Investigation Of Thermal Performance Research Articles

Thermal performance investigation of membrane-assisted radiant cooling system for localised outdoor cooling hub

Heat waves pose increasing threats to human well-being, especially in urban areas, and staying safe beyond comfort during heat waves is a crucial issue. Localised cooling hubs may provide thermal stress relief in the outdoor environment. For outdoor cooling applications, conventional air conditioning systems are not effective but energy-intensive, and the membrane-assisted radiant cooling system can be a potential alternative, which directly treats the radiant loads while minimising the convective heat loss to the ambient. In the present study, a numerical model is developed to analyse the heat transfer behavior of membrane-assisted radiant cooling for outdoor applications, considering the effect of solar and long-wave radiation and wind parameters. As the transmissivity of the membrane material plays a crucial role in reducing the amount of solar heat, the performances of three types of membranes, i.e., non-selective, mid-infrared selective, and sky-window selective, were compared and analysed at different times on a typical summer day in Hong Kong. The results indicate that the sky-window selective membrane, which allows only transmission of infrared in the 8–15 µm wavelength range, saves energy up to 44 % and 47% compared with mid-infrared selective and non-selective membranes, respectively. In the outdoor application, the equivalent convective heat transfer coefficient of the cooling panel can be reduced in the range of 2.2 W/m2K to 2.6 W/m2K. It is observed that, when the panel is not exposed to direct solar radiation, there is no advantage in using the mid-infrared selective membrane over the non-selective membrane. However, under direct solar radiation, a non-selective membrane-assisted cooling panel demonstrates poor performance, absorbing solar heat flux 2.27 times higher compared to MIR-selective membrane-assisted panel.

Investigation of annual thermal performance and techno-economical analyses of direct absorption solar collector by using nanofluids

In this study, the annual thermal performance and techno-economic analyses of a direct absorption solar collector (DASC) using nanofluids were investigated. According to the results of numerical analysis the difference between the specific heat gains was 126.5 W/m2, where difference for annual energy saving or enhancement for solar energy converting to useful was 224 kW/m2a. To sum up utilization of MWCNTs (0.05%) based nanofluids as heat transfer fluids in PTC supported the 13,5% of thermal efficiency in comparison of water. Furthermore, when nanofluids are used as a heat carrier in a solar collector, the cost of 1 kWh of thermal energy is 0.029 $/kWh, and when water is used, it is 0.034 $/kWh. The payback period of the initial investment amount of the nanofluid solar collector is 3.96 years, where the interest rate of the bank is calculated at 23%, and the payback period of the initial investment amount of the water solar collector is 3.99 years.

A critique on thermal performance and energy usage in  government office buildings in Trincomalee and the need for  sustainable retrofitting - a typological analysis

Buildings use a large amount of energy during their lifetime and are identified as the main contributors to the increasing energy demand. A proper understanding of the Thermal Performance (TP) parameters can result in a climate-responsive design and reduce indoor overheating. In the construction field, sustainable retrofitting is identified as another important field of research, where new technologies can be introduced to the existing built environment and enhance their efficiency. This paper mainly focuses on how different building typologies of the existing public office buildings are contributing to inefficient TP and energy usage, and how sustainable retrofitting can help to improve their energy performances. 27 existing public office buildings in urban and suburban areas in Trincomalee, were selected for the typology analysis, and with special attention to plan form, one case study under spread-out plan form was selected. The TP of the building was investigated through an on-site Thermal Performance Investigation and Computational Simulation (CS) process. It is proposed that the energy required for cooling a building can be reduced if efficient sustainable retrofitting design strategies can be used to improve the TP. The outcome is beneficial in the formulation of design guidelines for new and existing buildings.

Using a spiral fin to replace a wavy fin in the condenser of an air conditioner

An experimental and numerical investigation of an L-footed spiral fin's thermal performance for replacement of wavy fins used in condensers is presented. This condenser is used for air conditioners with a capacity of 2.64 kW–3.52 kW (9000–12,000 BTU/hr). Eight spiral fins with various fin pitches and fin diameters are studied. Each spiral fin is designed to have an area that is equal to that of a baseline wavy fin. The investigation found that the heat transfer coefficient and pressure drop obtained with the wavy fin are greater than those obtained with a spiral fin. Moreover, the spiral fin gives a performance index or “goodness factor” that is about 0.2–11.9 % greater than that of a wavy fin.

Thermal performance investigation of transient natural convective nanofluid flow in a square cavity with inclined periodic magnetic field

The goal of this paper is to analyze the thermal exhibition of transient free convective nanofluid flow in a square cavity with inclined periodic magnetic field using one-component thermally equilibrium homogeneous model. Distinct thermal settings (constant, parabolic, and sinusoidal) for the left heated wall are deliberated when the right wall of the cavity is cold and the horizontal walls are insulated. For numerical simulations, eight types of nanofluids consisting Cu, Co, Zn, and Al2O3 nanoparticles along with H2O and kerosene as base fluids have been employed. During numerical computation, the impacts of different factors (Hartmann number, Rayleigh number, nanoparticles volume fraction, period, and inclination angle) on the fluid flow and heat transfer are examined. The numerical results show that cobalt-kerosene nanofluid distributes the maximum heat transfer rate compared to other 7 types of nanofluids. The results also indicate that sinusoidal thermal scenery at the left heated wall delivers the uppermost average Nusselt number compared to the other types of thermal approaches. The optimum thermal performance is achieved at magnetic field's inclination angle δ=π3 and period number λ = 1 for the case of sinusoidal scenery.

Investigation of Thermal Performance and Chemical Stability of Metal Infused Salt Hydrate Phase Change Material for Thermal Energy Storage

Thermal energy storage (TES) is a technique that is considered a very desirable technology with a high potential to overcome the gap between demand and supply. Phase change materials (PCMs) are considered to be a highly favourable thermal energy storage materials. Besides that, PCM has certain drawbacks, such as lower thermal conductivity and higher light transmission; owing to this, the heat transfer rate and energy storage density are less. The performance of the PCMs can be improved by adding highly conductive nanoparticles. In this study, various weight percentages (0.1% - 5.0%) of Copper (II) oxide nanoparticles are dispersed with salt hydrate phase change materials with melting temperature 50 °C and investigated the thermal and chemical properties using Thermogravimetric analyzer, thermal conductivity analyzer, and Fourier transform infrared spectrum. Results shows that the prepared nanocomposites have chemically and thermally stable up to 467 °C. The thermal conductivity was increased by 62.64%, at 3.0 wt% Copper (II) oxide with salt hydrate PCM. The developed nanocomposites have better thermophysical properties than pure salt hydrate, which may be applied for TES applications like solar water heating, photovoltaic thermal systems, and electronic cooling systems.

Numerical Investigation of Thermal Performance of a Trombe Wall of a New Design with Glazing for Cold Climatic Conditions

Numerical Investigation of Thermal Performance of a Trombe Wall of a New Design with Glazing for Cold Climatic Conditions

Investigation of thermal performance and charging/discharging characteristics of finned coaxial evacuated tube collector filled with phase change material

Present numerical model simulates the charging (melting), discharging (solidification) and heat transfer phenomenon of a phase change material (PCM) filled in the finned type coaxial evacuated tube solar collector. Thermal performance of the proposed evacuated tube has been predicted with Paraffin wax as the PCM. Solar radiation data measured on March 13, 2022 at Srinagar (Garhwal), Uttarakhand, India (latitude 30.2247° N and longitude 78.7986° E) has been applied as heat flux (450–965 W/m2) on wall of the evacuated tube. Heat transfer fluid (HTF) at the varying inlet temperature flows through the tube and absorbs heat, consequently its temperature increases. Results predict that during the charging process, 90 % of the PCM was melted by 11:30 AM for 0.0063 kg/s mass flow of the HTF having inlet temperature of 303 K. For the same operating conditions, maximum temperature rise achieved by HTF is ≈ 30 K at 14:00 PM. In the absence of solar radiation, discharging process (during 18:00 to 23:00 PM) of the PCM occurs that liberates the heat which is carried by HTF. Hence, heating of the HTF is continued during this period, however, outlet temperature continuously drops as night progresses. For the considered inlet temperature of the HTF = 303 K, maximum and minimum outlet temperatures were found to be 316.87 K and 307.55 K respectively. Furthermore, mass flow rate of the HTF significantly affects the melting rate of the PCM. At the mass flow rate of 0.0063 kg/s, 99.36 % of the PCM was melted by 12:30 PM. Whereas, till 14:00 PM, only 91.68 % and 70.54 % of the PCM melts when mass flow rate increases to 0.016 kg/s and 0.026 kg/s respectively. Findings also confirm that by increasing the HTF inlet temperature from 288 K to 308 K, melting period of the PCM is reduced by 40 %. Hence, it may be concluded that varying intensity of the solar radiation has significant effect on the performance of the evacuated solar tube. Moreover, the performance also depends on various other operating parameters.

Thermal Modeling and Performance Investigation of Proton Exchange Membrane (PEM) Fuel Cell

Abstract This research paper presents analysis of heat generation problem in Proton Exchange Membrane (PEM) fuel cell using COMSOL Multiphysics software. PEM fuel cells are widely recognized for their high electrical power output and environmental sustainability. However, in a PEM fuel cell around 50 to 60 % of energy generated from chemical reactions is dissipated as heat energy. To address this issue PEM fuel cell stack model is designed and thermal modeling is carried out to evaluate its performance. Based on thermal modeling of surface temperature distribution of cell it is found that the cathode side of PEM fuel cell is warmer and generates more heat as compared to other parts due to the exothermic reactions,slow reaction rate,joule heating effect and material properties.Moreover, it is also found that there is uniform temperature distribution across the cell due to rapid heat conduction from cathode side to the surface of the cell.The results of this study show that due to more heat generation on cathode side temperature will tend to increase.This increasing temperature enhancesthe average cell current density but as the average cell current density increases it reduces the average cell voltage thus declining the efficiency of PEM fuel cell. Hence ,there should be an optimal temperature range between 60 to 80°C for the better performance of a PEM fuel cell. Findings of this study can serve as a valuable resource for understanding heat generation process in PEM fuel cell for the development of efficient and reliable fuel cell technology in future.

Thermal performance investigation of porous fins with convection and radiation under the influence of magnetic field using optimal homotopy asymptotic method

A study on enhancement of heat transfer in thermal systems by convective-radiative porous fin with temperature-invariant thermal conductivity is presented in this paper using optimal homotopy asymptotic method. The efficacy of the method is displayed through the verification of the results with the previous studies. Also, significance of various parameters of the nonlinear model on the heat transfer enhancement of thermal systems using the solutions presented by the method are discussed. The graphical representation of the thermal behaviour of the extended surfaces is presented for pictorial discussion. The results illustrate that the augmentations of the conductive-radiative, conductive-convective, porosity and magnetic field cause the extended surface temperature to reduce as a result of increased rate of heat flow via the passive device. The graphical illustrations show that the efficiency and effectiveness of the fin is high at low values of the radiative-conductive, convective-conductive, porosity and magnetic field parameters. This study will assist in proper thermal analysis of fins for effective thermal managements of engineering systems.

Thermal analysis and performance investigations of shell and tube heat exchanger using numerical simulations

The steam condenser is a crucial component in power plants, playing a vital role in influencing the overall performance of steam power plants. This paper delves into a detailed assessment of the thermal aspects and evaluation of steam surface condensers. To conduct this rigorous evaluation, we meticulously crafted a three-dimensional (3D) model of a multi-tube single-pass counter-flow heat exchanger using ANSYS Design-Modeller. Within this model, a multiphase mixture model was harnessed to replicate the condensation process that takes place within the condenser. After the model’s development, a series of computational fluid dynamics (CFD) simulations were expertly executed utilizing ANSYS Fluent Workbench. The simulations encompassed diverse cooling water flow rates and steam inlet velocities. Notably, two sets of CFD simulations were carried out: the initial set featured a velocity inlet in the condenser, while the second set involved CFD simulations with a pressure steam inlet. The findings derived from these simulations unveiled a noteworthy correlation between the condensation rate within the shell and both the rate of circulating water flow and the operational pressure of the condenser. Additionally, it was discerned that the condensation rate could be further influenced by the specific geometry of the condenser. In sum, this study concludes that optimizing the geometrical configuration and baffle arrangements holds promise for increasing the condensation rate and overall performance of steam condensers employed within steam power plants.

Heat transfer and thermal performance investigation on a visualized latent heat storage system in pilot-scale: Scalable medium-temperature thermal energy storage system

Large-capacity medium-temperature (100–300 °C) and high-temperature (>300 °C) latent heat storage (LHS) systems can enhance the reliability and performance of solar thermal utilization systems due to their characteristics of balancing the gap between energy supply and demand. In this study, a pilot-scale LHS system was developed and investigated, incorporating a mass of 270 kg of phase change material (PCM), specifically a commercial nitrate mixture. Moreover, the thermal energy storage unit featured a rectangular aperture at its center, covered by a quartz visualization window to facilitate the observation of the melting and solidification behavior of the PCM. The charging process lasted 111 min, with a mean average power, accumulated energy and efficiency of 11.90 kW, 79.33 MJ, and 77.67%, while those of the discharging process were 56.5 min, 12.99 kW, 44.11 MJ, and 71.41%, respectively. Furthermore, a comparative analysis was conducted concerning heat transfer performance and mechanisms during the charging and discharging processes. The heat transfer coefficients and average thermal resistances of the LHS system during charging and discharging were 613.08 W/(m2·K), 295.28 W/(m2·K), and 0.001984 (m2·K)/W, 0.005285 (m2·K)/W, respectively. The average thermal resistance observed during the charging process was notably lower than that observed during the discharging process, attributable to the variance in the predominant heat transfer mechanism. For a substantial portion of the charging process duration, heat transfer was dominantly governed by natural convection, whereas throughout a significant duration of the discharging process, heat transfer was primarily driven by thermal conduction.

Naturally ventilated folded double-skin façade (DSF) for PV integration - Geometry evaluation via thermal performance investigation

Studying the thermal performance of Double Skin Facades (DSFs) with vertical layers has dominated the literature, however, there is still a lack of in-depth research on the performance of DSFs with atypical geometries such as folded cases which can be applied to Building Integrated Photovoltaic (BIPV) systems to improve their performance. To this end, the study evaluates the influence of the fold geometry on heat transfer, flow structure, and airflow rate in the Folded DSF cavities under a hot climate in Iran using an efficient method titled “patching”; the method integrates Soltrace3 with a 2D steady-state CFD model by ANSYS-Fluent. The results show that the fold position and its depth can alter the DSFs performance significantly; the higher the fold depth the more distortion of the flow field inside the cavity; from a practical perspective, the fold position in the upper part of the cavity is suitable for BIPVs application since it can capture 250% higher amount of solar radiation compared to a conventional vertical-layer DSF as the Base Case; the net heat gain through outer layer could improve with increase of fold depth and reach at least 33% higher than the Base Case, meanwhile, the total electricity generation potential of folded cases could be up to 169% higher than the Base Case; thus, the study proved that if the architectural design is of interest, it is highly recommended to consider folded DSFs as a design option.

Investigation of Mechanical and Thermal Performance of Nanoclay Modified Concrete for Energy Efficiency

Investigation of Mechanical and Thermal Performance of Nanoclay Modified Concrete for Energy Efficiency

Investigation of thermal conductivity and thermal performance of heat pipes by structurally designed copolymer stabilized ZnO nanofluid

The present study concentrated on estimating the thermal conductivity, stability, efficiency, and resistance of a heat pipe for heat exchangers, which were essential for many industrial applications. To achieve this, copolymer of amphiphilic poly (styrene-co-2-Acrylamido-2-methylpropane sulfonic acid) poly (STY-co-AMPS) was synthesized by free radical polymerisation technique. The dispersant were used for homogeneous solution and stabilization of ZnO nanofluids. The effect of dispersant on the thermal conductivity of nanofluids was analysed using a KD2 pro thermal property analyser. There is a significant increase in fluid conductivity had a nonlinear relationship with the volume fraction. The maximum enhancement was observed at an optimized concentration of dispersant at 1.5 vol%. Same time, the influence of dispersant agent on the thermal conductivity of nanofluids were compared with linear polyelectrolytes. Further, the experimental values were compared to the existing classical models based on the reasonable aggrement, the prepared nanofluids were employed as a working medium. The conventional screen mesh heat pipe and the temperature distribution to the thermal resistance of the heat pipe was investigated experimentally. The result shows, optimum concentration of dispersants on nanoparticles exhibits an enhanced heat efficiency as compared with the base fluids. Further, the thermal resistance and temperature distribution show decreased behaviour by increasing the particle volume fraction and dispersant concentration.

Experimental and computational investigation of thermal performance and fluid flow in two-phase closed thermosyphon

Over the last two decades, energy recovery has become increasingly important in the transition from fossil fuels to green energy. Waste heat recovery, such as the two-phase closed thermosyphon (TPCT) type of heat exchanger, is a highly efficient energy recovery technique. However, accurately predicting the thermal performance and flow patterns in TPCTs is challenging due to the complex physics of phase-change phenomena. A new predictive model is suggested that can provide improved accuracy when predicting thermal performance and flow patterns in TPCTs. An experimental study was conducted to acquire the data, and the results were compared with computational results obtained from the new proposed model. The model uses the volume of fluid (VOF) model with the Lee model for the phase change process in OpenFOAM v2106. To increase accuracy, the saturation temperature and vapor density were defined as a function based on the mass balance in the TPCT. In addition, a simulation was conducted to predict the thermal performance and flow patterns in a TPCT, during which the effects of the empirical value of the mass transfer intensity factor were investigated. The study is expected to provide insights into phase-change modeling with high accuracy and an understanding of the thermal characteristics of TPCTs.

Experimental investigation of thermal and hydraulic performance of panel plate heat exchangers

Experimental investigation of thermal and hydraulic performance of panel plate heat exchangers

Comparative thermal performance investigation of the straight tube and square tube solar water heater

Sustainable energy is a need and demand of time to overcome issues related to greenhouse emissions and climate change and the most easily available and sustainable energy is solar energy which can be used for heating, cooking, and power generation. The most common application of solar energy is water heating and such hot water is used for domestic and industrial purposes for such purposes solar water heater (SWH) is commonly used; in the present work, an attempt has been made by changing the shape of pipe of copper pipe which is commonly used in SWH from a circular cross-section to square and comparing the results of the proposed model with conventional one. The K-type thermocouples measure the temperature at various locations of the experimental setup.

An experimental and numerical approach for thermal performance investigation of solar flat plate collector.

The present work aims to investigate thermal performance of a solar flat plate collector using water and Cu-MWCNTs nanoparticle-based hybrid nanofluid both experimentally and numerically. X-ray diffraction and FESEM with EDAX mapping were performed to characterize nanoparticles. The experimental setup was developed for thermal performance of FPC varying flow rates (0.5, 1.0, 1.5 LPM), inclination angle (25°, 30°, 35°, 40°, 45°), volume concentration (0%, 0.1%, 0.2%, 0.3%, 0.4%), and intensity (400 W/m2). The 3D numerical model having similar geometry as of actual flat plate collector was modeled using Fluents 15.0. The SST turbulence model was used to capture the chaotic changes in the velocity, temperature, and pressure fields. The experimental findings revealed 79.74% improvement in instantaneous efficiency at 0.4% vol., 1.5 LPM, 45° inclination angle, and 400 W/m2 intensity. The maximum deviation between the experimental and numerically calculated outlet and inlet temperature difference (ΔT) was 3.5% using a hybrid nanofluid. When numerical data are compared, instantaneous efficiency and heat gain both deviate by 2.8% and 2.9% from experimental values. Because of the numerical simulation analysis, it is possible to observe the temperature and flow pattern in flat plate collectors using nanofluids under a set of operating conditions, which would not be possible without the simulation.

Entropy generation and improved thermal performance investigation on a hydrogen-fuelled double-channel microcombustor with Y-shaped internal fins

To enhance the hydrogen-fueled micro-combustor's thermal performance for Thermo-photovoltaic applications, we propose and test a double-channel design featuring Y-shaped internal fins. This study investigates three key parameters in the thermal performance of a micro-combustor: the inlet velocity, the inlet equivalence ratio, and the combustor wall material. Further, we develop a new method to calculate the efficiency and exergy of the micro-combustor by considering the entropy generation and exhaust gas. It is observed that increasing the inlet velocity leads to higher mean wall temperature (MWT), standard deviation of wall temperature (SDWT), and radiation heat release rate. Increasing inlet velocity also enhances the thermodynamic second-law efficiency and exergy. The peaks of MWT and SDWT are achieved when the inlet equivalence ratio approaches unity. The inlet equivalence ratio value of unity also corresponds to the maximum radiation heat rate and improved second-law efficiency and exergy. Finally, changing the combustor wall material reveals that the silicon carbide demonstrates better thermal performance by rising MWT and the uniformity of the combustor wall temperature. Moreover, alterations to the combustor wall materials do not appear to have a significant impact on the heat loss resulting from entropy generation.