallic finned tubes to have increased energy storage and heat transfer rate. Experimental results were also helpful in the evaluation of the charging and the discharging characteristics of the PCMs. The air heater is studied for three different configurations. In the first configuration, is no PCM used. In the second configuration, RT44HC having higher melting point filled in semi-circular finned tubes (SFT) on the upper pass of double pass solar air heater (DPSAH) as a thermal storage medium (TSM) is used. While the third configuration is a combination of the second configuration and RT18HC having lower melting point, filled in circular finned tubes (FT) as TSM placed in the lower pass to enhance the thermal storage capacity of solar air heater (SAH). The heater's thermal performance is evaluated for all configurations separately. It was revealed that the third configuration containing RT44HC and RT18HC in upper and lower passes respectively is the best among others for optimum heater performance.

Experimental thermal performance analysis of fluid flow in a heat exchanger pipe with novel double strip helical screw tape inserts for utilization of energy resources

ABSTRACT Heat transfer enhancement is an essential parameter of heat exchangers, that can increase by increasing the value of heat transfer coefficient. So, researchers used different types of inserts, in which, single strip helical screw tape showed excellent enhancement in heat transfer, due to the formation of high-intensity swirl flow. However, to increase more intensity of swirl flow, Double strip helical screw tape inserts (DS-HST) used in present work. An experimental analysis is carried out to analyze thermal and friction factor characteristics of fluid flow in heat exchanger tube, with DS-HST, at twist ratio of 1.5, 2.5, and 3, in the range of Reynolds number from 4000 to 16000, at constant heat flux condition. Experimental results showed that Nusselt number and friction factor achieved excellent enhancement with double strip helical screw tape insert than single strip helical screw tape insert (SS-HST) with decreasing value of twist ratio. The correlation developed for Nusselt number at a range of Reynolds number, twist ratio and a number of strips. Moreover, Thermal performance factor achieved maximum value at twist ratio of 2.5 and 3 for DS-HST, than SS-HST inserts in the higher values of Reynolds number, at constant pumping power. So this range of turbulent flow showed the suitability of DS-HST inserts, which can reduce the size of heat exchangers or thermal applications, utilize energy resources, and decrease pollution in the environment.

Experimental Thermal Analysis in Rotary Friction Welding of Dissimilar Materials

Rotary friction welding process (RFW) is one of the most used processes in the world for manufacturing bimetallic components that require high mechanical strength. All process occurs in solid state at temperatures below the melting point of the involved materials, having as the main bonding mechanisms the diffusion and mechanical mixture. The purpose of this work was to carry out an experimental thermal analysis of the dissimilar joint AA6351 T6 aluminum and AISI 304L stainless steel during the friction welding operation through system of thermocouples. Gradients of temperature obtained had their data analyzed and recorded. Results of the experimental thermal analysis showed the behavior of the temperature in the bonding interface, how the dissipation occurs in the radial and longitudinal direction, heating rates, cooling, maximum temperatures reached, its relationship with the different stages of the process and the influence on mechanical properties of welded joint. This study is of great importance for relating the temperature distribution in the bonding interface with atomic diffusion and mechanical resistance of junction.

Experimental study and thermal analysis of the combustion characteristics of powder-activated cokes

The thermodynamic and kinetic parameters of two powder-activated cokes were investigated. Two powder-activated cokes were prepared from lignite and bituminous coal through the rapid preparation process by one–step activation. Variations in the specific heat capacity, thermal diffusivity, and thermal conductivity with the change in temperature were determined. The effects of heating rate and oxygen concentration on ignition temperatures of the two samples were studied. Ignition temperatures were determined using an improved TG/DTG tangent method and predicted by polynomial models. Ignition temperatures of bituminous coal (sample 2) were higher than those of lignite (sample 1). The kinetic parameters were investigated by the Coats–Redfern method. The effects of heating rate and oxygen concentration on the activation energy and the pre-exponential factor were determined. A kinetic compensation effect existed between the two kinetic parameters. The values of these parameters could be calculated directly by polynomial models and kinetic compensation effect equations.

Development of a Low-Cost, Wireless Smart Thermostat for Isothermal DNA Amplification in Lab-On-A-Chip Devices.

Nucleic acid amplification tests (NAAT) are widely used for the detection of living organisms, recently applied in Lab-on-a-Chip (LoC) devices to make portable DNA analysis platforms. While portable LoC-NAAT can provide definitive test results on the spot, it requires specialized temperature control equipment. This work focuses on delivering a generalized low-cost, wireless smart thermostat for isothermal NAAT protocols in 2 cm × 3 cm LoC cartridges. We report on the design, prototyping, and evaluation results of our smart thermostat. The thermostat was evaluated by experimental and simulated thermal analysis using 3D printed LoC cartridges, in order to verify its applicability to various isothermal NAAT protocols. Furthermore, it was tested at the boundaries of its operating ambient temperature range as well as its battery life was evaluated. The prototype thermostat was proven functional in 20–30 °C ambient range, capable of maintaining the required reaction temperature of 12 isothermal NAAT protocols with 0.7 °C steady-state error in the worst case.

Experimental investigation and thermal analysis of coupler-rocker ball bearing

Ball bearings are widely used in many machineries and industrial applications. Thermal behaviour of oscillating ball bearings is unknown due to its complex pendulum-like motion and is discussed in this research. In this research, the effect of operating conditions of the oscillating bearing performing coupler-rocker motion on the heat generation is experimentally investigated and verified using mathematical model. For this purpose, a coupler-rocker bearing testing rig was designed and fabricated and the test bearing is splash-lubricated in an oil sump. The loading of test bearing was done using two extension springs. The applied load on the bearing was varied from 0 to 750 N while the crank rpm was varied from 1200 rpm to 1800 rpm. Three lubricant grades were used namely, SAE30, SAE40, and SAE50. Experimental results showed that the temperature of coupler-rocker bearing approaches steady-state at about 12 minutes for all cases. The steady-state temperatures at variable conditions are observed to follow a linear trend.

Experimental investigation and thermal analysis of solar air heater having rectangular rib roughness on the absorber plate

This study presents experimental investigation and thermal analysis of solar air heater having rectangular roughness on the absorber plate. The solar air heater used for the experiment was locally fabricated. The maximum intensity of solar radiation, ambient and solar air heater temperature were 827.87 W/m2, 33.77 and 112.0 °C respectively during the day time period of 9:00–18:00 h operation. The calculated thermal efficiency value ranged between 14.0 to 56.5%. The simulated minimum and maximum temperature of the solar air heater were 21 and 127 °C respectively, which were in reasonable agreement with experiment result of 20 and 112 °C. Thus, the solar air heater was considered capable of handling processes such as drying of various agricultural products, water heating etc. with temperature control mechanism.

Nusselt number correlation for compact heat exchangers in transition regimes

A compact heat exchanger is characterized by high heat transfer rates in small volumes. Basically it can be considered as a solid metal block where hot and cold fluid streams flow through mini or micro channels. The fluids usually flow in laminar regime, but the equipment can also operate in transition and in turbulent regimes. However, no model for the transition flow regimes, applied to compact heat exchangers, is available in the literature, as the few papers in this subject are usually focused in the classical correlations. The present work performed a theoretical and experimental thermal analysis of the laminar and transition flows in a diffusion bonded cross flow compact heat exchanger and proposed a new Nusselt number correlation for the transition regime. The theoretical model and the main correlations for laminar, turbulent and transition regime are presented. To validate the model, a stainless steel cut plate heat exchanger, with 450 square channels of 3 mm edge, was manufactured. The test facility was designed to operate with hot water and air at ambient temperature. The tests were performed with different mass flow rates, operating with Reynolds numbers between 360 and 2500. The theoretical and experimental results compared well, with theoretical data located within the range of the experimental uncertainty. However, for high Reynolds numbers, greater than 1650, the difference between the results tended to increase. Due to limitations of existing correlations, a Nusselt number correlation for air flow in the transition region and the liquid under constant temperature conditions, based on the asymptotic correlation method, is proposed for compact heat exchangers. The new model provides a smooth transition from the developing laminar flow to the turbulent. To validate the equation, a new test set was performed, and the proposed correlation presented a good accuracy in the transition regime.

Experimental and Numerical Thermal Analysis of Multi-Layered Microchannel Heat Sink for Concentrating Photovoltaic Application

Concentrating photovoltaic has a major challenge due to the high temperature raised during the process which reduces the efficiency of the solar cell. A multi-layered microchannel heat sink technique is considered more efficient in terms of heat removal and pumping power among many other cooling techniques. Thus, in the current work, multi-layered microchannel heat sink is used for concentrating photovoltaic cooling. The thermal behavior of the system is experimentally and numerically investigated. The results show that in extreme heating load of 30 W/cm2 with heat transfer fluid flow rate of 30 mL/min, increasing the number of layers from one to four reduces the heat source temperature from 88.55 to 73.57 °C. In addition, the single layered MLM heat sink suffers from the highest non-uniformity in the heat source temperature compared to the heat sinks with the higher number of layers. Additionally, the results show that increasing the number of layers from one to four reduces the pressure drop from 162.79 to 32.75 Pa.

Design and Thermal Analysis of an Air Source Heat Pump Dryer for Food Drying

In this study, an experimental heat pump dryer was designed. The specific moisture extraction rate and moisture extraction rate were used as performance indicators to explore the influence of environmental factors and the style of the hot air cycle on heat pump drying. The average temperature and humidity in Nanjing’s summer, winter, and throughout the whole year were taken as the experimental ambient temperature and humidity. Garlic slices 3 mm thick, with an initial moisture content of 66.714% w.b., were dried until the end moisture content was 10% w.b. Experimental results and thermal analysis showed that the open and semi-open heat pump dryers were greatly affected by ambient temperature and humidity. The closed heat pump drying system was greatly affected by the bypass air rate.

Experimental and numerical thermal analysis of open-cell metal foams developed through a topological optimization and 3D printing process

This study focuses on the thermal analysis and comparing a lattice model and an optimized model of open-cell metal foams manufactured thanks to a metal casting process. The topological optimization defines the complex geometry through thermal criteria and a plaster mold reproduces it in 3D printing to be used in casting. The study of the thermal behavior conducted on the two open foam metal structures is performed based on several measurements, as well as numerical simulations. It is observed that the optimized metal foam presented less and non-homogenous local temperature than the lattice model with the gap of about 10 °C between both models. The pore size and porosity significantly affect the heat transfer through the metal foam. The comparison between numerical simulations and experimental results regarding the temperature fields shows a good agreement allowing the validation of the developed three-dimensional model based on the finite element method.

Thermal Analysis of a Disposable, Instrument-Free DNA Amplification Lab-on-a-Chip Platform.

Novel second-generation rapid diagnostics based on nucleic acid amplification tests (NAAT) offer performance metrics on par with clinical laboratories in detecting infectious diseases at the point of care. The diagnostic assay is typically performed within a Lab-on-a-Chip (LoC) component with integrated temperature regulation. However, constraints on device dimensions, cost and power supply inherent with the device format apply to temperature regulation as well. Thermal analysis on simplified thermal models for the device can help overcome these barriers by speeding up thermal optimization. In this work, we perform experimental thermal analysis on the simplified thermal model for our instrument-free, single-use LoC NAAT platform. The system is evaluated further by finite element modelling. Steady-state as well as transient thermal analysis are performed to evaluate the performance of a self-regulating polymer resin heating element in the proposed device geometry. Reaction volumes in the target temperature range of the amplification reaction are estimated in the simulated model to assess compliance with assay requirements. Using the proposed methodology, we demonstrated our NAAT device concept capable of performing loop-mediated isothermal amplification in the 20–25 °C ambient temperature range with 32 min total assay time.

Experimental thermal analysis and modelling of single point lathe cutting tools without cooling effect

This study investigated the use of tungsten carbide tool and high speed steel (HSS) tool when machining aluminum and mild steel. The parameters such as feed and speed of rotation were varied in order to observe their effect on machining operation. The experiments were performed without a coolant. FLIR thermo Cam P60 and Infra-Red Camera were used to record the observations. The highest temperature were recorded when feed rate was 2 mm. A comparison of experiments shows that HSS tooling produced high temperatures when machining mild steel. At 625 rev/min HSS failed when cutting mild steel at 2 mm feed rate. It was generally observed that temperatures generated between a tool and work piece is a function of feed rate, speed of rotation and tool material. These observations can aid the selection of a tool before a machining operation.

Experimental study and thermal analysis of a tubular pressurized air receiver

Abstract Pressurized air receivers potentially used in concentrated solar power plants are being developed and studied to achieve higher systemic efficiency from solar to electricity. In this article, a novel receiver with double spiral tubes coiled into conical type was proposed and fabricated. The design shows a bending limitation of a diameter of 60 mm in the bottom of the receiver. Some experimental tests were conducted under a solar furnace in the real weather condition. The results reveal that this kind of receiver could obtain high-temperature outlet air at 908 °C with relatively low direct normal irradiation (DNI) of around 785 W/m2. Based on the comparisons of the outcomes of 9 test cases, it could be concluded that the outlet air temperature is mainly dominated by the value of DNI, while the pressure drop is determined by both DNI and mass flow rate of the air. Besides, the thermal inertia of the receiver demonstrates benefits for stable output and quick recovery induced by small adjustments in the real operation process. All of these results and analysis provide a helpful reference for validation, optimization and operational strategies for this kind of pressurized air receiver.

Numerical and experimental thermal analysis of polyimide-based x-ray masks at the Canadian Light Source

In deep x-ray lithography (DXRL), synchrotron radiation is applied to transfer absorber patterns on an x-ray mask into thick photoresist to generate high quality microstructures. Fabrication of the required x-ray masks is a demanding process sequence and constitutes a bottleneck in DXRL technology. Polymer-based mask membranes offer many benefits during mask fabrication and operation, but usually suffer from large thermal distortions during x-ray exposure. These are due to the low thermal conductivity of most polymers (approximately 0.2 W/m K), which results in inefficient heat transfer to the cooled areas around mask and substrate. The power tuning capabilities at the Synchrotron Laboratory for Micro and Nano Devices beamline, Canadian Light Source, however, allow the beam power to be adjusted and consequently limit thermal distortions. In this study, x-ray masks based on 30 μm thick polyimide membranes are studied. Numerical simulations of the thermal and thermoelastic behavior were performed using the software package ansys r14.5. The beam power input parameters were calculated with the software lex-d. For experimental verification, a process to fabricate simple test masks was developed. The polymer membranes were processed on stainless steel sacrificial wafers and were patterned with 80 μm thick nickel absorbers in two macroscopic layouts. Five chromel/alumel (K-type) thermocouples where then bonded to the absorbers to measure the heat distribution. The measurements generally validated the numerical results. The simulated thermal distributions consistently overestimate the experimental values by approximately 4–6 K, which is mainly attributed to uncertainties in the experimental proximity gap settings. The thermal simulation results indicate that the dominant heating mechanism of the resist is conduction: Energy absorbed in the mask absorbers is conducted through the helium gas in the proximity gap to the nonexposed poly(methyl methacrylate) (PMMA) areas and the substrate (cooled to 18 °C). For 500 μm thick PMMA resist, exposed with a synchrotron beam power of 19.6 W, maximum temperatures in the mask are 31.0 and 25.8 °C in the resist below. Maximum single-axis resist deformations in the mask plane amount to 4.12 μm. At 250 μm resist thickness, the observed temperatures are only 25.4 °C in the mask and 22.3 °C in the resist, with maximum mask plane deformations of about 2.3 μm. Integrated over the entire absorber size of 60 mm, these deformations roughly double. Local structure accuracy results were obtained by measuring distortions in a micropatterned polyimide mask. Deformations verify simulation results, vary with the position on the layout, and scale with the incident beam power. At 3.3 W incident beam power, typical deformations around 1–1.5 μm and maximum deformations of 2.3 μm were measured in 100 μm thick resist.

Experimental thermal performance analysis of ground heat exchangers for space heating and cooling applications

In recent decades, ground source heat pump systems have become popular for space heating and cooling applications. In both modes of operation, GSHP needs to interact with the ground through GHX. The thermal performance analysis of single and double U-tube heat exchangers are discussed in this paper by focusing on its effectiveness, ground temperatures, heat extraction & injection rate and its effects on surrounding ground formations. Initially the method of calculating length of GHX for a given heat load is explained, then the effectiveness of GHX is defined. Experimental set up used to study the performance of single and double U-tube GHX at bureau of geological and mining research (BRGM), France is explained. Results obtained from the experimental study shows that the average effectiveness of single U-tube heat exchanger in heating and cooling modes are 0.34 and 0.40 respectively and for double U-tube, it is 0.46 and 0.57 respectively. In both the heat exchangers, the average effectiveness is observed to be high in cooling mode operation, the reason may be that in cooling mode operation, the temperature difference between the heat carrier fluid and the ground is found to be high compared to the difference observed during heating mode operation.