Investigation Of Thermal Performance Research Articles

Experimental Investigation of Thermal Performance of a Novel Alternating Cross-Section Flattened Tube Heat Exchanger

The air-side performance of a novel alternating cross-section flattened (ACF) tube heat exchanger was experimentally investigated. Three heat exchangers with an in-line tube arrangement and two tube rows were used as the test sections. The tube configuration is the highlight of the research work. ACF tubes with hydraulic diameters of 4.16, 4.75, and 5.20 mm were assembled as the heat exchanger. The experimental results showed that the ACF tube heat exchangers exhibited a prominent heat transfer characteristic with a reasonable pressure loss penalty. Performance evaluation criteria, as a nondimensional parameter, were employed to assess the heat exchanger performance. Finally, the j and f of the ACF tube heat exchanger were compared with those obtained from various shapes of noncircular tube and fin tube heat exchangers. All the details are examined and discussed in this study.

Investigation of thermal performance in dual‐fuel units

AbstractNumerical studies were carried out to investigate the thermal performance of the muzzle flow with strong shock discontinuities and gas–gas heat transfer mechanism in the base bleed unit (BBU) of an aerodynamic vehicle under the combined effects of muzzle flow and depressurization process. The process was modeled using the Navier–Stokes equations with chemical kinetics and interior ballistic equations. The results show that the muzzle phenomena with large temperature gradients and different wave structures appear after the supersonic vehicle enters into the free‐flight stage. The BBU also experiences a strong depressurization process with the release of high‐temperature propellant gas at 2200 K. However, the igniter combustion gas at a higher temperature of 3050 K in the BBU develops downstream and upstream repeatedly under the combined effects of the base wave and depressurization process, which makes the energy conversion process in the unit more complicated. With the projectile leaving the control of the muzzle flow, the BBU is full of the igniter combustion gas and the energy in the unit is uniformly distributed gradually. The high‐temperature area, at approximately 2750 K, propagates downstream along the axial and radial directions simultaneously until it finally dominates the entire unit. The maximum temperature of the combustion gas acting on the propellant surface is always 2740 K and the maximum heat flux remains approximately 1250 W/cm2 at later periods.

Investigation of Electrical and Thermal Performance of a Commercial PEM Electrolyzer under Dynamic Solicitations

Hydrogen generation through electrolyzers has gained a growing interest from researchers and industries to decarbonize transportation and electricity production. The performance of electrolyzers is strongly dependent on their operating conditions, such as the supply current, temperature, and pressure. To meet near-zero emissions, the electrolyzer must be supplied by low-carbon energy sources. Therefore, renewable energy sources must be considered. However, these sources are strongly linked with the weather conditions, so they have a high dynamic behavior. Therefore, this article is focused on the investigation of the effects of these dynamic solicitations on the electrical and thermal performance of electrolyzers. In this study, a proton exchange membrane (PEM) has been chosen to carry out this investigation. Experimental tests have been performed, emphasizing the relationship between the electrical and thermal performance of the PEM electrolyzer. The purpose of this work is to provide an optimal scenario of the operation of the electrolyzer under dynamic solicitations and consequently, to decrease the degradation of the electrolyzer.

Investigation of thermal performance and chemical stability of graphene enhanced phase change material for thermal energy storage

Phase change materials (PCMs) have received widespread thermal energy storage (TES) and release properties due to their unique characteristics. However, the PCMs suffer from poor thermal conductivity, resulting in the least thermal performance and heat transfer characteristics. This research focused on enhancing the heat transfer and storage characteristics by developing an organic paraffin wax composite by dispersing highly conductive graphene powder using a two-step technique. The results show that the developed nano enhanced PCM significantly improves the thermal conductivity by 72.2% at 0.6 wt% of graphene powder. Furthermore, the Fourier transform infrared spectrum shows there is no additional peak observed, means physically and chemically stable, and the reduced light transmission capability was enhanced by 32.0% than pure PCM. Due to its extreme characteristics, the developed PCM is an outstanding material for medium temperature solar thermal energy storage applications.

Thermal Performance Investigation at Different Temperature and Airflow Settings in a Conference Hall of Expo Building

The airflow distribution for a large space, such as a conference hall, is quite challenging to achieve a good and uniform thermal distribution. In the recent study, insufficient quantitative knowledge has been provided, notably for the appropriate supply air temperature and air velocity for the conference hall environment. In this study, a full-scale conference hall was simulated extensively for an expo building in Taiwan. A total of nine experiment numbers were carried out with various supply air temperature and air velocity settings. Through the use of a CFD approach, this study seeks to identify the ideal parameters for a comfortable and acceptable airflow distribution and temperature, with an eye toward potential compromises with an energy-efficient approach. The results demonstrate that the temperature distribution ranges from 18 to 26 °C, indicating an acceptable indoor thermal environment, depending on the parameter settings. The best settings for providing a pleasant indoor thermal environment are with a supply air temperature and air velocity of 15 °C and 1 m/s, which can keep the PMV index between −0.5 and 0.5. Utilizing a greater temperature setting may save energy, but sufficient air velocity must be addressed in order to meet the indoor thermal conditions. Furthermore, a greater air velocity may generate more noise and disrupt the situation in the conference hall, so it must be selected specifically.

Investigation of thermal behavior and performance of different microchannels: A case study for traditional and Manifold Microchannels

In this study, numerical investigation of forced convection of non-Newtonian nanofluid into Traditional Microchannel (TMC) and Manifold Microchannel (MMC) containing porous media is investigated. The bottom of the microchannel wall is kept at a constant temperature and the other walls are heat insulated. The inside of the microchannel is filled with porous media. This study addresses a new sample of microchannels (MMC and TMC) filled with porous material in a three-dimensional flow. The results show that increasing the Reynolds number and volume fraction of nanoparticles (φ) and decreasing the porosity, lead to heat transfer improvement. At low Reynolds numbers, there is no relative advantage over TMC or MMC. Finally, it is concluded that to achieve the acceptable performance evaluation criterion PEC (PEC> 1) at porosity ε= 0.9, thermal conductivity ratio (γ) must be γ <0.9. When thermal conductivity of porous foam is considered low, PEC variations and heat transfer rates in the traditional microchannel are uniform. For TMC and MMC in the maximum Reynolds number, the percentage of increase in heat transfer at ε= 0.9 compared to the absence of porous material is 13.5% and 26.26%, respectively. For MMC and TMC in minimum permeability and maximum Reynolds number, the percentage of reduction of heat transfer rate from n = 0.5 to n = 1.5 is equal to 0.86% and 0.37%, respectively.

Experimental and numerical investigation of thermal performance of a new design solar parabolic dish desalination system

• A new design of Solar Parabolic Dish Desalination System (SPDDS) was proposed. • Τhermal performance of SPDDS was investigated experimentally and numerically. • Optical simulation for SPDDS was performed using COMSOL model. • The model showed that thermal performance of absorber within glass enclosure was promising. • The maximum daily thermal efficiency of SPDDS was calculated to be 36.04%. The objective of the present study is to construct a cheap, new design of small-scale solar parabolic dish desalination system made from reused local recyclable materials without complex parts and power source with advantageous approach due to its unique configuration. The desalting system including a new design of cleanable vessel acts as a boiler that accommodate inside a glass box to minimize the heat losses by the wind. The proposed system was investigated by experiments and numerical model. Moreover, the optical efficiency of the system was simulated using COMSOL model. The experimental data using different levels of salt concentrations and brine masses was compared to those of numerical to validate the model. The model validation revealed that the mean bias error and mean percentage error for brine were −1.05 °C and 0.86%, respectively, while the maximum predicted concentration ratio reached ∼16,000 and ∼9000 for ideal and real reflectors, respectively. The experimental results of were compared to those numerical to validate the model using different levels of salt concentrations and brine masses. The obtained daily average values of radiative heat transfer coefficient proved the effective role of the glass box and vessel in reducing the heat losses to surroundings. At brine mass of 0.75 kg and salt concentration of 15 g/kg, the increase of the salt concentration from 0 to 200 g/kg decreases numerically the daily productivity and daily efficiency from 500 to 320 ml/m 2 .day and from 88.60 to 19%, respectively. Experimentally, the maximum instantaneous and daily thermal efficiency were found to be 53.40% and 36.04%,respectively, while the cost of freshwater production from the proposed system was 0.64 $/l.

Investigation of thermal performance of a shell and tube latent heat thermal energy storage tank in the presence of different nano-enhanced PCMs

Thermal energy storage is crucial for the sustainability of an energy supply system. One of the best thermal energy storage systems is latent heat thermal energy storage tanks. In the present study, a shell and tube heat storage tank is simulated based on computational fluid dynamics. The tank consists of 18 hot and cold tubes and the space between them is filled with paraffin as a phase change material (PCM). The effects of adding SWCNT and GNP nanoparticles are evaluated on the PCM in different heat fluxes. The simulation is implemented by developing the C++ code in OpenFOAM software, and the solution is performed with the PIMPLE algorithm and finite volume method. Results reveal that the melting volume ratio of the PCMs is independent of the inlet heat flux, and increasing the inlet heat flux only accelerates the melting process. Adding SWCNT to the paraffin reduced the melting time by 43% and stored 147% more latent heat energy in comparison to pure paraffin.

Investigation of Mechanical and Thermal Performance of Concrete with Scallop Shells as Partial Cement Replacement: Alternative Binder and Life Cycle Assessment

The adverse environmental impacts of building materials can be achieved by reducing the amount of cement in cementitious composites, specifically when incorporating wastes as partial replacement for Portland cement. In this work, we substitute cement with shell by-products while keeping useful specific properties. Scallop shells are good candidates to replace part of the Portland cement as they contain calcium and are available in abundance. We present an experimental and numerical study on the mechanics, hygrothermal behavior, and life cycle analysis of scallop shell concrete. In the fresh state, the replacement of cement by up to 10 wt.% of scallop shells does not significantly affect mortar properties. The results indicate that including 10% shells represents a decrease of up to 40% in the environmental impact, depending on the category of impact considered. Furthermore, the addition of Scallop shells makes the material more porous, leading to the facilitation of moisture transfer.

Investigation of high temperature thermal insulation performance of fiber-reinforced silica aerogel composites

Silica aerogel has been recognized as a promising material for thermal insulation applications in buildings, cryoengineering, and aerospace due to its ultralow thermal conductivity (0.014–0.020 W/(m·K)) and density (0.01–0.1 g/cm3). However, pure silica aerogel shows a high transmittance at the wavelength range of 2–8 μm, resulting in an ultrahigh radiative thermal conductivity at high temperature (> 600 K). To block thermal radiation at high temperature and to increase the mechanical performance of silica aerogel, ceramic fibers (e.g., SiO2, and SiC) with a diameter comparable to the wavelength of incident thermal radiation are usually introduced into the pure silica aerogel. Here, we developed a theoretical model to investigate the thermal conductivity of fiber-reinforced aerogel composites at high temperature, which considers the inclination angle, diameter and mass fraction of the doped fibers. Our modelling results show that aligning the doped fibers in the direction perpendicular to the incident radiation is the most effective way to reduce the radiative thermal conductivity. The optimal fiber diameter decreases from ∼ 5.0 μm to ∼ 2.5 μm when the temperature increases from 600 K to 1400 K. Owing to the trade-off relationship between the conductive and radiative thermal conductivities, there exists an optimal mass fraction of doped fibers to achieve the minimized thermal conductivity. The work helps to understand heat transfer in aerogel composites and to guide the geometric design of thermal insulation materials for high-temperature applications.

Investigation of thermal performance and life-cycle assessment of a 3D printed building

Due to the growing population and unsustainable development, global energy consumption is rising, contributing to more environmental issues such as global warming. On the other hand, this ever-increasing population leads to an increase in demand for housing. Nevertheless, the conventional construction industry is low-speed and energy-consuming. The emerging technology of 3D printing has been used in this industry recently, and it has brought some benefits such as less material waste, higher construction speed, and building complex geometries. The purpose of this study is to investigate the energy performance of a 3D printed building that has used two types of cement, namely reactive magnesium oxide cement (RMC) and calcium sulfoaluminate (CSA) cement, in their concrete along with thermal insulation and phase change materials (PCMs). Afterward, a life cycle assessment is performed on these two types of concrete, and the result is compared with the conventional Portland concrete. The results show that the use of RMC is very effective in terms of energy savings and waste than CSA cement. Also, according to the life cycle evaluation, it is concluded that the construction of a building using RMC and CSA cement instead of Portland cement reduces carbon dioxide emissions by 400 times.

Numerical investigation of thermal performance of a combined heat sink with various microchannel shapes

The influence of channel shape on a combined heat sink of three different channel forms is investigated numerically in this work. The channel shapes considered were the trapezoidal, inverse trapezoidal and hexagonal microchannel shapes. The goal of this study was to compare and identify the combined microchannel shape that performed best under conditions of high uniform heat flux. The thermal performance of the combined heat sink was assessed using two criteria: lowest maximum temperature and lowest temperature elevation on the bottom of the combined heat sink where heat is applied. The uniform heat flux applied to the bottom of the combined heat sink was elevated from 100 𝑊/𝑐𝑚2 to1000 𝑊/𝑐𝑚2. For the maximum heat flux of 1000 𝑊/𝑐𝑚2and lowest pressure drop of 10kPa considered, in terms of temperature elevation on the bottom of the heat sink where heat is applied, the trapezoidal combined microchannel heat sink outperformed other channel shapes. When the minimized overall maximum temperature is considered, the hexagonal combined microchannel heat sink was the best combined heat sink.

Experimental investigation of thermal comfort performance of a radiant wall and ceiling panel system

The number of radiant heating-cooling systems in building applications is increasing it is because of low energy consumption, low operating temperature and high values they provide in terms of working compatibility with renewable energy sources. In this study, ground source heat pump integrated radiant panels installed on the wall and suspended ceiling of the office room in Yıldız Technical University Science and Technology Application and Research Centre were experimentally examined in terms of thermal comfort according to the relevant standards. Vertical air temperature differences and mean radiant temperatures were investigated. The mean air temperature differences at 0.1 m and 1.7 m were found to be 3,9 oC 2.9 oC 3.5 oC, 3.1 oC and 3.4 oC on average for the five different stands, respectively. PMV and PPD values were found to be 0.78 and 18.9% for February 12 (Case 1), 0.36 and 8.4% for February 13 (Case 2), respectively. In the experiment carried out under the conditions of Case 2, while the comfort conditions were provided in almost all of the day, the desired comfort conditions could not be achieved in Case 1 after 11 am.

Numerical and experimental investigation of heavy-duty EGR cooler thermal performance

Exhaust Gas Recirculation (EGR) cooler is a crucial automotive heat exchanger that decreases the temperature of the recirculated exhaust gas fed to engine cylinders to reduce the NOx emissions. The high temperature gradients in the heat exchanger and its varying hot and cold operation makes it necessary to accurately determine the temperature distribution of the EGR cooler to evaluate vulnerability to various thermal failures. This study demonstrates a thermal assessment of EGR cooler using detailed CFD simulation methods developed and validated with comprehensive experimental design and measurements. The experimental data including detailed boiling detection is collected on a gas burner test bench for eight different working conditions of the EGR cooler with conditioned cooling with an average of 3% repeatability error. The detailed and highly resolved CFD model which includes the heat transfer enhancing features of the heat exchanger is validated at these working conditions and resulted in an average of 1% difference in temperature and maximum 5% difference in pressure drop values. The developed detailed CFD methodology reduces the amount of EGR performance and boiling tests significantly and enables assessment of the EGR cooler at engine assembly conditions which affects the hot gas distribution and resulting temperature gradients. Furthermore, the CFD methodology and its correlation with the experiment proved that a coupled CFD methodology can be used instead of the development tests for analytical sign-off purposes as long as the detailed heat exchanger design is included in the CFD model. • A detailed CFD model with all geometrical features was built as essential alternative to EGR cooler tests. • The detailed CFD model does not require any additional numerical approach for pressure drop or heat transfer. • Acoustic Emission sensor was utilized for the more precise assessment of boiling level. • CFD predictions were validated with experimental data by using acoustic emission sensor measurements. • Predicted temperature and pressure change were validated by experimental results with high accuracy.

Thermal performance investigation of position function circuit board used in automotive exterior rear lighting

In this research, both numerically and experimentally, the thermal efficiency of a Printed Circuit Board (PCB) with two Light Emitting Diode (LED) chips was examined. The two LED lighting systems, which are single-cell LEDs, including PCB and copper plates, were manufactured, and tested under laboratory conditions to achieve this goal. The three-dimensional Computational Fluid Dynamics (CFD) model with natural convection effects prepared using the FloEFD software package to predict PCB surface temperature distributions. The goal was to perform comprehensive circuit board simulation and validate the numerical model built in this study using the experimental data during the studies. From the results, we can easily claim that higher temperature gradients are calculated and predicted near the LED chip because of heat generation. Data paths have played an essential role in the LED circuit board's temperature distribution. High-temperature variations are observed at short distances around the LED when the experimental and simulation results are compared. Temperature changes are minimized as they travel away from the LED chip. It is found that the error rate is below 5 percent overall between the experimental and simulation results. The numerical results were in proper alignment with numerical data obtained from the three-dimensional (3D) CFD model. Given thermal efficiency and using such models, this model can design and analyze Automotive Lighting Systems.

Investigation of Thermal Performance of 3D Printing Integrated Phase Change Materials in Building Structure

This paper aims to create an experimental building structure using 3D printing technology to reduce the interior temperature. Because of its sensitivity to high temperatures, particularly its low heat deflection temperature, and susceptibility to deterioration over time, the Polylactic acid (PLA) material has been preferred to print the layer. In this model, an effort was made to decrease the building's overall cooling load, which may result in a higher amount of ordinary power being required. For the study, a new model of the intended wall was developed and tested. The studies were carried out in two modes: the first without any PCM in the wall, and the second with an additional new model of PCM 3D-printing layer within the wall. The test results demonstrated that the PCM 3D-printing layer inside the wall building lowered the temperature of the outer wall surface, the inner wall surface, and subsequently the building temperature of the indoor area to a huge amount. The achievements are in the percentage peak temperature reduction of 9.8% for the wall's outer surface, 22.6% of the inner wall surface, and 13.4% of the room temperature. With the help of the PCM 3D-printing layer, the peak indoor temperature was decreased by 5℃.

Thermal performance investigation of supercritical methane in minichannel heat sink on flight vehicle actuator under geometry effect of cross section

With rapid development of high-power electromechanical actuator, the conventional cooling technologies become hard to meet the requirement of heat dissipation, the minichannel heat sink using supercritical cryogenic propellant methane is proposed for high power electromechanical actuator’s thermal control in flight vehicles, withstanding the extreme ambient of flight vehicles like gravity acceleration and replacing the air-cooled method under the rarefied atmosphere. However, the optimal working patterns especially considering both the factors of geometric and operation conditions need to be investigated thoroughly due to the complicated heat transfer mechanism of supercritical methane in minichannel of heat sink. Therefore, in the present article, based on the actual configuration of IGBT power module in flight vehicle actuator, the numerical models of minichannel heat sink under various cross sections with the same aspect ratio and hydraulic diameter, namely triangle, trapezoid, and rectangle, are established with the overall region of 50 mm × 100mm. The hydraulic diameter of fluid region in single channel is 1.5 mm, the size of solid region for computational domain is 3 mm × 5 mm (width × height) and the material is silicon. The overall channel number is 17, the inlet Reynolds number covers from 500 to 1500 and the operation pressure ranges 5 MPa to 7 MPa, while the ratio of mass flux to heat flux keeps constant. On this basis, the thermal performance, in especial the local heat transfer features of supercritical methane in minichannel heat sinks under three different geometric configurations of cross section is researched.

Experimental and numerical investigation of thermal performances of R290 and R1234yf refrigerants in a cold room

In today’s world, most of the currently used refrigerants in refrigeration systems have an important influence on global warming. This study presents the experimental and numerical consumption of thermal and energy performances comparison of new generation low GWP R290 and R1234yf refrigerants for a cold room. Evaporator temperatures of −9 °C, −6 °C, −3 °C, and condenser temperatures of 25 °C, 30 °C, 35 °C were utilized as the operational parameters. Results revealed that the highest COP values in the system for R290 and R1234yf were 3.99 and 3.41, respectively. An average 11.1% increase in the cooling capacity was determined with R290 compared to the R1234yf refrigerant. In the second part of the study, evaporator surface temperature and air velocity distributions in the cold room for R290 and R1234yf refrigerants occurring until the cold room temperature reached from the ambient temperature to 0 °C were numerically shown using Ansys Fluent 18.1. Numerical analysis using experimental data indicated that the evaporator surface had a lower temperature with R290 refrigerant than R1234yf. Results of the study highlighted the usability of R290 refrigerant instead of R1234yf in refrigeration systems in terms of thermodynamic performance.

Investigation on Silver Modification of Different Shaped Filler on the Heat Conduction Performance Improvement for Silicone Elastomer

The continuous miniaturization and multi-function of electronic devices have put forward high requirements for the effective removal of the heat generated in the system. Developing thermally conductive polymer composite-based thermal interface materials is becoming the research hotspot. In addition to the usually concerned intrinsic thermal conductivity of the filler itself, surface modification is one of the important ways to form an effective heat conduction pathway and improve the overall thermal conductivity of materials. In this work, we used silicon rubber as the polymer matrix and achieved the thermal conductivity increment via various fillers with different shapes. The adopted fillers are spherical aluminum oxide (Al2O3), linear carbon fiber and boron nitride sheets, which can be considered as zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) fillers respectively. We also prepared the silver-modified fillers and investigated the influence on the formation of heat conduction pathways and interfacial thermal resistance of different shaped fillers. An obvious increment in thermal conductivity of the composite with silver-modified fillers was observed compared to the composite with pristine fillers. Furthermore, through the practical thermal management performance investigation, we found the thermal conductivity increment did improve the actual heat transfer performance of composite elastomers functioning as thermal interface materials

Thermal performance investigation of Therminol55/MWCNT+CuO nanofluid flow in a heat exchanger from an exergy and entropy approach

Nanofluids have been extensively studied in recent decades and have been regarded as “next-generation heat transfer fluids” due to their superior properties. However, dispersion stability and application at higher temperatures are among the challenges that must be overcome. In this work, a new class of stable hybrid nanofluid based on multi-walled carbon nanotube (MWCNT) + cupric oxide (CuO) nanocomposite is produced with Therminol55 (TH55) as the base fluid. Nanofluids' thermophysical characteristics are investigated at varying concentrations (0.005–0.08 wt%), and they are subsequently employed as the heat transfer medium in a tube heat exchanger (HEX) for the turbulent flow regime. Thermal conductivity was significantly increased by 128.4% at the maximum nanocomposite concentration of 0.08 wt%. Despite this, nanocomposites enhanced the nanofluids' viscosity, which climbed gradually with concentration to a maximum enhancement of around 25% at 0.08 wt%. The heat transfer performance of the formulated nanofluids was numerically assessed and found to be good; for example, when compared to pure TH55, the heat transfer coefficient improved by up to 128%. The highest increase in Nu was 38.4%, while the maximum increase in pumping power was determined to be 103.88%. Furthermore, the maximum exergy efficiency was 47.84% at a 0.08 wt% concentration and a Reynolds number (Re) of 12500, which is somewhat higher than the 40.96% attained with pure TH55. The highest thermal performance factor was 1.31 for 0.08 wt %, exceeding the maximum thermal performance factors of 1.17, 1.11, 1.08, and 1.03 for 0.04, 0.02, 0.01, and 0.005 wt %, respectively. Consequently, a nanofluid made of MWCNT + CuO/TH55 might be a promising candidate for usage as a heat transfer fluid.