Fayi Yan^*, Xuejian Pei, He Lu, Shuzhen Zong

Frontiers in Heat and Mass Transfer, Vol.22, No.1, pp. 287-304, 2024, DOI:10.32604/fhmt.2023.045038

Abstract As compact and efficient heat exchange equipment, helically coiled tube-in-tube heat exchangers (HCTT heat exchangers) are widely used in many industrial processes. However, the thermal-hydraulic research of liquefied natural gas (LNG) as the working fluid in HCTT heat exchangers is rarely reported. In this paper, the characteristics of HCTT heat exchangers, in which LNG flows in the inner tube and ethylene glycol-water solution flows in the outer tube, are studied by numerical simulations. The influences of heat transfer characteristics and pressure drops of the HCTT heat transfers are studied by changing the initial flow velocity, the helical middle diameter, and… More >

Sira Saisorn^a,b, Somchai Wongwises^b,c,∗

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3007

Abstract Two-phase pressure drop during flow boiling has been studied for several decades. Obviously, the publications available on micro-channels are relatively small compared with those for ordinarily sized channels. Although the use of micro-channels yields several advantages, the pressure drop taking p lace in these extremely small channels is higher than that in the ordinarily sized channels because of the increased wall friction. The knowledge of the two-phase pressure drop characteristics in addition to heat transfer phenomena is essential to the design and evaluation of the micro-systems. In this paper, recent research on the flow boiling pressure drop in micro-scale channels… More >

Amit Agrawal^a,*, V.S. Duryodhan^a, S. G. Singh^b

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3005

Abstract An experimental study of flow boiling through diverging microchannels has been carried out in this work, with the aim of exploring reduction in flow instabilities during boiling in diverging microchannels. Effect of mass flux, heat flux and divergence angle on two phase pressure drop has been studied using deionized water as the working fluid. The experiments are carried out on three test sections with divergence angle of 4, 8 and 12 deg with nearly constant hydraulic diameter (146, 154 and 157 µm respectively), for inlet mass flux and heat flux range of 117 - 1197 kg/m² -s and 2.5 to… More >

Mainak Bhaumik¹, Anirban Sur^2,*, Kavita Dhanawade³

Frontiers in Heat and Mass Transfer, Vol.21, pp. 467-486, 2023, DOI:10.32604/fhmt.2023.044605

Abstract Pin fins are widely used in applications where effective heat transfer is crucial. Their compact design, high surface area, and efficient heat transfer characteristics make them a practical choice for many thermal management applications. But for a high heat transfer rate and lightweight application, aerofoil shape pin fins are a good option. This work focuses on an experimental model analysis of pin-fins with aerofoil shapes. The results were evaluated between perforation, no perforation, inline, and staggered fin configurations. Aluminum is used to make the pin fins array. The experiment is carried out inside a wind tunnel, and the heat supply… More >

Shaopeng Liu¹, Guowei Wang^2,3,*, Pengfei Liu¹, Dong Ye¹, Jian Song¹, Xing Liu¹, Yang Cheng^2,3

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.12, pp. 3045-3058, 2023, DOI:10.32604/fdmp.2023.029810

Abstract Foam drainage is the flow of liquid through the interstitial spaces between bubbles driven by capillarity and gravity and resisted by viscous damping. The so-called foam drainage gas recovery technology is a technique traditionally used to mitigate the serious bottom-hole liquid loading in the middle and late stages of gas well production. In this context, determining the optimal concentration of the bubble drainage agent is generally crucial for the proper application of this method. In this study, a combination of indoor experiments and theoretical analysis have been used to determine the pressure drop related to the foam-carrying capacity in a… More >

AlemKarima^a,*, Sahel Djamel^b , Nemdili Ali^c, Ameur Houari^d

Frontiers in Heat and Mass Transfer, Vol.10, pp. 1-7, 2018, DOI:10.5098/hmt.10.27

Abstract In the present paper, the effects of a new baffle design on the efficiency of a tubular heat exchanger are numerically investigated. It concerns butterfly baffles inserted in a cylindrical tube heat exchanger. We focus on the influence of the shape of baffles, the space between baffles (pitch ratio, PR) and the baffle size (i.e. the blockage ratio, BR) on the heat transfer and flow characteristics. Three geometrical configurations with different PRs are realized (PR = 1, 2 and 4) and five others with different blockage ratios (BR = 0.1, 0.2, 0.3, 0.4 and 0.5). The investigations are achieved for… More >

Yasushi Koito^a,*

Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-6, 2019, DOI:10.5098/hmt.13.26

Abstract This paper describes extended numerical analyses on vapor pressure distribution in a centered-wick ultra-thin heat pipe. Analyses were conducted by using a three-dimensional model developed by the author. Numerical results were obtained changing design parameters and operating conditions of the heat pipe. Discussion was made on the heat transfer limit as well as the vapor pressure drop. Moreover, a simple method was also presented to evaluate the vapor pressure drop in the ultra-thin heat pipe. Calculated results with the simple method agreed in 10 % with the three-dimensional numerical results. More >

Louay Abd Al-Azez Mahdi, Mohammed A. Fayad, Miqdam T. Chaichan^*

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.9, pp. 2201-2214, 2023, DOI:10.32604/fdmp.2023.027166

Abstract A theoretical study based on the Penalty factor (PF) method by Cavallini et al. is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and freezers. The following conditions are considered: stratified or stratified-wavy flow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25, 4.83, and 6.299 mm, condensation temperatures 35°C, 45°C, and 54.4°C and cover refrigerant mass flow rate spanning the interval from 1 to 7 kg/hr. The results show that the… More > Graphic Abstract

Amnart Boonloi^a, Withada Jedsadaratanachai^b,*

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-13, 2022, DOI:10.5098/hmt.18.2

Abstract This study numerically investigates pressure loss, heat transfer and thermal efficiency in round tube heat exchangers attached with various types of Vrings. A typical type A V-ring is compared with two types of modified V-rings (type B and C). The impacts of blockage ratios, b/D = 0.05, 0.10, 0.15 and 0.20 for all V-ring types in the turbulent region are discussed (Re = 3000 – 20,000). Flow directions in the round pipe attached with the V-rings are varied. The V-apex setting downstream is referred to as “V-Downstream, while the V-apex setting upstream is referred to as “V-Upstream”. The flow and… More >

Mohamed Shaimi^* , Rabha Khatyr, Jaafar Khalid Naciri

Frontiers in Heat and Mass Transfer, Vol.20, pp. 1-14, 2023, DOI:10.5098/hmt.20.23

Abstract This paper presents an exact analytical solution to the extended Graetz problem in microchannels and microtubes, including axial heat conduction, viscous dissipation, and rarefaction effects for an imposed constant wall temperature. The flow in the microchannel or microtube is assumed to be hydrodynamically fully developed. At the same time, the first-order slip-velocity and temperature jump models represent the wall boundary conditions. The energy equation is solved analytically, and the solution is obtained in terms of Kummer functions with expansion constants directly determined from explicit expressions. The local and fully developed Nusselt numbers are calculated in terms of the Péclet number,… More >