International Journal of Heat and Technology

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ISSN / EISSN : 0392-8764 / 0392-8764
Total articles ≅ 1,128
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, Georg Klepp, Birgit Glasmacher, Kamyar Mohammad Pour
International Journal of Heat and Technology, Volume 39, pp 755-762; doi:10.18280/ijht.390309

Due to the increasing energy cost, the efficiency of the industrial dryer as the energy-intensive processes should be improved. The designer should optimize the design parameters of industrial drying equipment to achieve the minimum drying energy consumption. SST k-ω turbulence model is used to simulate a real geometry for industrial drying applications. For the optimization of the impinging round jet, the specific drying energy consumption is set as the objective function to be minimized. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the specific drying energy consumption. It is found that the SST k-ω turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The minimum specific energy consumption correlates with high values of the jet to jet spacing, jet angle, and surface velocity and low values of the nozzle to surface distance and jet inlet velocity. The agreement in the prediction of the specific drying energy consumption between the numerical simulation and correlation is found to be reasonable and all the data points deviate from the correlation by less than 7%.
International Journal of Heat and Technology, Volume 39, pp 987-991; doi:10.18280/ijht.390336

The ignition delays of freely falling liquid fuel droplets in a high-temperature environment were determined experimentally as a function of the surrounding parameters and droplet composition. Two different groups of fuels have been categorized based on the viscosity and volatility of each fuel. In the first group, for diesel and kerosene, the ignition delay time decreases with increasing system temperature due to low viscosity and thereby high volatile nature of fuels. Whereas, in the second group, C-heavy oil and blended renewable fuel shows an increase in the ignition delay time with increasing the system temperature and thereby shows the negative temperature coefficient (NTC) behavior due to high viscosity and low volatile characteristics of those fuels. In the case of low viscosity carbon residue fuels with low ignition temperature, they may vaporize early and decrease in the ignition delay time. But for high viscosity carbon residue fuels and with high ignition temperature, it may prolong the vaporization time and thereby physical delay. Evidently, the physical parameters and therefore the physical delay are the predominant factors in the NTC behavior of such high hydrocarbon liquid fuel droplets.
Junfeng Qiao, Honge Wu, Yujun Niu
International Journal of Heat and Technology, Volume 39, pp 867-875; doi:10.18280/ijht.390321

Dondu Harish Babu, Nainaru Tarakaramu, , Ganganapalli Sarojamma, Oluwole Daniel Makinde
International Journal of Heat and Technology, Volume 39, pp 885-894; doi:10.18280/ijht.390323

This work explores the heat transfer flow characteristics of an incompressible non-Newtonian Jeffrey fluid over a stretching/shrinking surface with thermal radiation and heat source. The sheet is linearly stretched in the presence of a transverse magnetic field with convective boundary conditions. Appropriate similarity variables are used to transform the basic governing equations (PDEs) into ODEs. The resulting equations are solved by utilizing MATLAB bvp4c. The impact of distinctive physical parameters and dimensionless numbers on the flow field and heat transfer is analysed graphically. It is noticed that the measure of heat raised with increasing the Biot number and opposite effect with the rise of the suction parameter.
Wan Nurlaila Mat Desa, , Henny Sudibyo, Ghalya Pikra, Nugrahaning Sani Dewi, Nilofar Asim, Dalmasius Ganjar Subagio, Tinton Dwi Atmaja, Edy Riyanto, Kadek Heri Sanjaya, et al.
International Journal of Heat and Technology, Volume 39, pp 810-816; doi:10.18280/ijht.390314

In this study, a greenhouse solar dryer with double-pass multi-hollow collector for leaf drying was design, constructed, and evaluated. From the result, the double pass solar air collector with multi-hollow tube is capable of increasing air temperature by 5.5℃-10.8℃ compared to ambient air temperature. Thermal efficiency of the dryer was evaluated for passive and active modes, where 47.2% and 50% are recorded respectively. The moisture reduction on mass basis in passive and active dryer recorded was 44% and 74%, respectively. The specific moisture extraction rate (SMER) and specific energy consumption (SEC) of passive dryer was determined to be 0.198 kg per kWh and 5.047 kWh per kg, and active dryer at 0.210 kg per kWh and 4.769 kWh per kg, respectively.
Sai Sarath Kruthiventi, , Yarrapathruni V. Hanumanth Rao
International Journal of Heat and Technology, Volume 39, pp 913-918; doi:10.18280/ijht.390326

In the present study, numerical analysis of coiled tube heat exchanger used in J-T refrigerator is carried out. A computer code is developed to estimate the length of the heat exchanger by giving mass flow rate, diameter of tube and shell as input parameters. This code is verified against experimental data. Two different configurations are considered in this study viz., heat exchanger with wire fin wound around the inner tube of heat exchanger and without wirefin. Three different refrigerant mixtures are used to evaluate the performance of heat exchangers. The variations of temperature and heat transfer coefficient are brought out as result. Significant reduction in the length of heat exchanger is observed in all the cases. Mixture-1 causes 33% reduction in length of heat exchanger with wirefin. Similarly, for mixture-2 and mixture-3 the length is reduced by 15% and 30%. Additionally, heat transfer coefficient (HTC) values are also estimated for heat exchanger with wirefin and without wirefin. Considerable increase in HTC values is observed in the heat exchanger with wirefin.
Shobha Bagai, , Arvind Patel
International Journal of Heat and Technology, Volume 39, pp 711-726; doi:10.18280/ijht.390305

The present paper investigates the mixed convection in a two-sided and four-sided lid-driven square cavity in porous media. In the two-sided porous cavity, the left and right walls of the enclosure are maintained at constant but different temperatures, while the top and bottom walls are adiabatic. The top and the bottom walls of the enclosure move with a constant speed from left to right. In the four-sided porous cavity, the top and the bottom walls of the enclosure move from left to right and right to left, respectively, while the left and the right walls move from top to bottom and bottom to top, respectively, with a constant speed. The left and right walls of the enclosure are maintained at different heat fluxes, while the top and bottom walls are maintained at hot and cold temperatures, respectively. The governing equations are discretized by the fully implicit finite difference method, namely, Alternating-Direction-Implicit (ADI) method. The numerical results are analyzed for the effect of Darcy number (Da = 0.001, 0.01), Prandtl number (Pr = 7), Grashof number (Gr = 50,000), porosity (ε = 0.2) and viscosity ratio (Λ = 1, 3). The stability and convergence of the considered problem have been proved using the Matrix method.
Saleem K. Kadhim, Mohammed G. Al-Azawy, Sinan Abdul-Ghafar Ali, Mina Qays Kadhim
International Journal of Heat and Technology, Volume 39, pp 895-905; doi:10.18280/ijht.390324

Cardiovascular diseases were the main cause for loosing lives in the last decades due to the restricted blood flow states in the blood vessels areas. Numerical investigations have been conducted as the aim of this work to examine the blood flow, and wall shear stresses adjacent to the mono stenosis up to different degrees involved in the main, side and distal main branches as well as observe the pulsatile flow of blood in the left coronary artery through various percentage of stenosis. Both the Carreau non-Newtonian rheological model and the Newtonian model were utilized to model the blood fluid and wall shear stresses of left coronary artery, in a row, all the calculated data were validated with the previously published papers. It was found that the blood flow inside areas of the artery lie within the range of non-Newtonian rheological effects can be present, verifying the need to treat blood as non-Newtonian fluid; especially, with the case of 90% blockage.
Wei Liu
International Journal of Heat and Technology, Volume 39, pp 746-754; doi:10.18280/ijht.390308

The energy conservation of campus buildings is the most direct and effective means to promote the sustainable development of colleges and universities. Using the heat data collected by heat supply monitoring platform to perform real-time energy consumption analysis and heating energy efficiency evaluation is a prerequisite for realizing automatic heat supply control based on energy conservation and heating demand. This paper studied the energy conservation analysis and comprehensive energy efficiency evaluation of campus central heating system based on the heat supply monitoring platform. At first, the paper elaborated on the energy consumption analysis method of the campus central heating system based on the heat supply monitoring platform; then, it gave the energy balance equation and the exergy balance equation; after that, based on a few parameters such as the EHR (electricity to heat ratio), heating index, and water makeup rate, this paper evaluated the energy efficiency of the campus central heating system, and experimental results verified the effectiveness of the analysis and evaluation methods.
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