Heat Characteristics Research Articles

Heat recovery technology and energy-saving effect analysis apply to cleanroom exhaust waste heat characteristics

To investigate the efficient waste heat recovery (WHR) technology suitable for cleanrooms, the energy-saving effectiveness of three WHR technologies of heat pipe, liquid circulation, and solution absorption was compared and the comparison was conducted across four different climate regions: severe cold, cold, hot summer cold winter, and hot summer warm winter. The findings reveal that the energy efficiency ratio (EER) of the heat pipe WHR surpasses that of the other two technologies. Specifically, the EER values for the heat pipe WHR in the four climate regions are 21.0, 15.4, 14.1, and 7.3, respectively. Furthermore, a two-stage heat pipe WHR technology is proposed to enhance the heat recovery efficiency of the heat pipe WHR technology, and experimental research has been conducted. The results show that the average heat recovery efficiency reaches 61.64 % when the wind speed is 2 m/s and the new exhaust air temperature difference is 6–11 °C. Compared to the single-stage HPHE, the use of two-stage heat pipe WHR technology in the four climates regions resulted in 6.9 %, 12.8 %, 21.5 %, and 13.6 % higher net heat recovery, 7.1 %, 13.5 %, 16.6 %, and 40.2 % higher energy-efficiency ratios, and 8.2 %, 13.5 %, 12.2 %, and 37.3 % shorter static payback periods, respectively. The heat recovery solution shows a good application prospect in cleanroom WHR.

An MHD boundary layer flow of Casson fluid due to a moving wedge analyzed by the Bernoulli wavelet method

AbstractThe current study adopts a Bernoulli wavelet technique to explore the magnetohydrodynamic (MHD) boundary layer flow of a Casson fluid through a wedge. A nanofluid across a wedge has been investigated for its stable laminar MHD flow, heat, and mass transport characteristics. By choosing worthwhile non‐dimensional parameters, the governing boundary layer equation is reformed into a dimensionless Falkner–Skan equation. The consequent nonlinear equation is addressed via the Bernoulli wavelet method. For a range of different values of the physical parameters, the nature of the boundary layer flow is visually observed. Fluid velocity rises with rise in the values of Casson parameter, wedge parameter, and magnetic parameter. Local wall skin friction increases with increase in wedge parameter and magnetic parameter values. To ensure the accuracy of the findings, local wall skin friction is estimated and tested with other techniques that are already reported in the existing research.

Evaluation of acoustic-thermal simulations of invivo magnetic resonance guided focused ultrasound ablative therapy.

To evaluate numerical simulations of focused ultrasound (FUS) with a rabbit model, comparing simulated heating characteristics with magnetic resonance temperature imaging (MRTI) data collected during invivo treatment. A rabbit model was treated with FUS sonications in the biceps femoris with 3D MRTI collected. Acoustic and thermal properties of the rabbit muscle were determined experimentally. Numerical models of the rabbits were created, and tissue-type-specific properties were assigned. FUS simulations were performed using both the hybrid angular spectrum (HAS) method and k-Wave. Simulated power deposition patterns were converted to temperature maps using a Pennes' bioheat equation-based thermal solver. Agreement of pressure between the simulation techniques and temperature between the simulation and experimental heating was evaluated. Contributions of scattering and absorption attenuation were considered. Simulated peak pressures derived using the HAS method exceeded the simulated peak pressures from k-Wave by 1.6 ± 2.7%. The location and FWHM of the peak pressure calculated from HAS and k-Wave showed good agreement. When muscle acoustic absorption value in the simulations was adjusted to approximately 54% of the measured attenuation, the average root-mean-squared error between simulated and experimental spatial-average temperature profiles was 0.046 ± 0.019 °C/W. Mean distance between simulated and experimental COTMs was 3.25 ± 1.37 mm. Transverse FWHMs of simulated sonications were smaller than in invivo sonications. Longitudinal FWHMs were similar. Presented results demonstrate agreement between HAS and k-Wave simulations and that FUS simulations can accurately predict focal position and heating for invivo applications in soft tissue.

Role of metal inserts for ‘targeted’, ‘uniform’ or ‘controlled’ microwave heating objectives involving generalized sets of dielectrics (Group 1 – 4)

Microwave heating occurs volumetrically leading to faster processing than conventional heating processes. Over the last few decades, the potential of microwave heating has been investigated for various thermal processing applications such as food processing, material synthesis, fuel production and waste treatment/remediation. Current work investigates the role of the metal inserts towards targeted, uniform and/or controlled microwave heating for the four groups of dielectrics (Group 1 – 4) involving lateral and isotropic microwave incidences. The microwave induced heat generation and evolving temperature distributions within the materials in the absence and presence of the metal insert are numerically determined via the mathematical models comprising of Helmholtz equation, energy balance equation and an integro-differential boundary condition representing the scattering of the microwave at the air-material interface. Galerkin finite element method with biquadratic elements along with Crank-Nicolson time integration scheme has been employed to solve the governing equations. It has been found that the metal insert can suitably alter the heating characteristics leading to either faster heating, better heating uniformity or more intense targeted heating of the materials. Uniform microwave heating is generally difficult to attain except for very small samples. This work shows that the metal inserts can significantly reduce the heating inhomogeneity of the moderately large samples involving Group 1 to Group 3 materials. In addition, the targeted heating effect of the materials (Groups 1 to 4) can also be intensified by the use of the metal insert, as has been illustrated for various test cases. Especially, the metal insert can lead to targeted heating at the incident surface irrespective of the material or sample dimension, and that is difficult to attain except for the large samples. The metal inserts are also found to be efficient to control the rapid microwave heating experienced by the small samples of lossy materials (Group 1 and 3 materials) or accelerate the slower heating of the large samples resulting in significant energy savings, especially for Group 1 to Group 3 materials.

Response to palaeoclimate by Early Cretaceous terrestrial organic-rich shales in the Yin'e Basin: Evidence from sporopollen, n-alkanes and their compound carbon isotopes

The Cretaceous period is a typical representative of a ‘greenhouse climate’ in geological periods, and is also an important period for the formation of hydrocarbon source rocks, which has become a hot spot in the study of palaeoclimate and organic matter enrichment. In order to further explore the mechanism of action between paleoclimate and organic matter enrichment, the response mechanism of organic matter enrichment to palaeotemperature and palaeorainfall is finely characterised by synthesising the analysis of sporopollen, biomarkers and n-alkane carbon isotopes in this study. The sporopollen indicates that the palaeoclimate is generally temperate, semiarid to semihumid, and the n-alkane and n-alkane carbon isotopes indicate that the palaeoclimate and palaeorainfall have obvious fluctuations and synchronous characteristics of rainfall and heat. Based on the differences in palaeotemperature and palaeorainfall, the palaeoclimate can be further divided into three stages: cool-temperate and semiarid, warm and semihumid, and cool-temperate and semiarid. The trend of palaeoatmospheric pCO2 recovered from the carbon isotopes of normal alkanes C27, C29, and C31 is roughly the same as that of palaeotemperature, indicating that pCO2 is important in regulating palaeotemperature. According to the distribution pattern of organic carbon, different layers are divided into three sedimentary Units: I, II and III. Different sedimentary Units have good corresponding relationships with different palaeoclimatic stages. Under the cool-temperate and semiarid climate, lower palaeotemperature and higher palaeosalinity are not conducive to the prosperity of lake organisms. The formation of light grey mudstone, silty mudstone and carbonate has lower TOC, and the organic matter types are mostly II1 and II. Under a warm and semihumid climate, higher palaeotemperature and moderate palaeorainfall are conducive to the prosperity of lake organisms. The formation of oil shale and shale has higher TOC, and the organic matter types are mostly I and II1. However, excessive palaeorainfall brings much terrigenous debris, leading to the organic matter dilution. Therefore, palaeoclimate and palaeorainfall not only affect the abundance of organic matter, but also affect the types of organic matter. In the paper, the mechanism of organic matter enrichment is improved by delicately characterising the palaeotemperature and palaeorainfall.

Multifactor optimization for induction welding of carbon fiber reinforced thermoplastic composites based on response surface methodology

AbstractInduction welding of thermoplastic (CFRP) composites is one of the most promising welding techniques due to its high efficiency, flexibility, and selectivity of the heat area. However, the nonuniformity of the temperature field in the welding area poses a challenge to welding quality. In this paper, a multifactor optimization method devoted to the quality and efficient bonding of carbon fiber‐reinforced polycarbonate (CF/PC) composites was presented. A transient three‐dimensional finite element model was developed and validated to analyze the heating characteristics during the welding process. The mapping relationship between process parameters—equilibrium temperature and relative effective area were established to optimize the weld quality applying the response surface method. The single lap shear experiment was carried out to evaluate the mechanical properties of the welded joints, focusing on micro appearances and welding defects. The results show that the optimal process parameters are a current of 100A and a coil distance from the surface of 3.6 mm. Under the process parameter, the effective welding area is 0.3823 with an error of 4.25%.Highlights The transient three‐dimensional finite element (FE) model was established. The evaluation indicators for welding quality were proposed. The multifactor optimization method for process parameters was developed. The mechanical property and welding defects of welded joints is evaluated.

Flow and Thermal Characteristics of Couple Stress Fluid over a Stretching Surface with Hybrid Nanoparticles

In the current research, a mathematical analysis of couple stress fluid flow and heat characteristics through a stretchable permeable surface with hybrid nanoparticles is conducted. The solid nanoparticles of the aluminium alloys (AA7072 and AA7075) are suspended in methanol to create the hybrid nanofluid. The similarity approach is used to reduce the governing equations into the similarity equations. Then, MATLAB's bvp4c function is employed to solve the resulting equations. The solutions for the flow and temperature fields, as well as the skin friction coefficient and Nusselt number are presented in table and graphical forms. The results demonstrate that hybrid nanofluids excel as thermal conductors, significantly augmenting the heat transfer rate. The heat transfer rate is increased by 0.38% for the nanofluid, while 0.89% increment for the hybrid nanofluid compared to the base fluid. Furthermore, a larger couple stress parameter is found to be associated with a decrease in the fluid temperature and an enhancement in fluid velocity.

Numerical Investigations of the Thermal-Hydraulic Characteristics of Microchannel Heat Sinks Inspired by Leaf Veins

A microchannel heat sink (MCHS) is a potential solution for chip and battery thermal management. The new microchannel structure is beneficial for further improving the thermal-hydraulic performance of MCHSs. Inspired by leaf veins, six new channel structures were designed, and the effects of the channel structures (three parallel structures named PAR I, II, and III and three pinnate structures named PIN I, II, and III), channel depths (0.4, 0.8, and 1.6 mm), and heat fluxes (20, 50, and 80 kW/m2) were investigated via numerical simulation. The cooling medium was water, and the heating area was 40 × 40 mm2. Both PAR II and PIN III exhibit superior overall performance, characterized by the highest Nusselt number and the lowest heating wall temperature. Moreover, PIN III demonstrates the lowest standard deviation in heating wall temperature, while PAR II exhibits the lowest friction factor. The greater the channel depth is, the larger the solid–liquid contact area is, leading to a reduced wall temperature at the interface under identical conditions of inlet Reynolds number and heating wall heat flux. Consequently, an increase in the Nusselt number corresponds to an increase in the friction factor. The maximum value and standard deviation of the heating wall temperature increase with increasing heat flux, while the Nusselt number and friction factor remain unaffected. The overheating near the two right angles of the outlet should be carefully considered for an MCHS with a single inlet–outlet configuration.

A simulation study on the heating characteristics of residential buildings using intermittent heating in Hot-Summer/Cold-Winter areas of China

Radiant air conditioning system is an important heating method with better thermal comfort, less noise and greater energy-saving potential. However, different intermittent heating modes may significantly impact both the heating efficiency and indoor thermal comfort, which has been neglected in existing studies. Therefore, to obtain optimal intermittent heating modes for achieving higher energy efficiency and better indoor thermal comfort for the residential buildings in Hot Summer and Cold Winter areas, a TRNSYS model of the radiant air conditioning system was developed and validated. The indoor thermal comfort and energy consumption characteristics during the coldest day and entire heating season were simulated and analyzed based on four different intermittent heating modes. The results demonstrated that the supply water temperature of the air source heat pump unit and the radiant terminals stabilized at the set temperature in about 1 h during the start-up stage, and the indoor air temperature stabilized at 24.0 °C after 7.5 h during the shutdown stage. The proportion of time that meets first-level thermal comfort under the four intermittent heating modes was above 90.1% and even higher at over 96.1% when considering the sleeping period. Compared to the continuous heating mode, the four intermittent heating modes saved 22.3%, 25.8%, 40.4% and 48.4% of energy. Overall, the preferred intermittent heating mode for residential buildings with the radiant air conditioning system in Hot Summer and Cold Winter areas was identified as switching on from 7:00 to 15:00 and 19:00 to 3:00, while switching off from 15:00 to 19:00 and 3:00 to 7:00. This model not only considered the immediate benefits of improved indoor thermal comfort and energy efficiency, but also showed great advantages in developing sustainable construction.

Operational characteristics of the combined heat and power plant in the district heating system of Belgrade

The combined production of electricity and thermal energy (combined heat and power or co-generation) is the most efficient and convenient approach to reduce costs for energy at industrial power plants and district heating plants that use natural gas as fuel to produce thermal energy for various needs. This paper analyses the operational characteristics of the combined heat and power plant, which has been operating since January 1, 2021, at the Vozdovac Heating Plant as part of the Belgrade district heating system. The combined heat and power plant consists of three gas engine units with a total nominal electric power of 10 MW and thermal power of 10.1 MW, which use natural gas as fuel. The combined heat and power plant is used for district heating and preparing domestic hot water while electricity is sold to the local electric grid. The analysis in this paper focuses on the plant?s operational characteristics: the number of working hours, the total energy consumption and energy production, the efficiency as well as the operational and maintenance costs. Also, the impact of the drastic changes in the prices of natural gas, electricity, and maintenance costs in the last year on the financial profitability of the combined heat and power plant was analysed in particular.

ANALYZING THE HEAT AND FLOW CHARACTERISTICS IN SPRAY COOLING BY USING AN OPTIMIZED RECTANGULAR FINNED HEAT SINK

Rapid advancements in technology constantly keep the need for thermal systems, which have high performance, on the agenda and direct the attention of researcher-engineers to the studies on improving the heat transfer. Spray cooling process depends on many parameters including nozzle diameter, surface area, surface geometry, critical heat flux, mass flow, gravity, spraying angle, and surface slope. One would need results from many experiments to better analyze the spray structure. In the present study, by using the rectangular-finned heat sinks optimized for spray cooling and those called "general," the heat and flow characteristics in spray cooling were analyzed. Water was used as the cooling fluid and the cooling fluid was atomized by using an air-supported atomized. The experiments were conducted with six air-to-liquid ratio (ALR) values, three different jet heights, three different spraying times, three different fin heights, and three different fin widths. The results are presented in the Nusselt number-air-to-liquid ratio (Nu-ALR) and jet thickness-jet velocity (<i>t<sub>jet</sub> -U<sub>jet</sub></i>) diagrams. It was determined that the ALR value tended to decrease with increasing Nusselt numbers. For the determined ALR values, Nusselt numbers decreased as the fin height increased. It was concluded that Nusselt numbers tended to decrease at all fin widths as the ALR value increased. In addition, considering the parameters examined for the rectangular-finned heat sink, separate correlations were developed for the Nusselt number, spray angle, and jet thickness.

In situ theranostic platform combining highly localized magnetic fluid hyperthermia, magnetic particle imaging, and thermometry in 3D.

Theranostic platforms, combining diagnostic and therapeutic approaches within one system, have garnered interest in augmenting invasive surgical, chemical, and ionizing interventions. Magnetic particle imaging (MPI) offers a quite recent alternative to established radiation-based diagnostic modalities with its versatile tracer material (superparamagnetic iron oxide nanoparticles, SPION). It also offers a bimodal theranostic framework that can combine tomographic imaging with therapeutic techniques using the very same SPION. Methods: We show the interleaved combination of MPI-based imaging, therapy (highly localized magnetic fluid hyperthermia (MFH)) and therapy safety control (MPI-based thermometry) within one theranostic platform in all three spatial dimensions using a commercial MPI system and a custom-made heating insert. The heating characteristics as well as theranostic applications of the platform were demonstrated by various phantom experiments using commercial SPION. Results: We have shown the feasibility of an MPI-MFH-based theranostic platform by demonstrating high spatial control of the therapeutic target, adequate MPI-based thermometry, and successful in situ interleaved MPI-MFH application. Conclusions: MPI-MFH-based theranostic platforms serve as valuable tools that enable the synergistic integration of diagnostic and therapeutic approaches. The transition into in vivo studies will be essential to further validate their potential, and it holds promising prospects for future advancements.

Heating characteristics and identification method of carbonization defect composite insulators based on electric-magnetic-thermal coupling

Heating characteristics and identification method of carbonization defect composite insulators based on electric-magnetic-thermal coupling

Thermal effects associated with the crack of high-temperature superconducting magnetic levitation system

Based on the magnetic flux pinning characteristics of the non-ideal type II superconductor YBa2Cu3O7−x, the high-temperature superconducting magnetic levitation system has the advantages of self-stability in levitation and low energy consumption. Thermal stress, electromagnetic force, and other mechanical stress may cause the micro-cracks to expand and eventually lead to fractures in the application of superconducting materials, significantly affecting the superconductor’s ability to transmit current. The superconducting magnetic levitation system with low damping is prone to nonlinear vibration of large amplitude under external interference, which affects the system’s regular operation. Due to the limitations of experimental conditions, it is difficult to analyze complex physical phenomena with cracks and obtain the distribution characteristics of electromagnetic, heat, and force inside the superconductor in the nonlinear vibration process, as theoretical modeling can compensate for this deficiency. In this paper, we study the fracture behavior of the YBa2Cu3O7−x bulk superconductor under nonlinear vibration based on the flux creep and flow models. The temperature of the superconductor in the nonlinear vibration of the superconducting levitation system is calculated with center cracks. The flux flow phenomenon in the bulk superconductor for various cracks under the bifurcation vibration is presented. The results show that the temperature of the superconductor will dramatically rise in nonlinear vibration under thermal insulation conditions, and the distribution position is affected by the cracks. For the 15 and 12 mm center cracks, a large amount of heat is generated around the crack and causes the temperature to rise above the critical temperature.

HEAT AND FLUID FLOW CHARACTERISTICS OF FERROFLUIDS CIRCULATING IN A HEAT EXCHANGER WITH A MAGNETIC VORTEX GENERATOR

The current work is aimed at numerical investigation and analysis of entropy generation and thermal efficiency of Fe<sub>3</sub>O<sub>4</sub>/water nanofluids flowing through a heat exchanger considering multiple identical magnetic sources. The simulated domain corresponds to a minichannel heated from below at a constant temperature, while its upper wall is adiabatic. Numerical simulations were carried out using the finite volume method (FVM). To determine the new thermophysical properties of the magnetic nanofluid, the single-phase approach was adopted. The obtained results are presented as the Nusselt number, streamlines, isotherms, and generated entropy with other relevant parameters, namely, the magnetic field strength, number of magnet pairs, range of Reynolds numbers, and volumetric fraction of the nanoparticles. The investigation revealed that these parameters significantly influence the heat transfer mechanism. Selecting these parameters carefully is crucial for achieving enhanced generation of entropy and, consequently, desirable improvement in heat transfer.

Investigation of the conditions for the formation of moisture deficiency in Northern Kazakhstan using the method of hydrological and climatic calculations

The article investigated the conditions for the formation of moisture deficiency in the forest-steppe and steppe zones of northern Kazakhstan. The growth of moisture deficiencies affects the yield of grain crops. The work used statistical, cartographic, analytical, and analogy methods. The hydrological and climatic calculation method developed by V.S. Mezentsev and tested in Western Siberia and adjacent territories of Kazakhstan was used as the main method for obtaining the calculated heat and water balance characteristics of the studied territory. Meteorological data obtained at meteorological stations in agricultural areas was used as initial data. Using the regression equation, the dependence of cereal crop yield on humidification in the Akmola region and the estimated yield schedule for 2024 were built. On the territory of Northern Kazakhstan, quite close dependencies between the yield and the degree of humidification have been identified. The yield of grain crops in the Akmola region was influenced by a lack of moisture for 54%. In general, during the warm period of the average year, the soil moisture resources of the studied area are not able to provide favorable conditions for the appropriate growth and development of crops.

Photoacoustic detection of transient phase transformation of nanoparticles.

The controllable preparation of spherical micro/nano particles of various materials has been achieved via the technology of the laser synthesis and processing of colloids (LSPC) recently. However, there is limited in situ research on the evolution processes of nanoparticles in photothermal transient environments, such as solid-state crystal transformations and changes of state, which limits the understanding and application of LSPC. Photoacoustic (PA) signals are sensitive to the optical, thermal and elastic properties of the medium, and can be used to measure the thermal and spectroscopic properties of matter. In this paper, the PA signals generated by the interaction of the laser with the surrounding liquid medium (ethanol, water, glycerin, etc.) and nanoparticles (Ag, TiO2, CeO2, ZrO2, etc.) are studied when the tunable LSPC technique provides different photothermal conditions (such as thermal expansion, solid crystal transformation and evaporation). It is found that semiconductors with different bandgaps, as light absorbers, have the ability to selectively absorb laser beams of different wavelengths. By changing the wavelength, the PA intensity can be adjusted accordingly. In addition, based on the fast laser heating and tunable fluence characteristics of non-focused laser beams in LSPC technology, transient processes such as material phase transitions and changes of state can be excited separately by adjusting the laser fluence. Taking titanium dioxide as an example, the PA signals generated by laser selective excitation of A-R (anatase into rutile) phase transitions and rutile vaporization can be detected.

Flexible solid-solid phase change material with zero leakage via in-situ preparation for battery thermal management

<p>Composite phase change material (CPCM) has great potential in addressing the challenges associated with thermal energy storage and thermal management. However, the flexibility and latent heat capacity of CPCM exist contradiction, hindering its wide application, especially in thermal management field. Herein, a novel solid-solid polyurethane structured phase change material including as chain segments PEG4000 and hexamethylene diisocyanate coupling with expanded graphite (PHE5) has been proposed and prepared via in-situ approach. Expand graphite is uniformly distributed and the carbamate group is produced by in-situ preparation, the high latent heat and anti-leakage characteristics of PHE5 are beneficial to sustain a constant mass with zero leakage even under 150�� heating condition. At a 3 C discharge rate, the battery module with PHE5 can reduce the maximum temperature to 59��, which is lower than the PE-based module. Additionally, the battery system can maintain the temperature difference below 4.5��, ensuring uniform temperature within the battery module. The flexibility and controlling temperature capabilities of PHE5 can effectively dissipate heat during charge and discharge cycles, and the mechanistic analysis of PHE5 with anti-leakage property can enhance the battery thermal safety, achieving comprehensive protection throughout normal operating and extreme conditions. Thus, this research reveals that solid-solid CPCM with polyurethane structured can improve the flexible and anti-leakage properties via in-situ preparation, which will offer an effective thermal safety solution for battery module, substantially enhancing the safety of millions of drivers and passengers.</p>

Heat exchange characteristics of underground and pavement buried pipes for bridge deck heating conditions.

Geothermal energy is increasingly employed across diverse applications, with bridge deck snow melting emerging as a notable utilization scenario. In Jinan city, China, a project is underway to utilize ground source heat pumps (GSHPS) for heating bridges. However, essential operational parameters, including fluid medium, temperature, and heat exchange details, are currently lacking. This study addresses the thermal design challenges associated with ground heat exchangers (GHE) for bridge heating through a combination of numerical modeling and field experiments. Utilizing software Fluent, a refined three-dimensional multi-condition heat transfer numerical analysis was carried out. Field tests based on actual operating conditions were also conducted and the design parameters were verified. The results indicate that an inlet temperature of 5°C and an aqueous solution of ethylene glycol with a mass concentration of 35% as the heat exchange medium are suitable for the GSHPS in Jinan; Moreover, the influence of backfill material and operation time on the heat transfer efficiency was revealed and the suitable material with 10% bentonite and 90% SiO2 was suggested; Finally, based on the influence of the pipe spacing on the heating characteristics of bridge deck, the transition spacing of 0.2 m is given for the temperature response of the bridge deck. This comprehensive study contributes valuable insights through simulation and experimental analysis of the thermal environment variation, aiming to advance the development of GSHPS for bridge deck heating in Jinan, China.

Integration of phase change materials with multi-responsive halloysite nanotubes for efficient Pickering emulsification of high-viscosity oil

The low fluidity of high-viscosity oil usually hinders its emulsification. Facing this dilemma, a multiresponsive composite PCM with both in situ heating characteristics and Pickering emulsification properties was proposed.