Author: Dr.mohammed Ali Mahmood Hussien

Abstract: The compact sizing and lightweight characteristics of thermoelectric devices have garnered significant attention, leading to their widespread use across varied fields. This study experimentally investigates the application of thermoelectric refrigeration in air conditioning, employing a moderately designed system. A unique, multi-U shaped heat sink system was developed, wherein thermoelectric devices were affixed onto rectangular tubes befitting their dimensions, thereby facilitating water as an auxiliary medium for energy transfer. This design enabled the transformation of cold water from the system’s cold side to the indoor unit’s water-air heat exchanger, while hot water was directed to the outdoor evaporative cooling tank. A Peltier-type thermoelectric device was harnessed for this experiment. The devised setup was subjected to multiple tests to evaluate its thermal performance under the climate conditions of Najaf. Preliminary results validated the effectiveness of the water cooling methodology, with the water temperature observed to decrease to 14℃. Consequently, the room air was cooled by the water-air heat exchanger, reaching temperatures between 20℃ and 24℃. This study underscores the potential of integrating thermoelectric devices with innovative heat sink designs for efficient room air cooling. Keywords: Peltier devices, refrigeration, U-shaped, heatsink, multi-stage DOI: https://doi.org/10.18280/ijht.410421

Abstract It has been proven that mechanical elements display size-dependent behavior in structural and thermal fields at microscales. It has also been found that thermoelastic damping (TED) is one of the dominant reasons in confining the quality factor (Q-factor) of such elements. This paper aims to develop a novel formulation for evaluating TED in microbeams by accounting for the size effect on the mechanical and thermal areas via the nonclassical theory of modified strain gradient (MSG) and the non-Fourier heat conduction model of Moore-Gibson-Thompson (MGT). In the first step, the heat equation for beams is derived within the framework of MGT model. Through this equation, the function of temperature fluctuation can be obtained. Then, the constitutive relations of the beam according to MSG theory (MSGT) are extracted. By using the temperature distribution and nonclassical constitutive relations obtained, the maximum amounts of potential and wasted thermal energies during one cycle of beam vibration are calculated. Finally, by placing the value of these energies in the existing relationship for computing the value of TED, an explicit expression for TED is presented. With the aim of clarifying the sensitivity of TED value to the characteristic parameters of MSGT and MGT model, a variety of numerical data are provided. According to the obtained outcomes, the inclusion of size effect in the structural and thermal equations can cause a remarkable difference compared to the classical model. The dependency of TED on some factors like beam thickness and aspect ratio, vibration mode number and material of the beam is also investigated numerically. https://link.springer.com/article/10.1007/s11043-023-09632-w

DOI: https://doi.org/10.15587/1729-4061.2022.263587 Keywords: numerical simulation, multiphase flow, rippled channel, CFD, sinusoidal duct Abstract With the development of simulation technology and the ability to obtain accurate numerical results, as well as with the development of information technology, software that can solve numerical problems has become necessary to see physical changes that cannot be seen by the human eye. Multiphase stream field is settled utilizing the volume of fluid (VOF) method, and the flow equations are assessed and addressed mathematically by the notable limited volume approach. As a multiphase framework without mass exchange, air/water stream is considered. For practically all cases considered in this review, the heat transfer coefficient is higher. In any case, a critical punishment pressure drop was observed especially for high mass courses through undulating channels. A wavy channel with a variable wave height was simulated to see the variables of the flow process for multi-phase materials with a square cross-section, where different speeds were used for the inlet duct for air, water and steam. The results proved that the increase in the height of the channel wall wave works to obstruct the flow and thus increases the time required for the fluid to reach the exit area. The value of time required for steam and air to reach the exit area at the channel wall wave height of 25 mm and the flow velocity of 0.1 m/s was 6.01 s, which is the longest time it took for the fluid to reach the exit area compared to other cases. The pressure value reflects the amount of turbulence in the flow process, and it’s crucial for thermal improvements based on flow turbulence. The entrance flow velocity is 0.1 m/s and the wall wave height is 25 mm at a time of 2 s, when the pressure reaches 873.7 Pa.

Abstract In the present investigation, coumarin derivative 4-((4-amino-5-thio-1,2,4-triazol-3-yl)methyl)coumarin (ATTC) have synthesized as novel ecofriendly corrosion inhibitor and evaluated the corrosive inhibitive properties on mild steel in 1 M hydrochloric acid solution through weight loss, electrochemical impedance spectroscopy (EIS) and Potentiodynamic (PD) polarization techniques. The corrosion analysis results show that ATTC inhibitive corrosion by mechanism of adsorption and display inhibition performance around 96% at the concentration of 0.5 mM. From the morphology analysis by means of scanning electron microscopy (SEM) techniques of the protective film on mild steel surface, it was confirmed that adsorption of ATTC molecules appears on the mild steel surface through chemi-sorption, that additional retard the corrosion rate. The stability of ATTC molecule was investigated in the gaseous state and it has thio and mercapto forms. Based on of density functions theory (DFT) results, thio possess higher stability state compared with mercapto. From the thermodynamic parameters, it was found that the conversion of thio form to mercapto form is spontaneous and endothermic. Keywords: gravimetric coumarin mechanism ATTC SEM temperature inhibitor isotherm https://doi.org/10.1080/23311916.2020.1826077

ABSTRACT: The experimental and theoretical studies are evaluate the thermal performance of three parabolic trough collectors with manual tracking system connected in parallel. The collectors are designed and manufactured utilizing the existing Iraqi technologies and available local materials. The sun tracking system was assembled using mechanical components that were procured from the Iraqi market. The receiver plate is made from galvanized material and is covered with aluminum foil of thickness 2 mm. The absorber tube is fabricated from stainless steel material, which is coated with selective black paint that can absorb solar radiation with internal and external diameters of 30 mm and 33mm, respectively. Numerical analysis was used in the simulation to determine the performance of the thermal model in order to study the influence of convective heat transfer resulting from the effect of fluid flow, falling and reflected solar radiation on the absorber and focusing on the receiving tube. A computer program was used to calculate the performance equation of the collector. The experimental results revealed that the data of tested collector is lower than that of a typical collector. However, average collection efficiency of this collector is about 43% which is fairly acceptable within the designs of parabolic trough collectors. KEYWORDS: heat transfer, collector, parabolic, solar radiation, collector efficiency, tracking system

The thermal energy exchange by means of free convection between two sources of heat located in an enclosure with a rectangular shape on the bottom side with sawtooth periodic (repetition) upper wall has been studied numerically. The length of the two isothermal sources was about 20% of the total bottom surface length with a constant power. The impacts of the sawtooth waves and the separation of both heat sources in the heat exchange were analyzed during the numerical simulation. The working fluid was air with Prandtl number (0.72) and Rayleigh numbers that varied from 103 to 105. The finite volume method with SIMPLE algorithm was used to solve the governing partial differential equations (continuity, Navier Stokes and energy equations) and to analyze the flow and temperature fields inside the enclosure. The simulated data revealed that an increase in the distance between two heat sources results in a raise of the mean Nusselt Number for all the ranges of Rayleigh Numbers studied, while an increase in the sawtooth periodic results in a diminishing of the mean Nusselt Number for all the Rayleigh Numbers analyzed. Keywords: natural convection, rectangular enclosure, discrete heat sources, finite volume method https://doi.org/10.18280/ijht.370424

A new ecofriendly coumarin derivative, namely 4-((4-amino-1H-1,2,4-triazole-5(4H)-thione3-yl)methyl)coumarin (ATMC), was synthesized and the chemical structure was elucidated using Fourier Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR) and elemental analysis (CHN). ATMC was evaluated as a corrosion inhibitor and the concentrations were 0.1 mM to 0.5 mM for mild steel in 1 M hydrochloric acid in the temperature range of 303–333 K using gravimetric and surface analysis by means of scanning electron microscopy (SEM) techniques. The gravimetrical results show that ATMC inhibited the corrosion of mild steel in a strong acid solution with superior performance. It was found that the corrosion inhibition performance depends on the concentration of the studied inhibitor and the solution temperature. The inhibition efficiency increased with an increase in the concentration of the inhibitor and reached 96.5% at a concentration of 0.5 M and 303 K. Experimental and adsorption results are in good agreement. Keywords: gravimetric, coumarin, mechanism, ATMC, SEM, temperature, inhibitor, isotherm. Received: October 11, 2019. Published: December 20, 2019