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1. Thermal-hydraulic characteristics of supercritical pressure CO2 in vertical tubes under cooling and heating conditions

Author:
Guo, Jiangfeng; Xiang, Mengru; Zhang, Haiyan; Huai, Xiulan; Cheng, Keyong; Cui, Xinying
Source:
Energy 2019 v.170 pp. 1067-1081
ISSN:
0360-5442
Subject:
heat transfer; heat transfer coefficient,   etc   ; carbon dioxide; heat exchangers; models;     Show all 5 Subjects
Abstract:
... The thermal-hydraulic properties of supercritical pressure CO2 (SCO2) in vertical tubes under cooling and heating conditions were numerically investigated by using SST turbulent model with variable turbulent Prandtl number model. Under cooling condition, the peak of heat transfer coefficient appears near the pseudo-critical point, the buoyancy effect enhances local heat transfer for upward flow wh ...
DOI:
10.1016/j.energy.2018.12.177

2. Thermodynamic mapping of power cycles working around the critical point

Author:
González-Portillo, Luis F.; Muñoz-Antón, Javier; Martínez-Val, José M.
Source:
Energy conversion and management 2019 v.192 pp. 359-373
ISSN:
0196-8904
Subject:
heat transfer,   etc   ; enthalpy; entropy; temperature;     Show all 4 Subjects
Abstract:
... A new thermodynamic coefficient, called logarithmic factor of isobaric expansion, is defined for a better guidance in the cycle characterization of regenerative cycles working totally or partially at supercritical conditions. The logarithmic factor of isobaric expansion allows to generalize the characterization of cycles working around the critical point, agglutinating supercritical and transcriti ...
DOI:
10.1016/j.enconman.2019.04.022

3. Thermal and electrical performance of low-concentrating PV/T and flat-plate PV/T systems: A comparative study

Author:
Zhang, Heng; Liang, Kai; Chen, Haiping; Gao, Dan; Guo, Xinxin
Source:
Energy 2019 v.177 pp. 66-76
ISSN:
0360-5442
Subject:
heat transfer,   etc   ; electric power; geometry;     Show all 3 Subjects
Abstract:
... Photovoltaic/thermal (PV/T) technologies are used to comprehensively utilize photovoltaic and solar thermal, among which concentrating PV/T technology can enhance the performance of a PV/T system. To analyze the performance of a LCPV/T system with a geometric concentration ratio of 4, the LCPV/T system and a conventional flat-plate PV/T system were fabricated and experimentally studied under a con ...
DOI:
10.1016/j.energy.2019.04.056

4. Investigation of modified horizontal wing cut twisted tapes fitted with rod and spacer at trailing edge on heat transfer properties in Double Glazing V-Trough solar water heaters

Author:
Gnanaraj, D.; Vijayan, R.
Source:
International journal of green energy 2019 v.16 no.7 pp. 501-509
ISSN:
1543-5083
Subject:
heat transfer,   etc   ; friction; solar heaters;     Show all 3 Subjects
Abstract:
... An experimental analysis of heat transfer efficiency in double glazing solar water heating system having full-length Horizontal wing cut twisted tapes having twist ratio 3 fitted with rod or spacer of dimensions 125 mm, 250 mm, and 500 mm as length at the trailing edges has been dealt in this work. The experimental results have been compared with a plain tube with similar operating conditions and ...
DOI:
10.1080/15435075.2019.1590840

5. Experimental studies of organic Rankine cycle systems using scroll expanders with different suction volumes

Author:
Xi, Huan; Li, Ming-Jia; Zhang, Hong-Hu; He, Ya-Ling
Source:
Journal of cleaner production 2019 v.218 pp. 241-249
ISSN:
0959-6526
Subject:
heat transfer,   etc   ; mass flow; torque;     Show all 3 Subjects
Abstract:
... By using R123 as the working fluid, experimental studies for basic organic Rankine cycle (BORC) and organic Rankine cycle with a regenerator (RORC) are carried out, two scroll expanders with different suction volumes are installed and examined (1# expander with the suction value of 66 mL/r; 2# expander with the suction value of 86 mL/r). Comparison between the different system configurations and e ...
DOI:
10.1016/j.jclepro.2019.01.302

6. Effects of tube shapes on the performance of recuperative and regenerative heat exchangers

Author:
Tran, Ngoctan; Wang, Chi-Chuan
Source:
Energy 2019 v.169 pp. 1-17
ISSN:
0360-5442
Subject:
heat transfer,   etc   ; heat exchangers; prediction;     Show all 3 Subjects
Abstract:
... In the present work, the effects of tube shapes on the heat transfer and fluid flow characteristics of the shell-and-tube heat exchangers –including square, rectangular, circular, elliptical, equilateral- and isosceles-triangular shapes –are numerically investigated in detail. Six parameters –including (1) rectangular-tube ratios (⍺ = tube height/width), (2) triangular-tube ratios (β = two-side ed ...
DOI:
10.1016/j.energy.2018.11.127

7. Definition of cycle based comprehensive efficiency of a cooled turbine

Author:
Ba, Wei; Wang, Xiao-chen; Li, Xue-song; Ren, Xiao-dong; Gu, Chun-wei
Source:
Energy 2019 v.168 pp. 601-608
ISSN:
0360-5442
Subject:
heat transfer,   etc   ; air; energy; mixing;     Show all 4 Subjects
Abstract:
... As known that the cooling technology is commonly used in the turbine to protect the turbine blade. The mixing and heat transfer between the high pressure cooling air from the compressor and the turbine main flow would cause energy loss, and it will influence the gas turbine cycle performance. However, the existing definitions of the cooled turbine efficiency always take no account of the work whic ...
DOI:
10.1016/j.energy.2018.11.137

8. Influence of triangle tube structure with twisted tape on the thermo-hydraulic performance of nanofluids in heat-exchange system based on thermal and exergy efficiency

Author:
Qi, Cong; Liu, Maoni; Tang, Jinghua
Source:
Energy conversion and management 2019 v.192 pp. 243-268
ISSN:
0196-8904
Subject:
heat transfer,   etc   ; Reynolds number; exergy; nanofluids; nanoparticles;     Show all 5 Subjects
Abstract:
... An experiment is carried out to research the thermo-hydraulic performance of TiO2-H2O nanofluids in triangle tubes while taking the effect of twisted tapes into consideration. The theories of thermal and exergy efficiency are applied to estimate this system. The influence of mass fractions of nanoparticles (0.1 wt%, 0.3 wt% and 0.5 wt%), Reynolds numbers (Re = 800–9000), different structures of tr ...
DOI:
10.1016/j.enconman.2019.04.047

9. A decentralized biomass torrefaction reactor concept. Part II: Mathematical model and scaling law

Author:
Kung, Kevin S.; Ghoniem, Ahmed F.
Source:
Biomass and bioenergy 2019 v.125 pp. 204-211
ISSN:
0961-9534
Subject:
heat transfer,   etc   ; biomass; mathematical models; prototypes; torrefaction;     Show all 5 Subjects
Abstract:
... In Part I of the study, we proposed a simplified biomass torrefaction moving bed reactor design capable of decentralized, small-scale, and mobile deployment operated under an oxygen-lean condition. We built and validated a laboratory-scale test reactor. In the present study, we develop a mathematical description of the reactor and show that it produces reasonable fit to our experimental data. Cont ...
DOI:
10.1016/j.biombioe.2018.12.001

10. Which dimensional model for the analysis of a coated tube adsorber for adsorption heat pumps?

Author:
Dias, João M.S.; Costa, Vítor A.F.
Source:
Energy 2019 v.174 pp. 1110-1120
ISSN:
0360-5442
Subject:
heat transfer,   etc   ; adsorption; heat pumps; models;     Show all 4 Subjects
Abstract:
... This paper presents the analysis of a coated tube adsorber for adsorption heat pumps (AHP), starting from a well-established physical model and providing information on how many dimensions need to be considered for a given accuracy. A lumped-parameter model, one-dimensional (radial direction) and two-dimensional (radial and longitudinal directions) distributed-parameter models describing the adsor ...
DOI:
10.1016/j.energy.2019.03.028

11. Experimental performance of a two-stage (50×) parabolic trough collector tested to 650 °C using a suspended particulate heat transfer fluid

Author:
Widyolar, Bennett; Jiang, Lun; Ferry, Jonathan; Winston, Roland; Cygan, David; Abbasi, Hamid
Source:
Applied energy 2019 v.240 pp. 436-445
ISSN:
0306-2619
Subject:
heat transfer,   etc   ; prototypes; solar collectors; temperature; California;     Show all 5 Subjects
Abstract:
... A two-stage high-concentration collector has been developed which pairs a 45° half rim angle parabolic trough with a secondary compound parabolic concentrator to achieve 50× concentration on the thermal absorber. An experimental prototype fabricated and installed at the University of California, Merced was tested on-sun up to 650 °C using a suspended particulate heat transfer fluid (HTF). The prot ...
DOI:
10.1016/j.apenergy.2019.02.073

12. Improving the performance of volumetric solar receivers with a spectrally selective gradual structure and swirling characteristics

Author:
Zhu, Qibin; Xuan, Yimin
Source:
Energy 2019 v.172 pp. 467-476
ISSN:
0360-5442
Subject:
heat transfer,   etc   ; porosity; solar collectors; temperature;     Show all 4 Subjects
Abstract:
... The radiation loss at the front region of the volumetric solar receiver limits the solar to thermal efficiency of the receiver. With respect to the purpose of moving the highest temperature front of the receiver from the entrance to the inner position of the solar receiver, a spectrally selective gradual structure receiver with swirling characteristics is designed. A three-layer structure along th ...
DOI:
10.1016/j.energy.2019.01.166

13. An in-situ method of identifying ingredients of zeotropic refrigerants by inversion problem technique

Author:
Zhang, Ji; Yuan, Han; Mei, Ning; Li, Yan; Si, Hongyu; Cao, Peichun
Source:
International journal of green energy 2019 v.16 no.4 pp. 269-276
ISSN:
1543-5083
Subject:
heat transfer,   etc   ; Reynolds number; ingredients; temperature;     Show all 4 Subjects
Abstract:
... An inversion method is applied to identify ingredients of zeotropic refrigerants in a circular duct. In the case of low Reynolds number and constant fluid pressure, the temperature distribution of direct heat transfer problem can be solved numerically. The thermophysical parameters of zeotropic refrigerants are determined by using inversion problem technique, the ingredients of refrigerants can be ...
DOI:
10.1080/15435075.2018.1551222

14. Conjugate heat transfer in a duct using nanofluid by two-phase Eulerian–Lagrangian method: Effect of non-uniform heating

Author:
Borah, Abhijit; Boruah, Manash Protim; Pati, Sukumar
Source:
Powder technology 2019 v.346 pp. 180-192
ISSN:
0032-5910
Subject:
heat transfer,   etc   ; nanofluids; nanoparticles; powders; thermal conductivity;     Show all 5 Subjects
Abstract:
... The underlying physics behind the effect of non-uniform heating on the heat transfer characteristics for flow of Al2O3-water nanofluid through a duct having finite wall thickness subjected to sinusoidal heat flux has been numerically investigated in this study. The nanofluid is modelled as a single fluid with two phases using the Eulerian-Lagrangian formulation. The concomitant implications of the ...
DOI:
10.1016/j.powtec.2019.01.059

15. A new drag force and heat transfer correlation derived from direct numerical LBM-simulations of flown through particle packings

Author:
Kravets, B.; Rosemann, T.; Reinecke, S.R.; Kruggel-Emden, H.
Source:
Powder technology 2019 v.345 pp. 438-456
ISSN:
0032-5910
Subject:
heat transfer,   etc   ; hydrodynamics; interphase; models; powders;     Show all 5 Subjects
Abstract:
... In the present work a thermal Lattice-Boltzmann method (TLBM) is applied to study convection-diffusion problems and to determine averaged Nusselt numbers for particles being part of differently dense random packings. For the carried out numerical investigations a 3D TLBM framework is derived. Therein the hydrodynamic side is solved with a D3Q19 multiple-relaxation-time (MRT) collision operator and ...
DOI:
10.1016/j.powtec.2019.01.028

16. A comprehensive review on synthesis, stability, thermophysical properties, and characterization of nanofluids

Author:
Sezer, Nurettin; Atieh, Muataz A.; Koç, Muammer
Source:
Powder technology 2019 v.344 pp. 404-431
ISSN:
0032-5910
Subject:
heat transfer,   etc   ; nanofluids; powders; thermal properties;     Show all 4 Subjects
Abstract:
... Nanofluids are a new generation of heat transfer fluids that have attracted researchers' attention from diverse fields due to their anomalous thermal behavior and potential applications. In the past few decades, numerous studies have been carried out to investigate the thermal properties of nanofluids. A long-term stability is the first basic requirement in nanofluids research for maintaining thei ...
DOI:
10.1016/j.powtec.2018.12.016

17. Computational study on fluid flow and heat transfer characteristic of hollow structured packed bed

Author:
Guo, Zehua; Sun, Zhongning; Zhang, Nan; Ding, Ming; Bian, Haozhi; Meng, Zhaoming
Source:
Powder technology 2019 v.344 pp. 463-474
ISSN:
0032-5910
Subject:
heat transfer,   etc   ; equipment; industrial applications; powders; temperature;     Show all 5 Subjects
Abstract:
... The development of advanced packed beds has remarkable applications in the design of new equipment for related industries. Recently, a hybrid of the structured and random packed beds is proposed—the hollow structured packed bed (HSPB), which can be easily formed with ordered ring structures and a free channel along the centerline by the particle self-assembly feature in a random packed bed at 2 <  ...
DOI:
10.1016/j.powtec.2018.11.101

18. Comparative study on combustion and thermodynamics performance of gasoline direct injection (GDI) engine under cold start and warm-up NEDC

Author:
Liu, Qi; Liu, Jingping; Fu, Jianqin; Li, Yangyang; Luo, Baojun; Zhan, Zhangsong; Deng, Banglin
Source:
Energy conversion and management 2019 v.181 pp. 663-673
ISSN:
0196-8904
Subject:
heat transfer,   etc   ; cold; combustion; gasoline; temperature;     Show all 5 Subjects
Abstract:
... In this study, the chassis dynamometer tests for a gasoline-powered passenger vehicle were carried out under cold start and warm-up NEDC. The operating states, combustion and performance parameters of engine were measured continuously during vehicle driving cycles. Then, the combustion and thermodynamics processes under cold start and warm-up NEDC were compared and the influence factors for their ...
DOI:
10.1016/j.enconman.2018.12.043

19. A novel ultra-thin flattened heat pipe with biporous spiral woven mesh wick for cooling electronic devices

Author:
Zhou, Wenjie; Li, Yong; Chen, Zhaoshu; Deng, Liqiang; Gan, Yunhua
Source:
Energy conversion and management 2019 v.180 pp. 769-783
ISSN:
0196-8904
Subject:
heat transfer,   etc   ; cameras; copper; electronic equipment; permeability;     Show all 5 Subjects
Abstract:
... In this work, a novel biporous spiral woven mesh wick is developed to enhance the thermal performance of an ultra-thin flattened heat pipe for cooling high heat flux electronic devices. The biporous wick with different sized pores is hybrid woven using 0.05 and 0.04 mm diameter copper wires in every strand. Three different structures are designed to study the effect of the characteristic parameter ...
DOI:
10.1016/j.enconman.2018.11.031

20. Continuous power output criteria and optimum operation strategies of an upgraded thermally regenerative electrochemical cycles system

Author:
Guo, Juncheng; Wang, Yuan; Gonzalez-Ayala, Julian; Roco, J.M.M.; Medina, A.; Calvo Hernández, A.
Source:
Energy conversion and management 2019 v.180 pp. 654-664
ISSN:
0196-8904
Subject:
heat transfer,   etc   ; electrochemistry; models; thermal energy;     Show all 4 Subjects
Abstract:
... In order to utilize the low-grade thermal energy efficiently, a more realistic model of thermally regenerative electrochemical cycles system with continuous power output is proposed in which the heat transfer irreversibility, external heat leakage and non-ideal regeneration losses are taken into account. Besides, the symmetry of cells, which is necessary for a practical thermally regenerative elec ...
DOI:
10.1016/j.enconman.2018.11.024