Ralph L. Webb

Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-5, 2011, DOI:10.5098/hmt.v2.2.3001

Abstract This paper discusses the “Inlet Temperature Difference” (ITD) based heat-exchanger (and its variants) design methodology frequently used by designers of electronic heat sinks. The methodology is at variance with the accepted methodology recommended in standard heat-transfer text books – the “Log-Mean Temperature Difference” (LMTD), or the equivalent “effectiveness-NTU” design method. The purpose of this paper is to evaluate and discuss the ITD based design methodology and its deficiencies. The paper shows that the ITD based method is an approximation at best. Variants of the method can lead to either under or over prediction of the heat transfer rate. Its shortcomings… More >

Zan Wu^a, Zhaozan Feng^b, Bengt Sundén^a,*, Lars Wadsö^c

Frontiers in Heat and Mass Transfer, Vol.5, pp. 1-10, 2014, DOI:10.5098/hmt.5.18

Abstract Thermal conductivity and rheology behavior of two aqueous nanofluids, i.e., alumina and multi-walled carbon nanotube (MWCNT) nanofluids, were experimentally investigated and compared with previous analytical models. Information about the possible agglomeration size and interfacial thermal resistance in the nanofluids were obtained and partially validated. By incorporating the effects of interfacial thermal resistance, a revised model was found to accurately reproduce the experimental data based on the agglomeration size extracted from the rheology analysis. In addition, the thermal conductivity change of the alumina/water nanofluid with elapsed time was investigated. Thermal conductivity measurements were also conducted for alumina/water and MWCNT/water nanofluid mixtures. More >

Ankit Kanor, R Manimaran^*

Frontiers in Heat and Mass Transfer, Vol.7, pp. 1-5, 2016, DOI:10.5098/hmt.7.25

Abstract One of the effective liquid cooling techniques for microelectronic devices is attaching micro channel heat sink to the inactive side of chip. A micro channel heat sink is a device that decreases temperature by flowing coolant through micro channels. The present study focuses on the conjugate heat transfer analyses for different cross-sections (trapezoidal, hexagonal, octagonal and circular).After present study is validated with the published result in the literature, the comparative study of parallel and counter flow configuration is performed. Different geometries are modeled using CATIA V5 software and simulated in ANSYS Fluent R14. From these CFD simulations, preferred configuration of… More >

Kevin W. Irick^*

Frontiers in Heat and Mass Transfer, Vol.8, pp. 1-7, 2017, DOI:10.5098/hmt.8.2

Abstract The Single-sided Guarded Hot Plate Method for Comparative Testing of Thermal Radiation Barriers in Vacuum was used to evaluate the performance of a variety of aerogel insulation specimens manufactured by Aspen Aerogels® against one another and against multi-layer insulation (MLI). Testing at the Air Force Research Laboratory (AFRL) shows that the effective thermal resistance, R_e, of all tested aerogel specimens are virtually bounded by the performance of 5-layer and 10-layer MLI specimens over a mean specimen temperature, T_m, range of about 270K to 315K. More >

Mohammed Yunus^*, Mohammad S. Alsoufi

Frontiers in Heat and Mass Transfer, Vol.12, pp. 1-8, 2019, DOI:10.5098/hmt.12.11

Abstract Swift cooling systems, improved microprocessor chips, processors’ performance and power usage have increased production of an enormous amount of heat and high operating temperatures due to excess heat flux density in the field of microelectronics. A rapid cooling of electronic circuits and heat dissipation for the same size of pipe with the present technology as nano size circuits critically generate high heat flux beyond 100 W/cm2 is currently the challenging task with which we are presented. Cooling in the form of heat transfer should be managed using both thermal conductivity (evaporation) and phase transition (condensation) between the two solid interfaces… More >

Chadwick D. Sevart^* , Theodore L. Bergman

Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-18, 2019, DOI:10.5098/hmt.13.18

Abstract A design approach is proposed and demonstrated to identify desirable two-dimensional solid geometries, cooled by natural convection, that offer superior thermal performance in terms of reduced overall (conduction-convection) thermal resistance. The approach utilizes (i) heat transfer modeling in conjunction with (ii) various novel shape evolution rules. Predictions demonstrate the evolution of the solid shape and associated reduction of the overall thermal resistance. Parametric simulations reveal the dependence of the predicted solid shape on the evolution rule employed, the thermal conductivity of the solid material, and the strength of advection within the fluid. More >

Ming Zhao^* , Yang Tian

Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-10, 2019, DOI:10.5098/hmt.13.4

Abstract The field synergy principle and thermal resistance analysis were carried out for the heat transfer enhancement of a chip heat sink. Thermal analysis of the heat dissipation capacity is applied for setting up the gallery on the rib, changing the fan ventilation diameter, and changing the rib height. The results show that the analysis of field synergy principle agrees well with that of the thermal analysis, and setting up a gallery on the rib can improve the heat capacity of the heat sink. Meanwhile, the results also show that decreasing diameter of the ventilation causes heat capacity dropping because the… More >

B. Orr^a,* , R. Singh^a, T. L. Phan^a , M. Mochizuki^b

Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-6, 2019, DOI:10.5098/hmt.13.1

Abstract One of the problems with cooling an IGBT inverter chip is that its heat generation is not constant. These chips tend to produce heat in pulses which results in high peak chip temperatures. Transient modelling is required to determine the suitability of a heat sink and to ensure the max peak temperature is not exceeded. This paper demonstrates a method of transient thermal analysis using a thermal resistance / capacitor network. A sample heat sink was modelled and then experimentally tested to validate the model. A novel method of modelling phase change materials (PCM) using the thermal resistance / capacitor… More >

Ali H. Tarrad^*

FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.4, pp. 1111-1127, 2022, DOI:10.32604/fdmp.2022.021541

Abstract An analytical model was built to predict the thermal resistance of a vertical double U-tube ground-coupled heat pump that operates under steady-state conditions. It included a geometry obstruction factor for heat transfer throughout the backfill medium due to the presence of the second loop. The verification of the model was achieved by the implementation of five different borehole configurations and a comparison with other correlations in the available literature. The model considered a U-tube spacing range between (2) and (4) times the U-tube outside diameter producing a geometry configuration factor range of (0.29–0.6). The results of the model were utilized… More >

Jingying Li¹, Tiejun Zhu¹, Fengming Li¹, Dong Wang¹, Xianbiao Bu², Lingbao Wang^2,*

Energy Engineering, Vol.118, No.3, pp. 517-534, 2021, DOI:10.32604/EE.2021.014464

Abstract The single well geothermal heating (SWGH) technology has attracted extensive attention. To enhance heat extraction from SWGH, a mathematical model describing heat transfer is set up, and the key influence factor and heat transfer enhancement method are discussed by thermal resistance analysis. The numerical results show that the thermal resistance of rock is far greater than that of well wall and fluid. So, reducing rock thermal resistance is the most effective method for enhancing the heat extraction power. For geothermal well planning to drill: rock thermal resistance can be reduced by increasing well diameter and rock thermal conductivity; the temperature… More >