Relevant bibliographies by topics / Convective heat transfer coefficient (h)

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  2. Dissertations / Theses
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Academic literature on the topic 'Convective heat transfer coefficient (h)'

Author: Grafiati
Published: 5 June 2025
Last updated: 15 July 2025

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Journal articles on the topic "Convective heat transfer coefficient (h)"

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Jani, Jaronie Mohd, Sunan Huang, Martin Leary, and Aleksandar Subic. "Analysis of Convective Heat Transfer Coefficient on Shape Memory Alloy Actuatorunder Various Ambient Temperatures with Finite Difference Method." Applied Mechanics and Materials 736 (March 2015): 127–33. http://dx.doi.org/10.4028/www.scientific.net/amm.736.127.

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The demand for shape memory alloy (SMA) actuators for technical applications is steadily increasing; however SMA may have poor deactivation time due to relatively slow convective cooling. Convection heat transfer mechanism plays a critical role in the cooling process, where an increase of air circulation around the SMA actuator (i.e. forced convection) provides a significant improvement in deactivation time compared to the natural convection condition. The rate of convective heat transfer, either natural or forced, is measured by the convection heat transfer coefficient, which may be difficult to predict theoretically due to the numerous dependent variables. In this work, a study of free convective cooling of linear SMAactuators was conducted under various ambient temperatures to experimentally determine the convective heat transfer coefficient. A finite difference equation (FDE) was developed to simulate SMA response, and calibrated with the experimental data to obtain the unknown convectiveheat transfer coefficient, h. These coefficients are then compared with the available theoretical equations, and it was found that Eisakhaniet. almodel provides good agreement with the Experiment-FDE calibrated results. Therefore, FDE is reasonably useful to estimate the convective heat transfer coefficient of SMA actuator experiments under various conditions, with a few identified limitations (e.g. exclusion of other associative heat transfer factors).
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Zhang, Ruihao, Sixian Wang, Shan Qing, Zhumei Luo, and Zhang Xiaohui. "Research on convective heat transfer characteristics of Fe3O4magnetic nanofluids under vertical magnetic field." Thermal Science, no. 00 (2021): 151. http://dx.doi.org/10.2298/tsci201215151z.

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This paper focuses on the convective heat transfer characteristics of Fe3O4 /Water magnetic nanofluids under laminar and turbulent conditions. After verifying the accuracy of the experimental apparatus, the effects of magnetic field strength, concentration, Reynolds number and temperature on the convective heat transfer coefficient have been studied. The convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions were studied in depth, and the influence of each factor on the heat transfer coefficient was analyzed by orthogonal experimental design method. Under the laminar flow conditions, the convective heat transfer of magnetic nanofluids performed best when the Reynolds number was 2000, the magnetic field strength was 600, the temperature was 30? and the concentration was 2%. And the convective heat transfer coefficient (h) increased by 3.96% than the distilled water in the same conditions. In turbulent state, the convective heat transfer of magnetic nanofluids performed the best when the Re was 6000, the magnetic field strength was 600, the temperature was 40? and the concentration was 2%. The h increased by 11.31% than the distilled water in the same Reynolds number and the magnetic field strength conditions.
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Rozas, Carlos, Oswaldo Erazo, Virna Ortiz-Araya, Rodrigo Linfati, and Claudio Montero. "Experimental and Statistical Determination of Convective Heat and Mass Transfer Coefficients for Eucalyptus nitens Sawn Wood Drying." Forests 15, no. 8 (2024): 1287. http://dx.doi.org/10.3390/f15081287.

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This study aimed to develop a model using experimentally obtained convective heat and mass transfer coefficients to predict the effect of temperature, humidity, and drying rate on wood drying. Tangential wood samples of Eucalyptus nitens (H. Deane & Maiden) were used in the investigation. The experimental design consisted of two temperature levels (40 °C and 55 °C), two relative humidity levels (55% and 75%), and two air velocity settings (2 m·s−1 and 3 m·s−1). The experiments were conducted under a constant evaporation rate, spanning the maximum and critical moisture content in the wood. A statistical model using multivariate regression was created to predict the convective heat and mass transfer coefficients. The results indicated that the experimental data and empirical correlations exhibited an error margin of 37.77% and 37.86%, respectively. A significant positive correlation was found between the convective heat transfer coefficient and air velocity, temperature, and relative humidity, while the convective mass transfer coefficient showed a significant positive correlation only with air velocity and temperature. The model predicted the convective heat and mass transfer coefficients with high accuracy and statistical significance. Using the proposed method, we successfully obtained both convective coefficients, which enable accurate description of heat and mass flow during the convective drying of Eucalyptus nitens wood.
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Luo, Chuan, Chuan Li, Xiaorong Wan, and Zhengang Zhao. "Convective Heat Transfer Coefficient of Insulation Paper–Oil Contact Surface of Transformer Vertical Oil Channel." Coatings 13, no. 1 (2023): 81. http://dx.doi.org/10.3390/coatings13010081.

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Insulation paper is the primary inter-turn insulation material for transformer windings. However, insulation paper is a poor conductor of heat and seriously impacts the natural convective heat dissipation in the winding oil channels. In order to study the convective heat transfer performance of the transformer vertical oil channel, the heat transfer characteristics of the two-dimensional boundary layer of the insulation paper–oil contact surface were analysed, and a characteristic number equation with a roughness correction factor was established. Based on the similarity principle and modelling theory, an experimental apparatus was designed to determine the convective heat transfer coefficient of the insulation paper–oil contact surface. Coefficients were obtained for different qualitative temperatures and characteristic lengths. Parametric fitting of the experimental data was carried out to obtain the correction factors. The results show that the natural convective heat transfer coefficient h of the insulation paper–oil contact surface is positively and linearly related to qualitative temperature and inversely related to characteristic length. For temperatures of 312.9 K to 328.1 K and characteristic lengths of 3 cm, h ranges from 116.15 to 144.38 W/(m2· K). For temperatures of 319.0 K to 337.9 K and lengths of 6 cm, h ranges from 103.79 to 131.14 W/(m2· K). The correction factor of the characteristic equation coefficient is 1.067. The maximum deviation of h calculated with a coefficient of 0.63 and an exponent of 0.25 is 5.93%. The results are essential for modelling the transformer space thermal circuit and solving the hot-spot temperature problem.
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Anderson, Ann M. "Decoupling Convective and Conductive Heat Transfer Using the Adiabatic Heat Transfer Coefficient." Journal of Electronic Packaging 116, no. 4 (1994): 310–16. http://dx.doi.org/10.1115/1.2905703.

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In many heat transfer situations, such as those found in the electronics cooling field, more than a single mode of heat transfer occurs. For example, modules on a printed circuit board dissipate heat through convection to the air, through conduction to the board and through radiation to the surroundings. The adiabatic heat transfer coefficient, had, works well in such situations because it describes the change in wall temperature due to each incremental change in the convective heat transfer rate (due to conduction, radiation, or generation in the wall). The value of had is independent of the surface heat transfer distribution and can be used with the superposition method to interface between a convection solver and a conduction solver and “decouple” a conjugate heat transfer problem. If one uses the heat transfer coefficient based on the mean fluid temperature, hm, the problem is complicated because the value of hm is a function of the surface heat transfer distribution. This decoupling strategy is demonstrated through a series of numerical computations which solve the fully conjugate problem for laminar flow in a duct. These results are then compared to the decoupled solution. Excellent agreement between the fully conjugate and the decoupled solution is found for all cases when had and Tad are used to decouple the problem. Using hm and Tm can result in temperature prediction errors as large as 50 percent (for the cases studied here). The results show that when the Biot number (formulated as the resistance to axial wall conduction over the resistance to convection) is greater than 1.0 the adiabatic heat transfer coefficient should be used to decouple the problem. If the Biot number is below this value, h based on the mean temperature (for uniform surface temperature) can be used as the decoupler.
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Chowdhury, Manojit, Ankita Banerjee, Rahul Das, Shrilekha Das, and Kamlesh Prasad. "Influence of Temperature and Mass Flow Rate on Heat Transfer Characteristics in Parallel Flow Corrugated Plate Heat Exchanger." Journal of Agricultural Engineering (India) 62, no. 1 (2025): 120–34. https://doi.org/10.52151/jae2025621.1917.

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Efficient heat exchangers (HEs) are essential components in various industrial processes, enabling transfer of thermal energy between fluids. Current research investigated heat transfer and fluid flow characteristics of a corrugated surface type parallel flow plate heat exchanger (PHE) with water as a heat transfer fluid. The study aims to enhance our understanding of how these operational parameters impact heat transfer performance and provide insights into optimizing the design and operation of such HEs for improved energy efficiency. The performance of HE was evaluated at variable temperature and mass flow rate of pumped water. The thermophysical properties of hot and cold water, dimensions of HE, heat transfer coefficient and effectiveness of the PHE were estimated. Results revealed that the overall and convective heat transfer coefficient increased proportionally with temperature and mass flow rate of pumped water. The study found approximately 75% and 23% increase in the convective heat transfer coefficients (h) and overall heat transfer coefficient (U), respectively, when increasing the hot water mass flow rate from 0.03 to 0.09 m s-1. The heat transfer coefficient exhibited a linear relationship with Reynolds number (<2000) and Nusselt number (<100), indicating laminar flow. Moreover, maximum effectiveness (0.955) was achieved at 65°C with a higher mass flow rate.
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Gao, Ling, Wen Guang Geng, Xiao Xu Ma, Xiu Li Ma, Guang Liang Luo, and Xuan You Li. "An Experimental Investigation on the Heat Transfer Coefficient of Oscillating Heat Pipes." Advanced Materials Research 732-733 (August 2013): 78–82. http://dx.doi.org/10.4028/www.scientific.net/amr.732-733.78.

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This paper presents an experimental study on total heat transfer coefficient (ht) in oscillating heat pipe heat exchanger hot air flow tunnels, ht plays an important role in the oscillating heat pipes design process. In this paper, ht and the convective heat transfer coefficient (h) was investigated by experimentally and theoretical calculation respectively. From experimental study, the relationship between the ratio of heat transfer coefficient and the relative humidity is obtained. The results show that the ratio of ht to h increases from 5 to 20 as the relative humidity of the hot gas increasing from 19.22% to 60%. According to the experimental data, a matched curve and an empirical equation were presented, which can be described as ht=h(1.87783+0.09631x+0.0032x2).
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Xu, Qian, Yunbing Wu, Ye Chen, and Zhengwei Nie. "Unlocking the Thermal Efficiency of Irregular Open-Cell Metal Foams: A Computational Exploration of Flow Dynamics and Heat Transfer Phenomena." Energies 17, no. 6 (2024): 1305. http://dx.doi.org/10.3390/en17061305.

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An open-cell metal foam has excellent characteristics such as low density, high porosity, high specific surface area, high thermal conductivity, and low mass due to its unique internal three-dimensional network structure. It has gradually become a new material for enhanced heat transfer in industrial equipment, new compact heat exchangers, microelectronic device cooling, etc. This research established a comprehensive three-dimensional structural model of open-cell metal foams utilizing Laguerre–Voronoi tessellations and employed computational fluid dynamics to investigate its flow dynamics and coupled heat transfer performance. By exploring the impact of foam microstructure on flow resistance and heat transfer characteristics, the study provided insights into the overall convective heat transfer performance across a range of foam configurations with varying pore densities and porosities. The findings revealed a direct correlation between convective heat transfer coefficient (h) and pressure drop (ΔP) with increasing Reynolds number (Re), accompanied by notable changes in fluid turbulence kinetic energy (e) and temperature (T), ultimately influencing heat transfer efficiency. Furthermore, the analysis demonstrated that alterations in porosity (ε) and pore density significantly affected unit pressure drop (ΔP/L) and convective heat transfer coefficient (h). This study identified an optimal configuration, highlighting a metal foam with a pore density of 20 PPI and a porosity of 95% as exhibiting superior overall convective heat transfer performance.
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Schutzeichel, Maximilian Otto Heinrich, Thorben Strübing, Ozan Tamer, Thomas Kletschkowski, Hans Peter Monner, and Michael Sinapius. "Experimental and Numerical Investigation of a Multifunctional CFRP towards Heat Convection under Aircraft Icing Conditions." Applied Mechanics 3, no. 3 (2022): 995–1018. http://dx.doi.org/10.3390/applmech3030056.

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A combined experimental and numerical approach for the analysis of convective heat transfer from a multifunctional flat plate specimen under aircraft icing conditions is presented. The experimental setup including a heat control and measurement system that is installed in a de-icing test bed. The ambient temperature (θa=[253,283]K), air velocity (va={0,15,30}ms), and angle of attack (α={10,30}∘) are varied, and their influence on heat transfer during local Joule heating is discussed. The numerical approach utilises the results to compute the convective heat transfer coefficients (HTC) based on Newton’s convective heat transfer condition. Results indicate that the numerical model represents the heat transfer behaviour with high accuracy. The HTC for free convection was found to hold h¯≈2.5Wm2K and h¯≈[10,40]Wm2K for forced convection conditions with minor scattering. The increase in HTC under forced convection conditions has a significant effect on the overall heat transfer behaviour, resulting in high temperature gradients within the material. The functional optimisation of multifunctional structures will benefit from including application related convection conditions, dealing with resulting temperature fields by structural design. It is expected that multifunctional structures for de-icing as well as for structural energy storage, morphing structures, or stiffness adaptive structures with similar material constituents will benefit from this recognition.
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Farhadi, M., K. Sedighi, and M. M. Madani. "Convective cooling of tandem heated squares in a channel." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, no. 4 (2008): 965–78. http://dx.doi.org/10.1243/09544062jmes1078.

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This article elaborates on the numerical simulation of forced convective incompressi-ble flow in a horizontal plane channel and heat transfer over two isothermal tandem square cylinders. Finite-volume method was applied to discretize the momentum and energy equations. This study details the effects of S/ H (gap between two squares), Reynolds number, and blockage ratio on the characteristics of flow field and heat transfer. The blockage ratios and Reynolds numbers were chosen between 12.5 to 50 per cent and 100≤ Re≤300, respectively. Results are presented in the form of time-averaged streamlines, instantaneous contours of temperature and vorticity, and some characteristics of fluid flow and heat transfer such as time-averaged of the local and total Nusselt number, drag coefficient, and Strouhal number. The present results show that the gap spacing between squares at high blockage ratios does not have an obvious effect on heat transfer. On the other hand, this parameter plays a main role on the drag coefficient at a high value ( S/ H=4), which is because of the formation of the vortex cores in gap spacing and downstream of the second square. The heat transfer rate of the second square increases with the increase of S/ H. Increasing the blockage ratio has a negative effect on convective heat transfer of the second square. With the vortex shedding in the gap spacing, the drag coefficient and the Nusselt number both increase in the second square in comparison to the first square.
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Dissertations / Theses on the topic "Convective heat transfer coefficient (h)"

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Samayamantula, Sri Prithvi Samrat. "Development of a Computer Program for Transient Heat Transfer Coefficient Studies." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright15581072805784.

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Eferemo, Daniel. "Numerical investigation of the convective heat transfer coefficient of the human body using a representative cylindrical model." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26904.

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The principal objective of this study is to investigate, develop and verify a framework for determining the convective heat transfer co-efficient from a cylindrical model that can easily be adaptable to more complex geometry - more specifically the human body geometry. Analysis of the model under forced convection airflow conditions between the transition velocity of about 1m/s - calculated using the Reynolds number - up until 12m/s were carried out. The boundary condition, however, also included differences in turbulence intensities and cylinder orientation with respect to wind flow (seen as wind direction in some texts). A total of 90 Computational Fluid Dynamic (CFD) calculations from these variations were analysed for the model under forced convective flow. Similar analysis were carried out for the model under natural convection with air flow velocity of 0.1m/s. Here, the temperature difference between the model and its surrounding environments and the cylinder orientation with respect to wind flow were varied to allow for a total of 15 CFD analysis. From these analysis, for forced convection, strong dependence of the convective heat transfer coefficient on air velocity, cylinder orientation and turbulence intensity was confirmed. For natural convection, a dependence on the cylinder orientation and temperature difference between the model and its environment was confirmed. The results from the CFD simulations were then compared with those found in texts from literature. Formulas for the convective heat transfer coefficient for both forced and natural convection considering the respective dependent variables are also proposed. The resulting formulas and the step by step CFD process described in this thesis provides a framework for the computation of the convective heat transfer coefficient of the human body via computer aided simulations. This framework can easily be adaptable to the convective heat transfer coefficient calculations of the human body with some geometric modelling adjustments, thus resulting in similar representative equations for a human geometric model.
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Wasson, Rachel Ann. "Separation of the Heat Transfer Components for Diffusion Flames Impinging onto Ceilings." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50588.

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Two series of experiments were performed to determine the flow characteristics and to quantify the heat transfer components from a propane diffusion flame impinging onto a ceiling. A 0.3 m square sand burner with propane as the fuel type provided a steady-state fire. In the first series of experiments, measurements of gas temperature and velocity were made at 76 mm vertical intervals above the burner up to the ceiling. Fire heat release rates (HRRs) of 50 kW and 90 kW with free flame length to ceiling height ratios, Lf/H, of 2, 1.5, 1, 0.8, 0.85 were used to determine their effects on the measured parameters. Gas temperatures within the continuous flaming region were relatively constant, and measured to be independent of ceiling height and HRR, while velocities increased with elevation and were independent of ceiling height yet weakly dependent on HRR. Within the intermittent region, gas temperature was weakly affected by the presence of the ceiling at various heights, while the effect on velocity was more pronounced. HRR had an effect on both temperature and velocity within the intermittent region of the fire plume. Comparisons with existing fire plume correlations showed that the unbounded correlations can be used to provide a good approximation of the gas temperature for the ceiling bounded case; while the correlations for the velocity can only be used for elevations up to approximately 60% of the ceiling height. Elevations above this cutoff were significantly affected by the presence of the ceiling. The second series of experiments investigated HRRs of 50 kW and 90 kW with free flame length to ceiling height ratios, Lf/H, of 2, 1.5, and 1. Heat flux and gas temperature at the stagnation point of the ceiling were measured using hybrid heat flux gauges and an aspirated Type K thermocouple. Four methods of calculating the convective heat transfer coefficient, h, were developed and adapted; two reference methods and two slope methods. The components of heat transfer at the impingement point were separated using these calculated h values. The reference method 2, and both slope methods only required the use of the non-cooled hybrid gauge measurements and were in overall good agreement with one another. The reference method 1 differed significantly, being up to 15.8 times lower than the others. The trends in the two groups were contradictory, with the h calculated using the reference method 1 increasing with ceiling height while the others showed no strong trend with ceiling height. The disagreements between the methods greatly affected the components of heat transfer, particularly at the lowest ceiling heights. Convection calculated using the h from reference method 1 contributed only 2-5% of the total exposure heat flux at the lowest ceiling heights, whereas with the other methods convection contributed 20-50% of the total exposure heat flux. The limitations of each method are discussed. Further investigation is required for all methods to determine their applicability within the flaming region of a fire.<br>Master of Science
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Lima, Carlos Umberto da Silva. "Ebulição convectiva de refrigerantes halogenados escoando no interior de tubos horizontais de cobre." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-11072018-120902/.

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A presente pesquisa teve por objetivo o estudo da ebulição convectiva dos novos refrigerantes halogenados no interior de tubos horizontais de cobre. Uma busca na literatura pertinente ao assunto mostrou que a determinação do coeficiente de transferência de calor pode ser determinado por correlações que, aqui, foram classificadas como: 1- Estritamente Convectivas, 2- Superposição de Efeitos e 3- Estritamente Empíricas. Essas correlações mostraram-se inadequadas a generalizações. Uma bancada experimental foi concebida e construída, o que permitiu a obtenção de dados experimentais envolvendo uma ampla faixa de condições operacionais. Efeitos de parâmetros físicos como a velocidade mássica, fluxo de calor, temperatura de saturação e título, foram investigados. Os dados experimentais obtidos foram utilizados no desenvolvimento de uma correlação para o coeficiente de transferência de calor na ebulição convectiva que satisfizesse adequadamente esses dados obtidos para condições operacionais típicas de aplicações frigoríficas. A partir da análise efetuada foi proposto um modelo no qual foram introduzidos os adimensionais que envolvem os principais efeitos relacionados à mudança de fase. O modelo proposto apresentou resultados bastante adequados não apenas na correlação dos resultados experimentais obtidos na presente pesquisa como também em dados encontrados na literatura.<br>Present research has aimed at the study of convective boiling of recently introduced halocarbon refrigerants inside horizontal copper tubes. A comprehensive literature survey has revealed that the correlations for the convective boiling heat transfer coefficient can be divided into three main categories: (1) strictly convective; (2) superposition of effects; (3) strictly empirical. As a general rule these correlations are not fitted for generalizations. An experimental set up has been developed and constructed in order to raise data involving a relatively wide range of operational conditions. These data have been used to investigate effects of such parameters as heat flux, mass velocity, quality and evaporating temperature. In addition gathered data have been used in the development of a correlation for the heat transfer coefficient under convective boiling conditions typical of refrigeration applications. The model has been developed in terms of the main intervening non dimensional groups. The proposed equation correlated very well not only experimental data from present investigation but data obtained else where.
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Gupta, Abhishek. "Experimental and theoretical analysis of single-phase convective heat transfer in channel with resistive heater and thermoelectric modules for hydronic cooling and heating device." Cincinnati, Ohio : University of Cincinnati, 2009. http://www.ohiolink.edu/etd/view.cgi?acc_num=ucin1236202446.

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Thesis (M.S.)--University of Cincinnati, 2009.<br>Advisors: Dr. Michael Kazmierczak PhD (Committee Chair), Dr. Milind A. Jog PhD (Committee Member), Dr. Sang Y. Son PhD (Committee Member). Title from electronic thesis title page (viewed April 26, 2009). Includes abstract. Keywords: Peltier cooling; developing internal turbulent forced convection; heat pump and coefficient-of-performance. Includes bibliographical references.
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Hudjetz, Stefan. "Experimental investigation of heat exchange between thermal mass and room environments." Thesis, De Montfort University, 2012. http://hdl.handle.net/2086/9021.

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The different technologies of passive cooling concepts have to rely on a good thermal coupling between a building's thermal mass and indoor air. In many cases, the ceiling is the only surface remaining for a good coupling. Further research is necessary to investigate discrepancies between existing correlations. Therefore, the overall aim of the work described in this thesis is the investigation of heat transfer at a heated ceiling in an experimental chamber. Acoustic baffles obstruct the surface of the ceiling and impede heat transfer. However, there is nearly no published data about the effect of such baffles on heat transfer. Available results from simulations should be verified with an experimental investigation. Consequently, one of the primary aims of this work was to experimentally determine the influence of such acoustic baffles. A suitable experimental chamber has been built at Biberach University of Applied Sciences. The thesis describes the experimental chamber, the experimental programme as well as results from five different test series. With a value of ±0.1Wm⁻²K⁻¹ for larger temperature differences, uncertainty in resulting convective heat transfer coefficients for natural convection is comparable to that of results from an existing recent experimental work often recommended for use. Additionally, total heat transfer (by convection and radiation) results are presented. Results are given for natural, forced and mixed convection conditions at an unobstructed heated ceiling. Furthermore, results for acoustic baffles in both an unventilated and a ventilated chamber are shown. Natural convection results show a very good agreement with existing correlations. Under mixed convection conditions, convective heat transfer at an unobstructed ceiling decreases to the limiting case described by natural convection. Installation of acoustic baffles leads to a reduction in total heat transfer (convection and radiation) between 20% and 30% when compared to the case of an unobstructed ceiling.
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Zago, João Vitor. "Comportamento térmico e hidrodinâmico da ebulição convectiva do HFE-7100 em microdissipador de calor baseado em microcanais /." Ilha Solteira, 2019. http://hdl.handle.net/11449/191408.

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Orientador: Elaine Maria Cardoso<br>Resumo: Dissipadores de calor compactos, baseados em microcanais, têm se mostrado um meio eficaz para o resfriamento de dispositivos de alta densidade de energia, tais como microprocessadores, além de proporcionarem redução de material utilizado para a fabri-cação e do inventário de fluido refrigerante necessário. Sistemas bifásicos que operam com fluidos refrigerantes proporcionam coeficientes de transferência de calor elevados para baixos valores de velocidade mássica e uma distribuição de temperatura mais uni-forme na superfície. O presente estudo teve por objetivo avaliar experimentalmente o desempenho de um dissipador de calor baseado em microcanais, em condições de ebuli-ção convectiva saturada do fluido HFE-7100. O dissipador, em cobre eletrolítico, possui 33 microcanais de seção retangular com dimensões de 10 mm de comprimento, 200 μm de largura, 500 μm de altura e espaçados 100 μm entre si. A eficiência térmica do dissi-pador foi avaliada utilizando como fluido de trabalho o HFE-7100 (fluido refrigerante com baixo ozone depleting potencial, ODP, e global warming potential, GWP). Dados experimentais para o coeficiente de transferência de calor (CTC) e perda de pressão fo-ram obtidos em condições de escoamento monofásico e bifásico saturados, para diferen-tes valores de velocidades mássicas. As condições testadas foram de fluxo de calor im-posto (footprint) variando de 50 a 700 kW/m², com velocidades mássicas do fluido entre 392 e 875 kg/m²s, obtendo coeficientes de transferên... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Microchannel-based heat sinks have been shown to be an effective way of cool-ing high-density energy devices such as microprocessors, as well as reducing the material used to manufacture the exchangers and the required refrigerant inventory. Two-phase flow systems that operate with refrigerant fluids provide high heat transfer coefficients with low mass flux values and more uniform temperature distribution on the surface. The present study aimed to evaluate experimentally the performance of a heat sink based on microchannels under saturated conditions of convective boiling of HFE-7100 fluid. The analyzed heat sink has 33 rectangular section microchannels measuring 10 mm length, 200 μm wide, 500 μm high and spaced 100 μm apart. The heat sink was evaluat-ed using HFE-7100 (low ozone-depleting potential, ODP, and global warming potential, GWP) as working fluid. Experimental data for the heat transfer coefficient and pressure drop were obtained under saturated single and two-phase flow conditions for different values of mass velocities. An experimental apparatus was assembled and validated for the accomplishment of testing. As experimental conditions, the heat flux was applied in a range from 50 to 700 kW/m², with mass flux from 392 and 875 kg/m²s, obtaining a heat transfer coefficient of 60 kW/m² and pressure drop up to 12 kPa. By decreasing the mass flux and the input of the subcooling the HTC increases; the pressure drop increases monotonically with the increase in the mass fl... (Complete abstract click electronic access below)<br>Mestre
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Tangwongsan, Chanchana. "Measurement of in vivo endocardial and hepatic convective heat transfer coefficient." 2003. http://www.library.wisc.edu/databases/connect/dissertations.html.

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Hembram, Seeta. "Experimental Determination of Convective Heat Transfer Coefficient of Tissue Mimicking Gel." Thesis, 2013. http://ethesis.nitrkl.ac.in/4941/1/109BM0006.pdf.

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The present study deals with finding the convective heat transfer coefficient of agarose gel prepared at two different concentrations of 0.6 % w/v and 1.4% w/v. It is carried out with the help of very simple and easily available laboratory apparatus designed specifically for the determination of convective heat transfer coefficient of tissue mimicking gel. This paper demonstrates an experimental study on three reference temperatures corresponding to 60°C, 70°C and 80°C maintained in the water bath. The sample is designed in such a way that it behaves as a lumped parameter system characterized by a uniform temperature distribution within the system. The variation of temperature with time is recorded with the help of data acquisition system and LabView. The convective heat transfer coefficient of tissue mimicking gel is predicted by fitting the analytical result with the experimental result which ensures a goodness of fit in the range of 97% - 99%. The predicted value of convective heat transfer coefficient lies between 400-450 W/m2 K.
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"Estimation of thermal properties of randomly packed bed of silicagel particles using IHTP method." Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-12-1310.

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Accurate values of thermophysical transport properties of particle beds are necessary to accurately model heat and mass transfer processes in particle beds that under-go preferred processes and changes. The objective of this study is to use a proven analytical/numerical methodology to estimate the unknown transport properties within test cells filled with silicagel particles and compare the results with the previously published data. An experimental test cell was designed and constructed to carry out transient heat transfer tests for both step change conduction and convection heat transfer within a packed bed of silicagel particles. For a known step change in the test cell temperature boundary condition, the temporal temperature distribution within the bed during heat conduction depends only on the effective heat conduction coefficient and the thermal capacity of the particle bed. The central problem is to, using only the boundary conditions and a few time-varying temperature sensors in the test cell of particles, determine the effective thermal conductivity of the test bed and specify the resulting measurement uncertainty. A similar problem occurs when the heat convection coefficient is sought after a step change in the airflow inlet temperature for the test cell. These types of problems are known as inverse heat transfer problems (IHTP). In this thesis, IHTP method was used to estimate the convective heat transfer coefficient. Good agreement was seen in experimental and numerical temperature profiles, which were modeled by using the estimated convective heat transfer coefficient. The same methodology was used to estimate the effective thermal conductivity of the particle bed. Comparison between the experimental temperature distribution and numerical temperature distribution, which was modeled by using the estimated effective conductivity, illustrated good agreement. On the other side, applying the effective thermal conductivity, obtained from a direct steady state measurement, in the numerical simulation could not present agreement between the numerical and experimental results. It was concluded that the IHTP methodology was a successful approach to find the thermophysical properties of the particle beds, which were hard to measure directly.
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Books on the topic "Convective heat transfer coefficient (h)"

1

E, Poinsatte Philip, and United States. National Aeronautics and Space Administration., eds. Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. National Aeronautics and Space Administration, 1993.

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E, Poinsatte Philip, and United States. National Aeronautics and Space Administration., eds. Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. National Aeronautics and Space Administration, 1993.

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E, Poinsatte Philip, and United States. National Aeronautics and Space Administration., eds. Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. National Aeronautics and Space Administration, 1993.

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Cyril, Masiulaniec K., and United States. National Aeronautics and Space Administration., eds. Experimental technique and assessment for measuring the convective heat transfer coefficient from natural ice accretions. National Aeronautics and Space Administration, 1995.

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Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. National Aeronautics and Space Administration, 1993.

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Book chapters on the topic "Convective heat transfer coefficient (h)"

1

Herwig, Heinz. "Wärmeübergangskoeffizient α* (heat transfer coefficient h*)." In Wärmeübertragung A-Z. Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-56940-1_83.

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Ma, Jiaxing, Yong Liu, and Mengru Ma. "A Calculation Method of Convective Heat Transfer Coefficient in Ventilation Tunnels." In Environmental Science and Engineering. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-63901-2_68.

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Smith, G. D. J., G. C. Snedden, and R. D. Stieger. "Advances in the Measurement of Convective Heat Transfer Coefficient in Gas Turbine Applications." In Energy and the Environment. Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4593-0_15.

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Mohd-Ghazali, Normah, Oh Jong-Taek, Nuyen Ba Chien, Kwang-Il Chi, Nor Atiqah Zolpakar, and Robiah Ahmad. "Multiobjective Optimization of Microchannels with Experimental Convective Heat Transfer Coefficient of Liquid Ammonia." In Modern Advances in Applied Intelligence. Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07455-9_49.

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Mowade, Sanjay, Subhash Waghmare, Sagar Shelare, and Chetan Tembhurkar. "Mathematical Model for Convective Heat Transfer Coefficient During Solar Drying Process of Green Herbs." In Advances in Intelligent Systems and Computing. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-32-9515-5_81.

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Yuan, Leqi, Kun Cheng, Haozhi Bian, Yaping Liao, and Chenxi Jiang. "Numerical Simulation of Flow Boiling Heat Transfer in Helical Tubes Under Marine Conditions." In Springer Proceedings in Physics. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_86.

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AbstractLead-based cooled reactors in most countries and some small reactors at sea use helical tube steam generators. Compared with U-tubes, the convection heat transfer coefficient in the spiral tube is higher, the structure is more compact, and the secondary flow is generated under the action of centrifugal force and gravity, which can achieve the effect of wetting the inner wall of the tube. However, due to the importance of the steam generator in the reactor and the complexity of the flow and boiling in the helical tube, the aggregation behavior of bubbles, the distribution of the two-phase interface and the secondary flow in the tube will significantly affect the heat transfer characteristics, so the gas-liquid phase in the tube is studied. Distribution, changes in heat transfer coefficients, and fluid flow characteristics are very important.In order to study the boiling heat transfer characteristics of helical once-through steam generators under static and marine conditions to provide safe and reliable energy supply for offshore facilities such as marine floating, this study uses STAR-CCM+ software, VOF method and Rohsenow boiling model to study the heat transfer capacity and flow characteristics of flow boiling in a helical tube under swaying and tilting conditions. The gas-liquid phase distribution characteristics, secondary flow variation characteristics and convective heat transfer coefficient of the fluid under different swing functions and inclined positions are obtained by numerical calculation, and the law of physical parameters changing with the cycle is found. The research results show that the secondary flow and heat transfer capacity in the tube change with the cycle, and the change is most obvious at the tube length of 0.8m. 5% of the normal condition; when the inclination angle is 45°, the maximum increase of the convection heat transfer coefficient is 16.8%, and the maximum decrease is 6.6%.
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Yi, J. J., J. W. Song, M. S. Yu, and H. H. Cho. "Study on convective heat transfer coefficient around a circular jet ejected into a supersonic flow." In Shock Waves. Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-85181-3_80.

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Li, Changhe. "Design and Experimental Evaluation of Convective Heat Transfer Coefficient Test System in Nanofluids Spray Cooling." In Thermodynamic Mechanism of MQL Grinding with Nano Bio-lubricant. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-6265-5_5.

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Erben, Andreas, Alexander Geist, Immanuel Voigt, et al. "Smart Pressure Film Sensor for Machine Tool Optimization and Characterization of the Dynamic Pressure Field on Machine Surfaces." In Lecture Notes in Production Engineering. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34486-2_14.

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AbstractKnowledge of thermal interactions with the environment is essential for improving the performance of machine tools. Therefore, it is necessary to detect and quantify the convective heat flows at machine tool surfaces, that occur in the workspace as a result of cutting fluid use or outside the machine due to active air flow. Thin-film sensors made of shape memory alloys with integrated small temperature sensors are suitable for detecting very fine pressure differences and can be used to estimate convective heat transfer. By measuring the pressure differences, the dynamic pressure field at the surface can be determined. Since the pressure field correlates with the flow field, conclusions can be drawn about the flow velocity. This leads to more profound and extended possibilities to match flow fields from CFD simulations with measured data. At the same time, the surface temperature is also recorded by this sensor. Reference measurements of the temperature in the free flow are used to characterize the heat transfer. By knowing the pressures, temperatures and the correlating flow velocity near the wall, the heat transfer coefficient can be determined. Against this background, this paper demonstrates the behavior of shape memory alloys as fluid pressure sensors and addresses the development of such sensors for machine tools. For this purpose, sensor units are to be developed that can be placed as a sensor network (composite of several sensors on one surface) inside and outside the workspace.
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Li, Changhe. "Convective Heat Transfer Coefficient Model Under Nanofluid Minimum Quantity Lubrication Coupled with Cryogenic Air Grinding Ti-6Al-4V." In Thermodynamic Mechanism of MQL Grinding with Nano Bio-lubricant. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-6265-5_9.

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Conference papers on the topic "Convective heat transfer coefficient (h)"

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Jiang, Shu, and Jun Li. "Convective Heat Transfer Coefficient for Different Body Sizes: Comparison between Adult and Infant." In 16th Textile Bioengineering and Informatics Symposium. Textile Bioengineering and Informatics Society Limited (TBIS), 2023. https://doi.org/10.52202/070821-0037.

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Mele´ndez, Elva, and Rene´ Reyes. "Experimental Description of the Convective Heat Transfer Coefficient for Pool Boiling of Binary Mixtures on Porous Heating Surfaces." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47196.

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This work presents the experimental results of the effect of porous heating surfaces, and the Marangoni effect on the convective heat transfer coefficient for pool boiling, h. The porous heating surfaces fabricated for these experiments, and the interfacial tension gradients in the binary mixtures reduced the bubbles’ size and their coalescence in the proximity of the heating surface. The convective heat transfer coefficient was calculated for the boiling of pure water and three aqueous mixtures with 12, 16, and 20% weight of ethanol on five different porous coverings on the heating element. Some combinations of these variables were studied in a 32 factorial design, and represented by the response surface calculated. The maximum h for boiling of pure water on the bare surface of the heating element was 50 kW/m2 °C. Using the porous coverings, the maximum h value was 180 kW/m2 °C. For boiling the binary mixtures on the smooth heating element surface the maximum h value was 65 kW/m2 °C, while on the porous coverings the values of h attained a maximum of 220 kW/m2 °C. The maximum values of h correspond to the composition of 16% ethanol, and a porous covering with the smallest porous diameter.
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Chen, Li. "Study of Combined Method to Enhance Convective Heat Transfer." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0660.

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Abstract Experimental study of convective heat transfer in a tube with the combination of spring coil and flag-type inserts was performed to investigate the characteristics of heat transfer and flow drag. The test tube was a ϕ28 × 2 × 700 mm copper tube, and the working fluid was No.30 turbine oil. A piece of spring with the length of 100mm (wire diameter of 1.5mm and the pitch of 4mm) was set at the inlet of test tube, behind the spring 1–3 pieces of trapezoid shaped flag-type inserts made of stainless steel having a sweep angle of 76° length of 20mm width of 22mm and thickness of 0.3mm were hinged on a ϕ1.0 mm stainless steel vertical stick. It was shown that by means of the combined method heat transfer coefficient was greatly increased and the ratio of h/h0 was mostly higher than Δp/Δp0, also h/h0 increased in both the low and high Re regions. It was concluded that the advantages of these two components were combined and their disadvantages were reduced.
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ZACHERL, LORENZ, ALLYSON FONTES, and FARJAD SHADMEHRI. "THREE-DIMENSIONAL HEAT TRANSFER ANALYSIS OF HOT GAS TORCH (HGT)-ASSISTED AUTOMATED FIBER PLACEMENT OF THERMOPLASTIC COMPOSITES." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35756.

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In-situ manufacturing of thermoplastic composites using the Automated Fiber Placement (AFP) process consists of heating, consolidation, and solidification steps. During the heating step using Hot Gas Torch (HGT) as a moving heat source, the incoming tape and the substrate are heated up to a temperature above the melting point of the thermoplastic matrix. The convective heat transfer occurs between the hot gas flow and the composites in which the convective heat transfer coefficient h plays an important role in the heat transfer mechanism, which in turn significantly affects temperature distribution along the length, width, and through the thickness of the deposited layers. Temperature is the most important process parameter in AFP in-situ consolidation that affects bonding quality, crystallization, and consolidation. Although it is well known that the convective heat transfer coefficient h is not constant and has a distribution, most studies have assumed a constant value for h for heat transfer analysis, which leads to discrepancies between numerical and experimental results. It has already been shown by the authors that, unlike other studies assuming constant h value, using a distribution function to approximate the convective heat transfer coefficient h in a three-dimensional finite element transient heat transfer analysis the temperature distribution can be well predicted in thermoplastic composite parts and matches experimental data. In this study, the use of the proposed h distribution function is analysed and validated by several measuring points. Furthermore, experimental trials are carried out to validate the results from the simulation.
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Divo, Eduardo, Alain J. Kassab, Jay S. Kapat, and Ming-King Chyu. "Retrieval of Multidimensional Heat Transfer Coefficient Distributions Using an Inverse BEM-Based Regularized Algorithm: Numerical and Experimental Results." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0990.

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Abstract Surface maps of heat transfer coefficients (h) are often determined by transient liquid crystal or other similar transient experimental techniques. This involves (1) conducting an experiment with an impulsively imposed convective boundary condition on an initially isothermal test object, (2) measuring the resulting time-dependent surface temperature distributions, and (3) solving the one-dimensional transient heat conduction equation for different points on the convective surface. There are many practical cases where this approach fails to adequately model the temperature field and, consequently, leads to erroneous h values. In this paper, we present an inverse boundary element method (BEM)-based approach for the retrieval of spatially varying h distributions from surface temperature measurements. In this method, an efficient numerical algorithm requiring only a surface mesh is used to solve the conduction problem. At each time level, a regularized functional is minimized to estimate the time-dependent heat flux and simultaneously minimize the effect of experimental measurement uncertainties in surface temperature values on the calculated heat flux. Newton’s cooling law is then invoked to compute h. Results are presented from several numerical simulations and from a laboratory experiment. The method is applicable to unsteady as well as to steady-state convective systems.
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Davis, E. S., S. R. Duncan, and P. S. Grant. "Modeling and Validation of Substrate Heat Transfer Coefficient Distribution in Vacuum Plasma Spraying." In ITSC2006, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, R. S. Lima, and J. Voyer. ASM International, 2006. http://dx.doi.org/10.31399/asm.cp.itsc2006p0317.

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Abstract As the initial step of a process control design for a substrate surface temperature control solution for Vacuum Plasma Spraying (VPS), the distribution of heat transfer coefficient h between impinging plasma gases and the substrate coating surface is required. An embedded calorimeter approach was used to measure the distribution of the convective heat transfer coefficient over the surface of a substrate and the resulting distributions have been compared with empirical correlations and CFD model predictions of the plasma jet/substrate interaction, as a function of VPS process parameters.
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El-Jummah, Abubakar M., Reyad A. A. Abdul Hussain, Gordon E. Andrews, and John E. J. Staggs. "Conjugate Heat Transfer CFD Predictions of the Surface Averaged Impingement Heat Transfer Coefficients for Impingement Cooling With Backside Cross-Flow." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63580.

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A 10 row impingement heat transfer configuration with a single sided exit at the end of the impingement gap was modelled using conjugate heat transfer CFD. The predictions were compared with experimental results for an electrically heated, 6.35mm thick, metal wall of nimonic-75, which was impingement cooled. The geometry investigated was a square array of inline impingement 10 × 10 holes with X/D of 4.66 and Z/D of 3.06, where D = 3.27mm. The use of metal walls enabled the local surface averaged heat transfer coefficient h, to be estimated from an imbedded thermocouple that logged the rate of cooling when the heating was removed. Conjugate heat transfer analysis provided local h values, which were surface averaged for comparison with the measured h. The CFD results also provided velocity, turbulence and Nusselt number distributions on the target and impingement jet surfaces. The aerodynamics data enabled the pressure loss of the system to be predicted, which compared well with experimental measurements. The predicted surface distributions of Nusselt number were similar to the surface turbulence kinetic energy distributions, which demonstrated the importance of turbulence in convective heat transfer. Surface averaged heat transfer coefficients were predicted and are in good agreement with the measurements for five coolant mass flow rates. The predicted and measured results for surface averaged h were similar to measurements of other investigators for similar impingement geometries.
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Shevade, Shantanu S., Muhammad M. Rahman, and Rasim O. Guldiken. "Turbulent Multi-Jet Air Impingement for Applications in Commercial Cooking." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88635.

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Convective heat transfer coefficient and its interdependency with various key parameters is analyzed for turbulent multi-jet impingement. Air is used as the working fluid impinging on the flat surface via a three-nozzle arrangement. A thorough investigation of velocity and temperature distribution is performed by varying Nozzle Velocity, Height over Diameter ratio (H/D) and Spacing over Diameter ratio (S/D). Convective heat transfer coefficient, average impingement surface temperature, and heat transfer rate are calculated over the impingement surface. It was found that higher S/D ratios result in higher local heat transfer coefficient values near stagnation point. However, increased spacing between the neighboring jets results in less coverage of the impingement surface reducing the average heat transfer. Lower H/D ratios result in higher heat transfer coefficient peaks. The peaks for all three nozzles are more uniform for H/D ratios between 6 and 8. For a fixed nozzle velocity, heat transfer coefficient values are directly proportional to nozzle diameter. For a fixed H/D and S/D ratio, heat transfer rate and average impingement surface temperature increase as the nozzle velocity increases until it reaches a limiting value. Further increase in nozzle velocity causes drop in heat transfer rate due to ingress of large amounts of cold ambient air in the cooking space.
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Gnanasekaran, N., and C. Balaji. "A Correlation for Nusselt Number Under Turbulent Mixed Convection Using Transient Heat Transfer Experiments." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22428.

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This paper reports the results of an experimental investigation of transient, turbulent mixed convection in a vertical channel in which one of the walls is heated and the other is adiabatic. The goal is to simultaneously estimate the constants in a Nusselt number correlation whose form is assumed a priori by synergistically marrying the experimental results with repeated numerical calculations that assume guess values of the constants. The convective heat transfer coefficient “h” is replaced by the Nusselt number (Nu) which is then assumed to have a form Nu = a (1+RiD) b ReDc where a, b and c are the constants to be evaluated. From the experimentally obtained temperature time history and the simulated temperature time history, based on some guess values of a, b, and c, one can define the objective function or the residue as the sum of the square of the difference between experimentally obtained and simulated temperatures. Using Bayesian inference driven by the Markov chain Monte Carlo method, one, more or all of the constants a, b and c are retrieved together with the uncertainty involved in these estimates. Additionally, the estimated parameters are compared with experimental benchmarks.
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Hu, Xuejiao, Ankur Jain, and Kenneth E. Goodson. "Investigation of the Natural Convection Boundary Condition in Microfabricated Structures." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72698.

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Heat loss through surrounding air has important thermal effect on microfabricated structures. This effect is generally modeled as a natural convection boundary condition. However, how to determine the convective coefficient (h) at microscales is a debate. In this paper, a micro heater is fabricated on a suspended thin film membrane. The natural convection is investigated using the 3-omega measurements and complex analytical modeling. It is found that h seems larger than that at larger scales; however, it is also proved that the increased h is actually contributed by heat conduction instead of heat convection. A method of determining the phenomenal h that can be used for microfabricated structures is proposed by using the heat conduction shape factor.
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Reports on the topic "Convective heat transfer coefficient (h)"

1

Kedzierski, Mark A., and Donggyu Kang. Horizontal convective boiling of R1234yf, R134a, and R450A within a micro-fin tube :. National Institute of Standards and Technology (U.S.), 2017. http://dx.doi.org/10.6028/nist.tn.1966.

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This report presents local convective boiling heat transfer and Fanning friction factor measurements in a micro-fin tube for R134a and two possible low global warming potential (GWP) refrigerant replacements for R134a: R1234yf and R450A. Test section heating was achieved with water in either counterflow or in parallel flow with the test refrigerant to provide for a range of heat fluxes for each thermodynamic quality. An existing correlation from the literature for single and multi-component mixtures was shown to not satisfactorily predict the convective boiling measurements for flow qualities greater than 40 %. Accordingly, a new correlation was developed specifically for the test fluids of this study so that a fair comparison of the heat transfer performance of the low GWP refrigerants to that of R134a could be made. The new correlation was used to compare the heat transfer coefficient of the three test fluids at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux. The resulting example comparison, for the same operating conditions, showed that the heat transfer coefficient of the multi-component R450A and the single-component R1234yf were, on average, 15 % less and 5 % less, respectively, than that of the single-component R134a. Friction factor measurements were also compared to predictions from an existing correlation. A new correlation for the friction factor was developed to provide a more accurate prediction. The measurements and the new models are important for the evaluation of potential low-GWP refrigerants replacements for R134a.
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