Temperature is a crucial factor influencing the quality of sleep, as it directly affects thermal comfort during sleep. The present work reports the investigation of the thermal performance of high-density (HDF) and low-density (LDF) polyurethane foam mattresses impregnated with sodium-based Phase Change Materials (PCMs) and their efficacy in temperature buffering features. A controlled laboratory study comparing exposure to these mattresses was conducted by installing mattresses in an insulated wooden box and simulating body heat with incandescent light bulbs. Ten different mattress designs were tested, including variations such as the addition of PCM and perforations for maximum heat dissipation. A multichannel record system and a hygrometer were employed to constantly monitor the temperature and relative humidity, respectively. The results were both statistically significant and reliable, as confirmed by error and ANOVA tests (P < 0.0001). Among all the samples, it was found that PCM1/LDF possessed the most efficient thermal regulation capacity at a temperature difference of 6.98 °C, which is most suitable for improving sleep comfort. These results provide a way to enhance user thermal comfort by providing informative data for better mattress design.

The present numerical study focuses on investigating the effects of MHD mixed convection and Joule heating in a lid-driven Z-shaped cavity containing double rotating cylinders in a comprehensive manner. An ample range of practical applications, including nuclear reactor cooling, magnetically controlled solar collectors, metallurgical processes, and electronic device cooling, make it a captivating field of research. The current study considers a Z-shaped cavity that has a hot wall at the lower portion of the cavity and a cold wall at the top that is a moving lid, and other walls are kept adiabatic. It comprises two rotating circular cylinders that can rotate in both clockwise and counterclockwise rotation. The Galerkin finite element method-based computational process is utilized to resolve two-dimensional steady continuity, momentum, and energy equations under specified boundary conditions. Both quantitative and qualitative outcomes are assessed to predict the fluid flow and thermal behavior for a limited range of some pertinent parameters : Hartmann number (Ha = 20, 30, and 40), rotational Reynolds number (Re c = -10 and 10), heat generation coefficient (∆ = 0, 2, and 5), Grashof number (10 3 ≤ Gr ≤ 10 6), and Reynolds number (100 < Re < 700 ). Results reveal a maximum 40% and 45% reduction in the Nusselt number occurring for enhancing the magnetic effect and heat generation coefficient, respectively. Moreover, clockwise rotation of the cylinders or aiding flow facilitates over 38% elevation in the Nusselt number by improving overall flow circulation in the cavity. As well as increasing fluid Reynolds number leads to a 150% augmentation in the Nusselt number due to intensified turbulent flow. Hence, the comparative results of this meticulous numerical study, blended with novel geometrical contour, can be utilized to improve the thermal efficiency of other intricate systems.

The autoclave functions as a medical device used to sterilize hospital surgical equipment and instruments. Scarcity of electrical power and fossil fuel pollution in hospitals and rural health centers emphasizes the necessity to explore different energy resources for autoclave operation. Such situations require the implementation of Solar autoclaves as an operational alternative. This research explores how well solar-powered autoclaves operate in their capacity to conduct wet sterilization processes. The solar autoclave contains a pressure vessel with Fresnel lens and reflector and porous medium. Aluminum beads exists as low-density porous material that holds unique structural and thermal characteristics. Heat transfer performance improvements through aluminum beads derive from multiple effects which encompass fluid-solid contact mechanisms and porous matrix heat distribution ability followed by fluid-heat transfer. The steam temperature inside the vessel (porous material absorber model II) reaches its peak of 128 °C. The energy efficiency achieving its peak at ɳc 74% coincided with the mid of the day at 1 pm when solar radiation intensity was at its value of 913 W/m2 for solar autoclave (porous material absorber model II) while reached ɳs (25%) for solar autoclave (flat plate absorber model I).

The growing demand for cooling is contributing to a global energy challenge, making it essential to improve the efficiency of cooling systems to lower greenhouse gas (GHG) emissions and operational costs. This study focuses on optimizing the Absorption Refrigeration Cycle (ARC) to enhance performance and minimize energy consumption. A novel system, the Diffuser Absorption Refrigeration Cycle (D-ARC), has been developed to achieve this objective. In this system, a diffuser is positioned between the evaporator and absorber, resulting in higher pressure in the absorber compared to the evaporator. This increased absorber pressure reduces the circulation ratio and boosts efficiency. The study determines the coefficient of performance (COP), exergetic coefficient of performance (ECOP), and circulation ratio (f) for the D-ARC system at various generator temperatures. These calculations consider both traditional working pairs (NH3/H2O) and different ionic liquid working pairs, including NH3/[EMIM][BF4], NH3/[DMIM][DMP], and NH3/[EMIM][ETSO4]. A comparative analysis of D-ARC, E-ARC, and ARC reveals that the D-ARC system achieves superior COP and ECOP values. The highest COP and ECOP values are observed with the working pair NH3/[EMIM][BF4] (COP: 0.85, ECOP: 0.35), whereas the lowest values are found with the NH3/H2O pair (COP: 0.63, ECOP: 0.26).

In this study, an improved three-dimensional human thermoregulation model was developed. A stratified model of the segmented human geometry was introduced, characterizing distinct tissues and organs to activate their specific thermal responses and interactions. The main trunk geometry was modified to improve reliability and support applications such as personal cooling systems. The model accounted for heat transport via blood arteries and emphasized changes in skin thermal conductivity to simulate vasodilation and vasoconstriction mechanisms. Additionally, the thermal effects of direct solar radiation on the human body were integrated into the mathematical framework. The model was validated using documented experimental data across various hot and cold environmental conditions and compared with recent three-dimensional models. Results demonstrated that the enhanced model achieved better agreement with experimental data than existing unstratified segmented models. Improved stratification captured temperature variations across adjacent tissue layers, providing more accurate peripheral and core temperature distributions. A case study investigated strenuous military tasks performed under extreme heat, yielding significant medical insights. This advanced stratified anatomic model serves as a robust tool for predicting human thermoregulation during diverse activities, offering detailed core and skin temperature distributions. Furthermore, the modified sweepable geometry may enhance numerical methodologies for future three-dimensional studies.

This investigation explored the many-sided features of mild intensity movement and an incompressible magnetohydrodynamic (MHD) Poiseuille stream in a permeable fine cylinder, focusing on the characteristics of viscous blood. This review investigated the effects of temperature-subordinate thickness and fluctuating strain inclination on blood behavior. These discoveries offer little knowledge of advancing intensity moves and stream qualities in the blood through permeable small frameworks and are urgently needed for applications in biomedical and medical service settings. This review presents an extensive assessment of the overseeing Brinkman equation and energy equation, unraveling the complicated interaction of factors. By utilizing Galerkin’s finite element method, exploration has explored the nuanced connections between boundaries, such as suction/injection, the Darcy number, the consistency boundary, the Prandtl number, and time. Remarkably, the outcomes feature the enormous impact of these elements on the speed and temperature profiles of the blood. The volumetric stream rate was increased, the suction/injection boundary was decreased, and the Prandtl number was increased. Additionally, the Nusselt number increases when the suction/injection boundary and Prandtl number decrease. These findings coincide with the existing information.

The current study presented numerical simulation for a double pipe heat exchanger (DPHE) with a counter-flow, in order to study the effects of twisting ratio for wavy edge twisted tape and the diameter of the holes it contains. The impact factors, varying Reynolds number (6957-187837), twisted tape ratio (0.5-3) on heat transfer and pressure drop. The inner tube, carrying hot air, incorporates twisted tapes to enhance turbulence and heat transfer. The outer tube, containing cold oil, experiences the effects of the enhanced flow But The Reynolds range is investigated range, and working fluids are on the side of the inner tube and annular space is hot air cold oil . Results demonstrate significant improvements in oil outlet temperature. Nusselt number (Nu) increases with increasing Reynolds numbers and twist ratios, the maximum Nu for enhancement devices with Tr = 0.5 and 3 are 38% and 10.7% higher than for the plain tube. Increasing Reynolds number and twisted tape ratio generally lead to higher heat transfer rates but also increased pressure drop. Optimal configurations of (Tr=2 and hole diameter 30mm)gave a best thermal performance index of 1.11 and 1.24 respectively when balancing heat transfer and pressure drop. The findings provide valuable insights for designing and optimizing heat exchangers in applications demanding efficient heat transfer.

Traditional trans-critical CO 2 refrigeration cycles are energy-intensive, and their efficiency is influenced by outdoor conditions. This study presents a novel technique to enhance the efficiency of these cycles by integrating a thermoelectric sub-cooler tailored to Jordan’s climate. The trans-critical CO 2 refrigeration cycle, with a nominal refrigeration capacity of 14 kW, was modeled using Engineering Equation Solver (EES) software. A key aspect of this study is the incorporation of solar energy through a custom-designed photovoltaic (PV) system to power the refrigeration cycle, contributing to sustainable cooling technology. Key performance indicators, including refrigeration capacity, power consumption, and coefficient of performance (COP), were thoroughly investigated across varying parameters such as gas cooler pressure (8,000–13,000 kPa), evaporation temperature (-15 to 15°C), ambient temperature (28–40°C), current supply (5–15A), and the number of thermoelectric pairs (50–150). Results showed that increasing gas cooling pressure increased refrigeration capacity by approximately 79%. At a gas cooling pressure of 9,000 kPa, the thermoelectric sub-cooler increased refrigeration capacity by 55%. Increasing the evaporation temperature improved the COP by approximately 125% and reduced power consumption by 67%. At an evaporation temperature of -15°C, the thermoelectric sub-cooler improved performance by 7.5%. Lowering the ambient temperature also enhanced COP by 60% and reduced power consumption by 33%. At a 40°C ambient temperature, the sub-cooler improved COP by 7.6%. Experimental validation showed a 6% average deviation between simulation and experimental results for COP. The on-grid PV system designed with PVsyst software successfully met the cycle’s energy demands, achieving 45.3% energy savings.

In the presented research work, we have solved a new kind of problem of forced shock waves in a compressible inviscid perfect gas having dirty (dust) particles of small size in a one-dimensional unsteady adiabatic flow. The approach, which we have used, is referred to as generalized geometry approach. Here we investigated how the density of the zone, which is undisturbed, changes as a function of the position from the point of the source of explosion. In addition, we have obtained an analytically a novel solution to the problem in the form of a new rule of power of time and distance. Further, we have investigated the energy behaviour of forced shock waves and interaction within the environment containing dust particles. Also, the behaviour of the entire energy of a forced shock wave is expounded at different Mach numbers, respectively, for planar geometry, cylindrically symmetric geometry, and spherically symmetric geometry under a dusty gas medium. Furthermore, the findings show that dust particles in a gas produce a more sophisticated representation rather than the standard gas dynamics.

Regulation of the thermal performance of electrical components is a key aspect. Phase-change materials can be incorporated into a fin heat sink (FHS) to enhance thermal management by maintaining a stable temperature. Three types (square, triangular, and circular) of aluminum FHSs of different configurations are investigated numerically in this paper. Studies are conducted with and without PCMs. Paraffin wax, stearic acid, and polyethylene glycol are used as PCMs to find the best combinations for thermal cooling and to determine the impact of using PCMs in the heat sinks. The results obtained show that, by adding PCMs, temperature rise can be delayed, and polyethylene glycol performs better than other PCMs. Moreover, the square fin heat sink increases the thermal regulation period. As the height of the fins increases from 10 mm to 16 mm, thermal efficiency increases. Hence, the findings of this paper would be beneficial for effective thermal management in the electronic industry.

The chief objective of the present investigation is to study experimentally the hydraulic and thermal performance of a corrugated tube with copper foam cylindrical inserts (MFCI) containing a new types of inserts with the purpose to improve the procedure of heat transfer, which gives an elevated thermal enhancement factor (PEF) more than that of smooth tube beneath the similar operating circumstances. Also, in this paper, the study of the effect on the number of cylindrical insert was made from metal foam (10 PPI and porosity 0.9) on the Nusselt no. and Nusselt no. ratio as a double heat exchanger furnished with the suggested MFCI with various values of Reynolds numbers ranges from (1600) to (4000) via using water as the test fluid. The investigational outcomes revealed an enhancement in heat transfer as well as thermal performance of the corrugated tube with MFCI which being significantly augmented in comparison to those for smooth tube. Additionally, the average rise into the value of heat transfer is within (74%) and (90%) at the test range, relying upon the number of cylindrical inserts as well as Reynolds no., whereas the max. thermal performance is obtained to be around (2.4) for utilizing the corrugated tube having (4) cylindrical inserts at low Reynolds no. Furthermore, the outcome of the loss of pressure manifested that the corrugated tube’s mean friction factor is within 96% and 97% more than the smooth tube.

This topic has been studied using constant interior and exterior finishing materials (Thermostone, 200 mm thick (A), fired clay bricks, 240 mm thick (B), hollow concrete blocks, 200 mm thick (C), solid concrete blocks, 140 mm thick (D), and limestone, 200 mm thick (E)) due to the availability of many different types of building materials in Iraq and the lack of control over the use of the best. to demonstrate how each of these materials affects a building’s insulation to deliver the appropriate levels of comfort and achieve the greatest possible reduction in the electrical energy needed for air conditioning. A unique chamber was created for performing the actual trials on such walls in their natural environment, which was the climate of the city of Baghdad (zip code 10016,33 ºN latitude, 44 ° E longitude). And a unique room was created for performing real-world tests on those walls, either in their current state of operation or with the addition of thermal insulation (60 mm thick microfiber glass insulation materials). The values for electricity consumption are 199,138,121,101,92 kW/m2 without the insulator, but when the insulator is used, the values become 54,92,63,100,58 kw/m2 for the models Case-C1, Case-E1, Case-B1, Case-D1, and Case-A1. respectively, the percentage of the reduction in electrical energy consumed by the room’s air conditioner ranges from 25–60%, depending on the model compared to the conventional model, and the difference in savings is only 35%. The amount of savings in the electrical energy consumed by the air-conditioning unit used (to provide standard thermal conditions inside the building) will decrease when the insulator is incorporated into the structural components because the savings difference will be equal to 15% only when changing the quality of the wall used (described in the study) compared to the traditional method.

The paper focuses on the simulation and testing of a hybrid solid desiccant vapor compression air conditioning system under different hot-humid climates. The simulation is carried out by a BLUEJ programming framework. Air at the lowest achievable air temperatures from a solid desiccant cooling system is supplied to a standard vapor compression air conditioning system. The cooling capacities of the hybrid system under three modes indicating different supply air conditions to the cabin, are reported in the paper. From the performance study, it is inferred that the hybrid system provides significant energy savings compared to a standard air conditioner, especially in hot-humid ambient conditions. The solid desiccant cooling system thus establishes itself as an effective pre-cooler unit to a standard vapor compression air conditioning system.

This investigates the fluid flow, as well as the heat and mass transfer phenomena occurring within a vertical channel housing two immiscible fluids. It focuses particularly on slip effects, encompassing no slip, velocity slip, thermal slip, and multiple slips, each being applied with appropriate boundary conditions. The analysis thoroughly examines crucial characteristics such as variations in thermal conductivity and viscosity. By employing a sixth-order Runge-Kutta numerical method implemented via Mathematica, the study achieves precise solutions for complex scenarios. The extensive findings elucidate the intricate interactions among different slip mechanisms and relevant parameters, providing valuable insights for both theoretical comprehension and practical application in engineering contexts. Furthermore, this research offers significant insights into the dynamics of fluid flow, heat, and mass transfer under various slip effects. Noticeable variations in these slip effects are observed and visually represented. Engineering parameters such as Nusselt number, shear stress, and Sherwood number are meticulously calculated and analyzed using bar charts, offering insights into their impact and behavior.

The heat transfer in power-law fluids across three corrugated circular cylinders placed in triangular pitch arrangement is studied computationally in a confined channel. Continuity, momentum and energy balance equations were solved using ANSYS FLUENT (Version 18.0). The flow is assumed to be steady, incompressible, 2D and laminar. A square domain of side 300 Dh is selected after detailed domain study. An optimized grid with 98187 cells is used in the study. The convergence criteria of 10 -7 for the continuity, x-momentum and y-momentum balances and 10 -12 for energy equation were used. Constant density and non-Newtonian power-law viscosity modules were used. Diffusive term is discretized using central difference scheme. Convective terms are discretized using Second Order Upwind (SOU) scheme. Pressure-velocity coupling between continuity and momentum equations was implemented using the SIMPLE (Semi-Implicit Method for Pressure Linked Equation) scheme. Streamlines show wake development behind the cylinders, which is much dominant at large ReN and n. Isotherm contours are cramped at higher values of ReN and PrN, implying higher heat transfer. Global parameters like Cd and Nu are computed for the wide ranges of controlling dimensionless parameters, such as power-law index (0.3 ≤ n ≤ 1.5), Reynolds (0.1 ≤ ReN ≤ 40) and Prandtl numbers (0.72 ≤ PrN ≤ 500). The NuLocal plot attains a pitch near corrugation of surface due to abrupt change in velocity and temperature gradients. Nu increases with ReN and/or PrN and decreases with n under otherwise identical situations. Nu is correlated with pertinent parameters, namely, ReN , PrN and n.

During the Stelmor air-cooling process, the temperature distribution has a significant impact on the wire loops’ final mechanical properties. The temperature distribution during air-cooling process is accurately solved by establishing three-dimensional model and numerical simulation. The heat transfer coefficient at the high dense region is much smaller than that of wire loops at the low dense region, and changes periodically over time, according to a Computational Fluid Dynamics (CFD) simulation method. It is also found that the heat transfer coefficient on the cross section of the wire loop is very different, with a difference of 70-100 Wm-2K-1. Finally, the finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air-cooling process. Comparing the results with the measurement data, the simulation results and measurement data match up well.

The quest for augmenting dropwise condensation heat transfer performance has been the driving force behind the exploration of innovative techniques and approaches to fulfil the desired objective. Recent literature in condensation heat transfer unveils that dropwise condensation heat transfer improvements from Slippery Liquid Infused Porous Surfaces (SLIPSs) was central to the study of several researchers because these surfaces have shown excellent droplet mobility due to extremely low adhesion between the condensing liquid and the lubricant infused surface, thereby, promote dropwise condensation. As part of supplementing current research on SLIPSs, for the first time, the present study explores the potential of a semi-solid lubricant impregnated porous surface in enhancing the condensation heat transfer performance of a vertical condenser tube. The results of experiments conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in a saturated steam environment signify that Copper tubes with semi-solid lubricant impregnated porous surfaces are potential candidates for enhancing dropwise condensation heat transfer coefficient when compared to an untreated vertical Copper condenser tube. The highest enhancement is found to be 280% at a subcooling of 40°C. Also, the semi-solid lubricant impregnated porous surfaces are proficient in sustaining dropwise condensation for a time period of 72 hours without any degradation in the heat transfer performance. The method devised here for fabricating the semi-solid lubricant impregnated surfaces is simple, less expensive, and less time-consuming compared to the techniques reported earlier for fabricating the SLIPSs. Additionally, in this work an approach based on numerical optimization by a stochastic global optimization technique, namely, Genetic Algorithm, is proposed to retrieve the coefficients and the exponent in the mathematical expression of overall resistance, which in turn is used to compute the tube-side dropwise convection heat transfer coefficient.

This work investigates the effect of Joule heating and viscous dissipation due to electric double layer (EDL) and electroosmotic effect on steady fully developed electromagnetohydrodynamic flow in a porous microchannel. Dimensionless formulations of the Poisson-Boltzmann, momentum, and energy equations are derived for the electric potential, velocity profile and temperature distribution in the microchannel. Exact solutions for the temperature distributions and velocity profile were obtained using the method of undeterminate coefficients. The Debye-Hückel linearization is used to get exact solution for the electric potential. The results showed that Brinkmann number ( Br ) , Joule heating parameter ( J ) , Debye-Hückel parameter ( Κ ) , Hartmann number ( M ) , electric field ( E z ) and suction/injection parameter ( S ) have a substantial impact on flow formation and heat transfer. Using MATLAB software, graphical simulations are provided in order to deliver a greater understanding of the influence of relevant parameters on the results achieved.