Begell House Inc.
Heat Transfer Research
HTR
1064-2285
51
7
2020
SUPPLEMENTARY CORRELATION EQUATIONS FOR LAMINAR FORCED CONVECTION OF CROSS CREEPING FLOWS AROUND HORIZONTAL CYLINDERS AND WIRES AT Re ≤ 1
603-607
10.1615/HeatTransRes.2020029211
Antonio
Campo
Department of Mechanical Engineering, The University of Texas at San Antonio, San Antonio,
Texas 78249, USA
laminar forced convection
creeping flows
horizontal cylinders and wires
supplementary correlation equations for a mean Nusselt number
The heat convection literature contains correlation equations for laminar forced convection of fluid cross flows past horizontal cylinders and wires, which are applicable to Reynolds numbers of the order of Re = 1 and higher. The objective of the short communication is to develop supplementary correlation equations of compact form for the so-called creeping flows operating at low Reynolds numbers in the subregion with Re ≤ 1.
COMPARISON BETWEEN ADIABATIC AND NONADIABATIC ABSORPTION CHILLERS USING AMMONIA-LITHIUM NITRATE AND WATER-LITHIUM BROMIDE SOLUTIONS
609-621
10.1615/HeatTransRes.2019026621
Alejandro
Zacarias
Instituto Politécnico Nacional, ESIME Azcapotzalco, Av. de las Granjas 682, Col. Santa Catarina, 02250, Ciudad de México, México
J. A.
Quiroz
Instituto Politécnico Nacional, ESIME Azcapotzalco, Av. de las Granjas 682, Col. Santa Catarina, 02250, Ciudad de México, México
Geydy Luz
Gutiérrez-Urueta
Departamento de Ingenieria Mecánica-Eléctrica, Universidad Autónoma de San Luis Potosi,
Dr. Manuel Nava No. 8, Zona Universitaria Poniente, 78290, San Luis Potosi, México
M.
Venegas
Unidad Asociada de Ingenieria Termicay de Fluidos CSIC-UC3M; Departamento de Ingenieria Termicay de Fluidos, Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Leganes, Madrid, Spain
Ignacio
Carvajal
Instituto Politécnico Nacional, ESIME, UPALM, Ciudad de México 07738, México
J.
Rubio
Instituto Politécnico Nacional, ESIME Azcapotzalco, Av. de las Granjas 682, Col. Santa Catarina,
02250, Ciudad de México, México
ammonia-lithium nitrate
water-lithium bromide
adiabatic absorption
nonadiabatic absorption
chiller
This work deals with the comparison of the performance of a single-effect absorption chiller using two main configurations: equipped with a nonadiabatic absorber or an adiabatic one. Simulations were developed based on thermodynamic balances, operating with ammonia-lithium nitrate (NH3−LiNO3) and water-lithium bromide (H2O−LiBr) as working pairs. Parameters of evaluation are the coefficient of performance COP, circulation ratio f, and driving heat rate Qg. Results illustrate that the nonadiabatic absorption system presents better performance parameters for a given operating point, attributable to a higher concentration change in the absorber for a fixed cooling capacity. When the generator temperature Tg is varied, a strong influence on the performance parameters f, Qg, and COP is observed. However, from a certain value of Tg its variation has a less influence on the performance. When the condenser temperature increases, the COP decreases. The contrary happens if the evaporation temperature is increased. This is valid for both adiabatic and nonadiabatic cases.
A COMPREHENSIVE STUDY ON THE THERMAL CONDUCTIVITY OF HIGH-EFFICIENCY ALUMINUM POROUS MICROCHANNELS
623-639
10.1615/HeatTransRes.2020029130
Jingang
Yang
Jilin Jianzhu University, Changchun, 130000, China
Hao
Wang
Jilin Jianzhu University, Changchun, 130000, China
Ang
Liu
Jilin Jianzhu University, Changchun, 130000, China
microchannel
axial fins
COMSOL analogue
heat transfer coefficient
PEC
AMCA flat tube is the key part of the condenser. This paper introduces a new type of microchannel heat sink (MHS) composed of a porous extruded aluminum flat tube in response to the increasing demand for heat transfer efficiency. In order to investigate the heat transfer characteristics of the heat sink, a mathematical model of three-dimensional conjugate heat transfer was first established. The availability of the submodel was obtained by the experimental and simulated contrast diagrams of the resistance coefficient and Nu number. Secondly, the effects of the height-to-width ratio of different channels and the number of channels on the heat transfer performance of the microchannel heat sink were studied. The thermal conductivity resistance, convective resistance, and heat capacity resistance of the three components of thermal resistance were calculated in detail. Furthermore, the flow resistance coefficient eventually increased in order to achieve an enhanced heat transfer. This study also provided a reference for the design of this type of heat sink.
INTEGRATED INFLUENCES OF INCLINATION, NANOFLUIDS, AND FINS ON MELTING INSIDE A HORIZONTAL ENCLOSURE WITH CROSS SECTION OF MAJOR CIRCLE SECTOR
641-688
10.1615/HeatTransRes.2019031101
Mahmoud
Jourabian
National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu, China
Shouqi
Yuan
National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu, China
Jinfeng
Zhang
National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu, China
Yalin
Li
National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu, China
Ahmad Ali Rabienataj
Darzi
Department of Mechanical Engineering, University of Mazandaran, Babolsar, Mazandaran, Iran
constrained melting
lattice Boltzmann method
major circle sector
inclination
nanoparticles
partial fin
Combined effects of inclination with respect to gravity, Cu nanoparticles, and stainless steel partial fins on constrained ice melting with natural convection inside a horizontal enclosure with cross section of major circle sector are examined. Two-dimensional temperature-based lattice Boltzmann method (TLBM) in single-phase framework is applied to treat the solid-liquid phase change process in the presence of nanofluids. Pertinent variables such as transient liquid fraction, average Nusselt number on hot surfaces, average temperature of PCM, and maximum velocity in molten PCM are investigated. It is found that influences of nanofluids and partial internal fins on thermal performance of the horizontal enclosure and interface morphology are related to inclination angle despite the negative effects of increment of viscosity, weakening of natural convection flow, and decrease of storage capacity.
EFFECTS OF LOCAL THERMAL NONEQUILIBRIUM ON THE ONSET OF CONVECTION IN A MAGNETIC NANOFLUID LAYER
689-705
10.1615/HeatTransRes.2020031119
Amit
Mahajan
Department of Applied Sciences, National Institute of Technology Delhi, Delhi–110040, India
Mahesh
Sharma
Maharaja Agrasen University
local thermal nonequilibrium
instability
magnetic nanofluid
magnetic nanoparticles
natural convection
In this article, a numerical study of convective transport in a magnetic nanofluid (MNF) subject to an applied magnetic field has been carried out using the local thermal nonequilibrium (LTNE) model. A two-phase model consisting of the effect of Brownian motion, thermophoresis, and magnetophoresis is considered. The temperature within the fluid phase is assumed to be different from the temperature within the particle solid phase. The Chebyshev pseudospectral method is used to solve the eigenvalue problem for small-amplitude perturbation. The present study focuses on two different environments: (i) gravity environment and (ii) microgravity environment. In both environments, the results are derived for water-based and ester-based magnetic nanofluids (MNFs). The effect of various important parameters such as thermal diffusivity ratio ε, interphase heat transfer NH, thermal capacity ratio γ, the modified diffusivity ratio NA, concentration Rayleigh number Rn, Lewis number Le, the Langevin parameter αL, and the nonlinearity of magnetization M3 is observed at the onset of MNF convection for free-free boundaries. The value of the critical thermal Rayleigh number Rac and the critical magnetic Rayleigh number Ngc decreases as the values of NH, γ, NA, Rn, Le, and M3 increase, whereas, the values of both Rac and Ngc increase as the value of ε increases. The system is found to be more stable for ester-based MNFs as compared to water-based MNFs in both gravity and microgravity environment.